There seems to be confusion when it comes to the nutritional benefits/ risks about Soy. If you’re into plant-based nutrition, soy is a common resource. The nutritional value is second to none and the variety of soy products that replace meat and dairy are invaluable, especially in the plant-based world. Hopefully the information below will help debunk some of the myths about soy, estrogen, GMO’s…
Soy and estrogen
Soy contains phytoestrogens (“plant estrogens”) called isoflavones which are said to be weak estrogens, but it’s actually more complicated than that. Isoflavones have both estrogenic and anti-estrogenic effects. . The evidence suggests that, because of their complex relationship with different estrogen receptors, soy isoflavones have beneficial anti-estrogenic effects in breast tissue while also having beneficial estrogen-mimicking effects in bone tissue.
Soy contains isoflavones, a type of phytoestrogen that is 1000 times weaker than human estrogen and does not behave exactly like human estrogens in our bodies. Isoflavones block some of estrogen’s effects and mimic others, generally resulting in health benefits. They also have antioxidant and anti-inflammatory properties. Soy has the highest protein and fat content of any legume and is high in iron and fiber.
The dominant isoflavone in soy is genistein, with daidzein and glycitein composing the remainder. Within soy, isoflavones are almost entirely bound to sugars, producing the respective compounds genistin, daidzin, and glycitin. Soy isoflavones have been linked with numerous health effects, but the strength of the relationships and whether the effects are beneficial are strongly debated.
The original interest in soy was fueled by geographic epidemiology—the observation that populations that consume a lot of soy, particularly those in eastern Asia, have less breast cancer, prostate cancer, and cardiovascular disease, and fewer bone fractures. Additionally, women in these populations report fewer menopausal symptoms, such as hot flashes, and both men and women have a lower incidence of aging-related brain diseases. Since lifestyle can affect chronic disease development, and diet is a major lifestyle factor, traditional Asian diets drew considerable attention.
Although initial research overestimated the amount of soy consumed by Asians, the cumulative evidence of numerous biomarker studies has confirmed that their diets are significantly higher in both isoflavones and lignans (another phytoestrogen) compared to the typical Western diet. Studies have further shown that when Asians emigrate to Western nations such as the United States and adopt the “Western” diet, their disease rates change.
WOMEN’s HEALTH: Soy has been shown to prevent breast cancer in the amounts consumed in Asia. A 2008 review showed that women averaging one cup of soy milk/ 1/2 cup of tofu per day had a 30% lower risk of developing breast cancer versus women who avoid soy. Soy has also been shown in many studies to reduce the risk of recurrence in breast cancer survivors. A recent study showed that breast cancer survivors who consumed the most soy had a 21% lower risk of dying of any cause over the 9 year study, compared with low-soy consumers. Soy reduces the risk of endometrial cancer and can reduce menopausal hot flashes.
MEN’S HEALTH: A large 2010 systematic review showed that soy does not affect testosterone levels, sperm concentration, or sperm quality. Soy may lower the risk of prostate cancer by up to 50%. THYROID: Soy does not affect the thyroid in people with normal thyroid function and iodine levels. Whether or not you eat soy, you should meet your daily iodine needs (150mcg/day). If you take thyroid hormone, you may need the dose adjusted if you change your soy intake.
CARDIOVASCULAR RISK: Soy lowers blood pressure and LDL cholesterol.
Some worry about estrogen and GMOs/pesticides from soy, but most dietary estrogen comes from dairy and meat products. Unlike soy phytoestrogens, animal estrogens DO mimic human estrogen in our bodies. Similarly, most GMO soy is used to feed chickens, pigs, and cattle, which are then consumed by people. Much of the soy grown for human consumption is non-GMO.