Gut Feeling for Probiotics Benefits May Be Overstated, UCSF Study Shows

Note: The study was supported by funding from the National Institutes of Health and the Clinical and Translational Science Institute at UCSF.

By Suzanne Leigh

The protective effects of probiotics against colds, tummy bugs and more serious conditions have been exalted – and contested. Now a new study headed by UC San Francisco researchers further fuels the probiotics debate by finding that there is no clear evidence that a supplement of the “friendly” bacteria strain of lactobacillus prevents eczema, a frequent precursor to asthma.

Probiotics, sold as dietary supplements and found in yogurt, kefir and fermented foods, are believed to enhance the defensive action of the cells that line the gut by stimulating healthy immune function and by inhibiting the growth of viral and bacterial pathogens. They are described by the World Health Organization as “live micro-organisms which when administered in adequate amounts confer a health benefit on the host.”

In the study, which publishes in the journal Pediatrics and is available online on Aug. 7, 2017, the researchers compared the impact of the probiotic among children who had received it for the first six months of life, with those who had not. All infants were at high risk of developing asthma, due to one or both parents having the condition, which is caused by both hereditary and environmental factors.

Infectious Exposure May Impact Asthma

Exactly half of the 184 newborns received capsules of the probiotic. The second group of 92 newborns received placebo capsules with the same look and feel as the probiotic.

The goal was to see if the probiotic would lessen the risk of eczema and asthma.

“Environmental factors during early infancy can affect immune system development and risk for allergic disease,” said first author Michael Cabana, MD, director of the division of general pediatrics at UCSF Benioff Children’s Hospital San Francisco.

“One theory is that the absence of infectious exposure at a critical point in immune system development leads to a greater risk for eczema and asthma. Additionally, lack of key bacteria in the infant intestinal microbiota has been associated with the later increased risk of allergic disease. Supplementing with specific probiotic strains may modify the entire microbiota community patterns and decrease this risk,” he said.

But the researchers found little difference between the two groups: at age 2, 30.9 percent of the placebo recipients were diagnosed with eczema, versus 28.7 percent of the probiotic group.

Eczema incidence is significant because it frequently precedes asthma.

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