Fat, fibre and cancer risk in African Americans and rural Africans.
Level 3 - non-randomized controlled study
Non-randomized controlled dietary intervention / food exchange study
PubMed 25919227 · doi:10.1038/ncomms7342
What was done
Researchers conducted a closely supervised 2-week reciprocal dietary exchange study between middle-aged African Americans and rural South Africans. African Americans were switched to a high-fibre, low-fat traditional African-style diet, while rural Africans were switched to a high-fat, low-fibre Western-style diet. Mucosal proliferative biomarkers of cancer risk, gut microbiota, and metabolic profiles (including short-chain fatty acids and secondary bile acids) were assessed before and after the diet exchange.
What was found
Baseline colon cancer incidence was cited as 65 per 100,000 in African Americans compared to <5 per 100,000 in rural South Africans. Following the 2-week food exchange, reciprocal changes occurred in mucosal biomarkers and metabolomic markers: African Americans had increased saccharolytic fermentation and butyrogenesis along with suppressed secondary bile acid synthesis, with opposite patterns observed in rural Africans on the Western-style diet. Specific numeric values, effect sizes, and statistical variance for the biomarker changes were not reported in the abstract.
Why it matters
This study provides direct proof-of-concept that colonic microbiota, metabolomic outputs, and mucosal biomarkers associated with colon cancer risk respond rapidly and reciprocally to changes in dietary fat and fibre.
Limits
The abstract does not report the sample size (n). The intervention was brief (2 weeks), evaluating intermediate surrogate biomarkers rather than long-term clinical cancer outcomes. Numeric values and statistical precision for the intervention results are omitted from the abstract.
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