ST. LOUIS (April 19, 2021) — A recent surge in evidence from an array of sources highlights the nutritional and health attributes of soy protein for men. These sources include newly published research, the recently released 2020-2025 Dietary Guidelines for Americans and an authorized FDA health claim.
Nutrition scientists increasingly recognize the importance of maintaining muscle mass and strength throughout life. Consuming sufficient dietary protein helps to achieve this goal, but some have questioned whether or not the type of protein matters. In response, researchers statistically analyzed the results of 9 clinical studies involving men engaged in resistance exercise training.1 According to the findings, supplementation with soy protein led to gains in muscle mass and strength to the same degree as supplementation with animal protein (including whey protein which is often considered to be the gold standard protein for building muscle).
“Despite a persisting belief among some people that those involved in resistance exercise training need to consume animal protein to reach optimum results, our work found that soy protein performs just as well,” said Heidi Lynch, PhD, RDN, associate professor of kinesiology, Point Loma Nazarene University, and one of the authors of the analysis. “The results confirm that supplementing with soy protein leads to similar gains in strength and lean body mass as whey protein.”
Experts recommend that individuals trying to bulk up consume about twice as much protein as sedentary individuals (1.6 g/kg body weight or about 0.7 g/lb). Older individuals may also need more protein than younger people. A recently published study from China found that simply adding an additional 16 grams of protein daily maintained or increased muscle mass and strength and the physical performance of older men and women with low lean mass, even though they were not participating in strength building exercises and were consuming the recommended amount of protein at the start of the study.2 Again in this study, soy protein performed as well as whey protein.
In most studies that have examined the impact of protein supplementation, the participants are consuming an omnivorous diet, a diet that includes both plant and animal sources of protein. An exception is a study conducted at the University of Sao Paulo and published earlier this year that compared the effects of adding soy protein to the diet of vegans with adding whey protein to the
www.thesoynutritioninstitute.com diet of omnivores.3 After 12 weeks of resistance exercise training, those consuming the vegan-soy diet experienced gains in muscle mass and strength similar to those consuming the omnivore-whey protein diet.
Soy protein is a good choice for men wanting to bulk up and it may directly lower blood cholesterol levels; however, some men may be reluctant to consume soyfoods because of misguided concerns that plant estrogens (isoflavones) in soybeans cause unwanted effects. Recent research puts those concerns to rest. In 2021, a statistical analysis of 41 clinical trials involving nearly 2,000 men, found that neither soy protein nor isoflavones had any impact on testosterone or estrogen levels.4
“Time and time again, research has shown that soy protein is a great choice for your health and won’t negatively impact your hormone levels,” Jim White, RDN, American College of Sports Medicine Exercise Physiologist, owner of Jim White Fitness & Nutrition Studios said. “With so much misinformation circulating, it is imperative that we look to credible sources such as these studies.”
These hormone findings concur with the conclusions of a comprehensive technical review of the safety of soyfoods and isoflavones that was published in March of this year.5 In addition to hormone levels, this review examined other outcomes specific to men, such as sperm and semen parameters and gynecomastia (breast enlargement in men). Soy received a clean bill of health.
Important to note, the U.S. Food and Drug Administration (FDA) authorized a health claim in 1999 stating, “25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease.” Additionally, while evaluating the evidence in support of the cholesterol-lowering effects of soy protein, the FDA also rejected concerns about the safety of soy.
Finally, in the 2020-2025 Dietary Guidelines for Americans soyfoods received several important mentions.6 For example, tofu and tempeh, and soy protein powders were specifically included in the protein category. Fortified soymilk and soy yogurt were the only plant-based dairy alternatives considered by the guidelines to be nutritionally appropriate substitutes for milk and yogurt.
Soyfoods provide high quality protein in varying amounts: tofu (6-13 g protein/3 oz), tempeh (11- 17 g protein/3 oz), edamame (9-11 g/0.5 cup), soymilk (7-8 g/1 cup), soy nutrition bar (6-14 g/1 bar), and soy-based burger (9-16 g/1 patty).7 An abundance of research, FDA soy protein heart health claim, and inclusion of soy in the Dietary Guidelines demonstrate that soy is a healthful, nutritious choice for men (and women) of all ages.
The Soy Nutrition Institute is a scientific organization dedicated to research on soy and health. Established in 2004, the organization includes a scientific advisory board and research and health professionals from soy-related companies and organizations including the United Soybean Board, IFF, ADM, Cargill, Kellogg, Danone North America, Medifast, Impossible Foods, Herbalife, Soylent, House Foods America, Benson Hill, LIVEKINDLY, the Agricultural Utilization Resource Institute (AURI), the United States Soybean Export Council, American Soybean Association’s World Initiative for Soy in Human Health, and the Soyfoods Council. For more information about the Soy Nutrition Institute, visit www.thesoynutritioninstitute.com.
1. Messina, M., Lynch, H., Dickinson, J. M., Reed, K. E. No difference between the effects of supplementing with soy protein versus animal protein on gains in muscle mass and strength in response to resistance exercise. Int J Sport Nutr Exerc Metab. 2018; 28(6), 674-685. doi:10.1123/ijsnem.2018- 0071
2. Li C, Meng H, Wu S, et al. Daily supplementation with whey, soy, or whey-soy blended protein for 6 months maintained lean muscle mass and physical performance in older adults with low lean mass [published online ahead of print, 2021 Feb 18]. J Acad Nutr Diet. 2021;S2212-2672(21)00006-X. doi:10.1016/j.jand.2021.01.006
3. Hevia-Larraín V, Gualano B, Longobardi I, et al. High-protein plant-based diet versus a protein matched omnivorous diet to support resistance training adaptations: A comparison between habitual vegans and omnivores [published online ahead of print, 2021 Feb 18]. Sports Med. 2021. doi:10.1007/s40279-021-01434-9
4. Reed KE, Camargo J, Hamilton-Reeves J, et al. Neither soy nor isoflavone intake affects male reproductive hormones: An expanded and updated meta-analysis of clinical studies. Reprod Toxicol. 2021;100:60-7.
5. Messina M, Mejia SB, Cassidy A, et al. Neither soyfoods nor isoflavones warrant classification as endocrine disruptors: a technical review of the observational and clinical data. Crit Rev Food Sci Nutr. 2021.
6. U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. 9th Edition. December 2020. Available at DietaryGuidelines.gov. 7. USDA Food Composition Databases, https://ndb.nal.usda.gov/ndb/search.
Irritable bowel syndrome (IBS) is a common disorder that affects the large intestine. IBS affects about one of out every 10 persons in the world although rates vary from region to region. Some research suggests that about 14% of Americans have IBS although the vast majority are undiagnosed.
Signs and symptoms of IBS include cramping, abdominal pain, bloating, gas, and diarrhea or constipation, or both. Some people can control their symptoms by managing diet, lifestyle and stress.
The role of food allergy or intolerance in IBS isn’t fully understood but science-based evidence indicates that the Low FODMAP Diet can help manage the gastrointestinal symptoms associated with IBS. And soyfoods can be part of the Low FODMAP Diet.
