Many patients misunderstanding lactose intolerance

The health effects of lactose intolerance in people who forgo consuming dairy foods have not been adequately studied to determine if such individuals have any nutritional deficiencies or long-term clinical sequelae affecting bone and cardiovascular health, according to a panel of experts assembled by the National Institutes of Health.

In a draft “state of the science” statement, the 14-member panel was not able to estimate the prevalence of lactose intolerance from a systematic review of 54 studies, but was able to conclude that a substantial proportion of people who have little or no lactose activity do not actually have clinical lactose intolerance and may be needlessly missing out on the health benefits provided by the nutrients in dairy foods, primarily calcium and vitamin D.

“One of the key problems that we recognize is that sometimes parents perceive themselves as being lactose intolerant when they’re not, and then impose that condition on their child without any testing.”

“Particularly in children and adolescents, it’s very difficult for them to receive the required amounts of calcium and vitamin D if they avoid dairy products completely,” said a professor of pediatrics at Mount Sinai Hospital, New York.

The panel defined lactose intolerance as gastrointestinal symptoms in an individual with lactose malabsorption that are observed following a blinded, single-dose challenge of ingested lactose but not after ingestion of an indistinguishable placebo. None of the studies in the panel's review used this definition or evaluated a representative sample of the US population.

Many of the studies that the panel reviewed did not verify whether GI symptoms resulted from lactose malabsorption (which may or may not be symptomatic) in people who have lost most or all lactase expression in their small intestine. These people, called lactase nonpersisters, form the majority of all people worldwide.

The panel also suggested that “determining the amounts of lactose that can be tolerated is an important step in developing evidence-based dietary recommendations that meet the needs of the individual.” Evidence suggests that adults and adolescents diagnosed with lactose malabsorption can ingest at least 12 g of lactose (equivalent to the lactose in 1 cup of milk) with no symptoms or minor symptoms.

In order that people with real or perceived lactose intolerance who do not eat dairy foods can obtain their nutritional benefits, the panel advised creating individualized strategies for patients, such as consuming small amounts of dairy foods with other meals and spreading their dairy intake throughout the day.

None of the panelists had relevant conflicts of interest.