The ubiquitous soybean has been at the center of many health discussions of late. We find it everywhere, and there’s still controversy about whether or not it’s good for us. Here’s more background to help you make a decision about soy’s place in your diet.
The soybean, a legume, is native to East Asia, and writings about the soy crop date back 5,000 years to an emperor in China. In its natural form, soy contains phytochemicals (known as anti-nutrients) that protect the plant from harm in the environment—like UV radiation, microbes and foraging animals—so that it can reproduce itself.
These anti-nutrients, which include phytic acid, enzyme inhibitors and goitrogens make soy in its natural form a poor choice for human consumption. But about 3,000 years ago it was discovered that when you introduce mold to the bean, the anti-nutrients are destroyed and the beneficial nutrients become available—also known as the process of fermentation. Forms of fermented soy such as miso, tempeh, natto and soy sauce also contain the health benefits of naturally occurring probiotics.
What does soy have to offer?
One of the reasons that soy is so prevalent is that soy crops produce more protein per acre than any other crop. Currently, the US is not only a top soy crop producer but also the top consumer of soy products because of its high protein content and its multitude of uses such as vegetable soybean oil, soy flour, animal feed and textured vegetable protein (TVP), which is used in a variety of dairy and meat substitutes.
Here are the main nutrients we get from soy:
Protein. Soy is a source of complete protein—it contains all of the essential amino acids that the body cannot synthesize on its own. Soy is further considered a good source of protein in that it contains less saturated fat than animal sources, making it a heart-healthy choice.
Omega-3s. Alpha-linolenic acid (ALA) is a fatty acid, found in soy and other plants, that converts to the omega-3-fatty acids EPA and DHA that are needed for normal growth, heart disease prevention, inflammation and chronic disease prevention.
Isoflavones (e.g. diadzein and genistein) are phytonutrients similar to estrogen (they’re also referred to as phytoestrogens because of their estrogen-like actions on the body). Isoflavones are known to help menopausal women with symptoms such as hot flashes and night sweats. Isoflavones have also been shown to help lower bad cholesterol and triglycerides.
Isoflavones have mixed reviews by medical professionals, however. While they may help to prevent estrogen-driven cancers because they block receptor sites for "bad estrogens" to bind to, their estrogen-like actions may also be harmful to those with a history of breast cancer.
Reasons to reconsider soy
Unfermented soy products, such as tofu, edamame and TVP, have been linked to some serious health conditions, including digestive and immune distress, allergies, ADD, PMS, reproductive issues, malnutrition and possibly cancer. Because soy is commonly used as the base for infant formula in place of dairy, infants are at risk for experiencing the anti-nutritive effects of soy. Vegetarians with a soy-based diet are also at greater risk.
Here’s more about the anti-nutrients in unfermented soy and why they can be a health risk.
Phytic acid is well known to bind necessary minerals such as zinc, copper, iron, magnesium and calcium, making them unusable in the body. We need all of these nutrients for proper growth, development, sustainability and healing.
Enzyme inhibitors interfere with the body’s natural ability to release enzymes to properly break down, absorb and assimilate the carbohydrates and protein in soy. Without the proper digestive enzymes, bacteria in the intestine can create digestive distress (gas, bloating, pain, discomfort). Because of this enzyme-inhibiting activity, soy is now a common food allergen or intolerance.
Goitrogens are phytochemicals that block the production of thyroid hormone. Without proper thyroid function, all systems slow down their ability to function at normal speed. Genistein, one of the goitrogens, is an isoflavone thought to have positive health benefits for menopausal women but is also knows to slow down overall cell energy and division. While this has made it appealing as an agent to slow down cancer growth, it can also slow normal cell growth.
Another concern about soy is the fact that nearly all of the US’s commercial soy crops are now genetically modified (GM). This means that the soy DNA has been manipulated for faster growth, resistance to pests or diseases, production of extra nutrients, etc. Some experts theorize that genetically modified food is more likely to create food sensitivities, as is seen with soy.
It’s clear that more research needs to be done on the risks vs. benefits of eating soy. In the meantime I would recommend sticking with fermented soy, such as tempeh, miso and soy sauce. Further, choose non-genetically modified, organic soy products whenever possible. And make sure you have plenty of variety in your diet, as this can help protect you from developing food sensitivities and allergies. Opt for almond, rice or coconut milk instead of soy milk, or get protein from nuts, brown rice and beans and other legumes such as lentils and peas. (Or explore Pharmaca's selection of soy-free protein powders.)
If you experience digestive distress when eating soy you may want to avoid it altogether—or consider adding digestive enzymes to a meal that contains soy. And play on the safe side if you have thyroid problems, as unfermented soy can exacerbate these issues. If you’re concerned about whether soy is right for you, consult a qualified health practitioner.
Kate Brainard attended Bastyr University’s doctorate program in Naturopathic Medicine. She currently manages Pharmaca’s La Jolla store.