As the best-selling author of Happy Gut and a medical doctor who specializes in gut health and once suffered from IBS (irritable bowel syndrome), I have experienced for myself, as well as see on a daily basis, how a disrupted gut flora opens the door for unfriendly microbes to step in and take over, creating all sorts of pandemonium that causes patients to gain weight, feel sick and tired, and become more disease-prone.


To avoid those and other problems, I strongly recommend buying a professional brand from a reputable health care professional or other vendor who stands by their products and undergoes third-party testing. Some of these professional brands have created advanced technology that preserves a probiotic supplement’s survival on the shelf and in your gut.
As a world-renowned neurologist and nutritionist, Dr. David Perlmutter has become somewhat of a household name when it comes to the linkage between what we eat and how we feel. He is known as “The Empowering Neurologist” and has been featured on the Doctor Oz Show, CNN, and NPR as well as in prominent publications like The New York Times, Forbes, Time Magazine, and the Wall Street Journal. If that wasn’t enough to spark your interest, Dr. Perlmutter is also the award-winning author of the Grain Brain Whole Life Plan, Brain Maker, and Grain Brain, all of which have become international bestsellers.
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.
Sugar is so easily accessible in Westernized cultures that it is easy to overindulge in it. But why do you crave it? There are several reasons. One, sugar usually means sucrose, which is composed of glucose and fructose. Glucose is the sugar in your blood, so consumption of sugar results in a temporary boost of energy. However, that blood-sugar spike causes insulin to be released to usher the sugar into cells for energy or fat storage, and shortly afterward your blood sugar drops. So then you feel a slump and reach for something to bring your blood sugar back up: more sugar.
The research also showed that while probiotics colonised the gastrointestinal tract of some people, the gut microbiome of others just expelled them. There was no way of telling from their stool sample which category people fell into. “Some people accept probiotics in their gut, while others just pass them from one end to the other,” says Elinav. They found that the probiotic colonisation patterns were highly dependent on the individual. That tells us that the concept that everyone can benefit from a universal probiotic bought from the supermarket is empirically wrong, he says.
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.
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?

Fermenting a cucumber into a pickle amps up a cuke's powers, infusing the crunchy veggie with probiotics. Like sauerkraut, not all pickles offer the good bacteria, though. Look for those made with brine (salt and water) rather than vinegar. These brands will list "live cultures" on the label (like Bubbies). You can also use water, salt, and spices to naturally culture pickles and other veggies—like beets, green beans, and carrots—at home with delicious results. One warning: remember that pickles are salty—one dill can easily offer up more than 10% of your sodium needs in a day.


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.
One review of probiotics benefits for necrotizing enterocolitis was bold enough to say, “The results confirm the significant benefits of probiotic supplements in reducing death and disease in preterm neonates. The … evidence indicate that additional placebo-controlled trials are unnecessary if a suitable probiotic product is available.” Regarding sepsis in developing countries (where it is overwhelmingly more common), a 2017 randomized, controlled trial claims that a large number of these cases “could be effectively prevented” if mothers are given a synbiotic (probiotic and prebiotic together) that contains the probiotic strain L. plantarum.
But what if investigators could design probiotics to treat specific individuals? Many researchers think personalized probiotics are the most promising path forward for patients with compromised gut microbiomes. Last year Jens Walter of the University of Alberta and his colleagues published a study that gives a glimpse of this potential future. The researchers decided to see what it would take to get the bacteria in a probiotic to successfully colonize the intestines of 23 volunteers. They chose a particular strain of Bifidobacterium longum that earlier studies had indicated could survive in the human intestine. In the study, the volunteers consumed either a drink containing 10 billion live B. longum bacteria or a placebo in the form of a glucose-based food additive (maltodextrin) each day for two weeks. Periodic fecal samples revealed higher than typical levels of B. longum in participants who did not consume the placebo.
This Korean staple relies on lactic acid fermentation (also called lacto-fermentation) to turn cabbage or other vegetables into a spicy, pungent side dish that's packed with vitamin C. Order it at Korean restaurants or buy it in the refrigerated section of your grocery store (King's Kimchi is widely available at Walmart). For some guidance on making your own, turn to The Art of Fermentation ($23; amazon.com). Then, use it to spike veggie-laden rice bowls, top on soup, or serve alongside meat. 

Following a healthy and active lifestyle and eating a balanced diet are the best ways to foster a bountiful gut flora. Taking care of your gut flora can help with things like irritable bowel syndrome and chronic constipation, among other things. Even if you’re not sold on pursuing probiotics for your allergies, they’re good to consider if you’re experiencing any gastrointestinal issues.
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