Lactase deficiency in the South African black population.

H2 breath analysis was carried out to determine the prevalence of lactase deficiency in different tribes of the South African Black population. Lactase deficiency was common (78%), despite the fact that two of the largest tribes (Zulu and Xhosa) are cattle herders and milk drinkers. This apparent anomaly is due to the consumption of a traditional fermented buttermilk, ("amasi" which has a low lactose content) instead of fresh milk. The most important reason for lactase deficiency, however, is that the South African Blacks originated in the West and Central African zone of nonmilking and took up dairying and milk use fairly recently. Thus they have not had enough time for genetic selection for lactase deficiency through life. The implications inherent in this study are that it would be more prudent to supply milk to developing countries in the form of a fermented milk product such as buttermilk. This is readily accepted by the Black population and would not be counter to accepted cultural practice.