Can Drinking Soy Milk Every Day Have Side Effects?

Soy milk is a great way to get some protein into your diet, despite the fact that soy's reputation as a healthy food has seesawed in recent years. However, as registered dietitian Alex Caspero writes in Women's Health, experts are now confident that drinking soy milk every day is good for you, with few side effects that can cause concern or discomfort.

Soy milk was once thought to cause health concerns, but for most people, soy milk is a healthy, nondairy alternative to cow's milk. (Image: OlenaMykhaylova/iStock/GettyImages)

Tip

Drinking soy milk every day is a good way to get daily protein without negative side effects. Three servings of soy milk each day will give you many of the benefits of cow’s milk.

Soy Milk's Reputation

Soy milk and other foods made with soybeans were once hailed as superfoods with no downsides. Soy is a nutrient-dense form of protein, eaten in many parts of the world more regularly than in the United States.

But then, an American Cancer Society study published in March 2017 indicated that soy could increase breast cancer risk, especially in premenopausal women, and researchers questioned the health benefits of soy. Newer research, however, doesn't bear this out.

A study led by researchers at Tufts University followed women who were diagnosed with breast cancer. Those who ate foods containing isoflavones, found primarily in soy foods, showed a 21 percent decrease in death rates from all causes. Furthermore, a study in the journal Fertility and Sterility showed no ill effects from the protein or isoflavones in soy on male testosterone.

The experts from the Nutrition Source at the Harvard T.H. Chan School of Public Health think that doubts about soy milk benefits were premature and that questionable study results may stem from wide discrepancies in how soy consumption is evaluated.

Soy Milk Benefits

The primary ingredient in soy milk is soybeans. Soy milk is packed with protein. Drinking soy milk every day, even three glasses of it, is unlikely to have negative side effects, and it is good for you. One advantage is that it does not have lactose, which makes it especially good for people who are lactose intolerant.

Soy milk has less saturated fat than almond milk. It also has the same amount of protein and similar nutrient content to cow's milk, except it has less calcium. Soy milk is often fortified with as much calcium as cow's milk has, however. Soy is high in isoflavones, which can reduce inflammation, and may help the body fight cancer-causing agents.

In a study at McGill University, researchers who compared unsweetened soy milk with rice milk, coconut milk and almond milk found that soy milk has the most balanced nutrient profile of the milk alternatives. The only negatives may come from added sugar, flavoring or other additives, so check the label carefully.

Nutritional Content of Soy Milk

The nutrients found in 8 ounces of soy milk include:

  • Calories, 101
  • Protein, 6 grams
  • Total fat, 3.5 grams
  • Carbohydrates, 12 grams
  • Dietary fiber, 1 grams
  • Sugars, 9 grams
  • Calcium, 451 milligrams
  • Iron, 1.08 milligrams
  • Magnesium, 41 milligrams
  • Phosphorus, 79 milligrams
  • Potassium, 300 milligrams
  • Riboflavin, 0.425 milligram
  • Vitamin A, 499 international units
  • Vitamin D, 120 international units

For vegans or a lacto-ovo vegetarians, you also want to make sure your soy milk has the essential amino acid methionine. The way some soy milk brands are processed may weaken this complete protein.

Taste and Allergies

Some people don't like the taste of soy milk. To avoid what some call a chalky aftertaste, nutritionists advise shaking the container or testing different brands.

If you take issue with the taste, you may prefer vanilla soy milk. This gives you most of the same benefits as unsweetened soy milk, but comes with 8 grams of added sugar, according to one brand's label.

Other people are actually allergic to soy milk. If this is you, you shouldn't drink it.

Soy Milk and GMOs

Some soy milk brands are made from genetically modified soybean crops. The U.S Department of Agriculture indicates that 94 percent of all soybeans grown in the U.S. are genetically modified as of 2014. According to an article on WebMD, the American Medical Association and the World Health Organization say that genetically modified food crops are safe, but if this bothers you, look for the Non-GMO Project label, available on several commercial soy milk products.

