B-QuiCK: Lactose intolerance

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Lactose intolerance

If a person reports gastrointestinal symptoms that consistently occur following the ingestion of milk or milk products

  • First rule out other possible causes of symptoms – particularly if symptoms are severe or persistent, e.g. irritable bowel syndrome, inflammatory bowel disease
    • Secondary causes should be strongly considered in children, e.g. rotavirus infection, giardiasis or coeliac disease
  • If there is no other obvious cause, a lactose-free diet should be trialled for two to four weeks; ensure the patient is aware of “hidden” sources of lactose which are common in processed foods
  • At the end of the trial, the patient should re-introduce lactose; if symptoms have improved during the trial and return when lactose is reintroduced, then this is sufficient to diagnose lactose intolerance
    • Do not routinely request skin prick or serum allergen-specific IgE tests unless cows’ milk protein allergy is suspected as lactose intolerance is not immune-mediated
  • If the dietary challenge is inconclusive or there is uncertainty, discuss with your local laboratory whether additional testing is available, e.g. breath hydrogen testing, or consult with a secondary care clinician

Management of lactose intolerance

  • Lactose usually does not need to be excluded from the diet; people should start with a more restricted diet and gradually increase the consumption of lactose-containing foods according to individual tolerance level
    • Most people can tolerate up to 5 g of lactose (approximately ½ cup milk) on its own, and up to one to two cups of milk in total per day, when eaten with other foods or spread out across the day
  • Some lactose-containing foods are better tolerated than others, e.g. yoghurt with live culture or dairy products with higher fat content
  • Lactose-free milks and alternative milks are usually not required but if used (or if sufficient quantities of cow’s milk cannot be consumed) must be fortified with calcium and vitamin D to meet the recommended intake
  • Probiotics or lactase enzyme supplements (not funded) may be beneficial for some people alongside dietary management, however, these are not routinely required and efficacy varies
  • Infants with lactose intolerance should continue breastfeeding and the mother does not need to eliminate lactose from her diet; lactose-free infant formulas are available, if required
  • A temporary lactose-free diet may be beneficial for people with secondary lactose intolerance, e.g. following a bout of infectious diarrhoea, to promote recovery from the primary illness
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