Dietary protein, the microbiota and gut barrier function: a gatekeeper of metabolic & immune health

The gut barrier functions to prevent the passage of bacteria and bacterial products into the systemic
blood circulation. If the gut barrier fails, bacterial products can infiltrate bodily tissues, causing
metabolic and immune dysfunction. The best example of this effect occurs in inflammatory conditions
that lead to a translocation of bacterial lipopolysaccharide (LPS) from the gut to the liver, where LPS
has been implicated in promoting the accumulation of ectopic fat and non-alcoholic fatty liver disease,
a common condition that contributes to the development of cardiovascular and terminal liver
diseases. We have new evidence to show that gut barrier function, as measured by an increase in gut
permeability, is also impaired in healthy men, a phenomenon known as 'leaky gut'. While there may
be different causes of this condition, there is emerging evidence to suggest that the fermentation
products of dietary protein may impair gut barrier function in the colon, especially in the absence of
fermentable carbohydrate. If this link can be substantiated, it would have major implications for the
over consumption of protein in the UK population, especially with respect to proposed dietary
recommendations to increase protein intake in middle-aged adults.