Have you considered any
of these "probiotic" products?

Probiotics can be loosely defined as “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host.” Essentially it is beneficial bacteria delivered in food or supplement form.

The belief is that modern factory processing kills many of the naturally occurring microbes in food, so companies add “good bacteria” back in. It started with yogurt and dietary supplements, then the market exploded. Now you can find probiotics in pizza, cereals, muffins and even chocolate.

The theory has also evolved. Early on it was “good bacteria crowd out the bad.” Today, researchers are more precise. Certain strains in specific doses can, in some situations, reduce harmful inflammation, ease some types of diarrhea, or help prevent particular gut problems. The key phrase there is “certain strains in specific doses.” Not “any product with the word probiotic on the label.”

There are still two big problems.

First, most of the bold health claims on commercial probiotic foods and supplements are not backed by strong trials on those exact products. There is now a growing body of research on probiotics, but the benefits are very strain‑specific and condition‑specific. That means a result from “Product X, Strain Y, at Dose Z, for Condition A” does not automatically apply to “any probiotic in any food for any purpose.”

Second, probiotics are regulated more like foods and supplements than like drugs. That means no requirement to prove clinical benefit before a product is sold. Labels may list a species, or even a strain, but they rarely come with robust evidence that this exact formulation at this dose has been shown to do what the marketing department promises. Where science is narrow and nuanced, marketing often rushes in and paints with a very broad brush.

Many articles about probiotics are written as testimonials. “Here is what probiotics did for me, therefore they will do exactly the same for you.” Bodies and microbiomes are individual. What helps one person might do nothing for another or, in rare cases, make things worse. What we need and increasingly have are controlled clinical trials on specific strains in defined patient groups, with clear outcomes and doses. Until the science catches up with the hype, here are a few areas where claims routinely outrun the evidence.

Claim #1 – Probiotics melt fat and cause effortless weight loss.

You have probably seen versions of this promise: “This probiotic yogurt/shot/pill changes how you absorb calories so the pounds fall off.” Reality is more complicated.

Over the last decade, researchers have run dozens of randomized trials looking at probiotics and body weight, body fat and waist size. The picture that emerges looks like this:

Some specific probiotic formulations, often capsules or fermented dairy containing selected Lactobacillus and Bifidobacterium strains in high doses, can produce small but measurable reductions in weight, body fat and waist circumference in people with overweight or obesity when taken for several weeks to months.

Many other trials show no significant effect at all.

When benefits appear, they are modest. We are talking about a few pounds over months, not dramatic transformations.

The results depend on the strain, the combination of strains, the dose, how long people take them, and the person’s starting health and lifestyle.

In other words, there is a big difference between “some carefully studied probiotic formulations can modestly help weight management in some people” and “any food with probiotics will burn fat.” Probiotic-spiked yogurt that is loaded with sugar can easily add more calories than any plausible metabolic tweak will remove. A few extra bites of dessert will wipe out the effect of even the most promising probiotic supplement.

If you want to manage weight, the pillars are still the same: what you eat overall, how much you eat, how active you are, how you sleep and how you manage stress. Probiotics are, at best, minor supporting players. They are not a license to ignore the basics and they are not a substitute for medical obesity treatments when those are indicated.

Claim #2 – Probiotics supercharge your immune system.

Another popular idea is that probiotics “boost immunity” so you do not get sick. Early studies found that some probiotic strains could nudge certain immune cells, like T-cells, in lab tests or in small human trials. The leap came when marketers turned “changes some immune markers” into “protects you from the flu” or “wards off infections.”

Here is the more sober version.

There is some evidence that certain probiotic strains can reduce the risk of very specific infections in very specific settings, especially in the gut. For example, some formulations may help reduce the risk of antibiotic-associated Clostridioides difficile infection in hospitalized or high-risk patients when used under medical supervision. There is also evidence that certain probiotic mixes can help prevent a severe gut complication called necrotizing enterocolitis in preterm, low-birth-weight infants. Those are narrow, high-risk situations guided by specialists, not general “immune boosting” for healthy adults.

For the average person walking into a grocery store, there is no strong evidence that popping generic probiotic supplements or eating probiotic-fortified snack foods will prevent colds, stop the flu, or make vaccines unnecessary. If you want immune protection against influenza, you still need a flu shot, not a yogurt drink.

Claim #3 – Probiotics protect against cancer.

Cancer-related claims are even more speculative. You might see references to large observational studies of people who eat more yogurt or fermented foods and have slightly different rates of certain cancers. The problem is that these studies cannot separate the effect of probiotics from everything else that tends to travel with them.

People who eat yogurt regularly may also eat more fruit, vegetables and fiber, exercise more, smoke less and have better access to health care. People who eat lots of salt-preserved or heavily pickled foods may be exposed to other compounds that increase risk. These dietary patterns and lifestyle factors make it very hard to pin changes in cancer risk on the presence or absence of probiotic bacteria in a single food.

