“Think of the children!” may one day be a slogan for a health campaign imploring people to eat more fiber.

Doctors and nutrition experts have been harping on the importance of fiber for years, particularly how most people in industrialized countries eat less than the recommended daily dose of 25 to 38 grams. After all, the nutrient, a diverse group of molecules that includes complex carbohydrates, helps keep you “regular.” Perhaps less well-known, fiber helps maintain a healthy, diverse population of gut microbes.

But eating fiber may not just benefit the microbial balance of the eater—it may also benefit that of the eater’s progeny, according to a new study in Nature.

In the study, researchers transferred the gut microbes of a healthy human into germ-free mice and then fed the animals either a high- or low-fiber diet. Expectedly, the microbial populations of animals on the low-fiber diet became less diverse after a few weeks. But when the animals within each group bred with each other, the microbial changes in the low-fiber group carried on to the next generation and the one after that. In fact, the changes stuck around through the four generations the researchers monitored. In the high-fiber group, microbial diversity flourished, generation-to-generation.

In each batch of the low-fiber group, the researchers tried to reverse the diversity-loss in the mice by feeding them high-fiber diets. It worked for the most part in the first generation of mice, but that became less and less effective in the subsequent generations. The last generation studied had the lowest microbial diversity even after eating a high-fiber diet—a mere quarter of the bacterial species found in their great-grandparents. The only thing that restored a healthy microbial population in those mice was a fecal transplant from the high-fiber mice, the researchers reported.

The finding suggests that prolonged, cross-generational damage to a gut microbe population may not be reversible with simple diet fixes.

On closer comparison of the microbe populations in the low- and high-fiber eating mice, the researchers found that the low-fiber group likely lost microbes that possessed fiber-digesting enzymes.

The gut microbes of humans produce thousands of enzymes that break down dietary fiber that the human body otherwise couldn’t use. The resulting scraps from microbe-digested fiber are fuel not only for the microbes and their neighbors, but for human cells too. And having a lush, diverse crop of microbes in the gut is suspected of helping elbow out deadly pathogens, such as Clostridium difficile. It's also been linked to a healthy metabolism.

Nature, 2015. DOI: 10.1038/nature16504 (About DOIs).