If ever there was a food that has a world of confusion, myths and worry around it, it’s soy. The very soy that gives natto and miso their health fame also is purported to cause breast cancer, damage your thyroid, digestive and malabsorption issues, and the list goes on. Especially for those of Asian descent who are accustomed to using tofu, tempeh, soy sauce and other soy products on a regular basis, it can be puzzling to hear that our food choices may be doing us harm. The problem with soy, as with almost every other food out there, is that if you do an internet search you can find arguments for both sides—soy isa health food or soy is a toxin. The truth is somewhere in between.
The first of the concerns with soy involvesits phytoestrogens also known as isoflavones. Unfortunately, these are commonly confused with estrogen and assumed to have the same effects as estrogen. What makes phytoestrogens interesting is that their function depends on the tissue that they are affecting. Sometimes they mimic estrogen’s effects and sometimes not. These functions can be helpful or harmful depending on the tissue and the person. For example, the influence of soy on bone health is still undetermined but it is often used to reduce menopausal symptoms such as hot flashes.
This brings up an important point. Asian countries have a long history of soy intake, with the average Japanese consuming 1-1.5 servings of soy foods daily (half from fermented sources such as miso and natto and the other half from unfermented tofu and edamame). China, particularly Shanghai, has a larger intake of soy with 2-3 servings a day but almost entirely from unfermented sources. In Asia, particularly among those who have had a lifelong intake of whole soy foods, there appears to be a lower risk of breast cancer and prostate cancer,and hot flashes among other menopausal complaints are rare.
What we can learn from Asian cultures leads us to the issue of cancer, particularly breast cancer. There is a big scare that soy causes breast cancer. As you can see from research on populations who have a regular consumption of soy, whole soy foods in reasonable amounts (1-3 servings/day) throughout the lifetime may actually lower the risk of not only breast cancer but also prostate cancer in men! What has the potential of being harmful is highly processed soy such as soy protein powders and “fake meats” as well as an excessive intake. It is beneficial to get protein from a variety of sources, so if you want to eat tofu or tempeh, choose unsweetened almond milk in place of soy milk, peanuts or pistachios instead of soy nuts, and olive or grapes oil to replace soybean oil. It is possible to get too much soy.
We can’t talk about soy without mentioning the looming threat of “moobs” or man boobs. Many men see consuming soy as a clear risk for feminizing effects, but the evidence just isn’t there. If you take a look at the Asian population we’ve been referencing as well as the scientific studies, isoflavones are exonerated and shown not to affect total or free Testosterone levels. Personal testimonies are weak evidence and many people overlook other foods, medications or behaviors that are the actual cause of their gynecomastia.
Besides dispelling these myths, soy actually can play a role in lowering cholesterol and is a complete protein which is great news for vegetarians. So the good news is you don’t need to be afraid or confused about soy. In fact, you could probably benefit from eating some whole soy foods including some fermented soy.
– Soy appears to be protective in whole food form when eaten from childhood
– Soy supplements and processed soy products do not appear to have the same benefits
– Care should be given to those with thyroid issues, personal or family history of breast cancer
– An intake of 1-3 servings of soy per daycan be part of a healthy diet
What is a serving?
– 3oz tempeh or tofu
– 1 cup soymilk
– 1/2 cup edamame/cooked soy beans
– 1/4 cup soy nuts
Soy foods that are questionable:
– GMO or non-organic soy
– soy lecithin: an emulsifier found in cooking spray, salad dressings, butter substitutes, chocolate
– soy protein concentrate or isolate: a powder extracted from defatted soy flour and
found in protein bars/shakes/powders, other fitness supplements, packaged soups and sauces, vegetarian meat substitutes and more
– soybean oil
– textured soy or vegetable protein: made from soy protein isolate/concentrate or soy flour and made into various shapes to replace or extend meat in dishes like chili, tacos and burgers
Written by: Michaela Ballmann, MS RD CLT
Nutrition Director, Newenwellness