Prevalence of thiamine deficiency in anorexia nervosa: a systematic review and narrative synthesis.

Thiamine is an essential vitamin that plays a crucial role in many biochemical processes in the body. Anorexia nervosa (AN) is one potential cause of a state of deficiency which can result in grave medical sequelae. There is limited available evidence of the prevalence of thiamine deficiency in patients who suffer from AN. The current study aimed to systematically review all available evidence on the prevalence of thiamine deficiency in cohorts with AN. Studies were included where thiamine status in a group of participants with AN was measured, either through self-reporting or objective measurement. Eight databases (Scopus, CINAHL complete, Medline complete, EMBASE, WEB OF SCIENCE, PROSPERO, COCHRANE DATABASE OF SYSTEMATIC REVIEWS and Cochrane Central Register of Controlled Trials (CENTRAL) were searched. PRISMA guidelines were followed. The study was registered on PROSPERO. A minimum of two researchers conducted each part of the review. The search identified 42 articles whose full texts were screened for eligibility, with 17 retained for qualitative synthesis. The prevalence rates of thiamine deficiency in AN varied from 5.9% to 100% when based on self-report dietary intake. When objective measurements were taken, rates ranged from 0% to 56.7%. The review suggested that age, body mass index (BMI), duration of illness and subtype of AN were not associated with thiamine status. The limited available evidence suggested that the use of supplements, prior treatment and higher energy intakes were associated with a reduced risk of developing a thiamine deficiency among individuals with AN. Poor study methodology including small sample size, inconsistent deficiency definition and study heterogeneity limits the conclusions that can be drawn. Ultimately, there is insufficient strength of evidence to draw definitive clinical recommendations. This review highlights the need for further studies with more robust methodology to help further inform clinical practice.