American Journal of Clinical Nutrition, Vol 27, 756-759, Copyright © 1974 by The American Society for Clinical Nutrition, Inc.

Lactase deficiency in a rural area of Mexico

¹ Head, Department of Genetics, Instituto Nacional de la Nutrición
² Member of the Department of Genetics, Instituto Nacional de la Nutrición
³ Senior Student of the Escuela Nacional de Antropología of Mexico, Recipient of a Student Research Fellowship from the Instituto Mexicano del Seguro Social of Mexico
⁴ Research Associate, Department of Genetics of the Hospital de Pediatría, Centro Médico Nacional, Instituto Mexicano del Seguro Social
⁵ Research Associate, Division of Nutrition, Instituto Nacional de la Nutrición

The prevalence of the adult type of intestinal lactase deficiency in three groups of residents of a rural area of Mexico was studied. Of the 401 individuals tested, 73.8% were intolerant, and the relative frequency of intolerance in each group was similar. However, traditional milk consumption habits of the lactose-intolerant individuals were quite different. In one group, few people had consumed any milk since they were breast fed; in another, over 50% ingested more than one glass of milk daily, and the other was intermediate. The symptomatology following the lactose load was more frequent in those individuals classified as intolerant, but some tolerant ones also had symptoms, whereas some of the intolerant ones did not. Whether low intestinal lactose levels interfere with milk consumption is not definitively answered by this study, but it seems clear that many individuals classified as intolerant are able to ingest milk without difficulty, at least in the relatively small quantities that are typical of this and many other regions of Mexico.