Consuming flaxseed may change the microbes in the gut to improve metabolic health and protect against diet-induced obesity, according to a study conducted in mice.
The organisms that live in the digestive tract (gut microbiota) play a role in regulating weight and the way the body processes sugar (glucose tolerance), according to the study published in the American Journal of Physiology -- Endocrinology and Metabolism.
The breakdown of dietary fibre in the gut -- a process called fermentation -- can produce favourable changes in the digestive system, such as an increase in beneficial fatty acids, which may reduce the production of fat tissue in the body and improve immune function.
Flaxseed is a fibre-rich plant that has been shown to improve cholesterol levels and inflammation in the colon, said researchers from the University of Copenhagen in Denmark.
However, there is little research on the fermentability of flaxseed and how flaxseed fibre affects gut microbiota.
Researchers studied mice assigned to four different diets: a standard diet that contained 4.6 per cent soy-based fibre ("control"); a high-fat diet that with no fibre ("high-fat"); a high-fat diet that contained 10 per cent indigestible cellulose fibre ("cellulose"); and a high-fat diet with 10 per cent flaxseed fibre ("flaxseed").
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The team measured the amount of oxygen the mice used, carbon dioxide produced, food and water consumed and energy expended.
Glucose tolerance was also measured near the end of the trial. At the end of 12 weeks, the researchers examined the animals' cecal contents -- bacteria and other biological materials in the pouch that forms the beginning of the large intestine (cecum).
The high-fat group had fewer bacteria associated with improved metabolic health, lower levels of beneficial fatty acids and more of a bacterium linked to obesity when compared to the other groups.
Bacteria levels in both the cellulose and flaxseed groups returned to healthier levels when compared to the high-fat group.
The flaxseed group was more physically active and had less weight gain than the other high-fat diet groups.
The mice that received flaxseed supplements also had better glucose control and levels of beneficial fatty acids that were comparable to the healthy control group, researchers said.
When examining the cecal contents, the team found evidence that the bacteria present ferment fibres from the thick, glue-like layer of the flaxseed shell.
The bacteria that perform fermentation then produce more beneficial fatty acids.
"Our data suggest that flaxseed fibre supplementation affects host metabolism by increasing energy expenditure and reducing obesity as well as by improving glucose tolerance," researchers said.
"Future research should be directed to understand relative contribution of the different microbes and delineate underlying mechanisms for how flaxseed fibres affect host metabolism," they said.