Study: Whole Grains, Gut Bacteria and Insulin

This article appears in the February 4, 2015 issue of AICR’s CRU.

Foods containing fiber reduce risk of colorectal cancer, with previous research suggesting that fiber's affect on gut bacteria may play a role. A new animal study published in the Journal of Nutrition offers new insights into this area and other chronic diseases, finding that whole grains may improve insulin levels and cholesterol.


Study researchers fed one group of mice flour made from whole grain oats and another group consumed refined flour lower in soluble fiber. Soluble fiber slows the passage of food through the digestive tract, which may help keep you feeling full longer. It is also linked to lower cholesterol and increased insulin sensitivity, important factors in the development of heart disease and type 2 diabetes.

Type 2 diabetes links to increased risk of some cancers, and some research also suggests that excess levels of insulin and insulin resistance play a role in colorectal cancer.

Both diets had the same amount of protein, carbohydrate, fat, and insoluble fiber.

After eight weeks, researchers found that the mice fed whole grain oat flour had lower blood levels of insulin, hormones associated with insulin resistance, and non-HDL cholesterol—known as “bad” cholesterol. Genes involved in how the liver regulates insulin were also more active.

When study researchers measured the bacteria in the mice's colon, they found that mice had different levels and types of bacteria. The group of animals consuming the whole grain oat flour had more of Lactobacillus genus bacteria, for example, which has recognized health benefits, and less of other types of bacteria compared to mice fed refined flour.

This work was supported by General Mills Bell Institute of Health and Nutrition

Albert Lihong Zhou et al. "Whole Grain Oats Improve Insulin Sensitivity and Plasma Cholesterol Profile and Modify Gut Microbiota Composition in C57BL/6J Mice." J. Nutr. February 1, 2015.

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