We have all heard the “eat more fibre” mantra and wondered what this is all about. So did scientists. Sure we have long known it is good for gut health and function. Recently with the exploration of the gut microbes – the microbiota – we have learnt that dietary fibre can support survival and growth of the good bugs. That we have written about before.
Now scientists have found another piece of the puzzle. Some of the fermentation products produced by the gut microbes from the dietary fibre that our own enzymes cannot digest have the potential to influence our appetite. That is incredible and provides a further insight into the obesity conundrum.
The new mechanism
Obesity is currently one of the most serious global threats to human health. Susceptibility to obesity is determined by genetic background, diet, and lifestyle. Now it has become apparent that the resident intestinal microbes in the large intestine also play an important role. During the process of microbial fermentation of non-digestible fibre, the short-chain fatty acids acetate, propionate and butyrate are formed.
While short-chain fatty acids can serve as an energy source, the scientists showed that they also act as signaling molecules for the free fatty acid receptor 2 (FFAR2) found in enteroendocrine L cells in the large intestine. These specialised gut cells secrete the appetite suppressing hormone peptide YY (PYY). FFAR2 signaling was found to drive an expansion of the PYY cell population within the large intestine, leading to increased circulating PYY. This is associated with a reduction in food intake and protection against diet-induced obesity.
Evidence points to the production of short-chain fatty acids by the gut microbiota as an important appetite regulatory signal.
So what are fibres?
Just to be clear, dietary fibre is the indigestible portion of food derived from plants. Chemically, dietary fibre consists of non-starch polysaccharides such as arabinoxylans, cellulose, and many other plant components such as resistant starch, resistant dextrins, inulin, lignin, chitins, pectins, beta-glucans, and oligosaccharides. Food sources of dietary fibre are often divided according to whether they provide predominantly soluble or insoluble fibre.
Soluble fibre is found in varying quantities in all plant foods, including in a range of legumes, in oats, rye, chia, and barley, in several fruits, in vegetables, in root tubers and in nuts, with almonds being the highest in dietary fibre.
Sources of insoluble fiber include whole grain foods, wheat and corn bran, legumes such as beans and peas, nuts and seeds and vegetables such as green beans, cauliflower, zucchini and celery.
So there you have a wide variety of healthy foods with the potential of reducing your hunger pangs and alleviate the risk of overweight and obesity.