The consumption of whole grain is associated with beneficial health effects, especially protective effects against cancer, diabetes, obesity and cardiovascular disease. One proposed protective mechanism is thought to be the effect on human gut microbiota.

Diet-microbe interactions within the colon are believed to have important roles in regulating mucosal physiology. Bacteria considered beneficial for human health include Lactobacillus and Bifidobacterium species. Functional foods targeting the human colon aim at stimulating the beneficial genera either directly by providing growth substrates (prebiotics) or indirectly by introducing live exogeneous bacteria (probiotics). Prebiotics are generally non-digestible soluble fibres such as inulin, oligofructose or galactooligosaccharides that may also mediate important health effects such as lowering blood triacylglycerides and improving mineral absorption.

Whole grains are rich in fermentable carbohydrates such as dietary fibre, resistant starch and oligosaccharides. Whole grain cereals consist of the physiologically distinct endosperm, germ and bran. They also contain many compounds such as antioxidants, lignans, vitamins and minerals that may protect against chronic disease. However, there is little information on the impact of specific whole grain cereals on the microbial ecology of the human colon and upon chronic disease risk.

A study by Costabile et al.¹ investigated the effects of whole grain wheat on the human intestinal microbiota compared with those of wheat bran in a double-blind, randomized, crossover study. The whole grain wheat and wheat bran were consumed as breakfast cereals. The relative impact of the whole grain wheat and wheat bran on biomarkers of gut health and blood lipid parameters was also determined. Numbers of faecal bifidobacteria and lactobacilli were significantly higher upon whole grain wheat ingestion compared with wheat bran. Concentrations of ferulic acid in blood also significantly increased. Daily consumption of whole grain wheat exhibited a noticeable prebiotic effect on the human gut microbiota composition.

¹ Costabile, A; Klinder, A; Fava, F; Napolitano, A; Fogliano, V; Leonard, C; Gibson, GR; Tuohy, KM (2008). Whole-grain wheat breakfast cereal has a prebiotic effect on the human gut microbiota: a double-blind, placebo-controlled, crossover study. British Journal of Nutrition 99 (1) 110–120.

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