Probiotics are living bacteria that exist naturally in fermented foods, including yogurt, sauerkraut, kombucha (here are 5 things you should know before you drink kombucha again), and even sourdough bread. Studies have found that some individual strains of probiotic bacteria can help digestion and boost immunity, even warding off allergies and colds. But beyond that, these foods have gone largely unstudied.
"It's not a case of being duped at the checkout counter," Reid says, but more an issue of researchers' being held up by crazy laws. Per Food and Drug Administration regulations, doctors can't conduct clinical trials on foods that contain probiotics without first registering them as drugs. If that were to happen, you'd find yourself having to ask your MD for a prescription for your favorite yogurt.
And that's held up a lot of research on the booming market for probiotic foods, putting you in the position of having to trust marketers and their often unsubstantiated and sometimes misleading claims. "Many of these products have never been tested in humans," he says. "I'm not saying they're bad, or that they're not useful. But companies are getting away with using probiotics in their products without doing their due diligence, and consumers have no idea which ones to get and what they do."
Related: 5 Tasty Cousins Of Kombucha You've Never Heard Of
Just because a food contains probiotics doesn't necessarily mean it or the bacteria are doing anything for you, he adds. Here are three other things you need to know about probiotics:
There are billions of good bacteria, and they all do different things.
There has been a lot of research on strains of probiotic bacteria, and independent studies have found that they can alleviate diarrhea, allergies, colds, yeast infections, colic in babies, and irritable bowel syndrome, among other things. And if you're trying to treat a yeast infection, you don't want to be stuck with a product that contains probiotics that only cure bad breath. You can treat a yeast infection with products containing Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14, but if you're trying to regulate your digestive system, opt for products that contain Bifidobacterium animalis DN 117-001.
Related: 7 Foods That Guard Your Body From Everyday Toxins
More does not always equal better.
There are 300 strains of probiotics on the market, but just 20 or so have been fully studied, Reid says. So buying a product that lists dozens of cultures on a label may not result in a better product. He adds that most food manufacturers combine strains, which could hinder the activity of some good bacteria.
Related: 5 Gut Mistakes You Don't Know You're Making
It's how you eat your probiotics that matters.
Probiotic pizzas and breads may well contain billions of live and active cultures—until you heat the pizza or make toast with your bread. Then you kill all the bacteria and reap none of the benefits. But you wouldn't know that from reading most food labels, Reid says.
"My point is not to rubbish probiotics," Reid says. He recommends them and takes them every day. "Even if there's a placebo effect with these products, that's great." He just hopes that regulatory agencies will step up to the plate and start requiring more of food companies, asking them to test their products so that consumers are less confused by the shopping process.
His final recommendation: Eat as many probiotic-rich whole foods as you can, such as yogurt, homemade sauerkraut (here's how to make sauerkraut in a jar) and kimchi (not the bottled stuff, though, which has usually been pasteurized, killing all the good bacteria), sourdough bread, and kefir. Also bolster your diet with foods containing prebiotics, nondigestible carbohydrates that help spur the growth of probiotics in your gut. You'll get those from whole grains, bananas, onions, garlic, honey, and artichokes.