Q & A: Pros and Cons of Probiotics Researchers are trying to understand how these good bacteria, taken in pill form as a supplement, may play a role in promoting good immune function. Harvard's Dr. Athos Bousvaros discusse the current thinking on probiotics.

Q & A: Pros and Cons of Probiotics

A Potential Boon for Kids with Diarrhea


Probiotics have been used to treat diarrhea in children.


Dr. Cornelius Van Niel, a primary-care pediatrician at Sea Mar Community Health Centers in Seattle, published an article in the April 2002 issue of Pediatrics reviewing all the studies of Lactobacillus treatment in children with acute infectious diarrhea.


Q: What were your findings? Was the Lactobacillius treatment effective in children?


We found that children with this condition who took Lactobacillus [various strains and species, in nutritional supplement form, not in yogurt form] had a shorter duration of diarrhea (on average 0.7 days shorter) than those who took placebo. Also, they had fewer episodes of diarrhea, i.e. fewer stools, on the second day of treatment than those in the placebo group.


Interestingly, the children who took higher doses of Lactobacillus had shorter duration of diarrhea, and it seems that a daily dose of at least 10 billion viable bacteria is necessary to have a beneficial effect.

There are antibiotics — drugs that attack bad bacteria. And there are probiotics — good bacteria that are present in certain foods, such as yogurt. Researchers are trying to understand how these good bacteria, taken in pill form as a supplement, may play a role in promoting good immune function.

NPR talked about the emerging world of probiotics with Dr. Athos Bousvaros, an Assistant Professor of Pediatrics at Harvard Medical School and Associate Director of the Inflammatory Bowel Disease Program at Children's Hospital Boston.

Q: In the last decade, there's been an explosion of research on probiotics. What's been learned?

Researchers have shown that certain strains of intestinal bacteria are beneficial. And by beneficial, that means they can make certain vitamins such as Vitamin K. They can aid in the digestion of certain nutrients.

Probiotics may also modify the immune system to make it a little less likely to develop auto-immune problems. They can induce certain cells to produce a group of protein chemicals in the body called cytokines, which can be either "up regulatory" (good when you trying to fight infection and need to "turn on" the immune system) or "down-regulatory" (turning down the immune system when you're not fighting infection so you don't develop auto-immune diseases). Probiotics, at least in animal models, have been shown to do some of that.

Medical researchers have been testing probiotics in connection with a range of conditions from allergy and eczema to inflammatory bowel disease. Is there evidence that probiotics might be an effective treatment?

The data is still emerging. There are many good, quality-controlled trials in the medical literature that suggest that probiotics might work. For example, Dr. Erika Isolauri in Finland has shown that early administration of probiotics to mothers delivering infants at risk for allergy, and to those infants once they are born, will reduce the likelihood that the children will develop allergies. Dr. Susan Prescott in Australia has shown that giving probiotics to babies with eczema may reduce eczema severity.

These studies, however, raise further questions, such as: what dose should be used? For which diseases? At what age and how early in the course of the disease do you have to give the probiotic? Will the effect of the probiotic wear off if you stop giving it?

All of these questions have not been answered.

I published a big study looking at Lactobaccillus GG in kids with Crohn's disease who were already doing fairly well on medication. We put them on the probiotic or a placebo for two years. We followed them for two years and looked for whether the probiotic group had a lower rate of relapse and whether there were any differences between the two groups. We didn't find any differences.

Were you surprised you didn't find any differences?

Well, you go into studies with an open mind. I was hoping it would help kids, and when you get negative results you're a little disappointed. But there were some problems with my study as there are with all studies. Maybe the patients were just too well. We had a low rate of relapse in both arms of the study (both those taking the probiotic and those taking the placebo). So maybe this was the wrong population of patients to study. I picked Lactobacillus GG to use in my study because there was a lot of data on children and I was comfortable with its safety. But did I pick the right strain and dose to use? You can't know these things when you start a study. I'd like to do a follow-up with patients with ulcerative colitis.

Why might probiotics benefit patients with both irritable bowel and inflammatory bowel disease?

We do believe these conditions may be turned on, in some way, by various species of micro-intestinal flora. And perhaps, if you modify the intestinal micro flora and get rid of a species that's stimulating diarrhea and cramps in people with irritable bowel or if you modified a species that's pro-inflammatory in people suffering with Crohn's or ulcerative colitis, you might help people out. So there's a sound theoretical rationale for trying these things. But the evidence supporting their efficacy is not there yet.

Where does this leave the probiotic manufacturers and supplement makers who are touting the benefits of probiotics?

There are lots of people making extravagant claims, and there's a snake-oil component to this. Since the FDA does not approve these supplements, there's the opportunity to take preliminary research and run with it from the marketing standpoint.

What do you tell patients about brands of probiotic supplements that haven't been well-studied? There are a lot of new probiotic products sold in the vitamin aisles at drugstores.

I tell them I don't know what's in the products in terms of purity and efficacy and whether the bacteria is live or dead. I don't necessarily discourage patients from taking probiotics I haven't heard of, but I recommend them with caution. I say, you can try it. It's probably safe, but I don't know if it's going to work.