Press Release Source: American Association for Cancer Research

American Association for Cancer Research: Diet Rich in Soy Protein Lowers Estrogens Associated with Breast Cancer
Monday September 23, 12:19 pm ET

PHILADELPHIA, Sept. 23 /PRNewswire/ -- Consuming tofu and other soy-based foods significantly lowers levels of a class of estrogens normally associated with breast cancer risk in postmenopausal women, according to a new study published in the September issue of the American Association for Cancer Research (AACR) journal, Cancer Epidemiology, Biomarkers & Prevention.

The study found a link between soy-rich diets consumed by Asian women in Singapore and reduced levels of an estrogen called estrone, the predominant form of estrogen in women following menopause. High estrogen levels have been shown to increase the risk for breast cancer among postmenopausal women.

Specifically, the study found that estrone levels were about 15 percent lower among women who consumed the highest amounts of soy protein. No other easily modifiable lifestyle factors analyzed by the scientists yielded such a dramatic hormone reduction.

"Results from this study support the hypothesis that high soy intake may reduce the risk of breast cancer by lowering endogenous estrogen levels, particularly estrone," said Anna H. Wu, the study's lead investigator and professor of preventive medicine at Keck School of Medicine of the University of Southern California, Los Angeles, Calif.

Also participating in the study, titled "Soy Intake and Other Lifestyle Determinants of Serum Estrogen Levels among Postmenopausal Chinese Women in Singapore," were Mimi C. Yu and Frank Z. Stanczyk, both at USC; and Adeline Seow and Hin-Peng Lee, with the Department of Community, Occupational and Family Medicine at the National University of Singapore.

Historically, breast cancer rates among Asians in Japan and China have been significantly lower than their female counterparts in the West. At one time, low-risk Asian women had one-sixth the breast cancer rate compared to high-risk whites in the United States and other parts of the western world. Reasons for this difference have remained largely unknown. However, Asians are clearly as "genetically susceptible," since Asian-American women have roughly the same breast cancer incidence as their white American neighbors.

Moreover, from the 1970s to the 1990s, breast cancer incidence more than doubled in Singapore and Japan. While earlier age at menarche, increasing numbers of women without children and delay in childbearing may offer a partial explanation, changes in other lifestyle practices are likely to play a role.

"Aside from answering some basic questions about soy consumption and breast cancer, this study may provide some insight into the underlying increase in breast cancer in Asia," said Dr. Stanczyk, a co-investigator and professor of research in obstetrics/gynecology at the Keck School of Medicine at USC.

Study participants included 144 healthy postmenopausal Chinese women in Singapore currently enrolled in a population-based prospective investigation of diet and cancer risk. Information on diet and other lifestyle factors was obtained from a structured questionnaire administered through direct interviews.

Each of the 144 postmenopausal women, ranging in age from 50-74 years, was asked to estimate her usual eating frequencies and portion sizes for 165 food and beverage items consumed during a year. The questionnaire also requested information on demographics, lifetime use of tobacco, menstrual and reproductive history, medical history, and family history of cancer.

The Chinese population in Singapore (and elsewhere in Asia) is particularly suited for studies on the effects of soy-based foods because this food has been a staple in the traditional Asian diet. Six kinds of soy products (plain tofu, taupok, taukwa, foopei, foojook and tofu far) and soybean drink were included in the questionnaire.

In addition, as part of a Singapore Food Composition Database, levels of daidzein, genistein and glycitein were measured in the main types of soy foods consumed in Singapore, allowing the researchers to calculate intake of total isoflavones among individual subjects.

Isoflavones, the main constituent of soybeans, are believed to be responsible for anti-cancer effects observed in an accumulating number of human and animal studies.

"However, the effect of soy on the breast is controversial," said Dr. Wu. "There are some in vitro studies of breast cancer cells -- animal studies, as well as short-term soy intervention studies in women -- suggesting that soy isoflavines may have stimulatory effects."

Added Dr. Mimi Yu, principal investigator of the Singapore Chinese Health Study and a professor of preventive medicine at the Keck School of Medicine at USC: "Though our study is suggestive, more work needs to be done before any specific dietary recommendations can be made about consuming soy proteins to protect against breast cancer."

Blood sample analyses not only showed lower estrone levels among those consuming the highest quantities of soy protein, they also showed similar patterns when correlated to consumption of isoflavonoids. However, estrone levels did not decline in a linear manner with increasing soy intake; an apparent reduction was only seen among those in the top 25 percent of soy protein consumers.

The study also showed that hormone levels remained unaffected by other dietary and lifestyle choices. These included consumption of alcohol, coffee, tea, fat, fiber and various micronutrients, including vitamins A, C and E, along with calcium and carotenoids. Physical activity also did not significantly influence serum hormone levels.

Among the study's other findings was an association between increased estrogen levels and women with a high body mass index (BMI), a measure of weight that accounts for height.

"There is a suggestion that weight change (particularly weight increase) has a profound influence on breast cancer rates in Asian-American women," said Hin-Peng Lee, co-principal investigator in the Singapore Chinese Health Study. "The same may now be happening to their relatives on the Asian side of the Pacific."

The study also may open new avenues for basic research to determine how soy proteins work to reduce estrone levels on the molecular level. The scientific team hypothesized that isoflavones may inhibit certain enzymes responsible for estrogen production and metabolism.

"Our findings of a reduction of estrone levels in association with soy intake may represent a reduction in the production and/or an increase in the elimination of estrone," said Dr. Stanczyk. "Future studies may offer new insights into this mechanism."

