You Probably Shouldn't Be Taking That Probiotic, This Digestive Expert Says

As a dietitian who's worked in a gastroenterology practice for the better part of a decade, one of the most common questions my patients ask me is, "Should I take a probiotic supplement?" More often than not, my answer is "no." This surprises most people.

We're all increasingly bombarded by advertising and popular media messages suggesting that the answer to all that ails us resides in the gut. The relatively poor condition of the modern American gut microbiota -- that complex ecosystem of microscopic bacteria and yeasts that inhabits our intestines -- is being linked to all manner of health issues, from obesity and metabolic diseases to depression and autoimmune disease. The typical conclusion based on these compelling health headlines is that taking pills full of "probiotic" bacteria is an essential component to basic health maintenance -- no less important than brushing your teeth or washing your hands. But that conclusion is false.

For what it's worth, I'm hardly alone in this perspective. If you interview any researcher who studies the gut microbiota for a living, there's a very good chance that he or she doesn't take probiotic supplements, either. It's not because we don't believe that a diverse gut microbiota plays an essential role in human health on a whole host of dimensions. Rather, it's because we don't believe that the vast majority of commercially-available probiotic supplements make a significant difference in improving the diversity or health of the gut microbiota. We don't believe they typically improve actual human health outcomes, either.

How can it be that the gut is so vitally important to human health, and yet experts like me don't recommend routine supplementation with "good bacteria" meant to support a healthy gut ecosystem? Here are a few reasons:

1. Probiotics are non-specific.

The term "probiotic" is as general as the term "vitamin." If you ask me whether you should take a vitamin, I'd need to know which vitamin and for what. If you're vitamin D deficient, for example, then taking a vitamin B12 supplement won't help.

[See: Pharmacist-Recommended Vitamins and Supplements.]

"Probiotic" is a catchall term to describe any species or strain of bacteria or yeast that may have a demonstrated benefit for human health. Its relevance to you will depend on your own health status, and whether that particular species or strain at that particular dose has been shown in well-controlled studies to be helpful for people with similar health issues.

Most products being sold today, however, have not been scientifically tested for benefit, and among those that have demonstrated some promise, the effect has been pretty modest. So the chances you'll choose a product that helps you in a specific way are as slim as finding a needle in a haystack. And, if you're lucky enough to find that needle, don't expect it to morph into a silver bullet.

2. Current probiotic supplements are like a drop in the ocean.

Your gut is home to over 100 trillion microbes from over 1,000 different species. Commercial probiotics typically contain between one and two different species of microbes in doses of 1 million to 25 million colony-forming units. In other words, one typical supplement contains 0.0001 of 1 percent of the total microbial population of your gut. It also represents 0.1 percent of the species diversity of your gut's rich, diverse, complex ecosystem. In this way, probiotic pills really are like a drop in the ocean; unlikely to infiltrate and change this complex ecosystem in a measurable and sustained way. Indeed, studies have shown that supplemental probiotics do not have a significant or lasting effect on the composition of the gut microbiota as evidenced by comparisons of stool before and after probiotic supplement use.

3. We can't be sure what's even in that pill.

Most of the critters we host in our guts can't even be grown in a lab, meaning that many of the probiotics being sold are selected based on their convenience for the marketer, not their efficacy for the consumer. Moreover, many probiotics don't contain what they say they do; numerous researchers have audited commercially-sold probiotic supplements and compared their contents to what was being claimed on the label. In half or more of cases (depending on the study), they don't match up.

[See: Pharmacist-Recommended Stomach or GI Products.]

4. Supplemental probiotics can be harmful.

You may have heard that supplements including probiotics are worth taking as an "insurance policy" to cover your nutritional bases. But I don't buy this concept (which is based on the assumption that such pills are harmless) because I routinely see adverse side effects from both supplements in general and probiotics in particular. The most common problem I've seen among probiotic users is the development of small intestinal bacterial overgrowth (SIBO), particularly among people who have risk factors including slow gut motility, use of acid-reducing medications called proton-pump inhibitors or certain prior intestinal surgeries. Even though probiotics are "good bacteria," if they take up residence in the wrong neighborhood of your gut, they'll do more harm than good.

This doesn't mean that there aren't any good reasons to take a probiotic, though. There are a select few species or strains of probiotics that have been well-tested and shown to have a benefit for certain health conditions, including constipation, ulcerative colitis, high cholesterol and antibiotic-associated diarrhea. One yeast-based probiotic has been shown to protect against infection with C. difficile, which is associated with life-threatening diarrhea. It's not a bad idea, then, to temporarily use a probiotic supplement if you (or your child) must take a course of antibiotic medications -- and this is particularly so if you have a past history of C. difficile infection. But, as for routine supplementation of probiotics for healthy people seeking general "immunity" or well-being benefits? I wouldn't bother.

I believe that someday soon, researchers will develop a "version 2.0" probiotic supplement that will be worth taking. It will likely be a complementary cocktail of multiple strains of bacteria, and quite possibly, it may be individually tailored to a person based on his or her health status (or DNA or stool sample). Perhaps it will even take the form of a freeze-dried "poo pill" derived from supremely healthy master donors that will replace an entire microbial profile with a healthier one.

[See: 10 Weird Things That Can Make You Poop.]

But until that time, I believe that the best way to keep your gut's microscopic residents healthy and thriving is to consume a healthy, diverse, high-fiber diet that nourishes them, rather than trying to force interloping critters into their tightly-knit community.

Tamara Duker Freuman, MS, RD, CDN, is a registered dietitian whose NYC-based clinical practice specializes in digestive disorders, celiac Disease, and food intolerances. Her personal blog, www.tamaraduker.com, focuses on healthy eating and gluten-free living.