The discussion on the benefits versus dangers of soy continues to percolate. There are those that feel that the fact that much of the soy available is GMO (genetically modified), makes it “dangerous.” Others recognize the stellar nutrient profile of this bean. The conflict continues despite the fact that there’s no clear randomized double-blind study to support the strong concerns. Putting that discussion aside for a moment, the second most prominent reason for people to avoid soy (excluding a true allergy), is the fear of its so-called estrogenic properties. The latest research appears to significantly undermine those concerns.
Soy’s effect on health
This latest research gathered and evaluated findings from a number of previous studies, including some from 2016. The research on soy is quite robust and has looked at its impact on heart disease, kidney health, bone health, breast cancer, cognitive function, and thyroid health. Soy contains isoflavones, which are a class of phytoestrogens, compounds in plants with activity similar to estrogen. That “similar to estrogen” phrase has likely driven people’s fear of soy. So much so that some advertisers have grabbed onto those fears to push their own soy free, danger free product ads. Ask the average man if he eats soy foods, and he will likely respond, “Oh no — I don’t want to grow breasts or become feminine.”
Both the American Heart Association and The American Cancer Society endorse consumption of soy foods based on current science, and concur with its health benefits.
It should be noted that this latest evaluation of the soy research was done by Mark Messina, Ph.D., an adjunct professor at Loma Linda University. He has had significant links to the soy industry and was director of the Soy Food Institute. He has been actively presenting findings in support of soy as a quality protein that warrants a regular role in one’s diet. He has also been involved in research trying to bust myths associated with soy. He suggests in this new research that it appears to be time to bust the myth that soy has “significant estrogenic effects.”
Soy is not estrogen, but...
Much of the information suggesting that soy has estrogenic properties (and similar impact on health) comes from mice and rat studies in which large quantities of soy consumption occurred. Dr. Messina suggests that the value of these studies is limited because the amounts of soy consumed so were so large, and also because rats and mice metabolize soy isolflavones much differently than humans.
In fact, just about a year ago the EFSA (European Food Safety Authority) determined that isoflavones in food supplements do not pose a health risk to post-menopausal women. Levels in supplements are not sufficient to increase endometrial thickness nor sufficient to cause tissue changes at the cellular level that would increase the risk of malignancies. The EFSA further determined that the same guidelines used to assess isoflavones in supplements could be used as a guide for soy intake.
Prior research has shown that phytoestrogens do bind to certain estrogen receptor sites, but despite this similarity to estrogen, do not mimic the properties of estrogen.
A separate new study released February 1, 2017 reaffirms the safety of soy food consumption (genestein seems to improve overall immunity against cancer) after diagnosis and treatment of breast cancer (even during Tamoxifen therapy) with one caveat. The antitumor effect only seems to happen if you were already consuming soy foods long term before the diagnosis. Cancer experts are not comfortable, based on this new study, in recommending that you start consuming soy foods as a new dietary habit if you are diagnosed with breast cancer. They write that they would like to see more research to explain why there is significantly less anti-tumor benefit seen if soy food consumption is a new habit versus continuation of a habit already in place.
Safe daily range of soy consumption
The EFSA determined that a daily dose of isoflavones in the range of 35 to 150 mg per day is safe. Those in support of soy also point to the intake of soy products in Japan, a culture that introduces lifelong consumption of edamame and other soy foods to babies and young children. This culture has low rates of breast cancer.
Current recommendations suggest an upper daily limit of 100 mg of soy isoflavones daily, which translates into 25 grams of soy protein. That equals three servings of soy in a day’s worth of eating. Options include: 1/2 cup of cooked soybeans, 1/2 cup tempeh, 1/2 cup of tofu, 1/4 cup of soy nuts, 1 cup plain soymilk. Choose fortified soy milk with calcium and vitamin D to replace dairy milk. Popping edamame out of the shell is a fun way to get kids to consume a nutritious, protein-rich food. Soybeans contain all nine essential amino acids, making it a stellar protein source. Soybeans also can be an excellent source of dietary iron.
Health benefits of soy
Soy appears to improve cardiovascular health markers, possibly thanks to its balance of healthy fatty acids or the lack of saturated fat typically associated with (animal-based) protein rich foods. Soy intake seems to have a positive impact on total cholesterol, and specifically LDL. Soy isoflavones may help to limit hot flashes (Japanese women have low rates), and improve arterial health in menopausal women. More research is needed to prove preliminary claims that soy intake may help to limit breast and prostate cancer.
Most dietary experts believe that the best way to benefit from isoflavones is to eat soy foods (the less processed the better), as opposed to taking soy supplements. Food sources provide fiber and healthy fat in addition to the isoflavones. It’s also important to realize that when foods are healthy, more isn’t always better. Stick with two to three servings of soy foods daily to benefit from this very healthy food.