12 January - 20 June 2016

Short term changes in the diet can alter gut bacteria

18 Dec 13

A letter published in Nature by David et al. has investigated how the human gut microbiome responds to short term macronutrient changes.  The paper notes that changes to gut microbial communities from food are now suspected of contributing to the increase in chronic illnesses in the developed world including obesity and inflammatory bowel disease.  To understand how diet changes can affect gut microbiome, the scientists recruited ten volunteers, including one vegetarian, who consumed either a diet based on meat, eggs and cheese (around 1777 kcal), or a plant based diet (around 1695 kcal) composing of grains, fruit and vegetables for five days. Each day the team sequenced the microbial RNA in the volunteers' faeces to identify which gut microbes were present.  David et al report that the animal- based diet increased dietary fat from around 33% before intervention, to around 70% of kcal and dietary protein from around 16% to 30% of kcal.  Fibre intake was zero during intervention in the animal diet whereas at baseline it was around 9g per 1000 kcal, while the plant-based diet increased fibre intake to 26g per 1000 kcal, decreased fat intake to around 22% and protein to around 10%.  David et al found that the animal-based diet had the greatest impact on gut microbiota, noting that there were significant differences in 22 clusters, whereas only 3 clusters showed significant abundance changes while on the plant-based diet. They note in particular that there was an increase in the abundance and activity of Bilophila wadsworthia in those who consumed the animal-based diet. This organism feeds on bile acids, which aids the digestion of saturated fats in milk. An increase in B. wadsworthia has been linked to inflammatory bowel disease in mice. Those on the plant-based diet were found to have an increase in the number of bacteria which produce butyrate, a fatty acid which has been reported to reduce inflammations.

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