Founded in 1907, the American Association for Cancer Research (AACR) is a professional society of more than 19,000 laboratory and clinical scientists engaged in cancer research in the United States, Canada, and more than 60 other countries. AACR's mission is to accelerate the prevention and cure of cancer through research, education, communication and advocacy. Its scholarly activities include the publication of five journals (Cancer Research, Journal of Clinical Oncology, Molecular Cancer Research; Cancer Epidemiology, Biomarkers & Prevention; and Molecular Cancer Therapeutics). AACR's annual meeting has more than 15,000 participants and features presentations of new and significant discoveries in the cancer field. AACR's 10 specialty meetings cover all of the important areas of basic, translational and clinical cancer research.


Source: American Association for Cancer Research

http://biz.yahoo.com/prnews/020923/phm030_1.html

There's also evidence that soy is not a good thing:

http://www.brain.com/Merchant2/merc...Code=body_13500

In addition to the above:

Phytoestrogens: potential endocrine disruptors in males. Santti R, Makela S, Strauss L, Korkman J, Kostian ML. Toxicol Ind Health 1998 Jan-Apr;14(1-2):223-37.

A maternal vegetarian diet in pregnancy is associated with hypospadias. K. North, J. Golding, et al. BJU International
Volume 85 Issue 1 Page 107 - January 2000.

http://www.blackwell-synergy.com/se...7&goto=abstract

For those of you who don't know what hypospadias are - they are lovely birth defects of male reproductive organs, attributed to high estrogen content of vegetarian foods, tofu included.

More bad news concerning soy:

www.mercola.com/article/soy/avoid_soy.htm

I hear its merits too--so its hard to say.

I emailed the guy who makes the supplements I take, in which he includes 10 mgs. of soy isoflavones. I wanted him to take them out, but he thinks the benefits are so good in the research that as long as he keeps it at such a low level it is a good addition to his formula. But, he was definitely aware of the negative studies out there also.

Marj

I've busted my arse trying to make tofu work on my diet - it's the cheapest source of protein I can get my hands on. Nope, nothing. Always ended up retaining water somehow (may be related to estrogens) and feeling a bit bloated and too full to run in the mornings (may be related to protease inhibitors blocking absorption of protein and leaving it for GI bacteria to chomp on).

Then again, when I say "source of protein" that means that I would be eating it for every single one of my keto meals. Which is probably far more than normal. In other words, an occasional block of tofu may not hurt.

Studies which suggest health benefits from any soy product should be dismissed outright. Sales for this multibillion dollar industry are soaring and have been for years. What is the result from this euphoria? The article gives the clue.

Quote:

Moreover, from the 1970s to the 1990s, breast cancer incidence more than doubled in Singapore and Japan.

The soy manufacturers have huge budgets for advertising and funding studies. The results cannot be trusted.

Soy is an unhealthy bean as is shown in the web sites referenced above. Soy estrogen is NOT the same as human estrogen and highly suspicious as a cancer causing agent in itself. This pseudo estrogen causes early menarche in young girls and causes problems in boys with the sperm count in males plunging. Soy infant formula is a very bad choice for a child.

Soy protein is lacking in one of the essential amino acids and the others are in the wrong proportion for human or animal consumption.

Soy will someday join hydrogenated vegetable oil (trans fatty acids) in the list of restricted factory foods. Unfortunately, this may take 50 years before government agencies have the clout to go against the soy manufacturers.

Just say NO to SOY.

Kent

Looks like you've done your homework in the nutrition department!

Question--you seem to be into the type of exercise that I like--as far as energy is concerned I notice that I need to strike this balance concerning foods that isn't exactly what most people on here experience.

For instance yesterday was a high energy day for exercise. What I ended up eating early in the day was not high protein--but it was not high carb either. A cafeteria's offering of small dishes--a spinach salad (a little cheese was in it and oil), green beans with a little ham, and a cucumber salad with tomatoes, onions in a dressing that probably had a little sugar--and tea with sweetener.
I exercised after that very successfully--that pleasant buzz afterward and all. Then at dinner I had all protein mostly, organic chicken salad, non-sweet coleslaw, and pork rinds.

Today though I had heavy protein at lunch (more chicken salad, porkrinds, cheese, and a little salami--Nooo energy!! At least not for any real exercise. My potassium bottoms out easily so I drank some v8 and took a low dose supplement--but of course that takes time to help.

My thinking is maybe stick to low carb veggies for day and protein at night. Any thoughts?

Marj

I wouldn't beleive every bad thing I hear about Soy. Most of the cited studies againsts soy are related using it as a substitute to mother's milk or infant formula, or in conjunction with vegan diets. Their are big corporations on both sides of the debate.

Wa'il

Check the references listed for the article from Brain.com - there's a number of them reflecting studies in adults. If memory serves, there's been a large study of elderly men showing a reduction in cognitive function of those who consumed a lot of soy products.

I completely agree that there's big money on each side, but for sure the pitch of soy has been bent to it's advantage. A lot of people associate soy with Asian diets. Not really so - from what I understand, it's a story similar to grains - not until the advent of modern agriculture and food processing has soy been a staple of Asian diets.

Well. the way I look at it is--it seems as though the possible risks probably outweigh the benefits. The beneficial properties (nutritionally) exist in other foods that are definitely safe. It is the convenience that I am disappointed to let go of. And the carb-like qualities of the bread, pancakes and so on that you can make with soy. And though I don't seem to have problems with them the high gluten/low carb products are a problem for many people because of gluten sensitivity. I do think wheat is a water retainer for me though.

Was Atkins correct when he asserted in one of his books that pork rinds are essentially a pure protein matrix and that the fat isn't particularly high. (I guess I should read a label!!).

Marj