Although some probiotics have shown promise in research studies, strong scientific evidence to support specific uses of probiotics for most health conditions is lacking. The U.S. Food and Drug Administration (FDA) has not approved any probiotics for preventing or treating any health problem. Some experts have cautioned that the rapid growth in marketing and use of probiotics may have outpaced scientific research for many of their proposed uses and benefits.
This smooth, slightly tangy, and sippable yogurt contains a dozen different types of live active cultures. It's also 99% lactose-free, making it easier to digest for those with intolerant tummies. "If you have lactose intolerance, start slowly on kefir as a test. If you have no symptoms, go ahead and slowly increase your intake," advises Tallmadge. Plus, with 8 to 11 grams of protein per cup (depending on the brand), it can help fill you up for around 100 calories.
Bottom line: Probiotics are a promising field of research and may one day be used to treat or help prevent many disorders. But there’s not enough solid evidence to recommend their widespread use. Vague claims that probiotics "support good digestive health" are meaningless. Larger, longer and better studies are needed to test specific strains for specific conditions and to determine the proper doses and regimens. 

Once GI experts realized there is more to the lower gut than first assumed, the push to understand the diverse roles these bacteria play became urgent. Many mysteries still need solving, but clinical evidence increasingly indicates that people in good health should optimize lower gut bacteria. You can accomplish this by eating prebiotics to encourage the growth of your existing gut microbes, and probiotics to add to the ones that are already there.
Other foods without substantial research: miso (fermented soybean paste); tempeh; sauerkraut; aged soft cheese; sourdough bread; sour pickles; gundruk (nonsalted, fermented, and acidic vegetable product); sinki (indigenous fermented radish tap root food); khalpi (fermented cucumber); inziangsang (traditional fermented leafy vegetable product prepared from mustard leaves); soidonis (widespread fermented product prepared from the tip of mature bamboo shoots)
While past studies have investigated similar questions, they have all used patients' excrement as a proxy for microbe activity in the GI tract. Instead, Elinav, his colleague Eran Segal, (a computational biologist at the Weizmann Institute), and their teams spearheaded by Niv Zmora, Jotham Suez, Gili Zilberman Schapira, and Uria Mor of the Elinav lab collaborated with Zamir Halpern, Chief of Gastroenterology at the Tel Aviv Medical Center to measure gut colonization directly.
High cholesterol and triglyceride levels increase the risk of cardiovascular disease. Getting your cholesterol and triglyceride levels in an optimal range will help protect your heart and blood vessels. Cholesterol management may include lifestyle interventions (diet and exercise) as well as medications to get your total cholesterol, LDL, HDL, and triglycerides in an optimal range.

In seven people, however, these bacterial levels persisted for more than five months after the treatment ended. “We never expected they would survive more than a few weeks,” Walter says. A follow-up analysis determined that these seven people had begun the experiment with lower levels of B. longum in the first place. In other words, their gut ecosystems had a vacancy that the probiotic filled. That is exactly the kind of insight that clinicians need to create and recommend more effective probiotics. If a doctor knows that an individual with severe diarrhea has an undersized population of a particular beneficial microbe, for example, then prescribing the missing strain should increase the chance of a successful treatment.
Scientists are investigating probiotics, and their combined effects, by trying to classify the probiotic benefits of ingesting specific probiotic strains and understanding their role in the digestive tract. At present, the methodological and ethical limitations of human studies still make it difficult to fully understand the mechanisms of action of probiotics, but some explanations are available. Nevertheless, benefits linked to the consumption of probiotic strains have already been suggested (e.g. helping to support the immune system, help support digestive health), and others are still being investigated.
Here’s a startling fact: For every one human cell we have, there are ten bacteria cells in our body to match it. That means that the majority of DNA in our body isn’t even human; it’s from the 500 bacteria species that call us home.1 Thinking about that much bacteria might have your skin crawling, but the relationship between human and bacteria is really a perfect synergy: we give bacteria room and board, and in return, they work hard to protect our intestinal health, which ultimately protects the health of our immune system and overall well-being. But if we have that much bacteria already living in our gut, you might be thinking to yourself, what are probiotics’ benefits?

Women’s health expert Dr. Amy Myers is a goop-trusted authority on subjects from autoimmunity and Candida to thyroid dysfunction; and she’ll be speaking IRL at our first wellness summit on June 10. Here, Myers helps us evaluate the increasing buzz around probiotics, and outlines the ins and outs of selecting a particular supplement (whether hers or other brands). Plus, we’ve rounded up our probiotic essentials, from inner beauty powders to favorite fermentation recipes, in one guide:
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