Lactose intolerance- NIH consensus

National lnstitute of Health consensus panel on Lactose Intolerance

Lactose intolerance is a condition where symptoms of diarrhoea, abdominal pain, gas, and/or bloating arise after ingesting lactose-containing foods and beverages. The symptoms are produced by malabsorption of lactose, a sugar found in milk and other dairy products. Most mammals including humans stop making the lactase enzyme after the weaning period, so infact, adult acquired lactose intolerance is the normal state of affairs. However, this is genetically controlled and in some individuals there is evidence of persistence of lactase production. The gene(s) responsible for this persistence seem to have arisen in Northern Europe populations, where it is found in 90% of the population. The loss of lactase production and resultant lactose intolerance increases steadily as we move to Mediterranean, African and Middle Eastern countries.

 Many people with lactose intolerance – or who mistakenly think they have lactose intolerance – avoid dairy products. However, these products are important sources of calcium, other nutrients, and vitamin D (when fortified). Not getting enough of these nutrients may increase the risk for chronic health problems, including osteoporosis and decreased bone health. Symptoms of lactose intolerance are similar to those in many other digestive disorders such as diarrhoea predominant-IBS or inflammatory bowel disease. Some people have both lactose intolerance and another disorder like IBS. So diagnosis by a doctor is important to accurately determine what is wrong and how to best treat it.

 A National Institutes of Health (NIH) Consensus Development panel set out to assess the available evidence on lactose intolerance. The panel’s report reviews what is known about diagnosis, risk factors, treatment, and areas of research needed about this disorder.

 The expert scientific panel drafted its statement based on scientific evidence. The panel concluded that:

  •  Lactose intolerance is a real and important clinical syndrome, but its true prevalence is not known.
  •  The majority of people with lactose malabsorption do not have clinical lactose intolerance. 
  • Many individuals who think they are lactose intolerant are not lactose malabsorbers. 
  • Evidence-based dietary approaches with and without dairy foods and supplementation strategies are needed to ensure appropriate consumption of calcium and other nutrients in lactose-intolerant individuals.
  • Educational programs and behavioural approaches for individuals and their healthcare providers should be developed and validated to improve the nutrition and symptoms of individuals with lactose intolerance and dairy avoidance.


What amount of daily lactose intake is tolerable in people with diagnosed lactose intolerance?

Malabsorbed lactose is osmotically active within the small bowel, so that a large glass of milk containing 50 g lactose (approx. 200 mls), will lead to a significant secretion of sodium and water into the small bowel. As soon as the lactose enters the large bowel it is rapidly fermented by bacteria to other osmotically active compounds, which draw in more water and lead to diarrhoea. Among individuals appropriately diagnosed with lactose intolerance, differences in a variety of factors can greatly influence their susceptibility to develop intolerance symptoms. Differences in intensity of symptoms result from other factors including abdominal pain perception, and the psychological impact of pain. Determining the amounts of lactose that can be tolerated is an important step in developing evidenced-based dietary recommendations that meet the needs of the individual. The available evidence suggests that adults and adolescents who have been diagnosed with lactose intolerance could comfortably ingest smaller amounts such as 12 g (equivalent to 1 cup of milk) when administered in a single dose with no or minor symptoms and larger amounts of lactose if ingested with meals and distributed throughout the day, Indeed, some data suggest that the routine ingestion of lactose increases the amount of lactose that is tolerable in both adults and adolescents. There is no scientific evidence to identify the tolerable dose of lactose for children with lactose malabsorption.


The NIH consensus panel stressed the importance of additional scientific studies to better understand and manage lactose intolerance. Additional work needs to be done to improve the management of patients with IBS and a hypersensitive colon who also may have lactose intolerance.


Source: NIH Consensus Development Conference: Lactose Intolerance and Health. Draft Statement. February 24, 2010. (; Accessed Feb 26, 2010)

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