Short-chain fatty acids (SCFAs) are compounds considered as postbiotics, which are of increasing interest to the scientific community for their beneficial effects on our health. But what are they?
Short-chain fatty acids are molecules of up to 6 carbon atoms, produced by certain bacteria of the gut microbiota in the colon. These microbial metabolites are derived from the fermentation of complex carbohydrates, the fibres, which could not be digested and assimilated.
Their production therefore depends on the bacterial species present in the intestinal microbiota, the type of fibre but also the transit time.
These metabolites exist in different forms such as succinate or lactate. But acetate, butyrate and propionate are the majority (95%). They will either act directly on the intestinal cells or be transported in the bloodstream to act on other organs.
What are the roles of SCFAs for our health?
SCFAs have various roles, with common goals : maintaining our health while limiting the development of disease. Thus, many protective effects are mediated by these bacterial metabolites:
- they improve the intestinal barrier. SCFAs regulate the luminal pH: this results in the inhibition of pathogenic microorganisms and increases the absorption of certain nutrients. They also modulate mucus secretion and are the main source of energy for the cells lining the colon, the colonocytes;
- they modulate inflammation and immunity. Butyrate and propionate induce the differentiation of T regulatory cells, helping to control intestinal inflammation. For example, this reduces the risk of inflammatory bowel disease;
- they are also involved in various metabolisms. Propionate is used in the production of glucose in the liver, while acetate and butyrate are involved in lipid synthesis.
Their quantity and abundance can be considered as biomarkers of a health condition. Indeed, low production can be linked with obesity, insulin resistance, colorectal cancer, etc.
Where can we find them in our food?
To stimulate the production of SCFAs, fibre-rich foods such as vegetables, fruits and legumes are preferred. Especially those containing:
- FOS (Fructo-oligosaccharides), contained in asparagus, bananas, garlic, onions, etc;
- inulin, present in leeks, artichokes, wheat, rye, garlic or onions, etc;
- pectin, from apples, oranges, carrots, etc;
- resistant starch, from barley, beans, rice, pasta, potatoes, legumes, etc;
- arabinoxylan, contained in cereals;
- guar gum, contained in guar seeds.
Small amounts of butyrate can also be found in some dairy products.
So the more fermentable fibre you eat, the more SCFAs your gut bacteria will produce. And the more SCFAs you have, the healthier you will be.