FODMAP is an acronym that stands for: Fermentable – meaning they are broken down (fermented) by bacteria in the large bowel, Oligosaccharides – “oligo” means “few” and “saccharide” means sugar. These molecules made up of individual sugars joined together in a chain. Disaccharides – “di” means two. This is a double sugar molecule. Monosaccharides – “mono” means single. This is a single-sugar molecule. And Polyols – these are sugar alcohols (however don’t lead to intoxication!).
When consumed in foods and/or drinks, FODMAPs can be poorly absorbed in the small intestine and pass through to the large intestine, where two major events happen:
The FODMAPs are readily fermented by bacteria in the large bowel, contributing to the production of gas.
The FODMAPs are also highly osmotic, meaning that they attract water into the large bowel, which can alter how quickly the bowels move.
These two processes can then trigger symptoms including excess wind, abdominal bloating and distension, abdominal pain, constipation or diarrhea, or a combination of both.
Many soyfoods, although not all, can be part of the Low FODMAP Diet. If you have IBS, good choices are firm tofu (as opposed to silken tofu), soymilk made using isolated soy protein, soy cheese and tempeh. Tempeh is made by fermenting whole soybeans. It has an excellent texture and is highly nutritious and may help to promote the growth of friendly bacteria, which could lead to an assortment of health benefits.
Do soyfoods help or hurt breast cancer patients? That question has been hotly debated over the past 20 years. Although older animal studies raised some initial concerns, extensive human research not only suggests soyfoods are safe for women with breast cancer but potentially beneficial. Population studies show that consuming 1-2 servings of soyfoods per day after a diagnosis of breast cancer reduces recurrence and improves survival. Now, research published in Breast Cancer Research and Treatment that was conducted by investigators from several US universities suggests that breast cancer patients who consume soyfoods are less likely to suffer from menopausal symptoms and fatigue.
Women involved in this study were recruited from two California cancer registries. All women had completed primary treatment for breast cancer. In total, there were 192 Chinese-Americans and 173 Non-Hispanic Whites. Information on dietary intake and symptoms was obtained through a 1-hour-long survey administered via telephone. The dietary questionnaire included four questions specifically about soyfoods. Women were divided into three soyfood intake groups: none, low and high intake.
In addition to obtaining information on dietary intake, all women in the study were asked if they experienced any of 34 possible treatment-related symptoms and its severity within the past 12 months prior to the interview date. Symptoms were assessed using a five-level scale, from “not at all” to “very much.”
When all women were included in the analysis, the findings showed that high-soy-consuming patients were less than half as likely to report having menopausal symptoms in comparison to women who didn’t consume soyfoods. Symptoms included hot flashes or night/cold sweats, vaginal dryness/pain with intercourse and vaginal discharge. Similarly, high-soy-consumers were also about half as likely to suffer from fatigue.
The experimental design of this study doesn’t allow for definitive conclusions about the benefits of soyfoods to be made. However, given that other research shows that soyfoods may improve the prognosis of breast cancer patients and that soyfoods are excellent sources of protein and healthy fat, adding soyfoods to the diet makes sense for women with breast cancer. The results of the current study suggest that about two servings per day are sufficient to derive benefit. One serving is a cup of soymilk, one-half cup of tofu or edamame, or one ounce of soynuts.
Ever since the US National Cancer Institute first expressed interest 30 years ago in exploring the role of soy in cancer prevention, this topic has been rigorously investigated. Much of the focus has been specifically on cancer of the breast. That is understandable given that compared to the West, breast cancer mortality rates in soyfood-consuming countries are extremely low. But the rates of prostate cancer in soyfood-consuming countries are just as low. And new research suggests soyfoods could very well be one of the reasons.
To better understand the relationship between soy and prostate cancer a team of researchers from the University of Illinois analyzed 30 observational or epidemiologic studies. Observational studies examine how exposure to a particular factor, such as soy, among a given population, affects risk of developing a particular outcome, such as prostate cancer. When all studies were included in the analysis, those men consuming the most soy were 29% less likely to develop prostate cancer in comparison to men infrequently consuming soy. The results were similar when looking at either Asian or North American studies. However, whereas the consumption of unfermented soyfoods, such as tofu and soymilk, was very protective, no such protective effects were found for fermented soyfoods such as miso. Exactly why fermented foods weren’t protective isn’t clear.
Why is soy protective against prostate cancer? The answer appears to be because soyfoods are such rich sources of isoflavones. Isoflavones are naturally-occurring compounds found in very high amounts in soybeans. The results showed that among the Asian studies, the intake of genistein and daidzein, the two primary isoflavones in soybeans, was inversely related to risk. That is, the more isoflavones consumed, the less likely men were to develop prostate cancer.
In Asian studies, men in the highest intake group, consume about two servings of soyfoods per day. That amount is easy to incorporate into the diet given that a serving is one cup of soymilk, one-half cup of tofu or an ounce of soynuts. It isn’t clear why the isoflavones in soy are protective against prostate cancer, but it isn’t because they lower testosterone levels. Studies show quite clearly that consuming even very high amounts of isoflavone-rich soy doesn’t lower blood testosterone.
Applegate CC, Rowles JL, Ranard KM et al. (2018) Soy consumption and the risk of prostate cancer: An updated systematic review and meta-analysis. Nutrients 10.
The primary fatty acid in soybean oil is protective against diabetes
Linoleic acid is an essential omega-6 polyunsaturated fat.
It is the primary omega-6 fat in the diet and the primary fatty acid in soybeans.
New evidence indicates consuming linoleic acid is protective against diabetes.
Health authorities recognize that linoleic acid lowers blood cholesterol levels and as a result, risk of coronary heart disease. The cholesterol-lowering effect of linoleic acid is acknowledged by the American Heart Association and the 2015-2020 Dietary Guidelines. Furthermore, soybean oil was recently awarded a health claim for coronary heart disease based on its ability to lower blood cholesterol levels.
Less is known about the role that linoleic acid may have in protecting against other chronic diseases such as diabetes. The incidence of diabetes has increased dramatically over the past 20 years in large part because of the skyrocketing rates of obesity. Most people with diabetes, about 90%, over overweight.
To gain insight into the relationship between linoleic acid and diabetes an international team of researchers conducted a comprehensive statistical analysis of 20 different population studies from ten countries.1 This analysis involved nearly 40,000 participants. All of the participants were free of diabetes at enrollment. During the period the participants were followed, 4,347 individuals developed diabetes.
When the investigators looked at levels of linoleic acid in the body, such as in adipose tissue, it was found that those with the highest levels were 35% less likely to develop diabetes. These findings strongly suggest consuming linoleic acid will protect against this disease.
This new analysis is especially noteworthy not only because of its size but because the researchers relied upon levels of linoleic acid in the body as the primary metric, rather than the amount of linoleic acid the study participants reported eating. Accurately assessing dietary intake is very difficult.
This new research indicates that dietary sources of linoleic acid, such as soybean oil, will not only lower risk of coronary heart disease but will protect against diabetes as well.
Wu JHY, Marklund M, Imamura F, et al. Omega-6 fatty acid biomarkers and incident type 2 diabetes: pooled analysis of individual-level data for 39 740 adults from 20 prospective cohort studies. Lancet Diabetes Endocrinology. 2017.
Much of the early excitement about the potential role of soyfoods in reducing risk of breast cancer was based on the knowledge that soyfood-consuming countries such as China and Japan have had historically very low rates of this disease. However, as these countries have experienced Westernization of their cultures, including a change in diet, breast cancer rates have dramatically increased.
