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Q. I just read in the Contra Costa Times today that eating soy discourages growth of cancer cells. I was told by a friend of mine that has a precancerous breast condition that she was not to eat any soy because it could speed up her precancerous condition. So what's up? Thanks.

Dr. Messina answer:
Thank you for your question. It is one that is much discussed within the scientific literature and there is actually evidence in support of both of your statements.

That is, some types of studies show soy and compounds in soybeans inhibit the growth of cancer cells in vitro (in test tubes) and the development of mammary (breast) tumors in rodents. Conversely, other rodent studies show that certain soy products stimulate the growth of existing mammary tumors that respond to estrogen (estrogen receptor positive). Note that in these studies unprocessed soyfoods do not stimulate tumors.

Because neither in vitro nor animal studies reliably predict effects in humans whenever possible the human research should carry the most weight. In this regard, clinical (human) research that has evaluated the effects of soy or the plant estrogens in soy on indicators of breast cancer risk are supportive of safety. That is, these studies suggest soy does not increase breast cancer risk or exert estrogenic effects on breast tissue. Thus it would appear that soy is safe for all women although it must emphasized that these studies are not definitive. Nevertheless, the position of the American Cancer Society is that the consumption of up to 3 servings of traditional soyfoods per day, such as tofu, miso, tempeh, and some types of soymilk, is safe for breast cancer patients. In regard to breast cancer prevention, there is very exciting evidence that soyfoods reduce breast cancer risk quite markedly although it may be that, to derive protection, it is necessary to consume soy during childhood and/or adolescence.

Q. Hello, I eat fermented soy that was highly recommended for woman's health. Would this help to increase the size of my breasts?

Dr. Messina Answers:
Thank you for your question. There is evidence that soy is beneficial for women's health but none indicating that soy will increase breast size. In regard to the former, studies suggest that soyfoods and certain compounds in soybeans promote bone health and alleviate hot flashes in menopausal women. Also, soyfoods are very heart healthy and excellent sources of high-quality protein. Thus, women are well-advised to eat soy every day.

Q. I have been taking Soy milk every day for the past two years... I have now noticed that at age 32 my breasts have begun growing again... I have jumped up a bra size in a matter of four months...

Is this just a coincidence? I am a US size 4/ UK 8 so the growth is definitely not linked to weight gain. I have actually gone down a dress size since turning vegetarian and taking more soy based products.

Dr. Messina answer:
Soy is unlikely to be the cause of your breast enlargement although the vegetarian/soy diet has contributed to your weight loss. In regard to the former, although soy does contain phytoestrogens (technically called isoflavones), evidence indicates the soybean phytoestrogens don’t affect hormone levels in women or men. Further, there is little evidence that the phytoestrogens cause changes in the breast (based on mammograms and breast biopsies) although the changes studied relate to cancer risk not size.

Vegetarians tend to have lower body weight and a lower body mass index than non-vegetarians although there may be many reasons for this. Generally, because of the greater intake of plant foods and fiber, vegetarian diets are less energy dense. Lower energy dense diets are recommended for weight loss. There are some data to suggest soy protein may specifically help with weight loss although this research is quite speculative. Finally, soymilk is certainly a healthy food as it provides high-quality protein and most soy milks are fortified with vitamin D and calcium. The phytoestrogens may also directly promote bone health.

Q. The FDA's recommendation of 25 grams soy protein per day in four different servings is generally not followed by the consumers in Third World Countries. People made aware of this fact. Indeed about 15 grams of soy protein my be adequate and safe for healthy beings. What is your opinion?

All the organizations involved in popularizing the soybeans for food uses must create awareness among the users. It should also be made customary to indicate the serving size in their nutritional labeling. Can you give your expert advice?

Dr. Messina answer:
Thank you for your excellent question.

In the process of awarding the heart disease health claim in 1999, the U.S. FDA extablished 25 grams soy protein per day as the threshold intake for cholesterol reduction. The FDA concluded that it was reasonable to consume four servings of soyfoods per day and on this basis allows products that contain at least 6.25 g soy protein per serving to include information about the health claim on the product label. However, the FDA did not state that the 25 grams soy protein should be consumed in four serving, i.e., it is perfectly reasonable to obtain this amount in 2 or even 3 servings.

