0   /   100

The effect of diet on the gut microbiome

The effect of diet on the gut microbiome
Start Reading

It has long been known that diet is one of the main factors affecting the gut microbiome, but how diet-induced changes in the microbiome affect pathophysiological processes in the host is much less understood.

In overweight or obese individuals, it is known that the composition of the microbiome differs from that of individuals of normal body weight. Many people at some point in their lives try to diet to lose weight.

Researchers from Charité – Universitätsmedizin Berlin and the University of California, San Francisco, have studied how the microbiome composition changes in people on very low calorie diets and have been able to demonstrate for the first time that very low calorie diets significantly change the composition of the human gut microbiome.

To investigate the effects of dieting, the research team studied 80 older (post-menopausal) women for 16 weeks, ranging in weight from slightly overweight to severely obese. With a daily intake of 800 calories, regular analysis of stool samples showed that the diet reduced the number of microorganisms present in the gut and changed the composition of the gut microbiome.

The experiment found that, although metabolic efficiency improved, severe calorie restriction led to a reduction in bacteria and a structural change in the gut microbiome. The post-diet human microbiome was transplanted into mice kept in a germ-free environment, i.e. without their own microbiome, and mice that received the pre-diet microbiome served as a control group.
The results were striking: the animals that were given faeces after dieting lost more than 10 per cent of their body weight and their body fat decreased. The pre-diet faeces had no effect on the control group.

When the stool samples were studied in more detail, increased colonisation of a specific bacterium, Clostridioides difficile, was observed. While this micro-organism is normally found in the natural environment and in the intestines of healthy humans and animals, its numbers in the gut can increase with antibiotic use, causing severe inflammation of the intestinal wall. It is also known to be one of the most common hospital pathogens. Increased levels of the bacterium have been found in both participants who completed a diet and in mice who received gut bacteria after a diet.

Prof. Spranger summarised the results of the research thus:

“We were able to show that C. difficile produced the toxins that are typically associated with this bacterium and that this was associated with the weight loss of the animals.”

“A very low calorie diet severely alters our gut microbiome and appears to reduce colonization resistance to the hospital-acquired bacterium Clostridioides difficile. These changes reduce the absorption of nutrients through the intestinal wall, especially without causing relevant clinical symptoms. It remains unclear whether and to what extent this type of asymptomatic colonisation of C. difficile can harm or improve the health of the individual. This will need to be clarified in further studies.”

Jumpertz von Schwartzenberg R, Bisanz J.E., Lyalina S, et all, Caloric restriction disrupts the microbiota and colonization resistance Nature volume 595, pages 272–277 (2021)

Leave a Reply