Dietary fiber is a recognized contributor to the maintenance of intestinal health, as well as being associated with reduced rates of cardiovascular disease and mortality. However, few people consume the recommended amount because much of the grains consumed around the world are refined, which removes the fiber component. Not only the amount, but also the type of fiber is critical as poorly fermented fibers provide mainly a bulking effect, whereas highly fermentable fibers can create intestinal discomfort. Some of the literature to date describes the benefit of resistant starch because it can promote short chain fatty acid production, lower concentrations of protein metabolites (e.g., p-cresol), and reduce dietary-protein induced colonocyte DNA damage. The recent development of a high amylose wheat variety could allow the production of foods with high fiber (resistant starch) from refined grains. Gondalia and colleagues conducted a study to determine if consumption of high amylose wheat food products would improve markers of intestinal health. Their results are published in the June 2022 issue of The Journal of Nutrition.
Eighty healthy adults were recruited into a 4-arm, randomized-controlled, double-blind study. Subjects consumed a low-fiber diet for 2 weeks prior to being assigned to treatment groups: 1) refined low-amylose wheat (LAW-R), 2) refined high amylose wheat (HAW-R), 3) wholemeal low-amylose wheat (LAW-W), and 4) wholemeal high amylose wheat (HAW-W). They consumed bread (160 g/d) and biscuits (75 g/d) of their assigned treatment for 4 weeks. Samples were collected at baseline and after 4 weeks of the treatment to measure fecal biochemical markers. Abundance and diversity of the microbiota and perceived gut comfort were assessed at baseline, 2 weeks, and 4 weeks.
There were no effects of LAW and HAW on fecal output and excretion of total short chain fatty acids. However, after 4 weeks of consuming the HAW-R foods, subjects had 38% higher fecal butyrate excretion than those consuming the LAW-R foods, and had higher short-chain fatty acid producing bacteria than at baseline. LAW-R increased p-cresol concentration and abundance of p-cresol producing bacteria relative to the baseline measures. Consumption of HAW-R led to reduced concentrations of p-cresol and bacteria that produce it. Fecal consistency and digestive comfort were not influenced by the amount of amylose consumed. The authors concluded that increasing resistant starch intake through the use of refined high-amylose wheat led to improved gastrointestinal health by modulating microbiota and their metabolites.
Shakuntla V Gondalia, Brooke Wymond, Bianca Benassi-Evans, Pierre Berbezy, Anthony R Bird, Damien P Belobrajdic, Substitution of Refined Conventional Wheat Flour with Wheat High in Resistant Starch Modulates the Intestinal Microbiota and Fecal Metabolites in Healthy Adults: A Randomized, Controlled Trial, The Journal of Nutrition, Volume 152, Issue 6, June 2022, Pages 1426–1437, https://doi.org/10.1093/jn/nxac021.
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