Recent studies have shown that the symptoms of lactose intolerance can be relieved in some people by changing the population of their intestinal microbes, called the microbiome, to encourage lactose-digesting bacteria. Specifically, bacteria, called "lactic acid bacteria," eat the lactose but produce the byproduct lactic acid instead of gas. While lactic acid has no nutritional value, it does not produce the unpleasant symptoms of lactose intolerance. This adaptation of the intestinal microbiome may be how some ancient pastoral populations with no genetic evidence of lactase persistence tolerated a dairy-rich diet.
Ingesting lactic acid bacteria as a probiotic can alleviate the symptoms of lactose intolerance, but these bacteria may not persist in the colon. A promising new strategy is to "feed" the lactic acid bacteria a complex sugar that they can digest but humans cannot. In initial clinical trials, subjects using this "prebiotic" reported improved lactose tolerance and had a corresponding shift in their intestinal microbiome. Larger clinical trials are in progress.
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