Right now, there are no large, long-term randomized human trials showing that taking a commercial probiotic product prevents cancer or reduces cancer recurrence. On the other side, there is no convincing evidence that normal probiotic use causes cancer in humans either.

Most of the interesting anti-cancer work is on plant-based dietary patterns and specific compounds from vegetables, especially cruciferous vegetables like broccoli and cabbage, rather than on bottled probiotics.

Be very cautious about any cancer claims made for probiotic products. Focus your anti-cancer efforts on things we know matter, such as not smoking, limiting alcohol, maintaining a healthy weight, exercising regularly and eating a plant-rich diet with plenty of vegetables, fruits, whole grains and legumes.

Researchers thought multivitamins were beneficial for decades, until large-scale studies proved them wrong. Several vitamins turned out to be dangerous when taken in pill form. We urge caution with probiotics as well.

What about digestive health?

This is the area where probiotics are often sold the hardest. “Reset your gut.” “Balance your microbiome.” “Fix IBS naturally.” It's also an area where the details really matter.

Professional groups have now reviewed the totality of evidence. Their conclusions are far more conservative than the advertising you see online and on store shelves. Here's the short version:

For Crohn’s disease, ulcerative colitis and irritable bowel syndrome (IBS), the evidence for probiotics is weak and inconsistent. Guidelines do not recommend routine probiotic use for these conditions. If you have one of these diagnoses, talk to your gastroenterologist before taking any supplement that claims to “heal your gut.”

For acute infectious diarrhea in children, large studies do not support probiotic use as a treatment. Some guidelines specifically recommend against it for that purpose.

For pouchitis (a complication that can occur after surgery for ulcerative colitis), some specific probiotic formulations can help maintain remission. This is specialist territory, with very particular products and dosing.

In other words, there are a few niche digestive situations where the right probiotic can be helpful, but they are the exception. They are not over-the-counter “fix everything” remedies for general digestive discomfort.

To make sure you're getting what's appropriate, ask your doctor for specific species and strains of probiotics that are proven to help with the condition you have. Only buy products with the strain your doctor recommends.

Finally, check the package expiration date. Probiotics are living organisms and if you don't use them in time, their effectiveness may be diminished or rendered worthless.

---

UPDATE 10/4/2020

According to the Amerian Gastroenterological Association (AGA), probiotics aren't the wonder supplements companies have market them as. Here's what the AGA says:

Two important conclusions that clinicians can take away. First, the Institute found moderate evidence that probiotics do not reduce the duration or severity of diarrhea in children with acute infectious gastroenteritis. Ironically, diarrhea in children was one of the original indications for potential therapy using probiotics more than 100 years ago. However, only a minority of the studies tested strains of Bifidobacteria suggested by Tissier.

In contrast, there was moderate to high level of evidence that probiotics containing different strains of Lactobacillus and Bifidobacterium genera were beneficial in preventing necrotizing enterocolitis, the most frequent and devastating gastrointestinal disease in preterm, low birthweight newborns and mitigating its complications.

it is imperative that health care providers not fall prey to seductive advertising and meaningless structure/function claims.

---

UPDATE 2/23/2021

This information is from a press release issued on June 9, 2020 by the American Gastroenterological Association. However, we were only made aware of it on 2/23/2021 and so that's the date this page was updated. The text below is taken directly from that press release.

AGA does not recommend the use of probiotics for most digestive conditions

New AGA guideline finds that evidence to support use of probiotics to treat digestive diseases is greatly lacking, identifying only three clinical scenarios where current data suggests that probiotics may benefit patients.

There was insufficient evidence to recommend probiotics for treatment of Crohn’s disease, ulcerative colitis, irritable bowel syndrome (IBS) and C. difficile infection. For acute infectious gastroenteritis in children, AGA recommends against the use of probiotics.

“Patients taking probiotics for Crohn’s, ulcerative colitis or IBS should consider stopping,” says guideline panel chair Grace L. Su from University of Michigan, Ann Arbor. “The supplements can be costly and there isn’t enough evidence to prove a benefit or confirm lack of harm. Talk with your doctor.”

The guideline supports use of certain probiotic formulations in three settings: for the prevention of Clostridioides difficile (C. difficile) infection in adults and children taking antibiotics, for the prevention of necrotizing enterocolitis in preterm, low birthweight infants, and for the management of pouchitis, a complication of inflammatory bowel disease.

Call for a FREE Consultation (305) 296-3434
CAUTION: Check with your doctor before
beginning any diet or exercise program.

1/27/2013
Updated 12/4/2015
Updated 7/1/2020
Updated 10/4/2020
Updated 11/14/2020
Updated 2/23/2021
Full Article Update 3/13/2026