Can you permanently change your gut microbiome through diet?

Diet changes your gut microbiome quickly, but whether those changes actually stick is a different question. If you switch radically to a fully animal-based or plant-based diet, the composition of species shifts within just a few days. A diet high in animal products allows bile-tolerant bacteria to thrive; a diet rich in plants and fibre favours fibre-processing bacteria. This shift is measurable and reproducible, but microbes that enter via food establish themselves only temporarily.

The 'type' of your gut microbiome -- broadly speaking, the overall balance linked to your eating habits over years -- is more stubborn. Following a different diet for ten days already shifts small things, but the big picture does not change that quickly. That pattern appears to be more connected to how you have been eating for years than to what you ate last week. Lasting change therefore requires lasting adjustment of your dietary pattern.

The first 1,000 days after birth are the period in which the gut microbiome is most malleable. Disruptions during that phase, through diet or environment, have been linked to a higher risk of inflammatory diseases, immune problems and obesity later in life. In adulthood, the microbiome is more stable and fundamentally harder to change. In older adults too, living environment plays a role alongside diet: people in a nursing home have a different microbiome composition than people living independently.

In people with irritable bowel syndrome, a low-FODMAP diet (which restricts fermentable carbohydrates) can reduce symptoms, but it also has a downside. It simultaneously lowers the number of beneficial bacteria and the diversity of the gut microbiome. Individual responses vary considerably. Experts therefore recommend not following this diet for longer than necessary and reintroducing foods in a stepwise manner.

The picture regarding artificial sweeteners such as sucralose and saccharin, and regarding colour and texture enhancers in processed food, is still unclear. Animal and laboratory research suggests effects on bacterial diversity, but short-term studies in humans show hardly anything at normal consumption levels. Whether long-term use does have measurable consequences for the human gut microbiome has not been sufficiently investigated.