An Interview with Dr. Mark Messina

An Interview with Dr. Mark Messina

Mark Messina, Ph.D., Adjunct Associate Professor, Department of Nutrition, Loma Linda University and President of Nutrition Matters, Inc., organized the 6th Annual Symposium on the Role of Soy in Preventing and Treating Chronic Disease, bringing together scientists from all over the world. Presentations were grouped by:

Absorption of Soy Bioactives; Inflammatory Diseases; Equol; Cancer;
Cardiovascular Disease; Immune function; Diabetes; Menopausal Symptoms; Osteoporosis; Cognitive Function; Weight Control.

In this issue of the Soyfoods Forum Dr. Messina answers questions about soyfoods and their role in preventing and treating chronic disease. CLICK here for the complete interview.

For a summary of the 6th Annual Symposium on the Role of Soy in Preventing and Treating Chronic Disease please go to www.talksoy.com/soyconnection

Q. Dr. Messina, you’ve been organizing these symposia for several years now and you’ve worked with the best scientists from around the world. What do you think, today, is the greatest benefit of incorporating soyfoods into the US diet?

A. I think what has become clear is that the greatest benefit of soyfoods is really their collective impact. Soyfoods possess many desirable nutritional qualities and although no single quality is remarkable, collectively the effects of soyfood intake on overall health is impressive.

There are several areas for which these qualities may lead to substantial benefits but consider just the case of coronary heart disease. Soy protein modestly lowers bad cholesterol and triglyceride (another type of fat that raises risk of heart disease) levels and slightly increases levels of good cholesterol.

Full-fat soyfoods are also good sources of an omega-3 fatty acid that independently lowers risk of heart disease. Plus, because soyfoods are low in saturated and cholesterol-free, when substituted for many of the more traditional sources of protein in the U.S. diet that tend to be high in cholesterol and saturated fat, soyfoods end up lowering blood cholesterol levels. Furthermore, the isoflavones in soybeans may also exert coronary benefits. So, although no single coronary effect can be considered to be outstanding, certainly collectively these effects will contribute to a significant reduction in the risk of coronary heart disease.

Q. In all the research that’s been presented at this and past symposia are there definite dietary recommendations for soy to be made for certain diseases?

A. No and yes. With the exception of coronary heart disease, for which the U.S. Food and Drug Administration has established that 25 g of soy protein per day reduces cholesterol levels, no formal intake recommendations have been issued.

All of the other proposed benefits of soy, such as protection against cancer and osteoporosis are still speculative. This having been said, the evidence from both the epidemiologic and clinical studies suggest that, to derive maximum benefit from soy, it is necessary to consume two to three servings of soyfoods daily. One serving of a traditional soyfood is for example, one cup of soymilk or 1⁄2 cup of tofu. This two to three serving amount of soy provides about 15-25 g protein and 50 to 75 mg isoflavones.

Of course, consuming even one serving per day is likely to be helpful if for no other reason than because these foods provide high-quality protein but are low in saturated fat and cholesterol. Thus, soyfoods give you something you need but not a couple of things we tend to get too much of.

Q. What information was new to you at this symposium?

A. Soy has been intensely researched for the past 10 years. So most of the time new research findings provide new insight or a slightly different perspective into an existing hypothesis rather than indicating that soy exerts a possible health effect not previously identified. I do think there were two or perhaps three particularly intriguing findings presented at the symposium.

One of these involves hot flashes. More than 25 hot flash trials have been conducted but overall the results have been very inconsistent. Some studies show that hot flashes in postmenopausal women are reduced in response to soyfoods or isoflavones whereas about an equal number show no improvement. A new analysis of 11 published trials that used isoflavone supplements (as opposed to soyfoods) to reduce hot flashes appears to explain some of the inconsistencies in the scientific literature. Only one of the six trials using soygerm isoflavone supplements significantly reduced hot flashes whereas there was a significant improvement in each of the five trials using Novasoy supplements, or supplements similar to Novasoy. The difference between the two types of supplements is the amount of genistein. In the soygerm supplements there is relatively little genistein whereas in Novasoy supplements genistein is the main isoflavone. This is also true in the soybean itself, where genistein is the main isoflavone.

