We’ve been taught to avoid germs and bacteria since we were kids. Whether it’s sudsing up our hands or deep cleaning our homes (without harmful chemicals), we’re constantly trying to get rid of the microscopic culprits.
But it turns out eating bacteria can actually be a good thing. Numerous studies have found that foods fermented by lactic acid-producing bacteria (a beneficial kind of bacteria found in decomposing plants and milk products) may actually help keep your gastrointestinal systems healthy and functioning properly.
“Regularly consuming fermented foods helps bolster the population of good bacteria in the gut,” says Josh Axe, D.N.M., author of Eat Dirt: Why Leaky Gut May Be the Root Cause of Your Health Problems and 5 Surprising Steps to Cure It.
While the topic of gut health isn’t exactly first-date material, there are plenty of reasons to get excited about fermented foods.
Long before refrigerators or freezers, ancient people used fermentation to keep foods from going bad, Axe says. Put simply, fermentation is an enzyme-controlled, chemical breakdown of an organic substance (think: sugar turning to alcohol or milk turning sour).
“When a carbohydrate gets converted by yeast, bacteria, or carbon dioxide, it’s fermented,” says Leah Silberman, R.D., cofounder of Tovita Nutrition in New York City. The process is anaerobic, meaning it takes place without oxygen, which is why fermented foods and canning go hand in hand. “Fermentation was used to preserve foods through canning and jarring, and now it’s making headlines for health benefits,” Silberman says.
Certain products like kombucha (fermented tea), kimchi (fermented vegetables), miso (fermented soy), yogurt and kefir (fermented milk), and sauerkraut (fermented cabbage) get a lot of buzz because they contain live microorganisms called probiotics. If that word sounds familiar, it’s probably because probiotics are having a bit of a moment. Several studies show links between probiotics and increased gut health and suggest they can help reestablish a healthier intestinal tract and benefit digestion. However more research is needed to back up some of the health claims made about probiotics (read: weight loss, clearer skin).
Additionally, not all fermented foods are healthy. Products like bread, cheese, and beer are fermented by lactic acid-producing bacteria but typically don’t contain live microorganisms due to cooking or pasteurization. And as Silberman reminds us, it’s important to read food labels carefully. “Ketchup can be loaded with sugar; pickles can mean you overload on salt,” she says. That doesn’t mean you should avoid them entirely, but moderation is key.
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Fermented foods can taste a little funky. “Some people just don’t like fermented foods, so the idea is to start small,” Silberman says. And pay attention to serving sizes. “For instance, with [store-bought] kombucha, sometimes there are two servings in one drink, so just start with half the drink,” she says. Axe agrees and recommends one serving of probiotics each day from your food of choice.
If you’re specifically looking for fermented foods that contain probiotics, make sure you pick items from the refrigerated section of the grocery store and read labels. Room-temp sauerkraut won’t have any living microorganisms, and even some yogurts can be heat-treated after fermentation, killing most of the helpful bacteria. If a food contains either living microorganisms or probiotics, they may be included in the ingredient list—or the label may say “unpasteurized” or “live and active cultures.” (The most common probiotics found dairy foods are Lactobacillus, Bifidobacterium, and Streptococcus thermophilus.)
If you do your own refrigerated canning, there is a slight chance of listeria or botulism. However negative side effects are rare, and fermented foods have had a generally good safety record for thousands of years.
Can’t get past the taste and would rather take a supplement? Check with your doctor first. Remember supplements aren’t regulated by the FDA, and some studies have found discrepancies between what’s on the label and what’s actually inside certain probiotic supplements.