Primary lactase deficiency and past malarial endemicity in Sardinia

Background. It has recently been suggested that primary lactase deficiency might have been selected for by malaria, as occurred for beta-thalassaemia and glucose 6-phosphate dehydrogenase deficiency. However; recently we have found that the prevalence of primary lactase deficiency in the area of Sas sari (Northern Sardinia), where, in the past, there was intermediate malari al endemicity, is comparable to that observed in the adult population from other areas of Southern Italy where malaria was less endemic. Aims, To address the problem further we have determined the prevalence of p rimary lactase deficiency, glucose 6-phosphate dehydrogenase deficiency def iciency and beta-thalassaemia trait in the populations of three Sardinian v illages which differ in altitude above sea-level, socioeconomic features, h istory of endemic malaria and prevalence of b-thalassaemia and glucose 6-ph osphate dehydrogenase deficiency. Subjects, We tested 138 adult males: 53 were from Fonni (a non-malarial mou ntain village, with a strong pastoral tradition), 38 from Lode (a village w ith a similar pastoral tradition, but high malarial endemicity in the past) and 47 from Terralba (a lowland fishing village with an agricultural tradi tion and heavy malarial morbidity and mortality). Methods, A blood sample was obtained in all subjects for determination of H bA2 and glucose 6-phosphate dehydrogenase activity. Lactase deficiency was assessed by measuring breath hydrogen production after oral administration of lactose (50 g), by gas-chromatography. Results, The frequencies of glucose 6-phosphate dehydrogenase deficiency an d of beta-thalassaemia trait in the non-malarial village of Fonni were stri kingly low, compared to frequencies found in the two villages (Terralba and Lode) with a very high past malarial morbidity. In contrast, there was no significant difference in the prevalence of lactase deficiency in the three groups of subjects from the three villages. Conclusions, These data obtained in Northern Sardinia do not support the hy pothesis of a selection of primary lactase deficiency by malaria. For defin itive conclusions, however the malaria hypothesis should be tested in other parts of the world.