“Soy” Should I Eat This?

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Duke Student Health Nutrition Services

Thumbnail As a dietitian I am often asked questions about soy foods acting like estrogen in the body, are they safe? Do they contribute to breast cancer? I will admit over the years the information has been varied, but for the past several years researchers have found more and more information confirming that eating soy in moderation even as a breast cancer survivor is not a problem.

Since it is breast cancer awareness month I decided to do some additional research and explain for you in more detail. 

First of all let’s think about where you might find soy in the diet, the following is a list of dietary sources:

  • edamame (raw soy beans), 
  • soy milk, soy cheeses, soy yogurts 
  • tofu (which is made from the bean curd) 
  • tempeh (fermented soy)
  • miso (a Japanese flavoring made from fermented soybeans)
  • vegetarian foods like veggies burgers 

Phytoestrogens (estrogen hormone-like chemicals found in plants) known as isoflavones are the concerning component of soy, when it comes to breast cancer risk. It is important to know that although these compounds do  act like estrogen, they are far less potent than human estrogen.

Large studies of healthy women who reported details about their diet and were followed for many years, have shown no association between moderate soy intake and breast cancer rates.  Studies in Asian women have found a lower risk of breast cancer rates with higher soy consumption (4 or more servings per day), whereas studies in the U.S. have not found any association between how much soy a woman consumes and her risk of breast cancer.   Other things to consider of course are lifelong dietary and lifestyle patterns not noted in these studies.

What about soy intake for breast cancer surviviors? There are studies that show that small amounts of soy are safe and may be protective for surviors. However the best advice is to discuss the pros and cons with your health care provider until more conslusive data is available.

If you are a guy and worried about developing “moobs” if you eat soy, stop. There is little research to suggest that this is an issue, except for an unusual case where a 60 year old male was drinking 3 quarts of soy milk per day—in case you are wondeirng that’s 12 cups- don’t do that! Reasonable amounts- 3-4 servigns per day are safe.

When it comes to taking supplements research is finding mixed results, basically the jury is out and the recommendation is to “avoid concentrated sources of soy such as soy-containing pills or powders, or supplements containing high amounts of isoflavones.” (American Cancer Society).

When making the decision to consume soy or not, remember that tofu and other soy foods have considerable health benefits and are linked to lower rates of heart disease. Because they are excellent sources of protein, soy foods may replace other less healthy foods in the diet and therefore help lower cholesterol. Also soy is an excellent good quality protein alternative for those who follow a vegetarian or vegan diet. 

Bottom line: avoid pill and powdered soy supplements and enjoy soy foods in moderation.

The American Institute of Cancer Research (www.aicr.org) and The American Cancer Society (www.cancer.org)