For example, since 2003, breast cancer has become the most common type of cancer among women in Taiwan and the fourth leading cause of female cancer deaths. In fact, the incidence of breast cancer has doubled within just two decades. The good news is that new research from Taiwan indicates that greater soyfood consumption could help stem this unwelcomed tide.
This suggestion comes from a study of 233 breast cancer patients and 236 women similar in age but without breast cancer. To determine dietary intake, each study participant filled out a questionnaire that included questions about the intake of 28 frequently-consumed food items. The women also indicated whether they were a vegetarian.
From the questionnaire, the researchers were able to identify 5 different dietary patterns: 1) high meat 2) high processed meat 3) high fruits and vegetables and soyfoods 4) high consumption of desserts and sugar and 5) high consumption of fermented food. The results indicated that the high meat and high processed meat dietary patterns were associated with an increased breast cancer risk. Conversely, a vegetarian diet was protective against breast cancer.
To determine the impact of soyfood intake on risk of breast cancer the investigators estimated the amount of isoflavones the women in this study consumed. Isoflavones, which are purported to be anti-cancer agents, are found in uniquely rich amounts in soyfoods. Women with breast cancer consumed significantly lower amounts of isoflavones than women without breast cancer. And most importantly, women who consumed more than 22 milligrams of isoflavones per day were 63% less likely to develop breast cancer in comparison to women who consumed fewer than 22 milligrams daily.
Twenty-two milligrams is the amount of isoflavones found in one serving of a traditional soyfood, such as one cup of soymilk or ½ cup of tofu or edamame. These results from Taiwan strongly indicate that consuming a more plant-based diet and as little as one serving of soy daily is protective against breast cancer.
“If you’re worried about high blood pressure, a new systematic review of scientific evidence has good news: Changing your diet really can make a difference,” according to a recent article in the Tufts Health & Nutrition Letter.
Soy protein is best known for its ability to lower elevated blood levels of cholesterol. In recognition of this ability in 1999, the FDA awarded soyfoods a health claim for reducing risk of coronary heart disease. Less well known is that soy protein may also lower blood pressure. Blood pressure is a major risk factor for coronary heart disease.
More than a decade ago a commentary in the Canadian Medical Association Journal suggested soy protein could be the next “anti-hypertensive” agent. This commentary was written in response to a clinical study that found soy protein lowered systolic blood pressure (top number) by more than 4 points and diastolic blood pressure by almost 3 points. Since that study was published several statistical analyses of the clinical studies have been published all of which confirm that indeed soy protein lowers blood pressure. The largest analysis included 27 clinical trials. In theory, over time the reduction in blood pressure in response to soy protein could reduce of stroke, heart attack and overall mortality by 4 to 10%.
Of course, although to dramatically lower blood pressure by making dietary changes requires adopting a comprehensive approach but the evidence is clear that soy protein should be part of that overall mix. In addition to soy protein, that mix should include lots of fruits and vegetables and foods that are low in sodium. Fortunately, soy protein is easy to incorporate into the diet. Foods such as tofu, soynuts, edamame and soy burgers are all rich sources of soy protein.
Maintaining strength is an important key to preventing age-related functional decline. Research out of Brazil shows one way to do that is to engage in a resistance exercise program and to supplement the diet with soy protein.
For this study, 32 postmenopausal women began resistance exercise training 2-3 times per week. Half of the women were asked to consume a cup of milk after exercise and the other half were asked to consume milk but to which had been added 25 grams of soy protein. At the 16 week study period, both groups of women experienced increases in muscle mass and strength. However, women who consumed soy protein had significantly greater gains in strength for bench press and knee extension and for all 8 exercises combined.
The amount of soy protein added to the diet – 25 grams per day – is notable because research suggests that at this intake level, soy protein will lower both cholesterol and blood pressure. These benefits make adding soyfoods and soy protein to the diet an especially good choice for women wanting to become stronger.
Typically, soyfoods provide anywhere from 6 to 15 grams of protein per serving. So it is relatively easy to add 25 grams of soy protein to the diet. For those not wanting to eat soyfoods, two scoops of soy powder (isolated soy protein) provide about 25 grams of protein.
Liver disease is a huge worldwide public health problem. Not the type of liver disease associated with alcohol consumption but what is called non-alcoholic fatty liver disease (NAFLD). NAFLD is the most common cause of chronic liver disease in the general population. Until very recently, NAFLD was almost never seen in children. However, that situation is changing because so many children are now overweight or obese. Having too much belly fat greatly increases the risk of developing liver disease. When children develop liver problems it means they have to suffer the consequences of their condition for decades.
Moderate weight loss is the first line and the most effective intervention in NAFLD therapy, however, there is usually poor compliance on behalf of patients and less than 50 percent achieve weight loss goals even in supervised clinical trials. Based on the results of previously published research, Iranian researchers decided to conduct a first of its kind trial to determine whether the soybean isoflavone genistein favorably affects patients with NAFLD. Genistein is one of the three isoflavones in soybeans. These soybean constituents have been widely studied for their health benefits.
For this study, 82 patients with NAFLD were given either a placebo or genistein daily for 8 weeks. Both groups were instructed to continue to consume their usual diet and exercise habits.
At the end of the study, the genistein group had lower levels of insulin and was better able to use the insulin they produced. In addition, genistein reduced oxidation and inflammation. Finally, genistein reduced the percentage of body fat of the patients. Each of these changes suggests that genistein is useful in the management of liver disease and may actually help to prevent its onset.
Although for this study the researcher used genistein supplements, all of the traditional Asian soyfoods such as tofu and tempeh and soymilk are rich in genistein. Longer term studies are needed before definitive conclusions can be made but the current study plus the previously published research on this topic point toward soyfoods as being able to play a key role in the dietary management of liver disease.
Soymilk is different from the nut milks
More Americans than ever are drinking plant milks. As cow’s milk consumption drops and milks made from soybeans, almonds or coconut gain in popularity, the dairy industry is reacting. Their recent effort to limit the term “milk” to secretions from cows is part of a strategy to protect the industry’s market. Dairy farmers say that allowing other beverages to be called milk is misleading, causing consumers to believe that plant milks and cow’s milk have similar nutritional profiles.
It’s a weak argument. There is no evidence that consumers equate plant milks with cow’s milk. In fact, just the opposite is probably true. One factor driving people away from cow’s milk to plant-based options is a negative perception of the health aspects of cow’s milk.
Cow’s milk is valued largely for its calcium content, but most plant milks are fortified with this nutrient to similar levels. (Both cow’s milk and plant milks depend on fortification for vitamin D.)
Protein is a different story. Unless they are fortified with protein, milks made from nuts are extremely low in this nutrient. In contrast, soymilk rivals cow’s milk since it is rich in high-quality protein. It also provides healthy fats and a variety of vitamins and minerals, including iron, which is absent from cow’s milk.
Nut milks tend to be low in nutrition overall. The nutrients they provide come almost exclusively from the fortificants (vitamin D, calcium, etc.) added to them because they contain very little in the way of nuts. For example, a cup of almond milk contains the equivalent of just four almonds. The reason unsweetened almond milk is so low in calories is because it contains so few almonds!
