There are four significant takeaways from this study: (1) murine gut mucosal probiotic colonization is only mildly enhanced by antibiotics, (2) Human gut mucosal probiotic colonization is significantly enhanced by antibiotics, (3) After taking antibiotics, probiotics delay gut microbiome and transcriptome reconstitution in mice and humans, (4) Autologous fecal microbiome transplant (aFMT) restores mucosal microbiome and gut transcriptome reconstitution. 
Because there's a huge variety of probiotic products available on the market, many people struggle to find the right one for them. "There are many different strains of bacteria in different combinations within different probiotic supplements," explains Brooke Scheller, a clinical and functional nutritionist. "For example, a probiotic may contain a single strain of bacteria or many. It may also contain other vitamins, minerals, or other ingredients that may tout health benefits," she says. There are many different dosages, delivery systems (powder, tablets, capsules), and formulations (refrigerated vs. shelf-stable), and some probiotics also contain prebiotics, which basically act as fertilizer for the probiotics. (Related: Why Your Probiotic Needs a Prebiotic Partner)

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.

Though most probiotics are formulated for both men and women, Garden of Life’s Raw Probiotics for Women is manufactured with women in mind. This probiotic has a whopping 85 billion live cultures and 32 different probiotic strains to target everything from gut and vaginal health to thyroid and nutrient absorption. It contains two popular probiotics, Lactobacillus acidophilus and Bifidobacterium, and is gluten-free, soy-free, and made without fillers or binder—which is great for anyone with dietary restrictions or allergies. Each container comes with 90 capsules; the recommended dose is three capsules per day.
Third-party testing: Lastly, it's important to remember that probiotics are an unregulated supplement. "Find out whether there is third-party data verifying the potency, purity, and effectiveness of the product," suggests Dena Norton, a registered dietitian and holistic nutrition coach. "Remember that dietary supplements aren't regulated, so you can't necessarily just trust the claims on the label." Check out AEProbio, a site that has compiled research on specific brands of probiotics available in the U.S., recommends Scarlata, and an NSF seal is always a good marker to look for.

In a separate study involving 21 healthy volunteers, also published today in Cell, the same group of researchers found that taking probiotics after treatment with broad spectrum antibiotics may actually delay the return of people's normal gut microbiome. This goes against the idea that probiotics can help "repopulate" people's gut bacteria after antibiotics wipe them out.
These are live microorganisms that will not provide the promised benefits if they don't remain alive. The manufacturer and consumer must pay close attention to the conditions of storage at which the particular microorganism will survive and the end of their shelf life. The potency will indicate the number of viable bacteria per dose, and the purity has to do with presence of contaminating or ineffective bacteria.

Twenty-one volunteers were given a course of antibiotics and then split into three groups. The first group were left to let the microbiome recover without any interventions, the second group were given probiotics and the third were given a fecal transplant of their own gut bacteria which was collected before the antibiotic treatment. The study found that the probiotics easily colonized the gut of the second group, but worryingly, rather than aiding the return of the normal gut microbiome, the probiotics actually significantly delayed it for months compared to both the group that had no intervention and the people who received a transplant of their own gut bacteria.
When reading a probiotic label, it should reveal the genus, species and strain of the probiotic. The product (usually in capsules or probiotics pills) should also give you the colony forming units (CFUs) at the time of manufacturing. Also, the majority of probiotics can die under heat, so knowing the company had proper storing and cooling of the facility is also important.

Because there's a huge variety of probiotic products available on the market, many people struggle to find the right one for them. "There are many different strains of bacteria in different combinations within different probiotic supplements," explains Brooke Scheller, a clinical and functional nutritionist. "For example, a probiotic may contain a single strain of bacteria or many. It may also contain other vitamins, minerals, or other ingredients that may tout health benefits," she says. There are many different dosages, delivery systems (powder, tablets, capsules), and formulations (refrigerated vs. shelf-stable), and some probiotics also contain prebiotics, which basically act as fertilizer for the probiotics. (Related: Why Your Probiotic Needs a Prebiotic Partner)
The good news keeps stacking up for probiotics, the good-for-you bacteria that keep your GI system functioning in tip-top shape. "Research is finding that a healthy microbiome may play a role in reducing inflammation, a risk factor involved in illnesses ranging from colds to cancer, heart disease, arthritis, and cognitive decline," says Katherine Tallmadge, RD, author of Diet Simple. In addition, the bacteria may help burn body fat and reduce insulin resistance, she says. So to stay slim and healthy, consider adding more probiotic foods to your diet. Start with these truly yummy 13.
However, these naturally-occurring bacteria can easily become imbalanced causing a variety of symptoms from stomach upset to feminine health problems. Probiotics can help get things back on track. Taken in supplement form, probiotics are either live or dormant strains of the same bacteria that your body wants and needs to stay healthy. Over time, these supplements can restore your body’s natural bacteria and prevent some of the most common stomach symptoms, yeast infections, and even urinary tract infections.

