Yes, we’ve established that many factors influence your microbiome. Diet is one of them. Still, how quickly can dietary interventions change your gut microbiome? Can it be done in only 5 days? Researchers sought to answer just that.

They selected two contrasting diets – chosen to “span the global diversity of modern human diets” – and asked people to follow either for 5 days.

The two diets varied according to their primary food source: a ‘plant-based diet’, rich in grains, legumes, fruits and vegetables; and an ‘animal-based diet’, which was focused on meats, eggs and cheeses. 

By eating either way, what would happen to the microbial populations? 

  Plant-Based vs. Animal-Based

 

Our microbiomes can rapidly switch between plant-eating and meat-eating modes.

When we change our diet, the bacteria in our guts react very quickly. Within mere days, certain species step into the light, whilst others fade: they activate different genes, have different metabolic tricks, and secrete different substances.

When we change our diet, the bacteria in our guts react very quickly. Within mere days, certain species step into the light, whilst others fade

Overall, bile-tolerant bacteria became more common in the animal diet. Bile, a bitter fluid that breaks down fats, is made in greater amounts when we eat more fatty food. One of these – Bilophila wadsworthia — has been shown to cause inflammatory bowel disease. Others made substances such as deoxycholic acid (DCA), which increase risk of liver cancer. Although both these studies were conducted in mice, the negative effects could potentially translate to humans and, thus, need to be investigated.

Changed gut communities do different things. 

Plant-based feeding made them better at breaking down carbohydrates; whilst eating animals powered protein digestion. All this, happened – very quickly. Certain changes were clear from day one. By day four, the owner’s stool sample could be used to accurately predict what diet they were on. 

There were co-evolutionary links too. Eating plant-based led the active genes in the gut bacteria to quickly resemble those in plant-eating mammals. Meanwhile, meatier eaters had microbiomes more like carnivores.

Nevertheless, it took only 2 days post-diet for things to return to normal. Our gut microbiomes, it seems, are pretty fickle – change is easy, but impermanent. Maintenance of our preferred dietary patterns is a prerequisite. 

Our gut microbiomes, it seems, are pretty fickle – change is easy, but impermanent. Maintenance of our preferred dietary patterns is a prerequisite. 

In concert, these results demonstrate that the gut microbiome can rapidly respond to altered diet, potentially facilitating the diversity of human dietary lifestyles.

This video explores the different diets they investigated, and what they found about their impact for your gut health and overall wellbeing.

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