Faecal pH, dietary fibre intake, and proneness to colon cancer in four South African populations.

In a series of South African populations, mean faecal pH values were found to be: rural and urban blacks, 6.12 and 6.15; Indians 6.21; coloureds (Eur-African-Malay), 6.29; these are significantly lower (p less than 0.01) than that of whites, 6.88. Apart from that of the coloureds, mean values for series of children and adults did not differ significantly. In the populations mentioned, corresponding mean dietary fibre intakes of children's mothers (or associates of mothers) were all relatively low, namely, roughly 25 g, 18 g, 20 g, 21 g, 23 g, respectively. Frequency of colon cancer (also other non-infective bowel diseases, e.g. appendicitis) is very low in rural and urban blacks, is low in Indians and coloureds, yet much higher in whites. Thus, in these different ethnic populations, rarity or low frequency of colon cancer is associated more with low faecal pH than with level of dietary fibre intake, suggesting that components additional to fibre have a role in determining the milieu intérieur of the bowel and its proneness to disease.