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.

The U.S. Clinical Guide to Probiotic Products1, Canadian Guide to Probiotic Supplements2 and the WGO Global Guidelines for Probiotics and Prebiotics3 provide suggested effective amounts of specific strains for treating certain health conditions, such as constipation or IBS. All 37 products listed the species of bacteria they contained, but only 14 listed amounts of individual strains. We found that 9 of those 14 products provided beneficial bacteria at effective levels. The Center for Responsible Nutrition recommends4 the industry move toward specifying strains as a best-practice because whether a product works and for what purpose depends on its strains.
Most bacteria are included through the fermentation process. Fermentation helps extend the shelf life of perishable foods. It is a slow decomposition process of organic substances induced by microorganisms or enzymes that essentially convert carbohydrates to alcohols or organic acids. The lactic acid supplies the bacteria that then add the health benefits to the food. You can purchase foods that are fermented or ferment them yourself.
"When certain types of probiotics are placed in contact with skin cells, they calm the parts of the cells that may want to react to the presence of bad bacteria that they see as a threat. These healthy signals produced by the probiotics stop the skin cells from sending 'attack' messages to the immune system that result in flares of acne or rosacea."

Because chronic inflammation is at the root of many diseases and health conditions, the fact that probiotics exert this effect in the gut, where 80 percent of the immune system lies, is crucial. The immune-boosting benefits of probiotics seem to be particularly helpful for the quality of life of seniors. Currently, research is underway to test whether probiotics can “reduce inflammation and improve gut immune health in HIV-positive individuals” who haven’t yet undergone treatment.
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.
Billions Of CFU – One of the first things you will notice on a bottle of probiotics is the phrase “X Billion CFU.” Probiotics vary in the number of billions of cultures they pack in each capsule, but the lingo always stays the same. CFU stands for Colony Forming Units, so if the bottle reads 5 Billion CFU, it means that there are 5 Billion Colony Forming Units per capsule. The higher the number, the more flora contained in each pill.

A 2014 review by Cochrane—an independent network of experts who serve as rigorous arbiters of medical research—found that probiotics may be particularly useful in a hospital's neonatal intensive care unit. The addition of beneficial bacteria to a nutritional regimen seems to significantly reduce the likelihood of developing necrotizing enterocolitis, which is a devastating, poorly understood and often fatal gut disease that primarily afflicts preterm infants—especially the smallest and most premature among them. Researchers think that many cases of the disease begin with an opportunistic bacterial infection in the not yet fully developed intestine of an infant. As the illness progresses, gut tissue becomes increasingly inflamed and often starts to die, which can, in turn, rupture the intestine and flood the abdominal cavity with pathogenic microbes that proliferate to dangerous levels. Researchers estimate that 12 percent of preterm infants weighing less than 3.3 pounds will develop necrotizing enterocolitis and that 30 percent of them will not survive. Standard treatment involves a combination of antibiotics, feeding via intravenous tubes, and surgery to remove diseased and dead tissue. Probiotics probably prevent the disorder by boosting the numbers of beneficial bacteria, which may deter the harmful ones.
Immunity and colds/flu.There’s a close connection between the bacteria in your colon and the immune system. Several studies, including one in 2012 in the British Journal of Nutrition, have found that certain probiotic strains boost measures of immune response—but whether this translates into any clinical benefits is uncertain. Studies have been inconsistent, for example, as to whether probiotics will actually curb colds and other upper respiratory infections. In 2014 a review in the British Journal of Nutrition, which looked at 20 clinical trials, linked probiotics to shorter duration of colds, but not necessarily reduced incidence or severity. Similarly, a 2015 Cochrane review of 12 clinical trials concluded that certain probiotics may help prevent or shorten such infections, though the quality of the studies was poor. 

The U.S. Clinical Guide to Probiotic Products1, Canadian Guide to Probiotic Supplements2 and the WGO Global Guidelines for Probiotics and Prebiotics3 provide suggested effective amounts of specific strains for treating certain health conditions, such as constipation or IBS. All 37 products listed the species of bacteria they contained, but only 14 listed amounts of individual strains. We found that 9 of those 14 products provided beneficial bacteria at effective levels. The Center for Responsible Nutrition recommends4 the industry move toward specifying strains as a best-practice because whether a product works and for what purpose depends on its strains.

Billions Of CFU – One of the first things you will notice on a bottle of probiotics is the phrase “X Billion CFU.” Probiotics vary in the number of billions of cultures they pack in each capsule, but the lingo always stays the same. CFU stands for Colony Forming Units, so if the bottle reads 5 Billion CFU, it means that there are 5 Billion Colony Forming Units per capsule. The higher the number, the more flora contained in each pill.