The other new finding relates to the cholesterol-lowering effects of soy protein. As noted previously, in 1999 the U.S. Food and Drug Administration approved a health claim for soy and coronary heart disease based on the cholesterol-lowering properties of soy protein. However, some studies show only very modest reductions in response to soy protein whereas others show more pronounced reductions in cholesterol. Parenthetically, the American Heart Association recently concluded that soy protein lowers LDL cholesterol only about 3 percent although a recently conducted meta-analysis found a 5.3% reduction. At the symposium, James Anderson, MD, from the University of Kentucky, evaluated the scientific literature in this field and concluded that when cooked soy protein is put into baked products the reduction in cholesterol is less than when soy protein is put into unbaked forms, or liquid forms. This is a very interesting but very speculative hypothesis that needs much further research before it can be accepted.

Unfortunately there was inaccurate media coverage of this analysis by Dr. Anderson. Many of the stories reported that uncooked or raw soy lowered cholesterol and that cooked soy did not. All of the soy protein used in the studies analyzed by Dr. Anderson was cooked, it was just a question of into what type of product the cooked soy protein was incorporated. Both types of products lowered cholesterol; it was just that some were more effective than others. Certainly no one is recommending consuming raw soy.

Finally, a third area the data continue to emphasize is the important role that isoflavone metabolism has in determining whether the benefits from soyfoods are realized. It is now well-established that individuals differ markedly in the way in which they metabolize isoflavones. This difference leads to vastly different serum levels of isoflavones and their metabolites. Differences in metabolism may explain why studies so often produce conflicting results. Increasingly, these types of differences among individuals are recognized as determining how individuals react to foods, herbs, supplements, and drugs.

Q. Would you list the top 10 health benefits for soy?

A. Established

High-quality protein
Low in saturated fat and cholesterol free
Contain an omega-3 fatty acid
Cholesterol reduction
Contain isoflavones

Possible

May reduce breast cancer when consumed early in life
May reduce prostate cancer
May reduce bone loss in postmenopausal women
May reduce risk of heart disease
May alleviate hot flashes

Q. Are there diseases for which the recommendations or benefits may have changed due to recent research?

A. Not really, but I think the strength of the evidence in support of the different proposed benefits has changed, which is not surprising. But I don’t think any of the new research changes perspectives on the role of soyfoods in the diet. This is because to substantially reduce risk of chronic disease requires a comprehensive lifestyle approach. Diet is just one part of that and soy is just one part a healthy diet.

Now in regard to specific diseases in my opinion the evidence that adult soy intake reduces breast cancer risk is not as strong as it once was. Conversely, the evidence that soy intake during adolescence reduces later risk of developing breast cancer is even stronger.

For heart disease, estimates of the magnitude of the cholesterol-lowering effects of soy protein have been reduced whereas more emphasis is now being placed on the coronary benefits of soy unrelated to cholesterol reduction.

For osteoporosis, results from the clinical trials involving postmenopausal women are generally encouraging although certainly not totally consistent. However, a new epidemiologic study, and the only one which included fractures as an end point (others included bone mineral density) found that among postmenopausal Chinese women high-soy consumers were about one-third less likely to develop fractures as were Chinese women who consumed relatively little soy.

Q. Soy has been recognized for its benefits for specific populations, i.e., pre- and postmenopausal women, hypercholesterolemics, and for certain cancers. Would you give us a quick review of the benefits of soy in the diet for each of these categories?

A. Heart disease: modest cholesterol reduction, modest reduction in triglycerides, small increase in good cholesterol, possible improvements in arterial health. Large amounts of soy protein appear to lower blood pressure in people with elevated blood pressure although it may be that many proteins have this effect.

Osteoporosis: Possible reduction in bone loss associated with aging and menopause

Cancer: Possible reduction in breast cancer but increasingly evidence suggests protection requires consuming soy during adolescence. For prostate cancer, the evidence suggests consuming soy later is life is sufficient to derive protection but this is still speculative.

