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Soy is a popular legume of Asian origin. People who follow a vegetarian diet often use soy to replace meat. However, there is some controversy surrounding the benefits and risks of consuming soy, as some producers now genetically modify the plant.

Soybeans are healthful and rich in protein, giving them numerous nutritional uses. People can eat them, drink them in milk alternatives, and take them in the form of supplements.

Manufacturers may also extract the oil from soy and use it to make ecologically friendly fuel, as well as candles, crayons, and engine lubricants.

In this article, learn more about soy, its potential health benefits and risks, and the best forms of soy to consume.

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Soybeans can play a role in a variety of meals and supplements.

Soybeans are a high protein plant food that people can prepare and eat in a variety of ways. They belong to the pea family.

Soybeans come in many colors, including:

  • Green soybeans: Young green soybeans are also called edamame. People can steam them and eat them out of the pod as an appetizer. Shelled edamame is also available in salads, stir-fries, and soups.
  • Yellow soybeans: Producers typically use yellow soybeans to make soy milk, tofu, tempeh, and tamari. They also play a role in the production of soy flour for baking.
  • Black soybeans: Several Asian food cultures use simmered or fermented black soybeans in traditional dishes.

Soy milk and cheese are also options for those looking to replace dairy in the diet.

Soybeans also provide soy oil, which people can use for cooking or as an ingredient. After removing the oil from soybeans, people can use the remaining material to make food for farm animals and pets.

Some manufacturers make protein powder and isoflavone supplements from soy. Isoflavones are plant compounds that have a similar structure to estrogen.

Less processed organic soy is the most healthful option. Some examples include:

  • cooked soybeans
  • edamame
  • soy milk
  • tofu
  • tempeh
  • soy nuts

A range of soybean products are available for purchase online.

Soy is a complete protein. This means that it contains all nine essential amino acids. It is an important source of protein for many people, especially those who follow a vegan or vegetarian diet.

According to the United States Department of Agriculture (USDA), 100 grams (g) of cooked green soybeans without salt contains:

  • 141 kilocalories
  • 12.35 g of protein
  • 6.4 g of fat
  • 11.05 g of carbohydrate
  • 4.2 g of fiber

Soybeans are low in saturated fat and high in protein, vitamin C, and folate. They are also a good source of:

The nutritional content of other soy products may vary based on how manufacturers have processed them and which ingredients they have added.

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Soy is an important protein for many vegetarians and vegans.

Some research suggests that including soy in the diet could have several potential health benefits.

We cover these in more detail below.

Soy has links to more healthful cholesterol levels, which can help lower the risk of heart disease.

In 2015, researchers conducted an analysis of studies to look at the effect of soy on people's cholesterol levels. They found that consuming soy significantly reduced levels of total cholesterol, triglycerides, and low density lipoprotein (LDL) cholesterol in the arteries.

LDL cholesterol is also known as "bad cholesterol," as it can lead to clogging in the arteries.

The review authors also found that soy intake significantly increased high density lipoprotein cholesterol. This type is also known as "good cholesterol" because it helps remove LDL cholesterol from the arteries.

People with high cholesterol levels had more significant decreases in their LDL cholesterol than people with optimum cholesterol levels.

Also, less processed soy foods — including soy milk, soybeans, and soy nuts — were more effective than soy protein extracts or supplements.

Managing obesity

One 2019 study in the journal Molecules looked at the effect of soy isoflavone supplements on body weight in rats.

In the study paper, the authors report that certain compounds in soy isoflavones prevented the buildup of fat around the rodents' organs.

The researchers conclude that soy isoflavone supplementation has potential for managing obesity.

Reducing breast cancer risk

A 2019 review of studies indicates that the isoflavones in soy can help reduce the risk of hormone associated cancers, including prostate cancer and some breast cancers.

Some studies in the review found that Asian women who consumed soy isoflavones had a reduced risk of cancer both before and after menopause. Soy isoflavones may help reduce the growth and spread of hormone associated cancers.

According to the American Cancer Society, however, it is not clear if more processed soy products — such as soy protein isolates or textured vegetable protein — offer the same benefits for cancer prevention as whole soy foods.

Soy protein isolates are proteins from which manufacturers have removed the rest of the bean. Textured vegetable protein is a soybean product with the fat removed.

Reducing the risk of type 2 diabetes

According to the same 2019 review of studies, soy isoflavones may also reduce the risk of diabetes, though the mechanism through which they may achieve this is still unknown.

In type 2 diabetes, the cells of the body absorb less sugar from the bloodstream, which leaves it to circulate and cause harm. Insulin is a hormone that allows blood sugar, or glucose, to enter the cells for conversion into energy.

Soy isoflavones may improve insulin sensitivity, meaning that the cells respond more to insulin and absorb more glucose.

Treating osteoporosis

Soy isoflavones may also be an effective alternative to hormone replacement therapy (HRT) for women with osteoporosis. This is a condition that affects bone growth and leads to easy fractures.

In women, one of the possible causes of osteoporosis is estrogen deficiency. HRT aims to replace this estrogen in the body. However, it can cause severe side effects and increase the risk of stroke, breast cancer, and coronary heart disease.

Several studies in this review suggested that soy isoflavones were as effective as HRT for restoring bone density.

Some people have concerns about the consumption of soy. We cover these concerns in more detail in the sections below.

Thyroid function

There is some concern that soy intake may interfere with thyroid function.

In one 2016 study of 548 women and 295 men who ate soy foods as part of a vegetarian diet, researchers found that women with higher soy intake had a higher chance of having elevated levels of thyroid stimulating hormone (TSH).

A high TSH level may signify an underactive thyroid. Researchers did not find the same results in men.

The authors explain that soy is likely to be safe. However, consuming excessive amounts may create health risks in some people, such as those with undiagnosed hypothyroidism.

Genetically modified organisms

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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."

There are many concerns around the health impacts and environmental safety of genetically modified crops.

According to the USDA, in 2014, farmers used 94% of soybean farmland in the U.S. to grow genetically engineered soybeans.

In one review, researchers suggest that eating GMOs could lead to illnesses that are resistant to antibiotics. Its authors also questioned the long term safety of GMOs, as they are a relatively recent development.

Also, the amount of potentially beneficial isoflavones may be lower in genetically modified soybeans. The transfer of allergens and the formation of new allergens are additional risks of GMOs.

Despite concerns about GMO crops, the 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 take place on the real health impact of genetically modified crops.

To avoid GMOs, look for 100% organic soy products or those labeled as non-GMO.

Moderate amounts of whole soy foods included as part of a varied and healthful diet may offer health benefits.

Soy isoflavone supplements in particular can also help reduce the risk of hormone associated cancers and osteoporosis in women, as well as type 2 diabetes in both men and women.

More research is necessary on both organic and genetically modified soy to assess their overall benefits and risks.

Q:

Does soy being in a veggie burger make it more healthful than a meat patty?

A:

There are pros and cons to both types of burgers. Both a soy based veggie burger and a meat patty contain complete proteins, meaning that they include all of the essential amino acids. However, many soy based veggie burgers are highly processed.

In general, consuming less processed, whole foods is ideal for reaching optimal health. An unprocessed meat patty will have more bioavailable iron and contain more B vitamins and zinc than a soy patty, but soy has more isoflavones, which studies have shown to reduce the risk of certain cancers.

Many health experts suggest limiting red meat to decrease the risk of disease — particularly heart disease. Both soy veggie burgers and meat burgers can be part of a healthful diet, but people should keep individual health goals in mind. Focusing on less processed versions of both of these is ideal for good health.

Natalie Olsen, RD, LD, ACSM EP-C Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.