It’s important to note that there are different types of strains of probiotics. The probiotics benefits of one probiotic strain may be completely different from the health benefits seen from another probiotic. If you want to use probiotics to address a specific health concern, it’s vital to select the right probiotic for the right condition — or you can consume a wide range of probiotics in your food to be covered.
Then, study participants were divided into one group that consumed a standard probiotic strain available in commercial supplements and a control group that was given a placebo. After two months of treatment, the researchers found that some people were so-called “resisters” who expelled the gut microbiomes in probiotics; others were identified as “persisters” who successfully colonized the generic probiotic strains in their GI tracts.
More common than diarrhea is the opposite problem — constipation. In a search for studies on the benefits of probiotics in treating constipation, researchers found that probiotics slowed "gut transit time" by 12.4 hours, increases the number of weekly bowel movements by 1.3, and helped to soften stools, making them easier to pass. But the jury is still out on specific recommendations when it comes to the benefits of probiotics for constipation.
Probiotics may seem new to the food and supplement industry, but they have been with us from our first breath. During a delivery through the birth canal, a newborn picks up the bacteria Bacteroides, Bifidobacterium, Lactobacillus, and Escherichia coli from his/her mother. These good bacteria are not transmitted when a Cesarean section is performed and have been shown to be the reason why some infants born by C-section have allergies, less than optimal immune systems, and lower levels of gut microflora.
Other uses. Many other claims are made for probiotics—that they lower cholesterol, alleviate allergic skin conditions (like eczema), treat ulcers and urinary tract infections, improve vaginal health, reduce the risk of colon cancer, ease anxiety and depression, and ward off traveler’s diarrhea. Good evidence to support these claims is lacking. Research on probiotics for weight loss has yielded inconsistent results, and even studies with positive results have mostly found very small benefits, as was seen in an analysis of 15 clinical trials in Obesity Reviews in 2018.
Many women are prone to yeast infections during or after antibiotic use. If you are one of these unlucky few, try taking a probiotic like the vH Probiotics with Prebiotics and Cranberry immediately before taking your antibiotics. (You may want to check with your doctor first though). These cultures may help with stomach upset and can also prevent a dreaded yeast infection!
MegaFood is our only top pick that’s certified vegan, as well as being gluten free and dairy free, making it a good choice for any food-sensitive or vegan probiotic seeker. It has fewer of our wishlist “general health” strains than Vita Miracle, but it still contains five. This could be a go-to if you eat vegan, even if you’re not recovering post-antibiotic.
“If someone has disrupted his gut microbial balance, this is where a probiotic can be of benefit,” says Gail Cresci, PhD, RD, an intestinal microbe specialist with Cleveland Clinic’s Department of Gastroenterology, Hepatology and Nutrition. “But whether it’s really going to help and whether you’re taking the right one are the big questions out there.”
The second piece of research investigated whether patients should take probiotics to help the recovery of the natural gut bacteria after treatment with antibiotics. The evidence supporting this is not entirely clear and the FDA does not officially recommend it, but there are some reputable sources which discuss their use, such as this blog from Harvard Medical School. Research has suggested that up to 60% of healthcare professionals in the U.S. recommend taking probiotics, but is this justified and could it even be harmful?
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.

We have to give a nod to the most famous probiotic food: yogurt. Whether you love Greek or regular, low-fat or full-fat, look for the phrase "live active cultures" on the label. And although choosing a plain yogurt has less added sugar than the flavored kinds, Tallmadge gives you the okay to choose a fruit-infused flavor if that's the only way you'll eat it. Just be sure to aim for fewer than 15 grams of the sweet stuff per serving; sugar can feed the bad bugs in your gut.


Prebiotics and supplementary ingredients — For probiotic bacteria to grow, they also need prebiotics. High-quality probiotic supplements have both prebiotics and other ingredients designed to support digestion and immunity. Examples of these ingredients are (preferably fermented) flaxseed, chia seed, cañihua seed, astragalus, ashwagandha, hemp seed, pumpkin seed, milk thistle, peas, ginger, mung bean and turmeric.
But sometimes you need a little help from outside sources in order to secure those benefits, which is why a lot of experts recommend getting an extra hit of probiotics through food. Fermented options — think keffir, sauerkraut, and kimchi — are a great place to start, says the International Scientific Association of Probiotics and Prebiotics, as are these other surprising foods with probiotics.
To factor strain-specific benefits into our efficacy score, we referenced the information in these guides. Products were rewarded for containing strains on these lists. Additionally, measured levels of each strain were compared to what is thought to be effective based on these guides, and scores were scaled accordingly. In cases where products did not list strain-specific amounts, or their listed strains were not included in these guides, total measured CFUs were compared to a general effectiveness threshold of 1 billion CFUs cited by research published in the American Journal of Clinical Nutrition11. 
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