Anyone looking for the heart-healthy benefits associated with tree nuts won’t get them from drinking commercial nut milks. On this one issue, the dairy industry is right: Consumers do need to know what they are purchasing and also need to know how different plant milks fit into overall dietary patterns.
For those who are limiting intake of animal foods, particularly families with children, soymilk is an especially good choice for ensuring adequate intake of high-quality protein. In fact, since intriguing research suggests the protein RDA may actually be too low for most population groups, the protein content of the different non-diary milks is probably an important consideration for just about everyone.
If the main use of plant milks is an alternative to cow’s milk in baking or to wash down the occasional cookie, milk is milk and one can choose whichever meets their own personal preferences. But if nutritional content is paramount, soymilk is clearly different from the nut milks.
The prevalence of diabetes is increasing throughout the world. In large part this is because of the increasing number of people who are overweight or obese as one of the main medical complications of obesity is diabetes. Fortunately, losing weight if obese can dramatically lower diabetes risk. Eating a more plant-based diet is also helpful as people who are vegetarians or near vegetarians are much less likely to develop diabetes. In fact, their risk is reduced by about 50% even after taking into consider their lower body weight. And now, research from Vietnam indicates that adding soyfoods to the diet is very protective against this disease.
For this new study, researchers enrolled 599 newly diagnosed cases of diabetes between the age of 40 and 65 and the same number of people without diabetes. The two groups were of a similar age and had similar numbers of men and women. Information on the frequency and quantity of soyfood consumption, together with demographics, habitual diet and lifestyle characteristics, was obtained from direct interviews. The researchers then determined whether people with diabetes were more or less likely to eat soyfoods.
The results showed that a higher intake of soyfoods was associated with about a 70% reduced risk. That is, those individuals who consumed about two servings of soyfoods per day were 70% less likely to develop diabetes. That level of protection is almost unprecedented. It’s not clear from this study why soy is protective against diabetes but other research has shown that soyfoods increase the body’s ability to use insulin and lower blood glucose levels.
American Heart Association Highlights the Coronary Benefits of Polyunsaturated Fat
A newly published presidential advisory from the American Heart Association (AHA) strongly advocates for Americans to replace the saturated fat in their diet with polyunsaturated fat. This advisory is timely because there has been a lot of confusion of late among the public about the role that dietary fat plays in heart disease. Actually, it is fairly obvious that the AHA advisory was written in response to this confusion. Well, the jury is in and saturated fat is out.
Despite all the public confusion, according to the AHA, evidence in support of replacing saturated fat with polyunsaturated as a means of reducing risk of coronary heart disease has actually strengthened over the years. That is good news for consumers of soyfoods and soybean oil because the predominant type of fat in soybean oil is polyunsaturated.
In fact, a key piece of information upon which the AHA based their conclusions was a statistical analysis of four clinical trials which showed that replacing saturated fat with polyunsaturated fat reduced heart disease risk by a statistically significant 29%. Of those four trials, soybean oil was the sole replacement in one and was a main source of polyunsaturated fat in two others. In the fourth trial the source of polyunsaturated fat was described only as “vegetable oil,” which likely was soybean oil. Therefore, the AHA advisory not only highlights the benefit of polyunsaturated fat but soybean oil in particular.
Soybean oil can make important contributions to the health of Americans
by Mark Messina, PhD, MS
Health Attributes of Soybean Oil and Its Contribution to US Diets
Soybean oil is the most widely produced vegetable oil in the United States. In 2014, over 20.6 billion pounds were produced with 1.9 billion pounds exported to more than 50 countries. It is also the most commonly consumed oil in American diets accounting for more than half of all US vegetable oil consumption and for a little over 7% of total caloric intake.1 Because soybean oil is nearly always marketed and labeled as vegetable oil, most consumers don’t recognize the extent to which it plays in a role in their diets.
The reason for this labeling approach isn’t entirely known. One theory is that it is linked to the introduction of “all vegetable” shortenings in the 1960s which successfully replaced lard and beef tallow-based shortenings and were largely soybean oil-based. “All vegetable” cooking oils soon followed in the marketplace.
Given the contribution that soybean oil makes to caloric intake, it is important to have an understanding of how it impacts the health and nutrition status of Americans. This is especially relevant given the impact of different dietary fats on coronary heart disease risk.
Fatty Acid Composition of Soybean Oil
Soybean oil is low in saturated fat which comprises about 12% of total fatty acids. About 29% of the fat in soybean oil is monounsaturated. Like sunflower, sesame, and corn oils, soybean oil is rich in polyunsaturated fats (PUFAs) which make up 59% of its total fat content.2 What sets soybean oil apart from these other oils is that the polyunsaturated fat is comprised of both linoleic acid and alpha-linolenic acid. Both of these fatty acids are essential nutrients. Linoleic acid is the essential omega-6 fatty acid while alpha-linolenic acid is an essential omega-3 fatty acid.
This is a unique aspect of soybean oil since most other oils that are rich in PUFAs contain only omega-6 fats and have only negligible amounts of omega-3 fats. Because of its widespread use, soybean oil accounts for over 40% of the US intake of both of the essential fatty acids.1
The omega-3 fat found in soybean oil is not the same as the long chain omega-3 fats that are found in fatty fish. Although these long chain fats have been linked to lower risk for heart disease, they are not considered essential. In part, this is because the body can synthesize them from alpha-linolenic acid, the omega-3 fat that is present in soybean oil.
Effects of Polyunsaturated Fat on LDL-cholesterol
Saturated fat has long been known to raise blood levels of LDL-cholesterol which is linked to increased heart disease risk. In contrast, polyunsaturated fat lowers LDL-cholesterol. Since the 1980s, the US Dietary Guidelines have recommended limiting saturated fat intake. The most recent recommendation is to consume a diet that provides no more than 10% of calories as saturated fat. The American Heart Association recommends limiting intake to only 5 to 6% of calories.3
Soyfoods and soybean oil fit well into diets that adhere to these guidelines. In 2006 the American Heart Association stated that “ … soy products … should be beneficial to cardiovascular and overall health because of their high content of polyunsaturated fats … and low content of saturated fat.”4
One of the first studies to directly demonstrate the cholesterol-lowering effect of soybean oil was published in 1993 by researchers from Pennsylvania State University.5 The study involved 18 healthy young men who consumed test diets for 26 days. The diets were 37% fat and 80% of total fat came from one of four different fats: cocoa butter, dairy butter, olive oil or soybean oil. Soybean oil was the most effective in lowering LDL-cholesterol levels. The ending LDL-cholesterol values for cocoa butter, dairy butter, olive oil and soybean oil were 113, 103, 92 and 83 (mg/dl), respectively.
Dietary fat and coronary heart disease
Headlines declaring that “bacon is back” have created misconceptions about the effects of saturated fat on heart disease risk. The confusion stems from population studies that have failed to find a connection between the intake of saturated fat and coronary heart disease. That is, in these studies, people eating diets high in saturated fat are no more likely to experience a heart attack than those whose diets are low in saturated fat.
However, recent research from Harvard University provides an explanation for these findings. The investigators analyzed two prospective cohort studies involving over 130,000 health professionals in the United States. One was the Nurses’ Health Study which includes 84,638 female nurses and the other is the Health Professionals Follow-up Study which involves 42,908 male health professionals. The participants were followed for approximately 30 years and their dietary intake was assessed every two years.
