Changes in microbial populations are more closely associated with food type than the nutrient profile listed on the packet.

The influence of diet on gut microbes seems to be highly personal, according to a comprehensive analysis of microbiome complexity.

Microbes residing in the gut are thought to influence health-related factors from glucose control to weight loss. Dan Knights at the University of Minnesota in Saint Paul and his colleagues looked at the impact of diet on gut microbes at a fine scale, assessing the microbiomes of 34 healthy people every day for 17 days. The researchers also scrutinized dietary records kept by the study participants.

The results suggest that the type of food consumed — for example, a leafy vegetable versus a piece of meat — is a better indicator of changes to the microbiome than is the food’s nutrition label. The team also found that a monotonous diet did not correspond to a stable microbiome: two participants who relied primarily on the meal-replacement beverage Soylent for nourishment still showed changes in their microbiomes over time.

Overall, responses to diet varied widely from person to person, suggesting that efforts to mould the microbiome will need to be tailored to individuals.