Should Everyone Be Taking Probiotics?

At the beginning of the 20th century, Russian scientist Elie Metchnikoff determined that a diet of fermented milk products resulted in a long, healthy life for Bulgarian peasants [source: Sanders]. Probiotics, meaning "for life" in Greek, became the term for the bacteria that was found in those fermented products. The bacteria have a very technical definition provided by the World Health Organization; they are "live microorganisms which, when administered in adequate amounts, confer a health benefit on the host" [source: Brody].

The two main types of bacteria considered to be probiotics include strains from the Lactobacillus and Bifidobacterium genera (other genera, such as Escherichia, Enterococcus and Saccharomyces have also been designated probiotics, but to a lesser and more questionable extent). Lactobacillus and Bifidobacterium are made up of different strains, each of which has a different health function. To truly understand the potential benefit to your body, you have to research the difference between Lactobacillus acidophilus and Lactobacillus rhamnosus.

In general, though, scientists believe that probiotics work by repopulating the gut with good bacteria, which can be eliminated along with bad bacteria during a course of antibiotics. Additionally, probiotics are believed to have the power to fight off pathogens and toxins, as well as strengthen the gut fortresses that will eventually have to do battle with the same.

How does this hypothesis of how probiotics work translate into a health benefit? In some cases, the evidence is a bit shaky. Right now, the clearest benefit of probiotics, backed up by scientific study, comes in the field of gastrointestinal conditions, such as antibiotic-associated diarrhea, acute infectious diarrhea (such as traveler's diarrhea) and irritable bowel syndrome. A meta-analysis of 19 studies showed that probiotics reduced the risk of developing diarrhea associated with antibiotics by 52 percent, and cut the risk and duration of infectious diarrhea as well. Probiotics are successful in treating diarrhea caused by rotavirus in children and ulcerative colitis. However, probiotics weren't shown to be effective for acute pancreatitis and Crohn's disease, according to the American Family Physician in a 2017 study.

Another study, published in 2018 in the journal Cell, suggested some people may be resistant to supplemented probiotic bacteria, and therefore get no benefit from it at all. The researchers also investigated whether probiotics can help the gut microbiome bounce back after a round of antibiotics, and they found that, though probiotics might have helped with diarrhea related to the antibiotic, they seem to have delayed the reconstitution of gut bacteria.

To actually create some effect in your body, probiotics need first-class travel on the journey that is your digestive system. They have to be encased in something strong enough to survive the acid-filled stomach, but not so strong that they don't dissolve in the intestines, where they do their best work. The bacteria can be damaged by air and moisture, so extreme care has to be taken in creating food products with probiotics. These items may not have a particularly long shelf life.

Further complicating the problem is the fact that in some instances, scientists aren't sure of the exact dosage of bacteria that will confer health benefits, and because we're dealing with live bacteria here, it's hard to know how many you add to a product end up remaining viable in each serving. Additionally, the only way to determine how many probiotics actually make it through the gastrointestinal tract is to examine the fecal matter of those who consumed the probiotics, a research study that certainly doesn't sound appealing. And even that number would be circumspect, because while the feces would reveal how many bacteria made it down the tract, it wouldn't reveal how many probiotics actually did the job they were supposed to do in the gut.

Not that you'll find this information on the package; critics of probiotics food worry that labels don't always indicate which bacteria are present or how much of the ingredient is there. Some manufacturers may just slap the probiotic label on an item that doesn't have enough bacteria to make any sort of difference. For now, consumers won't get any help from the U.S. Food and Drug Administration (FDA), either. While the FDA has strict rules about marketing items that claim to cure disease, they don't have restrictions for items that talk in fairly general terms about bodily health, which is why you'll see Activia marketing its asset as something that "may help reduce the frequency of minor digestive discomfort," as opposed to promising anything specific.

Such vague claims may lead a consumer to believe that probiotics should be added to a regular, everyday diet. But are there health benefits for those that are already healthy? There are few studies on how probiotics affect the immune system of a healthy person [source: Senok et al.]. The effects of probiotics are temporary, though, which means you have to keep consuming them, and if you're going to add a daily step to your routine, it may be more advantageous to consider measures with proven benefits, such as diet and exercise. Already nutritionists worry that consumers will add these products to their diet, rather than substituting them for something else, potentially leading to an excess of calories.

But what if you just love the taste of Activia yogurt, or you're already devoted to your probiotic supplement? Though there may be no definitive proof of the health benefits yet, there's also little evidence that you're doing harm to your body, either. Flatulence and abdominal discomfort are the only real side effects that have been reported [sources: Kligher and Cohrssen]. However, one important exception exists: In a study group of nearly 300 patients with pancreatitis, the patients who received probiotics rather than a placebo were more likely to require intensive care and surgical intervention, even though the severity of illness was roughly the same before the study. In the group taking probiotics, 24 people died, more than twice the number of deaths in the placebo group [source: Bakalar].

"Different probiotic strains have different effects, so it's important to look for a probiotic supplement that contains the strains of bacteria most likely to match your condition," says Irwin. "The dose of bacteria, called colony forming units, or CFU — is also important and should be high enough to meet benefits observed in clinical trials. The short answer here is if someone is looking for a probiotic to take, go for something that provides the greatest diversity in bacterial strains and the highest CFU."

Irwin also suggests getting advice from your doctor or dietician for the strains that might be right for you and buying probiotic brands that are reputable and have committed to transparency in scientific research. However, this is more easily said than done. A study published in the Sept. 17, 2018 issue of JAMA Internal Medicine pointed out there is very little government oversight of factories that manufacture probiotics, and the FDA found 50 percent of the 650 factories that manufacture probiotic supplements in the U.S. were cited for violations, most having to do with the product not living up to what was promised on the label. The study also says probiotics may lead to infections in people with immune deficiencies.

Of course, more study is needed to understand just how helpful probiotics are to our overall health, and it's important not to give them more credit than they're due.

"It's unlikely probiotic supplements are dangerous, but I don't think they're a magic bullet," says Irwin. "Healthy people are likely to get more benefit from having a diet rich in vegetables, fruit and whole grains. On the other hand, if someone has a poor diet and doesn't exercise regularly, their digestive bacteria may benefit from probiotic supplements, but they'll likely need to keep taking them to get lasting effects."

Learn more about probiotics in "The Probiotics Revolution: The Definitive Guide to Safe, Natural Health Solutions Using Probiotic and Prebiotic Foods and Supplements" by Gary B. Huffnagle. HowStuffWorks picks related titles based on books we think you'll like. Should you choose to buy one, we'll receive a portion of the sale.