One of the most popular and exciting studies that was conducted in Imperial CRF this year is now published in The American Journal of Clinical Nutrition with the senior author being Dr Garry Frost. The study “Increased colonic propionate reduces anticipatory reward responses in the human striatum to high-energy foods”, is suggesting that cravings for high-calorie foods could be reduced or even switched off by a new food supplement that is produced by bacteria in the gut.
Previous studies have shown that when bacteria in the gut digest a type of fibre known as inulin, they release a compound called proprionate, which can signal to the brain to reduce appetite. This finding encouraged researchers in Imperial and Glasgow Universities to develop an inulin-proprionate ester food supplement which released much more proprionate in the intestines than inulin alone and was tested in a study published in 2013. The results of this study showed that overweight volunteers who added the inulin-proprionate ester supplement in their daily diet, gained less weight over six months compared to volunteers who added only inulin to their meals.
The previously mentioned findings raised questions as to why the inulin-proprionate ester supplement had such an effect on weight loss and appetite.
The answer to that question was provided by the study published this July in The Americal Journal of Clinical Nutrition where 20 volunteers were given a milkshake that either contained an ingredient called inulin-propionate ester, or a type of fibre called inulin to consume. After drinking the milkshakes, the participants underwent an MRI scan, where they were shown pictures of various low or high calorie foods. The results showed that when volunteers drank the milkshake containing inulin-propionate ester, they had less activity in areas of their brain linked to reward – but only when looking at the high calorie foods. These areas, called the caudate and the nucleus accumbens, found in the centre of the brain, have previously been linked to food cravings. In addition, the participants were asked to rate how appealing they found the food shown in the pictures. The results reviled that the volunteers who had drank the inulin-propionate ester supplement milkshake, rated the high calorie foods as less appealing.
In a second part of the study, the volunteers were given a bowl of pasta with tomato sauce in addition to drinking either of the milkshakes. The results showed that the participants who drank the inulin-propionate ester ate 10 per cent less pasta than when they drank the milkshake that contained inulin alone.
As pointed out by Dr Garry Frost this finding is significant as we finally understand why and how this compound works (by suppressing the appetite for high-calorie foods through the reward system in the brain). He also added that eating the equivalent amount of fibre to naturally produce similar amounts of proprionate and achieve the same results, could be difficult as we would need 60g of fibre per day when the UK’s average daily intake is only 15g.
The research was funded by the National Institute for Health Research Imperial Biomedical Research Centre and the Biotechnology and Biological Sciences Research Council.Imperial CRF Study Update: CPAGH