To the Editor: Dr Holt and colleagues1
concluded that increasing the daily intake of calcium by up to 1200 mg
via low-fat dairy food in subjects at risk for colonic neoplasia
reduces proliferative activity of colonic epithelial cells and restores
markers of normal cell differentiation.
The epidemiologic situation among sub-Saharan Africans is the
converse of that indicated by the study of Holt et al.1
First, judging by admissions of patients to hospitals, colon cancer is
nearly absent in rural populations, and its incidence is low in urban
dwellers. For example, in Zimbabwe, according to the Cancer Registry in
Harare, the age-adjusted incidence rates for men and women are 6.6 and
3.0 per 100,000.2 In South Africa, colon cancer is
uncommon and adenomatous polyps are rare. As to level of calcium
intake, it is relatively low in almost all African populations, about
300 to 450 mg/d3; moreover, African women experience large
losses of calcium from high parity and long lactations. Clearly, a risk
factor in one context may have limited applicability in another. Even
among white populations, most studies that have observed a protective
effect of calcium were conducted in Nordic or
Anglo-Saxon
communities, but no study has demonstrated a protective effect of
calcium or dairy products in Hispanic communities.4