GERMAN LANGUAGE VERSION. Lactose tolerance. Map of Eurasia,African and Australia,showing the varying tolerance for lactose,the milk sugar found in dairy products from cow's milk (lower centre). Tolerance varies from complete (100 percent,white) to zero percent (dark blue),with varying shades between (see key at right). Lactose intolerance is due to an inability to metabolize lactose because the enzyme lactase is not present. Ingesting dairy products when intolerant can produce gastrointestinal discomfort,gas,bloating,cramps or diarrhoea. Tolerance is high in north-western Europe,but can be very low in some African and Asian countries |