Fitness + Well-being

When It Comes to Your Stomach, Is Soy Friend or Foe?


We hear a lot of conflicting information about soy. Some say it’s good for your health, while others seem to disagree.

So who are we to believe? Should we toss our soymilks and soy cheeses in the trash, or continue to enjoy our tofu burgers and soy-sages?

“There is definitely a place for soy products in a healthy diet,” says registered dietitian Karen Ansel, a Long Island-based nutritionist and spokesperson for the Academy of Nutrition and Dietetics. “Unlike many other plant foods, soy provides complete protein, meaning it contains all the amino acids our bodies need to synthesize protein.”

Ansel says that soy protein is of such high quality, that it’s “an excellent protein source for vegetarians or people who simply want to eat less meat.”

Soy is also a heart-healthy food, adds Ansel. “Not only is most of [soy’s] fat the heart-smart mono and polyunsaturated variety, seven percent of the fat is linolenic acid, a plant omega-3 fat which may reduce a person's risk of developing heart disease,” she states.

Sharon Richter, a registered dietitian based in New York City, says that soy also contains organic compounds called isoflavones which promote heart health. “For example, isoflavones such as genistein are believed to have estrogen-like effects in the body, and as a result are sometimes called ‘phytoestrogens.’ Some studies say it can help prevent heart disease and some cancers.”

Those extra estrogens, however, are the subject of much debate.  Richter claims that some scientific studies suggest that too many phytoestrogens can be harmful, and in some cases, may reduce fertility in women, or trigger an early onset of puberty in children, or disrupt the development of children and fetuses. (Although most of these studies were performed on rats, and therefore, may not translate to humans, she says.)

“Some feel that those with breast cancer [along with] children and men should avoid soy, but it still very controversial,” Richter adds.

People with thyroid issues, too, may want to think twice about ingesting soy products, according to Ansel. “If you take medication for an underactive thyroid, soy may interfere with your body's ability to absorb it, so I'd be sure to speak with your physician,” she says.

Yet some experts attest that soy interferes with much more when it comes to matters of the stomach. In an article titled “Newest Research on Why You Should Avoid Soy,” nutritionists Sally Fallon and Mary G. Enig, PhD, argue that soy inhibits the action of trypsin, an enzyme necessary for digestion in mammals.

According to Fallon and Enig, the trypsin inhibitors found in soy can result in “serious gastric distress, reduced protein digestion and chronic deficiencies in amino acid uptake,” as well as certain pancreatic ailments. They concede that “Much of the trypsin inhibitor content can be removed through high-temperature processing, but not all,” before adding that even a small amount of these inhibitors resulted in abnormal growth in rats.

“Once cooked, trypsin is deactivated,” says Richter, who claims that allergic reactions to soy are of more concern.

And, as Ansel also points out, the American Academy of Pediatrics and the American Academy of Family Physicians warn against soy for those with even minor soy allergies, as they can become more severe with repeated exposure. Infants, according to the AAP, should not be fed soy formulas as an alternative to cow’s milk formulas either, because those who are sensitive to or allergic to cow’s milk can develop an allergy or sensitivity to soy products as well.

That being said, Richter and Ansel both agree that the healthiest types of soy products are those that are minimally processed.

“I say stick with the simplest forms,” says Richter. “Read labels for recognizable ingredients such as edamame or soy beans.”

“I'm a big fan of whole soy foods like edamame and tempeh,” adds Ansel, explaining that the abundance of fiber found in whole soybeans is lost when they’re processed into certain foods like soymilks or tofus. “One thing I'd keep in mind is that just because a product has soy in it, [that] doesn't automatically make it a health food,” she says. “Super-processed soy foods such as soy ice cream may be no better for you than the real thing.”

That’s sound soy advice, but there’s still the matter of the soy burgers and soy-sages in our refrigerators. Above all, we should be listening to our guts. Because when it comes to soy, it's the body's advice we'll need to stomach.