Not only can a lack of fibre harm your own digestive system, there could be knock-on effects to your children, according to a new study. Although the evidence so far applies only to mice tested in a lab conditions, researchers suggest the same issues could be at play in humans too.

When groups of mice were given low-fibre diets, the diversity of their intestinal microbiome - populations of gut-inhabiting bacteria that aid digestion and fight off certain diseases - fell sharply. Not only that, but by the fourth generation, these changes were irreversible. If the same effect can be shown in humans, it's a strong argument for actively upping your fibre intake. 

"The extremely low-fibre intake in industrialised countries has occurred relatively recently," said lead researcher, Justin Sonnenburg from Stanford University. "Is it possible that over the next few generations we'll lose even more species in our gut? And what will the ramifications be for our health?"

We know that fibre and protein are packed with nutrition and help to keep us feeling full, as well as cutting down the risk of certain kinds of cancer, but this is the first time that researchers have suggested the effects could be passed on through the generations. 

Sonnenburg and his team transferred the gut microbes of a healthy human to hundreds of germ-free mice, then split the mice into two groups: one with a high-fibre diet and one with a low-fibre diet. The microbial populations of the animals in the latter group became less diverse, but the scientists also found that when these mice started breeding, the changes were passed on.

When the affected mice were fed with a high-fibre diet to increase their bacterial diversity, the resulting changes became less pronounced with each passing generation. By the fourth generation, the damage was almost impossible to reverse. Only a faecal transplant could restore a healthy gut in these mice, the researchers found.

Further analysis suggests that mice in the low-fibre group lost microbes with fibre-digesting enzymes in them. In humans, these enzymes digest and create energy from food that would otherwise pass straight through our bodies, so they're a vital part of our internal ecosystems. While the report isn't definitive proof that the same process would be observed in humans, it does suggest that more research into the effects of a low-fibre diet on successive generations should be done.

Scientists already believe that our modern way of living and the lack of fibre in our over-processed foods are leading to less bacterial diversity in our intestines. "Numerous factors including widespread antibiotic use, more frequent caesarean sections and less frequent breastfeeding have been proposed for why we see this depletion in industrialised populations," said one of the team, Erica Sonnenburg.

The study has been published in Nature.