Probiotics are supplements or foods with living organisms that can affect the microflora or microbiome living in the human intestinal tract. Your microbes do a ton of things from helping to digest your food to making vitamin K, and they can be damaged by infections and taking antibiotics.

How to get and keep healthy gut microbes is an active area of research since they may help the human gut function better. There have been reports of the transplant of microflora from one person to another to treat intestinal ailments.

Some of the studied probiotic organisms include Lactobacillus rhamnosus GG (LGG), Bifidobacterium lactis, and Streptococcus thermophilus.

There are lots of testimonials and anecdotes about probiotics and functional foods like yogurt, and there’s no shortage of studies, but a clearer picture of what probiotics can and can’t do is emerging from more rigorous research.

Some probiotics may, when given regularly, reduce certain common childhood gastrointestinal infections like rotavirus. They do not appear to be effective in preventing respiratory infections like the common cold.

Probiotics, when given at the start of a gastrointestinal infection like rotavirus, can shorten the symptoms of stomach flu by one day. LGG has been shown to be effective in doses greater than 1010 (100 billion) colony forming units daily.

When probiotics are started at the beginning of a course of antibiotics, they can reduce some antibiotic-associated diarrhea. The research does not support starting them after the diarrhea has already started.

Probiotics may be effective in reducing allergic disease such as eczema when given during pregnancy and lactation and for an infant’s first six months.

Babies with colic may benefit from probiotics; more study is needed to determine whether babies with colic cry fever hours per day when taking probiotics.

While initial results are encouraging, there is no agreement on the use of probiotics for ulcerative colitis, Crohn’s Disease, irritable bowel syndrome, and constipation. They are not recommended to prevent infections outside of the gastrointestinal tract, and they are not recommended to prevent or treat cancer.


While generally recognized as safe, probiotics are living organisms. They should not be used for at-risk children such as the immunocompromised, sick premature infants, and patients with intravenous catheters or other indwelling medical devices.

Where and What to Buy

Probiotics are sold without a prescription. And while they are over-the-counter, they are usually stocked “behind the counter,” meaning you have to ask the pharmacist for them.

Until there is better research, its difficult to say which strain is best and what the dose should be. Authors from a literature review1 recommended doses in the range of 5 to 10 billion colony forming units per day. Quality can be in issue., an independent lab, analyzed many brands and found some lacking.

Parents can enhance their child’s intestinal microbiome by breast feeding infants and minimizing the use of antibiotics when possible.

1Probiotics in Children. Pediatric Clinics of North American 54 (2007) 949-967.

2Clinical Report—Probiotics and Prebiotics in Pediatrics. Pediatrics 126 (2010) 1217-1231.

Read more about probiotics from the American Academy of Pediatrics here.

About Lisa M. Asta, MD

Lisa M. Asta, M.D. is board-certified by the American Board of Pediatrics and is a Fellow of the American Academy of Pediatrics, for which she is also a Media Representative (she has been interviewed for “Kids Health” on Health Radio, and quoted in Parenting Magazine, USA Today, and the New York Times, among other publications). She is a Clinical Professor of Pediatrics at the University of California at San Francisco and past pediatric chair at John Muir Medical Center in Walnut Creek. She graduated from Temple University School of Medicine and the Johns Hopkins University. Dr. Asta is also a writer whose fiction has appeared in Inkwell, Philadelphia Stories, Schuylkill, and Zeniada. Her essays have appeared in the Journal of the American Medical Association, Hippocrates, the San Jose Mercury News, and The New Physician Magazine. She is an occasional contributor to KQED public radio’s Perspectives series, and has written articles for Bay Area Parent, Valley Parent, Parents’ Press, and Parents Express, as well as online at,, and She wrote a chapter in The Field Guide to the Normal Newborn, ed. Gary Emmet, M.D. currently has two how-to videos for parents in production which feature Dr. Asta. For more on Dr. Asta’s writing, visit
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