In regard to your specific question, recognize first that there are data indicating that less than 25 grams soy protein will lower cholesterol and second thata the 25 grams soy protein pertains only to cholesterol reduction and should not be viewed as a guide to obtain the other proposed benefits of soyfoods. In fact for the alleviation of menopause-related hot flashes, improvement in endothelial function and other possible coronary benefits, and the inhibition of bone resorption, most clinical trials have used between 50 and 75 mg isoflavones. In traditional soyfoods each gram of soy protein is associated with about 3.5 mg isoflavones. Therefore, to obtain 50 to 75 mg isoflavones requires consuming about 15 to 20 grams soy protein. Furthermore, many large Asian epidemiologic studies have shown that the consumption of even lower amounts of soy protein and isoflavones is associated with improved health and lower disease rates.

Finally, remember that soyfoods are excellent sources of high-quality protein that come without the large amounts of saturated fat and cholesterol typically found in animal foods. Thus, consuming even moderate amounts soyfoods can help to improve the overall quality of the diet.

In conclusion, 15 grams of soy protein is a very reasonable daily intake goal. This amount is associated with health benefits in clinical studies and lower disease rates in many Asian epidemiologic studies. Fifteen grams of soy protein is not only easy to incorporate into the diet but is more consistent with the amount of soy consumed in Japan than is the 25 grams soy protein established by the FDA as the amount needed for cholesterol reduction.

Q. I have read on several bodybuilding websites that soy protein can contribute to gynecomastia or "man boobs". Is this factually correct?

Dr. Messina answer:
There is no clinical evidence whatsoever that soyfoods contribute to gynecomastia (Excessive development of the male breasts). First, extensive clinical research shows that neither soyfoods nor isoflavones affect testosterone levels in men. Unfortunately a few reports in the popular media mistakenly suggest that soy lowers testosterone but this is simply not the case. A critical review of the scientific literature showing soy does not lower testosterone will soon be published. Second, breast enlargement in few prostate cancer patients participating in a soy phytoestrogen supplement trial did occur. However, the amount of phytoestrogens consumed was about 30 times more than typically consumed by Japanese men. (Taking 30% more of many nutrients will result in far more severe consequences). Even more importantly, the authors of this study attribute the breast enlargement to the prostate cancer drugs the men were taking, not to the phytoestrogens.

Q. I have a soybean allergy. I have severe reactions to some store-bought salad dressings, snack crackers and cookies, and especially infant formulas. Why don't I have a reaction to soy sauce?

Dr. Messina answer:
Soy protein is classified as one of the big eight allergens. However, in reality, the incidence of soy allergy among adults is actually quite rare. Soy allergies are much much less common than allergies to milk or peanuts for example. In fact, a recent survey conducted by the U.S. Food and Drug Administration concluded that doctor-diagnosed soy protein allergy occurs in only about 1 out of 2,500 adults. Furthermore, this might actually be an overestimate because the common test for allergies - the skin prick test - leads to a lot of false positives. That is, people whose skin reacts to soy often don't actually exhibit symptoms when soy protein is consumed. Of course, if you are allergic to soy protein you shouldn't consume it. Soy sauce contains very little soy protein and it is fermented - these two factors might account for not having an allergenic reaction to soy sauce. By the way, salad dressing that contains soy oil contains very little if any soy protein so generally this product is not a problem for people who are actually allergic to soy protein.

For more information about soybeans and allergies CLICK HERE to read an article by Steve L. Taylor, Ph. D, professor in the Department of Food Science and Technology at the University of Nebraska, and co-director of the Food Allergy Research and Resource Program.

Q. There was just a blurb in today's Good Eating section of the Chicago Tribune about edamame. The writer stated that"it cannot substitute for thoroughly cured, cooked and processed soybeans...undercooking does not adequately eliminate the enzyme SBTI which inhibits digestion of proteins."  It goes on to state that full cooking requires sustained temperatures equivalent to between 15 and 30 minutes at a medium boil.  My 2-year-old eats edamame all the time and I am now concerned that I should be limiting her intake.  We buy it frozen (usually shelled already) and cook it in the microwave for 4 minutes.  Thanks for any information.

Dr. Messina answer:
Edamame are green soybeans, need only brief cooking and are safe to eat. These tender green beans are completely different from dried mature soybeans which must be soaked and cooked until tender. Their writer seems to have confused the two different forms.

Dr. Lester Wilson, university professor of food science and human nutrition at Iowa State University, responds that "the frozen edamame available in supermarkets and restaurants has been blanched before freezing and is reheated before serving (usually several minutes in the microwave). This heating inactivates or denatures the SBTI (soy bean trypsin inhibitor) that might otherwise bind with the trypsin enzyme and interfere with protein absorption."

Wilson goes on to explain that, while a tiny amount of trypsin inhibitors may remain, there's not enough to cause any harm. In fact, a tiny amount of trypsin may act as an anti-cancer compound.

