BETHESDA, MD. — The health effects of lactose intolerance in people who avoid dairy foods have not been adequately studied to determine if there are nutritional deficiencies or long-term effects on bone and cardiovascular health, according to findings from 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 concluded that a substantial proportion of people who have little or no lactase activity do not have lactose intolerance and may be missing out on the health benefits of nutrients in dairy foods, primarily calcium and vitamin D.
“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,” panel chairperson Dr. Frederick J. Suchy said in a press briefing. “Sometimes parents perceive themselves as being lactose intolerant when they're not and then impose that condition on their child without any testing,” said Dr. Suchy, professor of pediatrics at Kravis Children's Hospital at Mount Sinai Hospital, New York.
The panel defined lactose intolerance as onset of gastrointestinal symptoms in an individual with lactose malabsorption, after 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 U.S. population.
Many studies reviewed by the panel did not verify if gastrointestinal 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 so-called lactase nonpersisters form the majority of all people worldwide.
Evidence suggests that adults and adolescents who have been diagnosed with lactose malabsorption could ingest at least 12 g of lactose (equivalent to the lactose content of 1 cup of milk) with no or minor symptoms, the panel found.
The panel advised creating individualized strategies for patients with real or perceived lactose intolerance, such as eating small amounts of dairy foods with other meals and spreading dairy intake throughout the day. Calcium-fortified soy or rice drinks, fruit juices, soy products, dried beans, and leafy greens are good nondairy sources of calcium, the panel noted.
Disclosures: None of the panelists reported relevant conflicts of interest.
A copy of the draft statement is at http://consensus.nih.gov/2010/lactose.htm