Lower in Saturated Fat

Soy intake can slightly reduce your low-density lipoprotein, sometimes called your "bad" cholesterol, lowering it by about 3 percent. Soy isoflavones also appear to improve blood pressure.

Soy's Effects on the Body

Soy products, including soy milk, are often thought to reduce hot flashes in menopausal women and keep osteoporosis at bay. But according to Harvard researchers, soy has different effects on different people.

These researchers say that studies vary, in part, because some are conducted with animals, which may metabolize soy differently than humans. Also, people who have grown up consuming soy products throughout their lives are thought to be better able to reap soy's benefits.

Soy milk does have a reputation for causing gas, but most manufacturers are able to heat the soy enough to reduce the effects of soybean's gas-causing compounds.

Phytoestrogen and Soy

Phytoestrogen is a chemical found in soybeans that can act as a weak estrogen. This is why many women drink soy milk and eat soy products during menopause, to combat the body's natural drop in estrogen production.

Phytoestrogen was once thought to contribute to decreased sperm production in men, but those studies are inconclusive. Soy milk, however, typically doesn't contribute to higher estrogen levels in men and children. Its ability to boost estrogen in menopausal women, thus diminishing or preventing hot flashes, is not proven, however.

Anti-Nutrients and Soy

Soy milk contains some natural ingredients that can cut back on the body's ability to absorb some necessary nutrients and slow the digestion of protein and carbohydrates. These include trypsin inhibitors, lectins and phytic acids, along with indigestible oligosaccharides.

Manufacturing uses a heat treatment to diminish the effect of these compounds, and there are other processes that can improve some of these negative effects. Some of these include the use of fermented or sprouted soybeans.

Soy Milk and Thyroid Health

The thyroid gland regulates metabolism. Women with thyroid problems are often cautioned to avoid foods with soy. But this is debatable. If you take a thyroid replacement drug, wait four hours after you've taken your medication before drinking soy milk. Also, if you take a thyroid supplement, you should also wait four hours after consuming soy before taking concentrated iron and calcium supplements.

A study reported in Public Health Nutrition in 2016 showed that women with normal thyroid functioning should not have any problems drinking soy milk or eating other foods with soy. Women with borderline abnormal levels of thyroid-stimulating hormone, or TSH, however, may develop thyroid problems.

Some researchers in the 2016 study at Loma Linda University think differently, however. Women who are eating a normal, healthy diet, with soy and soy protein, may not have any problems from soy. These women may have had high TSH levels before adding soy to their diets. If you are at risk for thyroid problems, it's best to discuss drinking soy milk with your doctor.

Soy Milk Origins

Soy milk has been part of the mainstream American diet for only a few decades. Soybeans are native to China, where the plant has been grown for more than 3,000 years. Ancient Chinese people considered soybeans a necessity, but soy milk is a more recent development.

Chinese farmers domesticated soybeans around 1100 B.C. Soybeans spread to Japan and other Asian countries by the first century A.D. By the 18th century, soy sauce had gained a following in Europe. Ben Franklin sent soybean seeds to a friend to plant in his garden in 1770.

American farmers began growing soybeans as animal feed in the 1870s, and, until the 20th century, soybeans were mostly used for this purpose. In 1904, American chemist George Washington Carver discovered soybeans were a good source of protein and oil. He encouraged farmers to rotate soybeans with other crops to replenish the soil with nitrogen and minerals.

Henry Ford advocated drinking soy milk over cow's milk in the 1920s. In the 1930s, he opened a demonstration soy milk plant in Dearborn, Michigan, but Americans took little notice of soy milk until the 1990s.

Beany Taste of Soy Milk

Some say soy milk tastes beany and that it can cause gas, which is one reason Chinese parents typically didn't feed it to their children. Researchers in the 1930s cooked the beans longer and added sugar to help with the gas and the taste. But it took a while for the public to accept soy products.

Flavor researchers at Cornell pinpointed the culprits of the flatulence and bad taste. This research, along with research from the University of Illinois, Loma Linda University and several manufacturers, resulted in an improved flavor and reputation for soy milk. By the 1990s, when scientists published early research in the New England Journal of Medicine about its health benefits, soy milk became even more acceptable and available.

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