Results showed clear benefits of consuming foods rich in polyunsaturated fats. Replacing 5 percent of calories from saturated fat with polyunsaturated fat decreased risk for coronary heart disease by 25%. Replacing saturated fat with monounsaturated fat also reduced risk but to a lesser extent, about 15%. Replacing saturated fat with whole grains also had a beneficial effect, although it was much smaller reduction in risk of 9 percent. In contrast to the beneficial effects of polyunsaturated and monounsaturated fats and of whole grains, refined carbohydrates had no benefits. In fact, replacing saturated fat with refined carbohydrates and added sugars caused a slight increase in heart disease risk.
This explains the confusion about the effects of saturated fat on health. In an attempt to reduce saturated fat intake, many Americans turned to special reduced-fat products, which also happened to be high in refined carbohydrates like white flour. It placed them at greater risk for heart disease. The findings from the Harvard study show that both saturated fat and refined carbohydrates raise heart disease risk. But replacing saturated fat with polyunsaturated or monounsaturated fats or with whole grains lowers risk. It also lowers risk for overall mortality based on a follow up analysis of this group of 130,000 health professionals.6
Fat, blood sugar levels and inflammation
Not only does polyunsaturated fat have more robust effect on reducing LDL-cholesterol levels, it also helps regulate blood glucose levels. These findings come from an analysis of 102 clinical studies involving 4,220 adult men and women.7 The researchers measured the effects of different dietary patterns on levels of glycosylated hemoglobin, abbreviated as HbA1c. This is a long term measure of blood glucose levels, reflecting average blood glucose levels over a period of three months. Based on this comprehensive analysis, replacing 5 percent of calories from carbohydrate with saturated fat had no significant effect on HbA1c levels. In contract, replacing carbohydrate with polyunsaturated fat significantly lowered HbA1c. In fact, the authors of this analysis estimated that replacing 5 percent of energy from carbohydrate with 5 percent of calories from polyunsaturated fat could reduce risk of developing type 2 diabetes by 22.0% and cardiovascular disease by 6.8% based on the effects on HbA1c.
Finally, recent research has challenged the idea that vegetable oils promote inflammation, an underlying cause of a number of chronic diseases including coronary heart disease. Specifically, it has long been believed that diets with high amounts of omega-6 fats relative to the amount of omega-3 fats promote inflammation. Recommendations have been to aim for a ratio of about 4:1 for optimal health. In soybean oil, the ratio is much higher, about 8:1.
But evidence for any harmful effects of this higher ratio are lacking. In fact, in 2008, the Food and Agriculture Organization of the United Nations concluded that that there is no rationale for recommending a specific ratio of omega-6 fats to omega-3 fats.8 In agreement, In a review of this issue, internationally-recognized CHD expert William S. Harris concluded that the focus should not be on dietary ratios but rather on intake levels of each type of essential fat.9
In conclusion, as the most widely consumed vegetable oil in the United States soybean oil can make important contributions to the health of Americans. Its low content of saturated fat and high content of polyunsaturated fat makes it a perfect fit to heart-healthy diets. It is one of a very few good sources of both essential fatty acids, the omega-6 fatty acid, linoleic acid and the omega-3 fatty acid, alpha-linolenic acid. Soybean oil lowers LDL-cholesterol levels and population studies show that diets high in polyunsaturated fat lower risk of coronary heart disease and favorably affect blood sugar levels.
Mark Messina, Phd
Blasbalg TL, Hibbeln JR, Ramsden CE, Majchrzak SF, Rawlings RR. Changes in consumption of omega-3 and omega-6 fatty acids in the United States during the 20th century. The American journal of clinical nutrition. 2011;93:950-62.
Slavin M, Kenworthy W, Yu LL. Antioxidant properties, phytochemical composition, and antiproliferative activity of Maryland-grown soybeans with colored seed coats. Journal of agricultural and food chemistry. 2009;57:11174-85.
Eckel RH, Jakicic JM, Ard JD, et al. 2013 AHA/ACC guideline on lifestyle management to reduce cardiovascular risk: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol. 2014;63:2960-84.
Sacks FM, Lichtenstein A, Van Horn L, Harris W, Kris-Etherton P, Winston M. Soy protein, isoflavones, and cardiovascular health: an American Heart Association Science Advisory for professionals from the Nutrition Committee. Circulation. 2006;113:1034-44.
Kris-Etherton PM, Derr J, Mitchell DC, et al. The role of fatty acid saturation on plasma lipids, lipoproteins, and apolipoproteins: I. Effects of whole food diets high in cocoa butter, olive oil, soybean oil, dairy butter, and milk chocolate on the plasma lipids of young men. Metabolism: clinical and experimental. 1993;42:121-9.
Wang DD, Li Y, Chiuve SE, et al. Association of specific dietary fats with total and cause-specific mortality. JAMA internal medicine. 2016;176:1134-45.
Imamura F, Micha R, Wu JH, et al. Effects of saturated fat, polyunsaturated fat, monounsaturated fat, and carbohydrate on glucose-insulin homeostasis: A systematic review and meta-analysis of randomised controlled feeding trials. PLoS medicine. 2016;13:e1002087.
Fats and fatty acids in human nutrition. Report of an expert consultation. Food and Nutrition Paper 91. Food and Agriculture Organization of the United Nations. Rome, 2010.
Harris WS. The omega-6/omega-3 ratio and cardiovascular disease risk: uses and abuses. Current atherosclerosis reports. 2006;8:453-9.
Soy isoflavone inhibits metastasis
Genistein is one type of isoflavone found in soyfoods. New research in mice shows that genistein inhibits the spread of colon tumors to other tissues. Interestingly, genistein doesn’t affect the tumor itself—just its spread. This may help to explain why soyfoods are associated with decreased colon cancer metastasis in population studies. It also might provide a rationale for use of genistein in clinical practice to improve colon cancer prognosis. Soyfoods are the only foods containing significant amounts of genistein. More information here.
Soyfoods May Help Women Get Pregnant
Assisted reproduction technology (ART) includes fertility medication, artificial insemination, in vitro fertilization and surrogacy. It is reproductive technology used primarily for infertility treatments, and is also known as fertility treatment. ART contributes more than one percent of U.S. births. In a study involving over 300 women undergoing fertility treatment, those who consumed highest amounts of soy were nearly twice as likely to become pregnant as women consuming no soyfoods. As little as one serving of soyfoods per day may be enough to help women get pregnant. More information here.
Soyfoods linked to lower risk of colon and stomach cancer.
Isoflavones, which are phytochemicals found in soyfoods, have been linked to protection against a number of different cancers. In a recent analysis of 10 population studies, higher soy isoflavone intake was associated with a 24% reduction in the risk of developing colon and rectal cancer and a 33% reduction in the risk of developing stomach cancer. The consumption of only one to two servings of soyfoods per day appears sufficient to provide this proposed benefit. More information here.
Heart Disease Risk Increases with Long-Term Elevated Cholesterol
The relationship between elevated blood cholesterol and increased heart disease risk is well established. However, new findings show that people who have had high blood cholesterol over a long period of time are at even higher risk. Individuals who had elevated cholesterol for 11 to 20 years were twice as likely to develop heart disease as people who had high cholesterol for one to 10 years. It’s never too late to start eating a heart-healthy diet, however, and soyfoods can help in two ways. First, the protein itself directly lowers LDL-cholesterol (bad cholesterol). Second, soyfoods are rich in polyunsaturated fat. Eating more polyunsaturated fat instead of saturated fat lowers blood cholesterol and risk of heart disease.
