Lactose intolerance

Part of the review of food intolerance on A4Medicine. This review of lactose intolerance provides clinicians information about the pathophysiology and the different types of lactose intolerance.The symptoms and diagnosis are discussed and food containing lactose are described.Practical management tips are included and GPs should consider warning people about the possibility of calcium deficiency in those who start a lactose-free diet. A useful website – can be used by GPs when discussing this topic with parents

Inability to metabolise the carbohydrate lactose due to lactase deficiency Enzyme lactase-phlorizin hydrolase → known as lactase is a beta-galactosidase responsible for the hydrolysis of lactose to the monosaccharides , glucose and galactose These are absorbed by intestinal blood stream
○ glucose used as source of energy
○ galactose becomes component of glycolipids and glycoproteins
 Reduced intestinal lactase results in malabsorption of lactose

Unabsorbed lactose

Metabolised by colonic bacteria

Produces gas and short chain fatty acids

Abdominal cramps , bloating , diarrhoea , flatulence
 It is not a cause of rectal bleeding Absorption of Lactose requires lactase activity in the small intestine brush border to split the bond linking the 2 monosaccharides

Primary-Autosomal recessive Physiological decline in in lactase conc Lactase deficiency develops at various ages Some studies have shown that it is uncommon before 2-3 yrs of age Secondary-Follows damage to the small bowel mucosal brush border 2ary to gastroenteritis Resolves when the dis process is over WHO- diarrhoea should have lasted 2 weeks before consideration of lactose intolerance Congenital-Rare autosomal recessive disorder Manifests at birth soon after milk is introduced Lifelong disorder- failure to thrive and infantile diarrhoea Otherwise normal intestinal mucose Developmental-Occurs in premature babies
( < 34 weeks ) Improves once the intestine matures  Often confused with delayed non-IgE mediated cow’s milk protein allergy Lactose intolerance is not immune mediated Terms often used without a sense of different meanings
○ milk allergy
○ milk intolerance Often non IgE mediated disease symptoms are wrongly labeled as symptoms of intolerance

Symptoms-Abdominal pain ( often crampy ) Bloating Flatus Loose watery stool- an hour or two after ingestion of milk Borborgymi Some occasions nause and vomiting Peri-anal excorciation due to acidic stool Bowel symptoms only

Food wth lactose-In diet as mammalian milk and dairy products Only trace amounts in butter , skimmed mildk powder Widely used in food and pharmaceutical industry
○ bulking agent or filler
○ browning agent ( eg in bread )
○ add texture and bind water in processed meats as sausages and burgers , processed chicken
○ slimming products
○ soft drinks and lager beers

Diagnosi-Diagnosis usually clinical
○ suspect in people with abdominal symptoms after ingestion of milk and milk products Several tests available ( usually not needed )
○ Lactose tolerance test
○ Lactose hydrogen breath test
 Breath test using carbon-13 labelled lactose

Differential-Recurrent abdominal pain of childhood Irritable bowel symptoms Cow’s milk allergy Deficiency of other disaccharidases Infantile colic Diverticular disease Ulcerative colitis Coeliac disease Cystic fibrosis  Lactose intolerance
 can be diagnosed on clinical history and treated with simple dietary measures

Management primary lactase deficiency-Most people with primary deficiency can ingest up to 240 ml of milk ( 12g of lactose ) Advice to divide daily milk intake into several small portions and to take with other foods Yogurts ,curds and cheese may be better tolerated due to
○ thicker consistency → gastric emptying slower
○ lactose is partially hydrolysed by bacteria during preparation Encourage to gradually ↑ milk intake
○ causes changes in intestine that permit higher milk intake Milk-cereal mixtures
○ delay the entry of lactose into intestine → better absorption Ensure adequate calcium intake ( main source for vegetarians is usually milk ) Dietitian input Treat underlying cause Avoid antibiotics Most children with diarrhoea can continue taking breast or undiluted animal milk Complete avoidance for 4-6 weeks with gradual reintroduction in severe cases Malabsorption Failure to thrive ( congenital type ) Calcium deficiency  No current UK guideline on management of Lactose intolerance