Probiotic and prebiotic supplements are the third-most-used “natural product” in the United States, according to the National Institutes of Health.

Surrounding probiotics are numerous health claims about what these “good bacteria” can do for the average person’s health and wellness.

They’re a common topic among my patients, many of whom have digestive issues and diseases such as irritable bowel syndrome, Crohn’s disease and ulcerative colitis.

Let’s sort through how they work:

What’s the difference between probiotics and prebiotics?

Prebiotics are non-digestible, short-chain carbohydrates that promote the growth of some groups of beneficial bacteria. They serve as the fuel for probiotics.

Foods containing high amounts of prebiotics include fruits and vegetables such as onions, garlic, artichokes, asparagus, berries and bananas, as well as whole-grain foods, including oats and barley.

Probiotics are live microorganisms, such as bacteria and yeast, that may support healthy digestive and immune systems. They’re found in fermented foods, such as: 

• Buttermilk
• Cheeses containing live and active cultures, such as some Gouda, mozzarella, cheddar and cottage cheese
• Kefir
• Kimchi
• Kombucha
• Miso
• Pickles
• Sauerkraut
• Tempeh
• Yogurt

How much do we know about probiotics? What do probiotics do for us?

The benefits of probiotics originally were touted in the early 1900s by Russian scientist Elie Metchnikoff, who studied microbes in yogurt and sour milk. He linked Bulgarians’ sour-milk diets to their healthy, long lives.

In the last hundred years, we’ve learned through clinical studies that probiotics may be able to help ward off disease-causing microorganisms, aid digestion, help us absorb nutrients, improve immune function and reduce symptoms of irritable bowel syndrome, including constipation and diarrhea.

Some studies suggest probiotics can even help keep allergies and eczema in check, prevent vaginal and urinary tract infections, prevent pouchitis, and maintain remission of ulcerative colitis They may also improve health outcomes for those with major chronic illnesses, such as type 2 diabetes.

Among the myriad strains of probiotics, there’s no known strain that acts as a cure-all or single preventive aid for these conditions. But the still-limited research has shown that a rich, internal microbiome – one that includes a variety of probiotics and nutrients – can support a healthy digestive system and a well-functioning immune system.

When should I take a probiotic supplement?

Probiotics may help prevent “traveler’s diarrhea.” So, if you’re headed overseas, you could take a multi-strain probiotic supplement for about a week before travel and continue taking it throughout your trip.

Studies have also suggested that if you take a probiotic while taking an antibiotic, you’re less likely to get diarrhea caused by the antibiotic knocking your microbiome off-balance. Alternatively, you can also eat two or three servings of probiotic-rich foods throughout the day.

It’s recommended that you take the antibiotic and the probiotic supplement at different times of the day to keep the antibiotic from killing the supplement’s beneficial microorganisms right away. Taking the probiotic supplement for a month after your course of antibiotics may continue to help repopulate your gut with healthy bacteria.

Because probiotic supplements aren’t for everyone, you should check with your health care provider first to see if a supplement would likely benefit you.

When should I avoid probiotics?

Sick infants, anyone with a compromised immune system – either from illness or medication – people with short bowel syndrome, bacterial overgrowth and those whose health is weakened from a recent surgery should avoid probiotic supplements.

Because you could create a microbiome imbalance in your gut and because long-term effects haven’t been studied enough, unless recommended by your health care provider, it’s not advisable to take a probiotic supplement for more than six months.

Signs that a particular probiotic may not be right for you include bloating, constipation, diarrhea and irritability.

Eating two to three daily servings of probiotic-rich foods is currently the best way to maintain diverse, friendly bacteria in your gut.

What should I look for in a probiotic supplement?

Dietary supplements, unlike medication, aren’t regulated by the U.S. Food and Drug Administration. Therefore, it’s hard to know if the supplement bottle you’re buying lives up to its claims or even includes the ingredients listed.

Some independent companies function as supplement testers. Supplements with a seal of approval from the United States Pharmacopeial Convention, for example, are more likely to live up to claims of purity and potency.

Your gut is diverse, so your probiotic should be, too. For overall gastrointestinal health, look for a multi-strain probiotic with 30 to 50 billion colony-forming units (CFUs) and take it on an empty stomach once or twice a day. 

Some strains of probiotics need to be refrigerated. For those types, avoid ordering supplements from the internet, as refrigeration may not be maintained throughout storage or shipping.

The bottom line

We’re still gathering research on probiotics’ benefits for our health.

One day, when we know more about the individual strains and how they can help with certain health conditions, perhaps you could pull up to McDonald’s and order a burger that contains the specific probiotic strain that your body needs.

For now, while we’re a long way from determining the particulars surrounding those individual strains, the research shows that probiotics are low-risk and likely beneficial, especially when consumed through a nutrient-rich diet.

Alexandra Oumanets is a certified family nurse practitioner at The Ohio State University Wexner Medical Center who specializes in treating gastrointestinal diseases.