But can these teeny-tiny bacteria—found in dietary supplements and fermented foods—help you lose weight, too? They do live in your stomach, after all.
First: What the heck are probiotics anyway?
Probiotics are live microorganisms that naturally reside in your body already, according to the National Center for Complementary and Integrative Health (NCCIH).
“Probiotics are substances that encourage the growth of bacteria, specifically beneficial bacteria, that help to keep intestinal health in balance,” says Frances Largeman-Roth, RDN, author of Eating in Color. “A healthy balance of good bacteria in the body may help regulate weight and ward off a range of health issues.”
Those other health issues include digestive problems like irritable bowel syndrome (IBS), along with allergic skin diseases like atopic dermatitis, and even the common cold, per the NCCIH.
So, can probiotics help with weight loss?
Honestly, no one knows for sure—that's because most probiotic research has focused on how to improve digestive issues or immune health.
The most promising evidence on probiotics and weight loss comes from a 2013 study in The British Journal of Nutrition, which studied the effects of one strain of probiotics, lactobacillus rhamnosus (LGG).
Researchers followed 125 men and women throughout a 12-week weight-loss program, giving half the participants LGG and the other half a placebo. At the end of the trial, the women who took probiotics lost more weight than the women on the placebo. The probiotics group also went on to continue losing weight after the trial had ended (the placebo group only maintained).
That sounds legit, right? Well...kind of. Caroline Apovian, MD, director of nutrition and weight management at Boston Medical Center, says the difference in weight loss between the probiotic and placebo group in this study just barely qualifies as noteworthy.
“There was no weight loss difference overall between the probiotic and placebo groups,” she says, “but there was a significance when you separate [out] the women in the probiotic group.” Even then, she notes, the women in the probiotic group only lost about 1.8 kilograms (or just under four pounds) more than the placebo group.
Still, probiotics promote overall health, which never hurts when it comes to weight loss. “Gut bacteria lines the intestines and comes in contact with the food you eat, [so] the thought is that this may impact how you absorb nutrients,” says Amy Gorin, RDN, owner of Amy Gorin Nutrition in the New York City area.
It’s important to remember, however, that exactly how probiotics for weight loss may work is based on educated theories and speculation—it's unclear if or why there's a connection. Apovian adds that while it’s entirely possible that a probiotic-filled healthy gut could be more amenable to weight loss or weight maintenance, it also might be thanks to another kind of cause and effect.
“It may certainly be that those people who eat healthy have healthier guts and not the other way around,” she says. “As far as which came first [the healthy diet or the healthy gut], it’s likely the healthy diet.”
So...how can I add more probiotics to my diet?
While you can get probiotics through food, the easiest way to get some probiotics in your diet every day without fail is likely through a probiotic supplement.
But here's the thing: There are dozens of probiotic supplements on the market, with different supplements containing different strains. Unfortunately, according to Apovian, the few studies that have been done so far offer no real evidence about which probiotic strains might work best for weight-loss results. In the 2013 British study, LGG was chosen—but why? “They just picked one!” Apovian says.
If you still want to experiment with probiotics for weight loss, though, Gorin says to hit up your doctor for the go-ahead before taking any supplements—while probiotics are generally considered to be safe, they may cause some gastrointestinal upset at first, like bloating and gas.
Gorin notes that one study in Obesity found daily supplementation with VSL#3 may provide some protection against weight gain when eating a high-calorie, high-fat diet. However, the sample size was limited: only 20 non-obese men were studied.
Similarly, a 2013 study published in the Journal of Functional Foods found a link between loss of body fat and the probiotic strains lactobacillus fermentum and lactobacillus amylovorus (3 per cent and 4 per cent, respectively), but only 28 participants were studied.
But what if I don't want to take a supplement? Can I get probiotics anywhere else?
You sure can—in fact, it might be better to get your probiotics from food sources. “I would always urge people to eat food first," says Gorin—that way, you're getting other nutrients too, in addition to probiotic benefits.
Apovian agrees, saying that most probiotic foods are healthy foods and it certainly can’t hurt to eat them (which is pretty much her takeaway on probiotics overall: they may not do a ton of good, but they won’t really do much harm, either). Here are a few ways to get probiotics from food:
1. Stock up on yoghurt.
Fermented dairy products, like yoghurt and kefir, are high in the lactobacillus probiotic.
“Not all yogurt contains probiotics, so it’s important to read the label and visit the company’s website to look for transparency about this,” says Gorin. (Hint: look for the National Yogurt Association's “Live & Active Cultures” seal. Chobani and Fage brands are typically safe bets.)
If you would rather drink your dairy than eat it with a spoon, you can try kefir, a fermented drink made from cow’s or goat’s milk and cultures of yeast and lactic acid bacteria.
2. Load up on picked cabbage.
Like yogurt and kefir, vegetables that are fermented—especially pickled cabbage, like sauerkraut and kimchi—are reliable ways to pump up your probiotic ratio.
One caveat about pickled cabbage: Most of the products sold in U.S. stores have been through a heating process called pasteurisation for safety, which can destroy both good and bad bacteria. So, if you really want to reap the fermentation benefits, look for unpasteurised products or make your own.
3. Go all in on fermented cheeses.
So, cheese isn't likely to be first on your list when you think of probiotics, but it turns out, fermented cheeses like Gouda, cheddar, and Swiss are made with lactic acid bacteria, a probiotic, says Jackie Newgent, RD. Quality matters here too (more fermentation equals more probiotics), so make sure the person behind the counter points you to the finest aged Gouda there is.
Many purported health benefits of ACV are pretty conflated (and are not actually scientifically proven), but ACV really does have probiotics to help your gut health. Instead of taking it via shot (or diluted in water, even), try adding it to your salad dressings for an extra kick of healthy bacteria.
The bottom line: Probiotics won't work weight-loss magic—but they can help with gut health, so it doesn't hurt to give them a try.
This article originally appeared on Women's Health US.