SOURCE: DOI: 10.1161/CIRCULATIONAHA.114.012477
Soyfoods Linked with Improved Survival in Women with Breast Cancer
Women with breast cancer can safely consume soyfoods. In fact, eating soyfoods may improve the survival of breast cancer patients. That was the conclusion of the World Cancer Research Fund International after extensively reviewing the studies on soy and cancer. Other lifestyle choices that may improve prognosis include maintaining a healthy body weight, being physically active, eating foods containing fiber, and reducing total and especially, saturated fat intake. More information here.
Health Canada Set to Approve Health Claim for Soyfoods
Studies show that including soy protein in the diet can lower LDL-cholesterol (the “bad” cholesterol). Based on these findings, the US Food and Drug Administration (FDA) approved a health claim in 1999 about the relationship between soyfoods as part of a heart healthy diet. Since then 10 other countries have approved similar health claims for soy protein. That list is soon to expand as Health Canada recently announced their decision to award a health claim for soyfoods. More information here.
Dietary Protein Needs May Be Higher for Older Women
Women over the age of 65 may need as much as 50% more protein than the current RDA. Since calorie needs usually decrease with age, older women need to choose plenty of healthful, nutrient-dense, protein-rich foods. The high-quality protein in soyfoods can help women meet their protein needs without increasing their saturated fat and cholesterol intake. More information here.
Top Three Meat Alternatives are Made From Soy
While interest in meat alternatives continues to grow, many consumers have questions about meeting protein needs on meat-freed diets. These were the findings of survey among food shoppers conducted by Acosta Sales and Marketing. Soyfoods can easily address that concern since they are rich in high-quality protein. Not surprisingly, in fact, tofu is the best-selling meat alternative with 21 percent of shoppers purchasing it in the past year. Textured vegetable protein was purchased by 12 percent of shoppers and 10 percent have tried tempeh. More information here.
Soymilk fortified with Vitamin D and Calcium Can Help Prevent Deficiencies
Children who drink non-cow’s milk beverages are more likely to have low serum vitamin D levels than those who drink cow’s milk according to a study of 3,000 children in Canada. Although cow’s milk is fortified with vitamin D by law in both the United States and Canada, fortification of plant milks like soymilk is voluntary. Since sun exposure in many areas isn’t a year-round reliable means of meeting vitamin D needs, it is critical for children drinking soymilk to use brands that are fortified with this vitamin. Fortunately, the vast majority of soymilk sold in North America is fortified with both vitamin D and calcium. More information here.
A Low-Carbohydrate Diet Improves Quality of Life
The results are controversial, but there is growing evidence that low-carb diets can be useful in treating diabetes. Findings from a year-long Swedish study show improvements in physical function, vitality and general health in response to a diet in which carbohydrate provided only about 20% of the calories. For those who want to incorporate the healthful qualities of plant foods into their low-carbohydrate diets, there is a beneficial role for soyfoods. Soybeans are unique among legumes because of their high protein and low-carbohydrate content. Tofu, tempeh and soynuts are examples of healthful low-carbohydrate choices. More information here.
Soymilk Decreases Blood Pressure
Among Korean adults with high blood pressure, consuming two servings of soymilk caused systolic blood pressure to drop by almost 8 points within two hours. Interestingly, canned soymilk had less of an effect compared to soymilk consumed from glass bottles. Other studies support the blood pressure-lowering effects of soy protein. More information here.
Beans Beat Other Protein Sources for Protecting the Environment
Beans have a much smaller environmental footprint than beef, chicken and eggs. Researchers from Loma Linda University in California compared the resources required to produce 1000 grams of protein from either kidney beans or beef. The beans took approximately eighteen times less land, ten times less water, nine times less fuel, twelve times less fertilizer and ten times less pesticide. Beans also required fewer resources than protein from chicken and eggs. Soybeans are higher in protein than other beans, making them among the most environmentally friendly protein-rich foods. More information here.
Cow’s Milk is Linked to Higher Mortality and More Fractures
A study of more than 100,000 Swedish linked intake of cow’s milk with an increased likelihood of death. Among the women, drinking more milk was also associated with an increased risk of bone fractures. The authors of this study suggested that the milk sugar galactose was responsible for these adverse effects. Soymilk doesn’t contain galactose but does contain all the calcium and vitamin D found in cow’s milk. More information here.
Soybean Isoflavones Improve Dry Mouth
Dry mouth, which is characterized by decreased salivation, typically develops in middle-aged women. Unfortunately, there is a lack of consensus regarding the treatment of this condition. New research suggests that the isoflavones in soybeans might be helpful in this regard. The amount of isoflavones found in just one serving per day of soyfoods was shown to be effective in a recently conducted study. More information here.
Soyfoods are Associated with Lower Risk of Stomach Cancer
A statistical analysis of four Korean studies found that people with the highest intake of soyfoods had the lowest likelihood of developing stomach cancer. Eating more soyfoods reduced stomach cancer risk by 44 percent, whereas tofu intake lowered risk by 68 percent and soymilk by 32 percent. In contrast, consumption of the fermented soyfood miso was associated with an increased risk. This is most likely because miso can be very high in sodium. More information here.
Isoflavone-Rich Soy Protein Improves Vaginal Dryness
The reduced estrogen production that occurs with menopause causes a number of physical changes. One of those is vaginal dryness which affects close to one out of every three women. Research from Brazil shows that consuming about 90 milligrams of isoflavones daily, the amount provided by about three servings of soyfoods, alleviates vaginal dryness as effectively as the hormone estrogen. Soy can serve as a natural choice for treating vaginal dryness for women who prefer not to use estrogen replacement therapy because of the side effects. More information here.
A cornerstone of dietary advice has long been to replace saturated fat with polyunsaturated fat to reduce risk of heart disease. This is advice that has been challenged in the past few years, however. Health writers and some nutrition experts have questioned whether saturated fat is to blame for heart disease or whether other dietary components are the culprits. Suddenly, bacon and steak have become the new health foods.
Two new studies, however, reaffirm the wisdom of choosing unsaturated over saturated fats. One was an analysis of 13 prospective epidemiologic studies involving 300,000 subjects (1). These were all studies in which healthy individuals provided information about their dietary intakes at the beginning of the study and then were followed for many years to see how diets correlated with disease outcomes. The researchers, including several from Harvard University, divided the subjects into five groups according to the amount of polyunsaturated fat they consumed. Those in the group with the highest intakes were 15% less likely to have a heart attack and 21% less likely to die from coronary heart disease.
According to the results, a person consuming about 1,800 calories per day could reduce his or her risk of a heart attack by 9% by replacing the amount of saturated fat found in a typical fast food hamburger with the amount of polyunsaturated fat provided by about two-thirds of a cup of soynuts. The protective effect held even after the researchers adjusted for other heart disease risk factors and for other dietary factors like fiber and omega-3 fats. Replacing carbohydrate with polyunsaturated fats also provided benefits.
