Flaxseed fiber improves gut health and helps tackle obesity, study suggests

06 Feb 2019 --- Flaxseed fibers that ferment in the gut influence microbiota that can improve metabolic health, while protecting against diet-induced obesity. This is according to a study published in the American Journal of Physiology-Endocrinology and Metabolism. The study was carried out in mice and the data suggest that flaxseed supplementation may positively benefit obese individuals in reducing weight and improving glucose tolerance.

Gut microbiota play a significant role in weight regulation and glucose tolerance, which is how the body processes sugar. Fiber is broken down in the gut via a process called fermentation. This process may positively affect the digestive system by increasing fatty acids, which in turn reduce the production of fat tissue in the body and improve immune function. 

Previous research has shown that fiber-rich flaxseed may enhance cholesterol levels and ameliorate colon inflammation. However, there previously was not as much research on the fermentability of flaxseed and its effect on the gut. 

Researchers studied mice assigned to four different diets:

• a standard diet that contained 4.6 percent soy-based fiber (“control”).
• a high-fat diet that contained no fiber (“high-fat”).
• a high-fat diet that contained 10 percent indigestible cellulose fiber (“cellulose”).
• a high-fat diet that contained 10 percent flaxseed fiber (“flaxseed”).

The research team measured the amount of oxygen the mice used, levels of carbon dioxide produced, food and water consumed and energy expended. Glucose tolerance was also measured near the end of the trial. 

Twelve weeks later, the team 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. 

Mice that received flaxseed supplements also had better glucose control and levels of beneficial fatty acids that were comparable to the healthy control group. When examining the cecal contents, the research team found evidence that the bacteria present ferment fibers from the thick, glue-like layer of the flaxseed shell. The bacteria that perform fermentation then produce more beneficial fatty acids.

The researchers say the data suggest that flaxseed fiber supplementation affects the host metabolism by increasing energy expenditure and reducing obesity as well as improving glucose tolerance. They note that future research should be directed towards understanding the relative contribution of the different microbes and delineate underlying mechanisms for how flaxseed fibers affect the host metabolism.