As the emphasis on clean diets and reducing one’s environmental impact increases, so has our curiosity about plant-based diets. The only plant-based foods that contain all of the essential amino acids (complete proteins) are soy and soy-based products, like tofu, tempeh, and edamame.
In Western diets that are traditionally more meat-based, those who are converting to a plant-based diet have concerns about potential health effects of soy, particularly pertaining to possible disruption of thyroid function and sexual hormones due to the isoflavones in soy products.
Keep reading to get our take on whether or not the high protein content of this plant-based food is worth including in your diet despite the potential risks, and what exactly those risks are.
As previously stated, soy and soy products are a complete protein, containing all of the essential amino acids. Additionally, soybeans are full of fiber, vitamins, minerals, and other beneficial compounds, like phytochemicals (phyto meaning plant).
Among these phytochemicals are polyphenols, which are a type of antioxidant that may be protective of heart health, and that may moderate immune responses. One type of polyphenol in particular, the isoflavones, are large contributors to the supposed health benefits of soybeans. However, isoflavones are also a kind of phytoestrogen, meaning they bind to estrogen receptors in the human body. While isoflavones were often assumed to mimic estrogen, multiple studies have found that isoflavones act differently in the body depending on the person. Basically, depending on your gut microbiome, you either will or won’t absorb isoflavones the same way as someone else. Isoflavones generally have “a low estrogenic potency compared to estradiol” according to a recent study. Similarly, how well your body absorbs isoflavones will depend on the protein and fiber in the specific product that you purchase, which can vary from brand to brand. In other words, as long as your consumption of soy and soy products is low to moderate, you’re probably fine.
Soy products (edamame, tofu, tempeh, miso, soy milk) have been linked to a number of health benefits. For example, soy-rich diets may help lower LDL (bad) and raise HDL (good) cholesterol. They may also lower triglyceride levels. Those reductions may be even greater in those who consume soy protein in place of animal protein, but more research is needed to confirm if that is so.
Soy-rich diets have also been associated with a reduced risk of stroke and heart disease. In people with high blood pressure, soy may decrease blood pressure, but it does not appear to have the same effects for people with normal blood pressure. Isoflavones also appear to help lower insulin resistance, which is a risk factor for type 2 diabetes. High-fiber diets in general may be protective against colorectal cancer.
Although you may have heard that soy can feminize you, this is not true. Again, isoflavones act differently from estrogen and may actually be protective against the negative effects of estrogen. The American Cancer Society says that isoflavones may protect against hormone-dependent cancers.
One group of people that should watch their soy intake are those with underactive thyroids. Isoflavones may reduce absorption of thyroid medications. It is recommended to wait four hours or more between eating soy products and taking thyroid medication.
It seems that soy has more positive effects than negative effects. Soy consumption can bring a range of health benefits, particularly if eaten regularly. Be sure you are getting soy in whole and fermented form (edamame, tempeh, tofu, miso, soy milk) rather than from processed soy products (protein powder, soy yogurt, soy ice cream) that may contain other ingredients and have been associated with negative health outcomes.
There are only a few case studies that have been done on individuals that consumed soy in excess. The results of these case studies showed gynecomastia, hypogonadism, and erectile dysfunction. Keep in mind that this involved just two individuals who were studied, and who consumed an excess of soy. Their symptoms subsided after they stopped eating and drinking soy products. Most studies conducted with larger sample sizes have shown that soy and soy products do not have feminizing effects on men. Some studies show that the absorption of isoflavones may vary by ethnicity, while other studies show that ability of your gut to absorb isoflavones is not impacted by ethnicity. Again, this probably depends on the individuals that participated in the studies, respectively. If you feel like you are noticing these types of effects from consuming soy, then soy is probably not for you, but these types of side effects are not common.
Most studies have shown that daily consumption of soy products, 2 to 4 servings or less than 100 grams of protein from soy per day, does not impact testosterone levels.
In general, soy as a protein source for vegetarians and vegans is generally OK for your health. Reducing your animal protein intake and replacing some of this is also OK for your diet. Remember if you are following a vegan or vegetarian diet, you may need to supplement for B vitamins that are hard to obtain from plant-based sources.
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