If you're like millions of Americans, you may have tried or regularly drink plant-based milk alternatives like soy, almond, rice or hemp. They're considered a healthier alternative, but some people may be surprised to find the beverages can upset their stomachs as much as dairy, doctors say.
When doctors told Sarah Gmyr that her stomach pain was caused by lactose intolerance years ago, the 35-year-old from Stamford, Connecticut, switched to soy milk. "I could finally have lattes again!” she says.
But it wasn’t long before she started having stomach trouble again. “It got to the point where I was having problems eating, period,” says Gmyr. “Every time I ate, I got sick and bloated. My doctor was worried I might have ovarian cancer.”
After starting an elimination diet, Gmyr learned that she had problems with gluten — and the very soy she’d been using to replace dairy products. “Of course it was a bummer to learn that something I’d substituted for milk caused even more problems than I initially had,” she says.
Gmyr isn’t alone. It’s not uncommon for people who are lactose intolerant — or even those who have unexplained stomach problems — to turn to dairy substitutes, like soy or almond milk. But those alternatives might also cause problems.
"I do see patients who can't tolerate milk substitutes," said Dr. Kevin Ghassemi, a gastroenterologist in the division of digestive diseases at the David Geffen School of Medicine at UCLA. "I don't think those people generally have an allergy, but more of a nerve sensitivity. Something in those substitutes is causing the nerves going to the bowels to be irritated."
It's also possible that the initial improvement people experience when they start drinking a milk substitute is due to a placebo effect, Ghassemi said. Or it might be that it takes some time for the body to become sensitized to the protein in the substitute.
Sometimes it doesn’t take much.
Kelly Harrison remembers the day she added some almond milk to her coffee. A short while later, halfway through her usual 6-mile run, the 29-year-old New Yorker started to hyperventilate and break out in hives. Although she’d reacted to peanuts before, she’d never had a problem with any other nuts till that day. Benadryl calmed the reaction, but “it was a horrible feeling,” she says.
Gastroenterologist Dr. Octavia Pickett-Blakely suggests anyone wanting to switch to a milk substitute should go slowly. “I suggest starting out with a small amount to make sure that they are able to tolerate it,” says Pickett-Blakely, an assistant professor of medicine and director of nutrition and small bowel disorders at the Perelman School of Medicine at the University of Pennsylvania.
While some of the plant-based milks are fortified with calcium and vitamin D, don't expect them to have same amount as dairy, says dietitian Ann Condon-Meyers.
“Calcium is a real problem for everybody,” says Condon-Meyers, clinical dietitian at the Children’s Hospital of Pittsburgh at the University of Pittsburgh Medical Center. “Many vegans and vegetarians say you can get it from green vegetables, but you’d have to eat three cups of kale just to get close to the amount of calcium in only 8-ounces of [cow's] milk, and that’s only one-fourth of what you need as an adult. It’s hard to make up for that.”
Linda Carroll is a regular contributor to NBCNews.com and TODAY.com. She is co-author of "The Concussion Crisis: Anatomy of a Silent Epidemic” and the recently released “Duel for the Crown: Affirmed, Alydar, and Racing’s Greatest Rivalry.”