Bifidobacteria can be affected by the ketogenic diet

The ketogenic diet is increasingly popular due to its potential positive health effects, mainly related to the potential reduction of body fat content when following this diet. The diet is known to be strenuous to complete, due to the exclusion of common foods that contain carbohydrates, such as potatoes, bread, cereals, grains, bakery products, rice, etcetera. The main components of this diet are fatty foods such as fatty fish, avocado, eggs, vegetable oils, cheese, and vegetables. The aimed effect of the ketogenic diet is to stimulate the production of ketone bodies by the liver, which are produced as a result of fat metabolism. These ketone bodies serve as an energy source for the cell, have antioxidative properties, and protect against cellular damage and inflammation (source).

Since the microbiome is mostly affected by the diet, researchers aimed to investigate the relationship between the microbiome and this ketogenic diet. A research group led by prof. Turnbaugh at the University of San Fransisco found that especially bifidobacteria were decreased on a ketogenic diet, compared to healthy control subjects. In an in-depth study in mice, they created different groups of mice where they gave nutrition that contained different amounts of fat and carbohydrates for each group. They found that the amount of carbohydrates was the main cause of the ketogenic diet effects on the microbiome, namely the reduction of bifidobacteria species, specifically bifidobacterium adolescentis.

Furthermore, the researchers found altering levels of the inflammatory molecule Th17 in ketogenic diet subjects compared to controls, indicative of a decreased level of inflammation due to decreased immune response activity against potential gut pathogens, i.e. infectious agents. Th17 cells have an important role in the regulation of mucosal immunity and the stability of the mucosa (https://en.wikipedia.org/wiki/T_helper_17_cell). 
 
P.S. Interestingly, the ketogenic diet is historically used for the treatment of (children) with epilepsy (background).

Source: Gut Microbiota for Health
Original article: Cell press