I have seen a few memes going around about the dangers of soy. There has even been some news reports about the FDA pulling the "heart healthy" status of the apparently not-so-super food. So what is the deal with soy? Is it a nutritious, plant-based source of protein, or is it something to be avoided?
If you have been following Vego's social media accounts for a while you may have seen an article that I posted. So you may already know that I am pro soy, but please allow me to support my stance with some scholarly sources! I will do my best to present the facts clearly, and I will include my sources so that you can draw your own conclusion.
Soy contains a naturally occurring estrogenic compound called isoflavone, which are considered phytoestrogens (plant estrogens). The fact that this plant contains estrogen has freaked a lot of people out because an imbalance in this hormone level is associated with cancer, as well as fertility and thyroid issues! But, plant estrogens are not the same as the estrogen in our bodies, and these estrogens are found in many other foods such as flax. So why does soy get the bad rap?
Soy and Breast Cancer:
"Some people naively thought, 'Well, since they're estrogenic, they must be bad, because estrogen causes breast cancer.' We all know that in women, estrogen levels are associated with a higher risk of breast cancer," said Kucuk, an oncologist at Emory University's Winship Cancer Institute, who has studied the benefits of soy isoflavones. "There are two estrogen receptors (in the human body): alpha and beta. Alpha is the bad one. That's the one where, if something binds to alpha, it may increase the risk of breast cancer, because it makes breast cells grow. But beta, on the other hand, it causes the opposite effect," he said. "Soy isoflavones bind preferentially to estrogen receptor beta."
"Even though soy isoflavones bind to both estrogen receptors, they preferentially bind to the good estrogen receptor," Kucuk said. Kucuk added that more studies would indicate that women in regions where soy is primarily consumed, such as Japan and China, tend to experience lower cancer rates than women who consume Western diets.
Furthermore, soy may not pose a risk for women with breast cancer after all, according to a study published in the journal Cancer in September 2017. (Source: CNN)
Soy and Heart Disease:
The American Heart Association published a paper in the journal Circulation in 2006 that found, "soy products should be beneficial to cardiovascular and overall health because of their high levels of polyunsaturated fats, fiber, vitamins and minerals and low levels of saturated fat." But, in 2008, the AHA then stated that there was not enough evidence to claim a strong link between soy and reduced risk of coronary heart disease (PDF). The reason, while soy could be associated with a reduction in LDL, "lousy" cholesterol, there was not a strong correlation in increasing HDL, or good cholesterol.
I personally do not understand soy's fall from grace here since I haven't heard any news about the FDA yanking heart-health claims of foods such as oatmeal that are in the same category. "Countless research studies have shown that regular consumption of oats aids in reducing total cholesterol and LDL ("bad" cholesterol), but does not lower your HDL cholesterol." (Source: verywell)
Soy and Other Concerns:
Infertility: All of the articles that I have found on the concern that soy may negatively impact fertility have been done on animals. The findings have yet to be duplicated in humans. There are two points that I would highlight here: First, the studies done on lab rats were based on injecting isolates, not on digesting a whole-food soy product. Second, it does not appear to me that there are any fertility issues in the densely populated Asian countries that consume 30% more soy than Americans!
Thyroid: If you have a healthy thyroid, I have found no scholarly evidence for concern when it comes to consuming soy. BUT, if you have a thyroid condition that you are treating with medication then there is some cause for caution. There is concern that the plant estrogens in soy could hinder the effects of thyroid medications, but this does not mean that you must avoid soy completely! The Mayo Clinic recommends waiting a few hours before consuming soy after taking thyroid medication.
Formula: Most of the research that I have read cite animal-based research and use language like "could cause" or "may see" when it comes to projecting any adverse effects of feeding infants a soy based formula. Clearly more research is needed. This was all I could find based on a human study: "One of the few human studies was led by Brian Strom of the University of Pennsylvania in Philadelphia, in conjunction with the University of Iowa, and published in the 15 August 2001 issue of JAMA. In this study, adults who had been in a controlled feeding study during infancy completed a telephone interview about their health, development, and reproductive history. The only significant differences reported were that women who received soy formula as infants had slightly longer menstrual bleeding and more discomfort than women who had received cow’s milk–based formula." (Source: NCBI)
A Word About Scholarly Resources:
There are minimum standards in order for an experiment or study to by 'scientific.' Any "research" that only has 12 participants is NOT scientific! (I believe the minimum requirement for a sample population is 300.) So I would be leary of any "evidence" that is based on less than at least 100 random, human, participants! There are other things to consider like controls--do they control the dose, is it the same delivery system, is it the same quality, etc., across participants. ALL THAT SAID, you also need to consider who is funding the research! If nothing else, What The Health has taught us to follow the money when it comes to these studies.
A Word About Quality Sources of Soy:
Use your brains people! If you are eating a whole food or minimally processed source of soy like tofu, tempeh, or soy milk in reasonable amounts then you are good. If you are eating a ton of boxed burgers and other processed foods then you are not getting the best that soy has to offer, but all the junk that processed foods are known to contain! Now, I indulge in a vegan Boca on occasion and we use TVP on the truck. These foods consumed in moderation are a tasty addition to a vegan/vegetarian diet, just don't go eating them on the daily!
"Finally, other than allergic reactions, there is almost no credible evidence to suggest traditional soyfoods exert clinically relevant adverse effects in healthy individuals when consumed in amounts consistent with Asian intake." (Source: nutrition.org) And remember, in general a traditional Asian diet contains 30% more soy than the Standard American Diet, so as an American you would have to consume a significant amount of soy on a daily basis in order for the risks to outweigh the benefits!
www.precisionnutrition.com/soy-latest-research - tons of references here!