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Mars-Venus effect on friends in gut

New Delhi, July 29: Changes in diet intended to alter populations of intestinal bacteria may need to be designed differently for men and women, according to a new study that has found that gender can influence how gut microbes respond to diet.

The study by a team of scientists in Europe and the US has shown that in four vertebrate species, including humans, diet has a sex-specific effect on the host’s gut microbes — bacteria that inhabit the intestines and play a role in nutrition and disease.

Gut bacteria — a mixture of populations of multiple species of bacteria — help break down food and also produce molecules that are beneficial to the body, but some have also been suspected to cause intestinal cancer.

“All along we treated diet as if it works the same for men and women,” Daniel Bolnick, a biologist at the University of Texas who led the study said in a media release put out by the university. “Now, we’ll be approaching studies of (diet-based) therapies in a different way.”

The study’s findings appeared on Tuesday in the journal Nature Communications.

Many studies have over the past decade established how microbes that inhabit the human intestine promote nutrition and immunity; and disturbances in the relative diversity of these gut microbes may contribute to disorders such as obesity, diabetes or inflammation.

Indian researchers had earlier this year found disturbances in populations of gut microbes in malnourished children. Abhijit Chowdhury at the Institute of Postgraduate Medical Education and Research, Calcutta, and his colleagues had found that the populations of friendly bacteria drop and unfriendly bacteria rise in malnourished children. Those observations have stirred hopes that diet-based therapies may repopulate friendly microbes to treat malnutrition.

“Our findings suggest that dietary changes would affect men differently than women,” Bolnick told The Telegraph over the telephone. “So any therapeutic changes in the diet, specifically for the purpose of changing gut microbes, might have to be sex-specific.”

The first hint of differences in gut microbes between men and women emerged only earlier this year from a study on members of a modern hunter-gatherer community called the Hadza in Tanzania. The study, also published in the journal Nature Communications, had found that members of the Hadza community have far more diverse gut microbes — more species of bacteria — than members of “westernised” populations.

The study by Amanda Henry at the Max Planck Institute of Evolutionary Anthropology in Germany and her colleagues also found that Hadza men and women differed significantly in the type and amount of their gut microbes — something never seen before in any population.

The scientists reasoned that the microbial differences stemmed from different day-jobs for men and women of the Hadza — the men hunt animals and collect honey, while the women collect tubers and plants. Each sex eats slightly more of the food they hunt or gather.

“The differences in gut microbes reflect this sexual division of labour,” Stephanie Schnorr, a coauthor of the study on the Hadza said in a media release issued by the Max Planck Institute. “Women have more bacteria to help process fibrous plant foods.”

In the new study, Bolnick and his colleagues analysed microbes in two species of fish, mice, and analysed earlier studies on human gut microbes with a focus on sex differences, if any. They have found that certain species of microbes dominate in one sex, while others would dominate the other sex.

Bolnick cautions there is no therapeutic side to the findings yet.

“We already know that what people eat affects their (gut) microbes, but it does so differently in males versus females — this is new,” Bolnick said. This means that when we begin to develop dietary therapies to fix gut microbe problems, we need to take sex (gender) into account in a way that we have previously ignored.”