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Last Updated August 2022 | This article was created by editorial staff and reviewed by Beth Oller, MD

Probiotics are live, healthy microorganisms (bacteria and yeasts) found in your intestines. Probiotics are available in some foods and dietary supplements. Experts believe that these bacteria help you maintain a healthy digestive system by limiting the growth of “unhealthy” bacteria.

Path to improved wellness

The use of probiotics relates to digestive health. Although some probiotics have shown promise in research studies, strong scientific evidence to support specific uses of probiotics for health conditions is lacking. There is evidence that probiotics may be helpful in reducing or preventing diarrhea caused by infections and antibiotics. They also may improve symptoms of irritable bowel syndrome. As far as the U.S. Food and Drug Administration (FDA) is concerned, depending on a probiotic product’s intended use, it might be regulated as a dietary supplement, a food ingredient, or a drug. Probiotic products are not currently approved to treat a disease or health condition. 

Are probiotics safe?

Probiotics are similar to the “good” or “healthy” microorganisms already living in your digestive system. Medical studies have not shown probiotics to be harmful to healthy people. However, people who are very ill and people who have a weak immune system should be cautious about eating or drinking probiotic products or taking probiotic supplements.

Common side effects of consuming probiotics might include gas and bloating. While these are typically mild and temporary, more serious but rare side effects include allergic reactions to the probiotics or ingredients in the food or supplement.

Talk to your family doctor before you start taking probiotics or any type of dietary supplement. They can tell you if a probiotic supplement will affect any medical conditions you have. Be sure to tell your doctor if you are taking any prescriptions, over-the-counter (OTC) medicines, or other dietary supplements.

How are probiotics available?

Foods and drinks that contain probiotics include the following:

  • Soy drinks
  • Yogurt
  • Acidophilus milk (regular milk enriched with a healthy strain of bacteria)
  • Buttermilk
  • Some soft cheeses (for example, Gouda)
  • Miso (fermented soybean paste)
  • Tempeh (fermented soybean cake)
  • Kefir (drink made from fermented cow’s milk)
  • Kimchi (spicy fermented vegetables)
  • Unpasteurized sauerkraut

Look for labels that identify “live active cultures” or that include the full name of the bacteria on the nutritional label. There are many different types, or strains, of probiotics available. Most of these are of the Lactobacillus and Bifidobacterium variety. For example, Lactobacillus acidophilus is a type of probiotic found in yogurt and soy products. Probiotics are also available as dietary supplements in capsules, tablets, powders, and liquids. One commonly used supplement is acidophilus.

Things to consider

Many experts will tell you that the jury is still out on probiotics. Eating foods that contain probiotics is generally safe for most healthy people. Other people should steer clear of probiotics. These include people who have a weak immune system, including people who have cancer or those who have to worry about infection.

Probiotic supplements do not require FDA approval. This means that they are not regulated in the same way as prescription drugs are regulated. Supplements are not required to have the same safety testing as regulated drugs.

When to see a doctor

It is not unusual to have some gas and bloating when you begin eating or taking probiotics. These should go away in a few days. If they don’t, contact your doctor. Other side effects are rare, especially if you are healthy. However, if you begin to experience more severe abdominal pain or have abnormal stools, contact your doctor immediately.

Questions to ask your doctor

  • Should I be adding probiotics to my diet?
  • Can I get enough probiotics through food, or do I need a probiotic supplement?
  • Is it possible to get too many probiotics in my diet?
  • Are probiotic supplements safe?
  • Are probiotics safe for my child?
  • Can probiotic foods cause constipation?


National Center for Complementary and Integrative Health: Probiotics: What You Need to Know

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