Reviewed by Natalie Olsen, RD, LD, ACSM EP-C
There is some controversy surrounding the possible health benefits and risks of consuming soy, especially soy that has been genetically modified.
Soybeans contain almost 40 percent protein and 20 percent oil, giving them multiple uses. They may be used as food, in supplements, or for industrial purposes.
Read on to learn more about soy, potential health benefits and risks, and the best forms of soy to eat.
Is soy good for you
Soybeans can be used to make a variety of foods and supplements.
Soybeans are a high-protein food that can be cooked and eaten in a variety of ways. The beans can be green, black, yellow, or white.
Young, green soybeans are also called edamame. They can be steamed and eaten out of the pod as an appetizer. Shelled edamame can also be used in salads, stir-fries, and soups.
Yellow soybeans are typically used to make soymilk, tofu, tempeh, and tamari. They can also be used to make soy flour for baking.
Soybeans also provide soy oil, which can be used for cooking, or as an ingredient in many foods. After the oil has been removed from soybeans, the remaining material can be used to make food for farm animals and pets.
Soy is used to make soy protein powder, as well as soy isoflavone supplements.
Soy has many industrial uses. It can be used to make products including biodiesel, building supplies, carpeting, candles, ink, and paint.
a selection of soy products
Soy is an important protein for many vegetarians and vegans.
Soy is a complete protein, which means that it contains all nine essential amino acids. It is an important protein source for many people, especially vegans and vegetarians.
According to the United States Department of Agriculture's (USDA) National Nutrient Database, 90 grams (g) of cooked green soybeans contains:
127 kilocalories (kcal)
11.12 g of protein
5.76 g of fat
9.95 g of carbohydrate
3.8 g of fiber
Soybeans are low in saturated fat and high in protein, vitamin C, and folate. They are also a good source of fibre, calcium, iron, magnesium, phosphorus, potassium, and thiamin.
The nutritional content of other soy products differs based on how they have been processed and what other ingredients have been added.
Possible health benefits
Some research suggests that including soy in a diet could bring a range of potential health benefits, including:
Soy has been associated with healthier cholesterol levels, which can help lower risk for heart disease.
Researchers conducted an analysis of studies to look at the effect of soy on cholesterol levels. They found that consuming soy significantly reduced total cholesterol, triglycerides, and LDL cholesterol. LDL cholesterol is also known as "bad cholesterol" because of its link to fatty buildups in the arteries
Soy intake also significantly increased HDL cholesterol. This type is also known as "good cholesterol" because it helps remove bad cholesterol from the arteries.
People with high cholesterol levels had more significant decreases in their LDL cholesterol than people with healthy cholesterol levels. Less-processed soy foods, such as soy milk, soybeans, and soy nuts, were more effective than soy protein extracts or supplements.
Scientists carried out an analysis of studies that looked at the effect of soy isoflavone supplements on body weight in postmenopausal women.
Soy isoflavones are naturally occurring compounds that have similar properties to estrogen. Estrogen levels naturally decline as women age, which increases their risk for certain health conditions.
The researchers concluded that overall, soy isoflavone supplementation resulted in a significant decrease in body weight.
What are the health benefits of edamame?
Edamame are young soybeans that are harvested before they have fully ripened. Learn more about their nutritious content and possible health benefits here.
In the past, there was concern that soy may be harmful to women at high risk of developing breast cancer or those with breast cancer. Opinion is changing, however, as more research has been conducted.
In a review of studies, scientists reported that soy intake might reduce breast cancer risk, based on data from observational studies. The amount of soy that may be beneficial is 10 to 20 milligrams (mg) of isoflavones each day, which is similar to the typical intake in Asia, where women tend to experience less breast cancer.
This amount of soy intake may also be beneficial for women with breast cancer, as it could improve survival rates and decrease relapse.
According to the American Cancer Society, it is unknown if soy protein isolates (soy protein that has been removed from the soybean) or textured vegetable protein (a soybean product that has had all fat removed) offer the same health benefits as less-processed soy foods.
Possible health risks
Some people have concerns about the consumption of soy in a diet. These include:
There is some concern that soy intake may affect a person's thyroid function. In one study, researchers found that women with higher soy intake had a higher chance of having elevated thyroid-stimulating hormone (TSH). A high TSH level may signify hypothyroidism (an underactive thyroid). Researchers did not find the same results in men.
The authors discuss that soy is likely to be safe, but excessive amounts may be concerning for some people, such as those with undiagnosed hypothyroidism. Other studies have shown varied results regarding the effect of soy intake on thyroid function.
Genetically modified organisms
Genetically modified foods could potentially lead to illnesses that are resistant to antibiotics.
According to the World Health Organization (WHO), genetically modified organisms (GMOs) are "...organisms (i.e. plants, animals or microorganisms) in which the genetic material (DNA) has been altered in a way that does not occur naturally by mating and/or natural recombination."
Worldwide concerns regarding health impacts and environmental safety have arisen in regards to genetically modified crops.
According to the USDA, 94 percent of soybean farmland in the U.S. was used to grow genetically engineered soybeans in 2014.
In one review, researchers report that eating genetically modified foods could lead to illnesses that are resistant to antibiotics. They also questioned long-term safety, as GMOs are a relatively recent development.
The amount of potentially beneficial isoflavones may be lower in genetically engineered soybeans. The transfer of allergens and the formation of new allergens are additional concerns with GMOs.
Although many have expressed concerns regarding the safety of GMO crops, WHO also state that "GM foods currently available on the international market have passed safety assessments and are not likely to present risks for human health." However, more research needs to be done to understand the real impact GM crops have on health.
To avoid GMOs, look for organic soy products or those labeled non-GMO.
Best forms of soy to eat
The best types of soy to eat are those that are less processed. Some examples include cooked soybeans, edamame, soy milk, tofu, tempeh, and soy nuts. Some soybean products can be viewed here.
Although soy is a nutritious food, experts at MD Anderson's Cancer Prevention Center still recommend moderation. In regards to whole soy foods, moderate intake is considered to be 3 servings per day.
Listed below are serving sizes for common soy foods:
1 cup soy milk
1/2 cup cooked soybeans or edamame
1/3 cup tofu
In conclusion, moderate amounts of whole soy foods included as part of a healthful diet may offer health benefits.
More research needs to be carried out on the potential benefits and risks of consuming soy. Genetically engineered soy is a controversial product that also requires further study.