Lactose and fructose intolerance

Lactose intolerance results from a deficiency in the intestinal enzyme lactase. Lactase catalyses the division of disaccharide lactose in milk and dairy products into the monosaccharides glucose and galactose. Due to its genetic predisposition, part of the population already loses the ability to produce sufficient levels of the enzyme lactase in childhood. This inhibits the breakdown of lactose and promotes the development of lactose intolerance. In the event of lactase deficiency, the lactose reaches the colon colonised by bacteria, which in turn break it down. The resulting bacterial metabolites cause typical complaints, such as flatulence with pressure pain and diarrhoea. Statistically, about 10 - 15 % of the German population suffer from lactose intolerance.

Fructose intolerance is an autosomal recessive hereditary genetic disorder. It is caused by a deficiency of the enzyme fructose-1-phosphate aldolase B in the intestinal mucosa, liver and kidneys. Accumulation of the intermediate metabolites (fructose-1-phosphate) causes damage to the proximal tubules in the kidney, leading to acidosis and aminoaciduria. The disease is comparatively rare and is characterised by hypoglycaemia, sweating, tremor, vomiting and cramps after fructose intake.