What Happens in Your Gut When You Eat a Low Carb Diet

More and more people are eating a low carbohydrate diet as a way to lose weight without any consideration to the long-term effects on their health. There are concerns about the increased risk of diabetes with ketogenic-type diets that are both low in carbohydrates and high in fat. Low carb diets have also been linked in one study to a shortened life span. But new research suggests there are even more potential health issues linked to eating a low carb diet.

According to a new study published in Applied and Environmental Microbiology, which explored the effects of a low carb diet on the gut microbiome, this approach to eating may have consequences on our microbiome. Scientists at the Department of Biochemistry and Molecular Biology at the Wright State University in Dayton, Ohio used a “human gut simulator” to assess the effects of two different types of diet on the gut.

The study found that a high fat, low carb diet increased strains of bacteria that break down fats. The switch from a balanced diet to a ketogenic-type diet caused a reduction in whole bacterial groups, including: Bacteroides, Clostridium and Roseburia, all of which assist in the breakdown of protein and carb foods. The reduction in these bacteria produced a reduction in fatty acids and antioxidants—compounds that are needed to heal damage to DNA, as well as fight aging, inflammation and diseases like colon cancer.

Bacterial diversity in the intestines is important to our overall health. And, diet goes a long way toward ensuring the health of our microbiome. An earlier study published in the medical journal Nature showed that diet rapidly alters the microorganisms residing in our gut. The Harvard-based research found that what we eat can have drastic effects on both the numbers of microbes as well as the diversity of strains found in the intestines.

Additionally, the study showed that the microbiome can shift quickly in response to diet—in as little as 24 hours after eating a meal of animal protein, the scientists found that the microbes found in the food (bacteria, fungi and viruses) quickly colonized the gut. And, perhaps most notably, they discovered that an animal-based diet (high protein, high fat, low carb) caused the growth of microorganisms that are capable of triggering inflammatory bowel disease within only two days of eating these foods.

The study was a small-scale study that explored dietary extremes by getting participants to eat a breakfast of eggs and bacon, a lunch of ribs and briskets, and salami, prosciutto and assorted cheeses for dinner, along with pork rinds for snacks. Then, the participants switched diets and ate a plant-based diet of granola for breakfast, jasmine rice, cooked onions, tomatoes, squash, garlic, peas and lentils for lunch; and a similar dinner, with bananas and mangoes for snacks.

In another study researchers fed rats a diet of salami, chocolate, chips and biscuits—or, what they called, the “cafeteria diet.” As part of an obesity study published in the journal Age, researchers gave some of the rats probiotics while others did not receive the beneficial bacteria. Scientists found that the probiotics were effective in preventing obesity because they had an anti-inflammatory effect on the gut and the body.

While this type of research is still in its infancy, and indeed our understanding of the human microbiome is also in the early stages, it is clear that diet has a quick and profound effect on our gut and the microbes found in it. And, that’s not surprising when you consider a basic fact: beneficial microbes, or probiotics, are like all living beings: they need food to survive. Known as prebiotics, which is essentially the food for these beneficial bacteria, they are primarily found in the form of naturally-occurring sugars and fiber found in plant-based foods. Knowing that, it isn’t really surprising that when we eat more of these primarily-carbohydrate-type plant foods, we should expect to see the numbers of beneficial microbes increase in our gut. And, great health truly does begin in the gut.

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