Soy is quickly becoming the new gluten. And like most things that have to do with nutrition, soy in our diet is controversial. One hand you have the health benefits: soy is a complete protein source, low in calories and may reduce cholesterol and risk for heart disease. But then you have the potential negative health effects: possible infertility, premature puberty, GMO ingestion and maybe even cancer causing. So here’s a look at soy.
Soy is a plant protein that contains all of the essential amino acids necessary for your body to function properly. The soybean, Edamame, is a nutritional powerhouse with significant amounts of Manganese, Selenium, Copper, Potassium, Phosphorus, Magnesium, Iron, Calcium, Vitamin B6, Folate, Riboflavin (B2), Thiamin (B1) and Vitamin K. Soy is also used in many other foods such as tofu, milk, meat substitute products, tempeh and miso. A large percentage of the soy produced in the U.S. is used to produce soybean oil. What is left after the fat (oil) has been extracted is known as soybean meal and is either used as livestock feed or further processed to make isolated soy protein.
Because it is fairly cheap to grow and process, soy products are found in many processed foods. People with a diagnosed soy allergy have to be hypervigilant and knowledgeable. But the processing that soybean undergo removes most, if not all of allergic protein so most people with a soy allergy can consume items with soy oil and soy lecithin, which is commonly used as an emulsifier in may products.
So, why all the controversy around a simple legume? There are some known positive and negative benefits to soy, but there are also many claims that don’t have enough scientific research to be substantiated. Many studies have been done on mice, not humans, and the amount of soy consumed is much greater than any human would normally consume.
Soy and Heart Disease
This is one area where there is actual data that shows that replacing animal protein with soy will decease LDL cholesterol and hence may help reduce the risk for cardiovascular disease. A study published in 2006 in Circulation found that the decrease is small and amount of soy that would need to be eaten is significant, but incorporating soy may be good for your heart because it provides polyunsaturated fat and fiber that are not present in animal proteins.
Soy and Menopause
Although it makes sense that soybeans, which are rich in isoflavones (form of plant-based estrogen), could help with menopause symptoms such as hot flashes, the little research that has been done in this area doesn’t support soy as a treatment option.
Soy and Breast Cancer
In some tissues, phytoestrogens may actually block the actions of estrogens. So if soy’s estrogen-blocking action occurs in the breast, then eating soy would reduce the risk of breast cancer. This would be because estrogen stimulates the growth and multiplication of breast and breast cancer cells. But again, the research is mixed. Most human studies show a reduced risk or no effect regarding breast cancer, but studies on mice have shown an increase in the risk of developing it.
Soy & Thyroid
Soy is thought by some to be thyroid “poison” and it can affect the thyroid gland. But the amount needed far exceeds what humans would normally consume. A study published in Clinical Thyroidology (2011; 96(5):1442-1449) found “only very high doses of soy phytoestrogen supplementation may induce clinical hypothyroidism in a minority of patients with subclinical hypothyroidism.”
Soy & GMO
Yes, most soy is genetically modified and if you are trying to be GMO-free, there are soy products out there for you. If you look at the research, what you’ll find out is that more research needs to be done. A 2013 study showed GM soy had no definite positive or negative effects on rats. But in 2008, a study showed that GM products such as so increased food allergies. Since GMO products only started hitting the shelves 20 years ago, more research definitely needs to be done.
So should you include soy in your diet? The majority of current studies show that the typical amount consumed by most Americans is not only safe, but may also be beneficial. Again, it comes down to eating a moderate amount (1-2 servings) of a real food.
Joanne Perez, MS, RDN, LD is a Savannah-based dietitian who, after 20 years of food service and clinical dietetics, made the switch to nutrition communications and all things tech. She doesn’t believe in diets and thinks that life is too short to be anything but happy and healthy at any weight. Read her blog, Real Bite Nutrition, and follow her on Twitter and Facebook.