Lactose intolerance

How common is lactose intolerance?

Intolerance to lactose-containing foods (primarily dairy products) is a common problem. The prevalence of lactase deficiency in the United Kingdom is around 6%, but only half of those will experience symptoms after ingesting a glass of milk. Lactose intolerance is the most important cause of CHO malabsorption, other types of primary carbohydrate malabsorption (sucrase-isomaltase or trehalase deficiencies) being extremely rare outside certain populations in Greenland and Canada.

What are the causes of lactose intolerance?

Lactose malabsorption can be due to primary lactase deficiency or secondary to underlying intestinal disease.

There are three causes of primary lactase deficiency

  • Racial or ethnic lactose malabsorption
  • Developmental lactase deficiency- this is the most common form of lactase deficiency worldwide. Lactase activity is gradually lost due to reduced genetic transcription. This becomes symptomatic in adult life.
  • Congenital lactase deficiency

What are the symptoms of lactose intolerance?

Colonic symptoms like flatulence, borborygmi, bloating, and diarrhoea. These symptoms are caused by colonic bacterial fermentation of unabsorbed lactose to SCFA and H2 gas.

How do you diagnose lactose intolerance?

Hydrogen breadth (lactose tolerance) tests- H2 is produced by bacterial action on unabsorbed CH in the colon. Thus in CH malabsorption, a breadth H2 peak will occur 90 minutes after its ingestion when it first arrives in the colon and is broken down by the bacteria.  False positive results are possible particularly with small bowel bacterial overgrowth.
Concurrent antibiotic administration will alter the results of H2 breadth test as it relies on bacterial fermentation of carbohydrate. Further upto 18% of persons are H2 non excretors. The test will false negative in these pts as H2 is metabolised by bacteria to methane.

Do you really need H2 breadth test to diagnose lactose intolerance?

Trial of Lactose-Free Diet – This is a suitable alternative to breath testing and may be preferable in a large number of patients (for instance, all irritable bowel patients). It should be maintained for an appropriate length of time (at least two weeks).

It is important to remember that lactose malabsorption may be due to primary lactase deficiency or secondary to small bowel disease like coeliac disease and appropriate tests requested.

Does a negative H2 breadth test exclude lactose malabsorption?

A significant proportion of patients with symptoms suggestive of lactose intolerance have normal breath hydrogen tests. Consider the following

  • False negative test
  • Intolerance to other factors in milk like fat or milk protein allergy

How do you treat lactose malabsorption?

  • Dietary lactose restriction- Whole milk/chocolate milk may be better tolerated than skimmed milk as fat prolongs gastric emptying. Yogurts are better tolerated. Similarly cheeses generally contain much lower quantities of lactose.
  • Enzyme replacement- commercially available lactase does not completely hydrolyse all dietary lactose and the results in individual patients are thus variable. Lactase capsules can be sprinkled on or taken orally with lactose-containing foods, as can some of the other lactase preparations; however, the individual doses required and responses to individual products must be tested in each patient.
  • Calcium supplementation is needed to avoid the risk of osteoporosis.

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