In the second study, researchers looked directly at blood levels of polyunsaturated fat and their relationship to heart disease risk (2). Blood levels can be a better indicator of dietary intake since people often have trouble recalling what they eat. This study included 3,000 participants who were all at least 65 years old. The key finding was that a higher blood level of the main type of polyunsaturated fat was associated with 13% reduction in the risk of dying from all causes.
These two studies strongly emphasis the health benefits of foods that are low in saturated fat and high in polyunsaturated fat. Soyfoods can be part of a heart-healthy diet because they are low in saturated fat and high in polyunsaturated fat. Cooking with small amounts of soy oil can also improve the fatty acid profile of diets.
1) Farvid MS, Ding M, Pan A, et al. Dietary linoleic acid and risk of coronary heart disease: A systematic review and meta-analysis of prospective cohort studies. Circulation 2014.
2) Wu JH, Lemaitre RN, King IB, et al. Circulating omega-6 polyunsaturated fatty acids and total and cause-specific mortality: The Cardiovascular Health Study. Circulation. (2014).
Soyfoods are without effect on the age of onset of menarche
In many countries throughout the world, the age at which puberty occurs among girls—manifested as breast development, appearance of pubic hair, and onset of menarche—has been commencing earlier. For example, the mean age at onset of menarche (AOM) in Korea decreased from 16.9 to 13.8 years between 1920 and 1985. In the United Kingdom, between 1910 and 1993, it decreased from 13.5 to 12.3 years. And in the United States the AOM decreased by an average of 3 to 5½ months from 1960 to 1990.
These trends in pubertal development raise concerns because early onset of puberty may negatively influence the future health of adolescent girls. Most importantly in this regard, earlier menarche has been implicated in the etiology of breast and ovarian cancer; in fact, early menarche has been found to contribute more to breast cancer risk than early menopause. Therefore, the decline in the AOM may result in an increased incidence of hormone-related cancers.
A number of factors, such as body composition and body weight have been identified as influencing AOM. Dietary factors, such as animal protein and meat and milk and total dairy, have also been linked to pubertal timing. Hormonally-active agents, such as bisphenol-A, a chemical produced in large quantities for use primarily in the production of plastics, which is classified as an endocrine disruptor, has also been evaluated. Endocrine disruptors are chemicals that may interfere with the body’s endocrine (hormone) system and produce adverse developmental, reproductive, neurological, and immune effects. Because soyfoods are such rich sources of isoflavones, which are classified as phytoestrogens, there has been interest in understanding how these foods might affect the AOM.
Until recently, no study had evaluated the relationship between soyfood intake and AOM. But the existing evidence certainly didn’t suggest that soy would cause a decline in the AOM because as noted, earlier AOM is associated with an increased risk of breast cancer whereas there is substantial evidence indicating that consuming soy early in life is protective against this disease. In fact, population studies in the United States and China, suggest that risk can be reduced by as much as 50 percent by eating just one serving of soyfoods per day during adolescence. Nevertheless, because there is no substitute for actual data, researchers from Loma Linda University (LLU) decided to determine whether soy affects the AOM.
It is difficult to gain meaningful insight about soy and isoflavones from population studies conducted in Western countries because few people regularly eat soyfoods. However, the Seventh-day Adventist population, the group chosen by LLU researchers for their study, is very health-conscious and about 40% are vegetarians. Consequently, soy consumption is quite high among this group. In fact, more than 20% of the girls enrolled in this study consumed soyfoods at least 4 times per day and the mean number of servings per week was 12.9.
This cross-sectional study included a total of 327 girls; the age range was between 12 and 18 and the mean age was 15.0. Soy intake (categorized as total soy, meat alternatives, tofu/traditional soy, and soy beverages) as well as other pertinent characteristics of the participants was collected from a web-based dietary questionnaire and physical development tool while the AOM was self-reported.
The mean AOM was 12.5 years for the approximately 90% of the participants who had reached menarche. Consumption of total soyfoods and the three types of soyfoods examined were not significantly associated with the AOM nor was intake associated with the odds for early- or late-AOM. Adjustment for demographic and dietary factors did not change the results.
In conclusion, the results of this first of its kind study show that soy intake does not affect the age at which girls begin menstruation. These findings are certainly welcomed news because with all of the evidence linking early soy intake with a reduced risk of breast cancer, the consumption of soyfoods by girls is one dietary step that should be encouraged.
Segovia-Siapco G, Pribis P, Messina M, et al. Is soy intake related to age at onset of menarche? A cross-sectional study among adolescents with a wide range of soy food consumption. Nutr J. 13,54 (2014).
Soyfoods lower risk of ovarian cancer
The American Cancer Society estimates that in 2014, about 21,980 American women will be diagnosed with ovarian cancer and about 14,270 women will die from this disease. Ovarian cancer ranks fifth in cancer deaths among women, accounting for more deaths than any other cancer of the female reproductive system. A woman’s risk of getting ovarian cancer during her lifetime is about 1 in 72. Her lifetime chance of dying from ovarian cancer is about 1 in 100.
There are considerable geographic variations in the incidence of ovarian cancer, with higher rates reported in developed countries. The age-standardized rates in Europe and the United States are 10.1 and 8.8 per 100,000 women, respectively, but only 3.8 per 100,000 women in China. The difference in incidence rates among countries has generated interest in the role of lifestyle in ovarian cancer. Unfortunately, there is little information about the relationship of diet to ovarian cancer risk, but new evidence suggests that soyfoods may be protective. Soyfoods are uniquely rich sources of isoflavones, which are plant estrogens that may have cancer-preventative properties.
Chinese investigators conducted an observational study which included 500 women with ovarian cancer and 500 women without the disease. Information on habitual consumption of soyfoods, including soybeans, soymilk, fresh tofu, dried tofu, and soybean sprouts, was obtained through interviews with the participants. Based on their intakes of soyfoods, the researchers were able to estimate their intake of isoflavones. A typical serving of traditional Asian soyfoods like tofu and soymilk provides around 25 milligrams of isoflavones. The women with ovarian cancer had lower average intakes of soyfoods than the women who didn’t have cancer. Average soy intake of the women with cancer was 75.3 grams per day compared to 110.7 grams for those who didn’t have cancer. When they were divided into three groups according to the amount of soy consumed, those in the highest intake group (≥120 grams per day) were 71% less likely to have ovarian cancer than women in the lowest intake group (<61 grams per day). Similarly, isoflavone intakes were inversely associated with the ovarian cancer risk, with significant dose-response relationships.
The especially good news from this study is that the amount of soy associated with protection against ovarian cancer is equivalent to only about one serving of soyfoods per day, such as one cup of soymilk, or ½ cup of edamame or tofu.
Andy H. Lee, Dada Su, Maria Pasalich, Li Tang, Colin W. Binns, Liqian Qiu. Soy and isoflavone intake associated with reduced risk of ovarian cancer in Southern Chinese women. Nutr Res 2014
Plant-based diets and soy lower blood pressure
As many as 67 million American adults, or about one in three adults, have high blood pressure and just as many have prehypertension—blood pressure numbers that are higher than normal—but not yet in the high blood pressure range. Elevated blood pressure increases risk for heart disease and stroke and is a contributing factor in nearly 1,000 deaths per day in the United States.
Diet and lifestyle have significant effects on blood pressure. Obesity, high salt intake, and excessive alcohol use are associated with increased blood pressure. Physical activity and diets rich in the mineral potassium can help to keep blood pressure low.
