What effects does fasting have on the gut microbiome?

Fasting is a new popular dietary pattern.

There is strong evidence that certain fasting patterns can help prevent heart disease, diabetes, and high cholesterol, and can also help regulate blood sugar and blood pressure, but it’s not clear exactly how and to what extent the microbiome plays a role in this, and because the field is still nascent, there are relatively few high-quality human trials.

The researchers found that intermittent fasting (on alternate days) reshaped the composition of the mice's intestines to help them better protect against diabetes and common complications such as retinopathy, or impaired vision. What's more, the mice also lived longer.

Early animal experiments also showed that mice that fasted for 16 or 20 hours had an increase in Akkermansia (Akk bacteria), a known "beneficial" bacteria, while a decrease in Alistipes, another bacteria whose effects on the body are related to certain diseases and inflammation.

However, after the fasting period ended, this effect on the microbiome ceased.

In another study, people who adopted intermittent fasting (16:8 pattern, i.e. fasting for 16 hours and eating freely for 8 hours) showed no significant differences in the composition of their gut microbes.

In 2021, a review of the relationship between fasting, the microbiome, and weight management found that, on a macro level, changes in the microbiome can, to some extent, counteract short-term dietary changes.

But you have to make dietary changes long enough, such as fasting for an extended period of time, to have a lasting effect on the makeup of your gut bacteria that could, in theory, lead to all sorts of health benefits.

In another human trial in 2021, scientists studied the effects of fasting for 5 days on volunteers who switched to a Mediterranean diet. They found that the gut microbiome changed significantly and the volunteers' blood pressure decreased, even 3 months after the diet change. The volunteers even reduced their intake of blood pressure medication.

However, a recent study found that a very low-carbohydrate diet can promote the proliferation of a type of harmful bacteria in the intestines, which is not conducive to intestinal health.

Based on current research, it is still unclear what dietary pattern is friendly to both the human body and intestinal flora, and the conclusions of animal experiments show that methods that are effective for mice may not necessarily be effective for humans.

Are you fasting? What are your experiences?

https://www.inverse.com/mind-body/fasting-gut-health-science