Imperial College London
Eating a type of powdered food supplement, based on a molecule
produced by bacteria in the gut, reduces cravings for high-calorie foods such
as chocolate, cake and pizza, a new study suggests.
Scientists from Imperial College London and the University of Glasgow
asked 20 volunteers to consume a milkshake that either contained an ingredient
called inulin-propionate ester, or a type of fibre called inulin.
Previous studies have shown bacteria in the gut release a
compound called propionate when they digest the fibre inulin, which can signal
to the brain to reduce appetite. However the inulin-propionate ester supplement
releases much more propionate in the intestines than inulin alone.
After drinking the milkshakes, the participants in the current
study underwent an MRI scan, where they were shown pictures of various low or
high calorie foods such as salad, fish and vegetables or chocolate, cake and
pizza.
The team found 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 and the motivation to want a food.
The volunteers also had to rate how appealing they found the
foods. The results showed when they drank the milkshake with the
inulin-propionate ester supplement they rated the high calorie foods as less
appealing.
In a second part of the study, which is published in July
edition of the American Journal of Clinical Nutrition, the volunteers were
given a bowl of pasta with tomato sauce, and asked to eat as much as they like.
When participants drank the inulin-propionate ester, they ate 10 per cent less
pasta than when they drank the milkshake that contained inulin alone.
In a previous research study by the same team, published in
2013, they found that overweight volunteers who added the inulin-propionate
ester supplement to their food every day, gained less weight over six months
compared to volunteers who added only inulin to their meals.
Professor Gary Frost, senior author of the study from the
Department of Medicine at Imperial, said: "Our previous findings showed
that people who ate this ingredient gained less weight -- but we did not know
why. This study is filling in a missing bit of the jigsaw -- and shows that
this supplement can decrease activity in brain areas associated with food
reward at the same time as reducing the amount of food they eat."
He added that eating enough fibre to naturally produce similar
amounts of propionate would be difficult: "The amount of inulin-propionate
ester used in this study was 10g -- which previous studies show increases
propionate production by 2.5 times. To get the same increase from fibre alone,
we would need to eat around 60g a day. At the moment, the UK average is
15g."
Claire Byrne, a PhD researcher also from the Department of
Medicine explained that using inulin-propionate ester as a food ingredient may
help prevent weight gain: "If we add this to foods it could reduce the
urge to consume high calorie foods." She added that some people's gut
bacteria may naturally produce more propionate than others, which may be why
some people seem more naturally predisposed to gain weight.
Dr Tony Goldstone, co-senior author of the study from the
Department of Medicine added: "This study adds to our previous brain
imaging studies in people who have had gastric bypass surgery for obesity.
These show that altering how the gut works can change not only appetite in
general, but also change how the brain responds when they see high-calorie
foods, and how appealing they find the foods to be."
Dr Douglas Morrison, author of the paper from the Scottish
Universities Environmental Research Centre at the University of Glasgow,
commented: "We developed inulin-propionate ester to investigate the role
of propionate produced by the gut microbiota in human health. This study
illustrates very nicely that signals produced by the gut microbiota are
important for appetite regulation and food choice.
"This study also sheds new light on how diet, the gut microbiome and health are inextricably linked adding to our understanding of how feeding our gut microbes with dietary fibre is important for healthy living."
"This study also sheds new light on how diet, the gut microbiome and health are inextricably linked adding to our understanding of how feeding our gut microbes with dietary fibre is important for healthy living."
The research was funded by the National Institute for Health
Research Imperial Biomedical Research Centre and the Biotechnology and
Biological Sciences Research Council