Switching to a fibre-rich and low-fat diet increases colonic folate contents among African Americans

How dietary patterns impact colonic bacterial biosynthesis of vitamins and utilization by humans is poorly understood. Our aim was to investigate whether a reciprocal dietary switch between rural South Africans (traditionally high fibre, low fat) and African Americans (Western diet of low fibre, high fat) affects colonic folate synthesis. Colonic evacuants were obtained from 20 rural South Africans and 20 African Americans consuming their usual diets at baseline. For two weeks thereafter, rural South Africans were provided with a Western diet (protein 27%, fat 52%, carbohydrate 20% and fibre 8 g/d) and African Americans were provided with a high fibre, low fat diet (protein 16%, fat 17%, carbohydrate 63% and fiber 43 g/d). Colonic evacuants were again collected. No difference between groups at baseline in the folate content of 3-hour evacuants was observed. The high fibre low fat diet consumed by African Americans during the intervention produced a 41% increase in mean total folate content compared with baseline values (p=0.0037). No change was observed in rural South Africans consuming a Western diet. Mean total folate content of colonic evacuants was higher among African Americans at the end of the dietary switch (3107±1811 µg) compared to rural South Africans (2157±1956 µg) (p=0.0409). In conclusion, consistent with animal studies, switching from a Western diet to one higher in fibre and lower in fat can be expected to result in greater colonic folate content. Future research should confirm these observations are not transitory and understand the contribution of transit-time to the findings.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author