Changing Your Diet for ONE Day Has a Dramatic Impact

By Rachael Bieschke

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What a difference a day makes… even when it comes to your diet. Research from Harvard University suggests the bacteria in your gut may change dramatically in response to what you eat, making significant alterations from day to day.

In fact, when study participants ate all animal foods for one day, bacteria more able to tolerate bile (which helps break down fat) increased while those known to break down plant proteins seemed to “take a vacation.” Further, the bacteria even activated genes that helped the participants to process protein.

This clearly wasn’t a fluke, as when other participants ate a plant-based diet, they expressed genes known to help ferment carbohydrates. While it’s known that the gut bacteria of certain animals, such as rodents, are able to radically change in composition quickly to respond to different diets, this is the first time the same has been found in humans.

Researcher Lawrence David, a former Harvard researcher who is now an assistant professor at Duke University’s Molecular Genetics & Microbiology and Institute for Genome Sciences & Policy, said:

It’s exciting and gratifying to find out this holds up in people … We’re getting an increasing appreciation of how flexible and responsive the microbiome is, even on a very short time scale.”

The study may also shed light on how different diets may contribute to health issues. For instance, while eating an entirely animal-based diet, levels of a bacteria called Bilophila wadsworthia, which is linked to inflammatory bowel disease, increased.

It’s likely that the flexibility of the trillions of microorganisms residing in your gut is an ancient trait that may have helped to buffer the effects of nutritional changes. The researchers noted:

Foodborne microbes from both diets transiently colonized the gut, including bacteria, fungi and even viruses … In concert, these results demonstrate that the gut microbiome can rapidly respond to altered diet, potentially facilitating the diversity of human dietary lifestyles.”

As for what type of diet may best promote healthy gut bacteria, the jury is still out, but past research suggests limiting your consumption of sugar, which feeds bad bacteria, is important. You can also help optimize your gut bacteria by consuming probiotics. Yogurt, kefir and traditionally made (non-pasteurized) sauerkraut are examples of fermented foods that are naturally rich in these beneficial bacteria, although you can also find them in supplement form.


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