promote healthy gut bacteria

Researchers studied the substances produced during digestion when supplemented with oat and rye bran.

The number of adults who are clinically obese worldwide has tripled since 1975. In 2016, over 650 million adults were obese. The Western diet and lack of physical activity primarily have led to the obesity crisis. Western diets typically consist of high fat and sugar and little dietary fiber. Dietary fibers promote gut health by producing bioactive compounds and they are considered prebiotics.

Studies have suggested that diets high in fiber can lead to weight loss, stable blood sugar levels, and lowered cholesterol. Dietary fiber helps the gut to absorb nutrients and reduces liver inflammation more effectively. Scientists still do not fully understand the mechanisms by which dietary fiber promotes healthy gut bacteria. 

Researchers from the Institute of Public Health and Clinical Nutrition of the University of Eastern Finland, VTT Technical Research Centre of Finland, and the School of Biological Sciences of The University of Hong Kong investigated the different compounds produced by the gut and how they changed when dietary fiber levels were increased. Their results were published in the journal Molecular Nutrition & Food Research.

To determine whether fiber would promote healthy gut bacteria, the researchers studied mice that were randomly assigned to one of four diet groups for 17 weeks. Each diet group was provided the same amount of energy and macronutrients but differed in dietary fiber content. The groups were: western diet group (WD), western diet with 10% oat bran (OAT), western diet with 10% rye bran (RYE), and a control group. The fiber diet groups contained 50% dietary fiber.

During week 15 and 16, researchers performed tests to determine glucose tolerance, insulin tolerance, and other tests associated with liver disease. After statistically analyzing the test results, they determined both brans led to lower body weight and reduced the effects of the Western diet.

The rye bran diet was more effective in preventing weight gain than the oat bran diet. Both rye and oat bran helped to prevent the liver damage sustained by the animals on the western diet. The bran diets reduced liver inflammation and improved gut integrity. Diets high in dietary fiber also showed improved blood sugar, with oat bran being the most effective.

The study results confirmed that diets high in fiber promote healthy gut bacteria. Fiber in the diet helps the body to produce more short-chain fatty acids, which promote gut integrity and improve liver health.

Written by Rebecca K. Blankenship, B.Sc.,


Kundi, Z., Lee, J., Pihlajamäki, J., Chan, C., Leung, K., & So, S. et al. (2020). Dietary Fiber from Oat and Rye Brans Ameliorate Western Diet–Induced Body Weight Gain and Hepatic Inflammation by the Modulation of Short‐Chain Fatty Acids, Bile Acids, and Tryptophan Metabolism. Molecular Nutrition & Food Research, 1900580.

Obesity and overweight. (2020). Retrieved 6 July 2020, from

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