And, according to the research experts at Sunopta, who provide much of the edamame available in the US: "Edamame does not have the nutritional factors as the mature bean does. The enzyme the writer was referring to does not "turn-on" until the bean is completely matured. Also, edamame beans are blanched right after harvest at high temperatures that inactivate various enzymes that might cause digestive disruption.

Edamame is completely safe for children of any age to consume."

Q. Is soy safe (especially soy burger and soybeans) to eat daily if you are pregnant?

Dr. Messina answers:
Soyfoods have been consumed by Asian women during pregnancy for centuries without any apparent adverse effects. In fact, some evidence indicates that the consumption of traditional soyfoods has been encouraged specifically during pregnancy. Similarly, there is no evidence that the consumption of soyfoods by Western vegetarians adversely impacts the fetus. Supporting evidence for safety also comes from the many animal species that consume large amounts of soy as part of their typical feed and experience normal reproduction. Although a few studies have reported adverse effects in the rodent fetus, these studies have typically used very high amounts of compounds isolated from soyfoods, not soyfoods. Compounds isolated from foods often have very different effects than the foods themselves. Furthermore, there is considerable question as to whether rodent models can provide meaningful insight into the effects of soyfoods or soybean constituents on the human fetus. Typical soyfood consumption in Japan is from one to two servings per day although some evidence suggests optimal intake may be two to three servings per day.

Q. I'm concerned with a question that came up in conversation. How true is the claim that the process from soybeans to tofu can cause cancer?

Dr. Messina answers:
The proposed anticancer effects of soyfoods have been rigorously investigated for the past 15 years. Most focus has been on breast and prostate cancer. One of the more intriguing hypotheses is that soy intake during adolescence reduces breast cancer risk later in life. However, there is concern that soy might pose a risk to women with estrogen-sensitive breast tumors; that is, tumors whose growth is stimulated by the hormone estrogen.

In regard to prostate cancer there is evidence, although still very speculative, that soy may be useful for men with and without prostate cancer.

Concern about soy and breast cancer is based entirely on animal research. In two types of rodent models isoflavones (often referred to as phytoestrogens or plant estrogens) and certain soy products stimulate the growth of estrogen-sensitive mammary tumors. But it is important to recognize that the human research relevant to this issue does not raise concerns, although the data are by no means definitive.

Interestingly, animal studies have shown that, while isoflavone supplements and processed soy products such as isolated soy protein stimulate tumor growth, the unprocessed product soy flour does not. Also, flaxseed and components from flaxseed inhibit the stimulatory effects of the unprocessed soy products.

Thus, even if one were to accept the animal findings, one could eliminate risk by consuming unprocessed, more traditional soy products, such as tofu, soy milk, tempeh and edamame and/or adding flax to your soy meal. Also worthy of note is research showing that, when flax is added to isoflavone supplements or isolated soy protein, the tumor stimulating effects of soy are completely inhibited.

To summarize, animal research raises the possibility that certain soy products are contraindicated for breast cancer patients with estrogen sensitive tumors. The limited human data on this subject do not raise such concerns. The animal findings indicate that using unprocessed soy products such as tofu, soy milk, tempeh or edamame, or soy products or isoflavones in combination with flax, eliminates any theoretical risk.

Q. I am concerned about the high amount of sodium in veggie products. We eat Yves veggie deli meats for lunches , and all the other meat alternatives . I would like to know the nutritional breakdown of these foods. Are they harming me and my husbands health?

Dr. Pat Murphy, food scientist, answers:
I am not a nutritionist so I cannot answer the question completely about whether your family's health is affected by sodium content of the products you are using. But, you can check the sodium content of many foods by going to the USDA Food Composition Database and type in the food items CLICK HERE or by reading the label.

The sodium content of prepared foods, vegetarian or otherwise, is almost always higher than if you prepare similar items yourself. However, if you look at sodium content of vegetarian meat substitutes, you see they are usually about half the sodium amount as found in the analogous meat containing product. For example, a hot dog contains 500 mg sodium per serving while the meatless version contains 300 mg, not low but certainly less than the meat version. A vegetarian sandwich "meat" analog has about 100 mg sodium per slice while the meat version may have up to 550 mg sodium. Vegetarian meals prepared with soy ingredients such as tofu, soy milk, tempeh, and TVP, all available now in most supermarkets, can be low sodium by preparing them yourself since you will control how much salt is added.

CLICK HERE for a source of guidance on nutrition and food preparation found in the Dietary guidelines for Americans 2005 which recommends daily sodium levels of less than 2300 mg. Therefore the right choices in formulating your menus should be able to control sodium and still allow for an occasional vegetarian sausage product.