Intestinal lactase deficiency in Ceylon (Sri Lanka).

Lactose tolerance tests (LTT) in 200 normal adult Ceylonese have shown that 145 (72.5%) had a flat LTT, indicating a population prevalence of lactase deficiency of 66.2 to 78.8%. Jejunal lactase estimations in a smaller sample (41) confirmed this. Twelve of 55 subjects (21.8%) with a normal LTT had intestinal symptoms after lactose and intestinal lactase was low in most of them. It is suggested that little lactase is required to elevate the blood sugar but that more may be required to prevent diarrhea. On the other hand, 65.5% had no symptoms despite a flat LTT, and the possible reasons for this are considered.