Prevalence, cause and diagnosis of lactose intolerance in children aged 1-5 years: a systematic review of 1995-2015 literature.

Background and Objectives: To assess the prevalence, etiology, diagnosis of primary and secondary lactose intolerance (LI), including age of onset, among children 1-5 years of age. Suspected/perceived lactose intolerance can lead to dietary restrictions which may increase risk of future health issues. Methods and Study Design: MEDLINE, CAB Abstract, and Embase were searched for articles published from January 1995-June 2015 related to lactose intolerance in young children. Authors independently screened titles/abstracts, full text articles, for eligibility against a priori inclusion/exclusion criteria. Two reviewers extracted data and assessed quality of the included studies. Results: The search identified 579 articles; 20 studies, the majority of which were cross-sectional, were included in the qualitative synthesis. Few studies reported prevalence of primary LI in children aged 1-5 years; those that did reported a range between 0-17.9%. Prevalence of secondary LI was 0-19%. Hydrogen breath test was the most common method used to diagnose LI. None of the included studies reported age of onset of primary LI. Conclusions: There is limited recent evidence on the prevalence of LI in this age group. The low number of studies and wide range of methodologies used to diagnose LI means that comparison and interpretation, particularly of geographical trends, is compromised. Current understanding appears to rely on data generated in the 1960/70s, with varied qualities of evidence. New, high quality studies are necessary to understand the true prevalence of LI. This review is registered with the International Prospective Register for Systematic Reviews (PROSPERO).