. Credit: Getty Images

Our bodies thrive on bacteria—at least the good kind that help with digestion, energy levels, healthier skin and a stronger immune system.

Probiotics help keep a healthy balance of good bacteria in the gut. (Prebiotics, on the other hand, act as food for those good bacteria, helping to control the balance of the intestinal microbiome.)

But not all probiotics are the same.

“They all have different mixtures and numbers of bacteria,” says Dr. William Stern, a gastroenterologist at Rockville-based Capital Digestive Care. And while probiotics are measured in colony forming units, or CFUs, which estimate the number of viable bacteria in a sample, that figure isn’t always clinically important, Stern notes. “It’s not so much the number of bacteria but the type,” he says.

For example, beneficial bacteria often found in yogurt include Lactobacillus acidophilus, Lactobacillus casei and Bifidus, while sauerkraut typically has four species of useful lactic acid bacteria with similarly scientific names.

Probiotics also come in capsules, powders, liquids and other forms. When sold as dietary supplements, they don’t require FDA approval, so be wary—especially given that many commercial products claiming to contain probiotics have not been examined in research studies, according to the National Institutes of Health.


Stern points out that while there are a few conflicting studies, reputable research has shown probiotics to help with constipation, yeast infections, lactose intolerance, eczema and diarrhea caused by antibiotics and Clostridioides difficile (C. diff) infections, among other things. Research also suggests that probiotics occurring naturally in foods, as part of a healthy diet, may be preferable to supplements containing them, Stern says.

“In general, we believe they’re very safe,” he says. “But I’d be a little more cautious in very young people and in patients who are immunocompromised. In those situations, speak to a doctor before using.”

The field of probiotics overall has advanced considerably in recent years, spurred by global interest in the human microbiome, a term for the microorganisms in the body.


Scientists studying the microbiome are trying to home in on the role probiotics may be able to play in treating infectious diseases, inflammatory diseases and psychiatric disorders.

“That’s where a lot of the scientific [interest] is,” Stern says. “I think the layman’s interest is just in saying, ‘Putting good bacteria into my gut may make me feel better.’ ”

Foods that are good for gut health


  • Fermented cheeses 
  • Kefir
  • Kimchi
  • Kombucha
  • Miso soup
  • Olives
  • Pickled vegetables
  • Sauerkraut
  • Tempeh
  • Yogurt


  • Artichokes
  • Asparagus
  • Bananas
  • Berries
  • Garlic
  • Greens
  • Legumes
  • Oats
  • Onions
  • Peas

This story appears in the July/August issue of Bethesda Magazine.


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