Sex Hormones May Be Lurking in Your Food

Photo Travis Rathbone/Trunk Archive

By Jennifer J. Brown, PhD, Everyday Health

Whether you’re a meat lover or prefer plant-based protein like soy in your diet, the idea of sex hormones in your food might make you a bit queasy. Use of hormones as drugs carries potential risks as varied as bone loss from steroids, and heart disease risks from hormone replacement during menopause.

But is there reason to worry that you’re getting dangerous amounts of added hormone in your food?

Sex Hormones in Meat

The sex hormones estradiol, progesterone, and testosterone are given to cows in the form of an injected pellet in the ear. From there, hormone circulates to improve the animal’s gain weight, growth rates, and milk production. Added hormones are not allowed in farmed chickens or pigs in the United States.

“There are maximum safe limits that are set for hormones in meat,” says Richard J. Auchus, MD, a professor of internal medicine at the University of Michigan, a member of the Endocrine Society, and associate editor of the journal Endocrinology. For beef, the limit for added estradiol residue is 120 parts per trillion, a level that is actually vanishingly low, and set by the U.S. code of federal regulations.

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The amount of estrogen in 3 ounces of steak from an animal that had a hormone implant is 1.9 nanograms, compared with 1.3 ng in a cow that did not receive hormones, according to the College of Agricultural and Environmental Sciences at the University of Georgia Cooperative Extension. Cow milk has very low levels of estrogen as well, estimated at only about 59 nanograms per two cups.

To put the levels of hormone in perspective, when women take estradiol as a pill, they are getting much higher levels of estrogen in a day, says Dr. Auchus. For example, even low-dose birth control pills contain about 50,000 ng of estradiol each. “A lot of this gets metabolized by the liver,” Auchus explains. “The levels in meat are thousands of times off from what would be biologically meaningful.”

Sex Hormones in Plants: Phytoestrogens

Compared to the low levels in meat, plant-based protein sources — such as soy — contain a lot of hormone-related compounds. Called phytoestrogens, these are also sometimes referred to as isoflavones. While soy is at the top of the list, other plants high in phytoestrogens include black beans and red clover.

For example, phytoestrogen level per 100 grams (about 3 ounces) of the soy product miso is 42 milligrams, and 100 gm of tofu has about 23 mg, according to the USDA nutrition database. Other foods high in phytoestrogens include cereals fortified with soy protein, which can have as much as 94 mg per 100 gm, and meatless bacon bits, at about 120 mg per 100 gm.

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To compare this to the levels in meat, consider that 1 mg is equal to 1 million ng — and, as noted above, a piece of steak has only about 2 ng.

Despite the higher levels, consuming phytoestrogens from plants does not carry health risks, unlike hormones in birth control pills and hormone replacement during menopause.

“I do not tell patients to avoid foods that are high in phytoestrogens,” says gynecologist and Everyday Health columnist Lauren Streicher, MD. Dr. Streicher is an associate professor of Obstetrics and Gynecology at Feinberg School of Medicine at Northwestern University in Chicago. When patients with breast cancer ask her about estrogen in foods, she tells them, “In fact, estrogen doesn’t cause breast cancer, it’s estrogen and progestin together.”

As endocrinologist Auchus notes, “Even quite large amounts of food that are high in phytoestrogens don’t provide much biological effect.” And, he adds, phytoestrogens are mostly metabolized by the liver before they reach your blood. “There is no reason to avoid soy,” he says.

Diet Considerations for Soy

Registered dietitian Bonnie Taub-Dix, MA, RDN, CDN, columnist at Everyday Health and author of the book Read It Before You Eat It, says she often gets questions about soy products, because they’re among the highest in phytoestrogens.

She tells women that soy could be good for them. “I wouldn’t say it’s helpful to replace estrogen, but soy could help with lowering cholesterol, or reducing hot flashes or some symptoms of menopause,” says Taub-Dix.

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It’s not just what you eat, but how much matters too, she notes: “Because a little is good, doesn’t mean more is better. You have to look at the quantity. Soy and plant proteins can be healthy.” If you want to try soy, she recommends one serving per day, which is 1 cup of soy milk, or half a cup of tofu, edamame, or tempeh.

However, Taub-Dix cautions, you should read soy food labels carefully. “Some are fortified; some have more protein or added sugar,” she says. She does not recommend soy supplements because you can’t be sure how much you’re getting.

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If you’re concerned about sex hormones in your food — from animals or plants — you may have considered going organic. Added hormones are not permitted in organic meat. Still, even if hormones were not added during farming, all milk and meat has some level of hormones, because all animals just naturally have hormones.

Organic produce will not have different levels of phytoestrogens than other produce.

When in doubt, Taub-Dix says, “Go with the science.”

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This article originally appeared on Sex Hormones in Your Food