Double-blind study on the tolerance of four types of milk in lactose malabsorbers and absorbers.

Eighty Italian adults (53 females, 18-69 years, and 27 males, 18-60 years) underwent double-blind tests involving the intake of increasing amounts (125, 250, 500, 1000 ml/d) of four types of milk with normal or low lactose and/or fat content. The tests were completed satisfactorily by 71 subjects. Forty were lactose malabsorbers (LMs) and 31 were absorbers (LAs), according to a standard oral lactose tolerance test. Each subject reported on a questionnaire whether he/she experienced symptoms during the 24 h after milk intake, and the intensity of the symptoms, adopting a score of 0 to 12, according to an already tested procedure. The aim of the study was to investigate the relationship between lactose malabsorption or absorption and intolerance to milk in Italian adults, relative to lactose and fat contents, dose of milk and individual sensitivity. LMs reported symptoms overall more frequently and with greater intensity than LAs (P less than 0.001). The amount of milk ingested was positively associated with the frequency of symptoms both in LMs and LAs. Contrary to earlier findings, fat seemed to contribute to milk intolerance in LMs rather than to reduce it. According to analysis of variance individual differences accounted for 40 per cent of total variation in symptom frequency.