What probiotics can and can’t do


Probiotic supplements fill drug store shelves, offering claims such as serving to promote digestive health, aid with weight loss or improve emotions. Do probiotics deliver on these promises? Shahrad Hakimian, MD, a UCLA Health gastroenterologist in downtown Los Angeles, discusses the nature of probiotics and what physicians are still learning about them.

What are probiotics?

“Probiotics are foods or supplements containing live bacteria resembling the normal bacteria in the digestive system,” Dr. Hakimian says. “Bacteria are part of our microbiome, the trillions of microorganisms living in our gut. We’re still learning what these various bacteria do, but we know probiotics help the body function, help with digestion and help the body produce vitamins.” Probiotics are in foods that are fermented and have live organisms in them, meaning the food hasn’t been pasteurized. They include yogurt, kefir, kimchi, kombucha, pickles (fermented, not brined) and miso. Look for wording on the package that indicates the product contains live cultures.

Is it a good idea to take probiotic supplements?

“One size doesn’t fit all,” Dr. Hakimian says. “They have been used successfully in adults and children for certain conditions, including inflammatory bowel syndrome and ulcerative colitis. Doctors may also recommend taking them after a prolonged course of antibiotics. However, the data are inconclusive.” He notes that probiotic supplements may increase the risk of infection among people with a weakened immune system, a critical illness or a recent surgery. Also, there are different strains and dosages of probiotics, and not all probiotic supplements are of equal quality. “People shouldn’t take a daily probiotic to prevent specific diseases. The best way to promote a healthy gut is to have a generally healthy lifestyle and eat a balanced diet with lots of fruits, vegetables and other natural foods. Part of having a healthy microbiome is having a variety of good bacteria, not just large amounts of one type. You can’t achieve that by eating one specific type of food or taking one specific supplement. You get it by having a variety of foods from different sources.”

Another supplement to aid digestive health is prebiotics. What are those?

“Prebiotics are substances in food containing fiber that promote the growth of healthy bacteria. They go hand-in-hand with probiotics in maintaining a healthy gut,” Dr. Hakimian says. Prebiotics are found in foods including whole grains, vegetables, fruits, beans and legumes. He says that, as with probiotics, people should aim to get enough fiber through the food they consume rather than relying on supplements.

What are future directions in the study of probiotics?

“We think the bacteria composition in the body plays a big role in health,” Dr. Hakimian says. “We believe microbes have roles in various diseases — not only gastrointestinal diseases such as Crohn’s disease, ulcerative colitis and irritable bowel syndrome, but also others like diabetes, obesity, certain neurologic conditions and other autoimmune conditions.” He notes that UCLA recently opened the Goodman-Luskin Microbiome Center to advance understanding of the microbiome and its effect on health and, ultimately, to translate groundbreaking discoveries into new treatments. Areas under investigation include inflammatory bowel disease; obesity, metabolic disorders and eating behavior; the role of estrogen in gastrointestinal disorders; cardiovascular disease; liver disease; mental illness and pain; neurodevelopmental and neurodegenerative diseases; and substance use disorder. “This is an area with a lot of promise,” Dr. Hakimian says.

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