What is soy, exactly?
Soybeans are a type of legumes native to East Asia, being a crucial domestic crop throughout Asia for millennia. The first mentions of the soya bean, an alternative name of the crop, are between 7000 and 6600 BC in China, but it is very likely that they have been in widespread use even before that.
Today, soybeans are a staple food throughout Asia, where they are used to prepare a wide variety of products, starting from soy milk and soy sauce, to tofu and tempeh, which are meat alternatives, and even consumed raw in the form of edamame beans, which are immature soybeans commonly used as healthy snacks (pictured below).
Soy is also a key ingredient in many protein supplements, vitamins and processed foods. And finally, soybean meal is widely used to feed livestock. This means that soy products are more than simply widespread, they are quite challenging to avoid.
It is important to start from mentioning that soy products are some of the most cost-effective alternatives for both meat and dairy products. Soy products come in a variety of textures and flavors, such as milks, yogurts, cheeses, and meat substitutes, and they are usually widely available on the market.
But this is not the only reason why soy products are a great replacement for animal-derived produce, as they are also extremely nutrient-dense and provide a lot of protein, which is often lacking in meat- and dairy-free diets. Soy is a complete protein source, meaning that it contains all the essential amino acids the human body doesn’t produce.
Apart from that, soy is a good source for healthy fats, especially omega-3 fats. Finally, it contains a type of phytoestrogens called isoflavones that can also be beneficial to health. For your reference, the table above illustrates the nutritional content of one type of soy, edamame beans, but the overall nutritional value of other soy products will be similar.
Apart from being a great source of nutrients, however, soy can also be beneficial for those suffering from certain conditions, but it can also be possibly worse for others. A detailed review of the health effects of soy follows below.
1. Decreasing Cholesterol Levels
There is an extensive body of research suggesting that soy foods (but not soy supplements) may help lower the levels of bad cholesterol (LDL) and increase the levels of the good (HDL) cholesterol, especially among individuals who have higher than normal cholesterol levels.
A review study suggested that consuming only 47 grams of soy daily was associated with a 13% decrease in LDL cholesterol. This means that eating soy products can help stop the progression of atherosclerosis, as bad cholesterol is responsible for creating plaques in blood vessels, whereas HDL cholesterol helps clear those up.
2. Helps Relieve Menopause Symptoms
During menopause, women experience a range of uncomfortable symptoms (hot flashes, sleep problems, urinary symptoms, etc.) brought about by the shortage of female hormones called estrogens in the blood. Soy contains a type of phytoestrogens called isoflavones that can mimic the effect of human estrogens.
However, soy foods contain quite low levels of isoflavones, so in order to see a difference in symptoms, studies gave soy supplements to women and found that they, in fact, can be converted into estradiol (a type of estrogen) and partly compensate for the lack of estrogens observed in menopausal women.
A review article found that taking 54 mg of soy isoflavone supplements during a period of 3 months decreased hot flashes by over 20% and weakened all the symptoms by over 25%.
3. Improves Fertility in Women
Women who have difficulty conceiving or are currently undergoing a fertility treatment may benefit from soy. In a study, women who took 6g of soybean powder daily for a period of 6 months experienced more ovulations and an overall normalization of their menstrual cycles. On top of that, other studies suggest that soy supplements help women undergoing in vitro fertilization (IVF) get pregnant.
4. The Influence on Male Sex Hormones
Since soy contains phytoestrogens, men are sometimes afraid to include soy in their diet, claiming it may lower their testosterone levels. This is a crucial issue, as many protein powders and supplements advertised to promote muscle growth are soy-based, and if soy can affect the hormone balance in men, it may render these supplements worthless or harmful.
However, a review of 15 studies showed that it is completely safe for men to consume soy foods, protein powders up to 70g per day, and even isoflavone supplements up to 240 mg daily. In addition, there is even scientific evidence suggesting that soy can potentially lower the risk of developing prostate cancer, so not only is soy safe to eat in moderation, but it may even be beneficial for men.
5. Decreases the Likelihood of Developing Breast Cancer
The evidence about soy and breast cancer is very conflicting, as there is a large and growing body of evidence from Asian studies suggesting that a higher soy intake may decrease the likelihood of developing breast cancer, whereas the Western studies did not find any link between breast cancer and foods containing soy.
Scientists believe that this might be due to the fact than in Asian countries, people usually consume more fermented soy products compared to Western countries, and it may be the case that fermented soy foods has more cancer-fighting properties than regular ones.
6. The Effect On Thyroid Function
One of the most controversial findings regarding soy is that a test-tube study reported that goitrogens, compounds found in soy, may have a negative effect on the thyroid. Human studies did not confirm this finding and suggested that individuals with an enlarged thyroid do not have to avoid soy products as long as they’re meeting their daily nutritional needs in iodine.
In summary, consuming soy products in moderation is not only safe, but also very beneficial to everyone, and especially for those who follow a meat- and dairy-free diet. What’s more, consuming soy products may even be beneficial at decreasing cholesterol levels, improving fertility, relieving menopausal symptoms and lowering the risk of developing certain cancers.