Acetate (acetic acid)

Acetate (acetic acid) is by far the most abundant short-chain fatty acid in the colon, making up about half to two thirds of the total. Many gut bacteria produce it when fermenting fibre, especially bifidobacteria and Bacteroides. Acetate is measured in stool together with butyrate, propionate and the iso fatty acids (analysis “Short-chain fatty acids (SCFA)”).

What acetate does in the body

A large share of acetate reaches the liver, muscles and other tissues via the blood, where it serves as an energy source and as a building block for fats and cholesterol. In the gut, acetate is a starting material for other bacteria: butyrate producers such as Faecalibacterium prausnitzii use it to make butyrate. Together with the other short-chain fatty acids, acetate lowers the pH in the colon, which makes it harder for acid-sensitive microbes to grow.

Low acetate – what does it mean?

Low levels point to little bacterial fermentation – often with a low-fibre diet, after antibiotics or when acetate-producing bacteria such as bifidobacteria are scarce. Because butyrate producers depend on acetate, a low acetate value is always considered together with butyrate.

High acetate – what does it mean?

Raised levels show strong fermentation of carbohydrates. This can be due to a diet rich in carbohydrates and fibre, but also to sugars being incompletely absorbed in the small intestine and fermented only in the colon, for example with lactose or fructose intolerance. Fast gut transit also increases the share found in stool; bloating and soft stools may go along with it.

The interpretation is given in your report.