[Poor digestion of lactose. Its definition, prevalence in Mexico, and its implications in milk consumption].

We review the studies that have been carried out in Mexico related to prevalence of lactase deficiency. We also describe a study carried out in three regions of Mexico with different consumption of milk (Northern, Central & Southeastern), comprising 960 individuals of ages ranging from 1 to 99 years. They were evaluated in a double blind study in order to determine the prevalence of lactose maldigestion with habitual dosis of milk. Each subject received two treatments: a) 240 or 360 mL of intact milk according to age, and b) the same amount of milk but with the lactose hydrolyzed (> 90% hydrolyzed). The participants were classified as digesters or maldigesters of lactose using the hydrogen breath test. The prevalence of maldigesters was higher in the Central (30%) and Southeastern (22%) regions than in the Northern one (9%, p < 0.01). The prevalence increased with age from 4.5% (< 3 years), 13.6% (3 to 5.9), 20.8% (6 to 12.9), 21.8% (13 to 17.9) and 32.9% in adults. Lactose maldigestion affected consumption marginally.