Does Dietary Fibre Act On Your Brain?Thursday, May 15, 2014
However, I have often thought of this as a gut effect – perhaps volume increases, slowing gastric emptying or some other “local” impact on the GI system.
Now, a much publicized study by Gary Frost and colleagues, published in Nature Communications, suggests that it may well be due to a direct impact of a fibre metabolite on the appetite regulating centres of the brain – at least in mice.
In their study, the researchers fed mice a high-fat (HF) diet supplemented either with inulin (I) or cellulose (C) – both are fibres, but whereas inulin is readily fermented by the bacteria in our gut, cellulose is not.
After 8 weeks, mice fed the HF-I diet consumed significantly less food and gained less weight than those fed HF-C.
Using isotope labelling, the researchers demonstrated that the acetate produced in the gut as a result of fermentation of the inulin crosses the blood–brain barrier and is taken up by the brain.
They also showed that simply injecting acetate into the peritoneum results in appetite suppression and hypothalamic neuronal activation patterning.
Finally, they dilineated a pathway how acetate may affect neurotransmitters in the hypothalamus that mediate hunger and satiety.
From these findings, the researchers conclude that acetate (as derived from increased fibre intake) has a direct role in central appetite regulation.
As acetate is produced through the fermentation process in the gut, which in turn requires the right spectrum of gut bacteria, these findings also provide more support for the notion that our gut bugs can have a direct impact on appetite.
Frost G, Sleeth ML, Sahuri-Arisoylu M, Lizarbe B, Cerdan S, Brody L, Anastasovska J, Ghourab S, Hankir M, Zhang S, Carling D, Swann JR, Gibson G, Viardot A, Morrison D, Louise Thomas E, & Bell JD (2014). The short-chain fatty acid acetate reduces appetite via a central homeostatic mechanism. Nature communications, 5 PMID: 24781306