Hot flashes: evidence is inconsistent but definitely sufficiently encouraging for health professionals to recommend women try soyfoods for relief.

Q. Is there a difference in benefits depending on the form of soyfoods eaten?

A. This is a fascinating question and one that is hotly debated. There is a clear divergence of opinion on whether certain soyfoods are superior to others. One group recommends consuming primarily only the traditional Asian soyfoods such as tofu and miso whereas others believe that what matters most is the amount of isoflavones and protein consumed, because these are the two components that have been associated with specific health benefits in most studies.

Of course, in general, nutritionists recommend consuming whole foods whenever possible. This having been said, it may be difficult for Americans to get all of the protein or isoflavones they need by consuming only the traditional foods. Many of the more processed products have become popular precisely because they are so convenient. For better or worse, convenience is an attribute that does strongly influence food choices.

My personal advice is to try to get the 15 to 25 grams of soy protein and 50 to 75 milligrams of isoflavones from traditional Asian soyfoods and to use the more processed foods (including supplements), when the consumption of traditional soyfoods is insufficient to provide these amounts.

Q. Are there any concerns about the safety of soyfoods for the general public? For specific audiences?

A. It is true that, based on animal research, a few safety concerns have been raised but there are two areas that have received the most attention. One is the use of soy infant formula and the other is the use of soyfoods by breast cancer patients with estrogen-sensitive (tumors whose growth is stimulated by estrogen) tumors. In regard to formula it is important to first emphasize that breast milk is always considered to be the ideal source of nutrition for infants.

Soy formula has been used for about 40 years and currently about 20-25% of infants in the United States use formula at some point in their development. Considerable research indicates soy formula promotes normal growth and development; nevertheless, based on studies in rodents in response to the isoflavone genistein (one isoflavone in soybeans) concerns that soy might exert adverse hormonal effects in infants have caused some health professionals and advisory committees to recommend that soy formula be used only when the parents object to the use of cow’s milk formula or when clinically necessary. That is, if an infant is allergic to cow’s milk protein or is lactose intolerant.

In addition to promoting normal growth and development the human studies have thus far failed to any evidence of hormonal abnormalities. But these studies are not considered definitive. It is hoped that over the next couple of years research funded by the United States Department of Agriculture currently underway at the University of Arkansas will be able to definitively demonstrate safety.

In regard to breast cancer some types of animal studies have found that certain kinds of processed soy products stimulate the growth of estrogen-sensitive mammary (breast) tumors. Interestingly, other types of animal studies show the opposite, i.e., tumor inhibition. Importantly, the human evidence does not support the notion that any form of soy is harmful. For example, an epidemiologic study in China found that over the course of five years soyfood intake was unrelated to the survival of 1500 breast cancer patients. Similarly, isoflavone supplements did not adversely affect the contralateral breast (the breast in which the tumor did not originally occur) of postmenopausal breast cancer patients. Still, none of the human evidence at this point is able to definitively refute the animal data.

Therefore, breast cancer patients with a history of estrogen-sensitive breast cancer need to discuss with their health care providers the issue of consuming soy. Bear in mind however that even in the animal studies that the less processed soy products such as soy flour do not stimulate tumor growth.

Q. How do you suggest healthcare, foodservice and consumer education professionals communicate this information to their publics?

A. Really, I think it is quite simple. Soyfoods can be viewed as just another group of foods that can contribute to an overall healthy diet. They provide high-quality protein and may help to reduce the risk of several chronic diseases although the evidence, while encouraging, is still speculative. Americans currently consume about 80 grams of protein per day. Even if 20 grams of soy protein were to replace an equal amount of protein from other sources in the diet soyfoods would provide only about 25% of total protein intake.

Interestingly, there is substantial evidence that high-protein (but not necessarily carbohydrate restricted) diets can contribute to weight loss. Thus, as many Americans increase the protein intake it certainly makes sense for them to look toward soyfoods.

To our readers: please let us know if you’d like more information from Dr. Messina or other researchers about a specific area or disease and we’ll include it in future issues. www.Info@soyfoodsforum.com