Fibre for the future

A chronic lack of dietary fibre has been found to reduce the diversity of bacteria in the guts of mice. This effect is not fully reversed when fibre is reintroduced, and increases in severity over multiple generations. See Letter p.212 Over our history, humans have experienced major dietary changes, including a shift to low-fibre intake in Westernized populations, which is paralleled by a general loss in the diversity of the gut microbiota. Microbiota-accessible carbohydrates (MACs), which are abundant in dietary fibre, are the primary source of carbon and energy for the distal gut microbiota. This study shows that in mice on a low-MAC diet, the diversity of the microbiota is depleted and that this effect is transferred and compounded over generations, such that the low abundant taxa are progressively lost from one generation to the next, particularly those of the order Bacteroidales, which are proficient in the consumption of dietary fibre. This phenotype is not reversible simply by reintroducing dietary MACs, but requires supplementation of the missing taxa via faecal microbiota transplantation. These findings suggest that a change in diet alone may be insufficient to restore a healthy microbiota in individuals with dysbiosis.