A number of studies have shown that people eating vegetarian diets have lower blood pressure. To better understand this relationship, a team of Japanese researchers analyzed findings from a total of 39 observational and clinical studies that had looked at the relationship of vegetarian diets to blood pressure. In the clinical trials, adoption of a vegetarian diet led to a decrease of 4.8 points in systolic blood pressure and a 2.2 point decrease in diastolic blood pressure. In the 32 observational studies, which included a total of 21,604 participants, vegetarians had on average systolic BP that was 6.9 points lower, and diastolic blood pressure that was 4.7 points lower, than their nonvegetarian counterparts.
A vegetarian diet was as effective as commonly prescribed lifestyle changes to lower blood pressure, such as a reduction in salt intake or weight loss. It was also half as effective as drug therapy in lowering blood pressure which suggests that a vegetarian diet could reduce the need for medication.
It isn’t clear why vegetarian diets lower blood pressure. The lower body weights that are typical of vegetarians may be one reason, although it is only part of the explanation. Even after controlling for difference in body weight, vegetarian diets were still associated with lower blood pressure. Vegetarians also tend to eat more soy products which could also be part or the explanation. Studies have shown that soy protein lowers systolic blood pressure by about 2.5 points and diastolic blood pressure by about 1.5 points.
Yokoyama Y, Nishimura K, Barnard ND, et al. Vegetarian Diets and Blood Pressure: A Meta-analysis. JAMA Intern Med 2014;
Soy Infant Formula Given a Clean Bill of Health
First introduced almost 100 years ago, soy infant formula has been in widespread use since the 1960s. It has been estimated that more than 20 million Americans consumed soy infant formula as babies. Despite this long history of use, questions about the safety of soy infant formula have arisen. They are based largely on the high isoflavone content of soybeans.
Isoflavones are commonly classified as phytoestrogens, or plant estrogens. They are, however, very different from the hormone estrogen. Recently, researchers from universities in Belgium, Indonesia and Mexico evaluated the safety of soy infant formula in relation to growth, bone health, immunity, cognition, and reproductive and hormone functions. Their analysis included both population (epidemiologic) and clinical studies that compared soy infant formula with other types of infant formulas or with breast milk.
The investigators found that the height, weight and growth patterns of children fed soy infant formula were similar to those of children fed cow’s milk formula or human milk. In addition, serum hemoglobin, protein, zinc and calcium concentrations and bone mineral content were all found to be similar to those of children fed cow’s milk or breast milk. Immune measurements and neurocognitive parameters were similar in all the feeding groups.
Not surprisingly, the authors of this study concluded that modern soy infant formula is a safe option for infants. This position is identical to that of the American Academy of Pediatrics which has stated that soy infant formula is an effective alternative to human milk or formulas based on cow’s milk.
Finally, these conclusions are similar to those stemming from the Beginnings Study, a study underway at the Arkansas Children’s Nutrition Center (ACNC). The ACNC is studying development, nutritional status, and health of formula-fed children from birth through puberty. While numerous studies have compared the effects soy infant formula, cow’s milk formula, and breast milk on growth, few have followed the effects over such a long developmental period as the Beginnings Study. It’s also the only study to look at body composition and brain development and function by studying behavior, cognition, psychomotor and language development. A recent article by the lead investigator of the Beginnings Study concluded that there is no evidence of the adverse estrogenic effects that originally prompted the debate about soy infant formula, and there is no reason to restrict its use.
Vandenplas Y, Castrellon PG, Rivas R, et al. Safety of soya-based infant formulas in children. Br J Nutr 2014;1-21.
Bean Fiber Protects Against Prostate Cancer
Prostate cancer is the second most common cancer, after skin cancer, in American men. It is estimated that more than 230,000 new cases of prostate cancer will be diagnosed and nearly 30,000 men will die of this disease in 2014. The average age of diagnosis is 66 and one of seven men will develop prostate cancer.
The good news is that, while it can be a serious disease, most men diagnosed with prostate cancer have an excellent prognosis. In fact, more than 2.5 million men in the United States have been diagnosed with prostate cancer at some point in the past.
But while treatment is effective and survival rates are good, prevention remains important. A number of dietary factors, including fiber, may influence the risk of developing prostate cancer. Although high-fiber diets may protect against this disease, French researchers have found that the type and source of fiber may matter. They examined this relationship in a group of 3313 men. Over a 13 year period, during which time the men provided information about their diets, 139 of them were diagnosed with prostate cancer. Those who consumed the most total dietary fiber and insoluble fiber were about 50% less likely to have developed prostate cancer.
Insoluble fiber passes through the gastrointestinal tract relatively intact, and speeds up the passage of food and waste. As a result, it has a laxative effect and can help reduce constipation. Insoluble fibers are mainly found in whole grains and vegetables.
But it turns out that the source of the fiber may have an impact on risk. When the French researchers looked at the relationship of fiber from different foods to risk for prostate cancer, they found that fiber from legumes was very protective whereas there was no benefit to consuming fiber from cereals, vegetables and fruit. Just one-half cup of cooked beans can provide the amount of fiber that was associated with protection against prostate cancer in this study.
Soybeans are one type of legume that may have additional benefits for men’s health. In addition to being high in fiber, they are packed with phytoestrogens. This may be one reason why men in Asia, where soy is a common part of the diet, are only half as likely as western men to develop prostate cancer.
Deschasaux M, Pouchieu C, His M, et al. Dietary total and insoluble fiber intakes are inversely associated with prostate cancer risk. J Nutr 2014
About 20 percent of people who travel to the Rocky Mountains or other peaks over 8,000 feet experience acute altitude sickness. It’s due to oxygen deprivation and results in headache, loss of appetite, and trouble sleeping. Altitude sickness occurs most often when people travel quickly from lower altitudes to higher altitudes. It has nothing to do with fitness levels, and both men and women are equally likely to suffer from altitude sickness.
A related condition is chronic mountain sickness (CMS). Although acute altitude sickness occurs in people who are not accustomed to spending time at high altitudes, CMS develops during extended time living at a high altitude, generally over 10,000 feet.
It’s characterized by an increase in the size of red blood cells in combination with a low level of oxygen in the blood. It sometimes results in pulmonary hypertension, a type of high blood pressure that affects the arteries in the lungs and the right side of the heart. Severe pulmonary hypertension may lead to congestive heart failure.
New research from China suggests that the isoflavones in soybeans might be a treatment for CMS. Twenty-eight male patients suffering from CMS, who were living on the Qinghai‑Tibetan plateau at about 17,000 feet high were given 20 milligrams of isoflavones twice per day for 45 days. There was no placebo group, because the ethics committee refused to permit a study that allowed patients with CMS not to be treated. Consequently, the efficacy of isoflavones was based on comparing symptoms in patients before and after treatment. The dose of isoflavones in this study was equivalent to 1 ½ to 2 servings of soyfoods.
At study conclusion essentially all measures of CMS had improved. For example, in nearly half of the patients, the size of the red blood cells was no longer elevated. Also, pulmonary hypertension was markedly improved and oxidative damage was attenuated. These benefits came without any identifiable side effects. The authors of this research proposed that isoflavones are a potential low‑cost treatment for CMS.
Experimental and Therapeutic Medicine 7: 275-279, 2014