Rarity of colon cancer in Africans is associated with low animal product consumption, not fiber.
OBJECTIVE
To investigate whether the rarity of colon cancer in black Africans (prevalence, < 1:100,000) can be accounted for by dietary factors considered to reduce risk, and by differences in colonic bacterial fermentation.


METHODS
Samples of the adult black South African population were drawn from several rural and urban regions. Food consumption was assessed by home visits, food frequency questionnaires, computerized analysis of 72-h dietary recall, and blood sampling. Colonic fermentation was measured by breath H2 and CH4 response to a traditional meal, and to 10-g of lactulose. Cancer risk was estimated by measurement of epithelial proliferation indices (Ki-67 and BrdU) in rectal mucosal biopsies. Results were evaluated by comparison to measurements in high-risk white South Africans (prevalence, 17:100,000).


RESULTS
Epithelial proliferation was significantly lower in rural and urban blacks than whites. The diets of all the black subgroups were characterized by a low animal product and high boiled maize-meal content, whereas whites consumed more fresh animal products, cheese, and wheat products. Blacks consumed below RDA quantities of fiber (43% of RDA), vitamin A (78%), C (62%), folic acid (80%) and calcium (67%), whereas whites consumed more animal protein (177% of RDA) and fat (153%). Fasting and food-induced breath methane production was two to three times higher in blacks.


CONCLUSIONS
The low prevalence of colon cancer in black Africans cannot be explained by dietary "protective" factors, such as, fiber, calcium, vitamins A, C and folic acid, but may be influenced by the absence of "aggressive" factors, such as excess animal protein and fat, and by differences in colonic bacterial fermentation.
O'Keefe
S J
SJ
Gastrointestinal Clinic, Groote Schuur Hospital and University of Cape Town Observatory, South Africa.
Kidd
M
M
Espitalier-Noel
G
G
Owira
P
P
D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data*; D044383:Black People; D001944:Breath Tests; D002455:Cell Division; D003110:Colonic Neoplasms / Q000453:epidemiology* / Q000208:ethnology / Q000209:etiology; D004041:Dietary Fats / Q000008:administration & dosage*; D004043:Dietary Fiber / Q000008:administration & dosage*; D005232:Fatty Acids, Volatile / Q000032:analysis; D005243:Feces / Q000737:chemistry; D005260:Female; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012007:Rectum / Q000166:cytology; D013019:South Africa / Q000453:epidemiology; D011795:Surveys and Questionnaires; D044465:White People; D003313:Zea mays
D004041:Dietary Fats; D004043:Dietary Fiber; D005232:Fatty Acids, Volatile