Objective: To evaluate the prevalence of vitamin supplementation in Thai children aged 1-5 years at Queen Sirikit National Institute of Child Health (QSNICH), parental knowledge of vitamins, practices, and related factors such as nutritional status in vitamin supplementation.
Material and Method: A cross-sectional study was performed at the Well Child Clinic, QSNICH, from 1-31 May 2005. Five hundred parents of young children, aged 1-5 years were interviewed by using the questionnaire to obtain information regarding knowledge and practices of vitamin supplementation. Weight and length/height were measured and nutritional status was assessed using the Thai growth reference. The relationships among vitamin supplement, nutritional status, and other related factors were analyzed using Chi-square test. The p-value <0.05 was considered statistically significant.
Results: Prevalence of vitamin supplementation was 76%, including vitamin C 62%, multi-vitamin (MTV) 35%, and codliver oil 20%. Regarding parental knowledge of vitamins, 57% of them knew the health benefits but 74% did not know the toxic effects of vitamins. The reasons for vitamin supplementation were poor feeding 63%, under-weight 23% and unhealthy status 14%. Vitamins were obtained from over-the-counter 59%, health services 40%, and friends 1%. Vitamin supplementation was significantly higher in children over 2 years of age, whose parents knew the benefits of vitamins, and in those children with malnutrition.
Conclusion: The prevalence of vitamin supplementation was high in malnourished children, over 2 years of age whose parents had knowledge about benefits of vitamins. Parents should be warned about the dangers of high dose of vitamin consumption.

Keywords: Vitamin supplementation, Thai children, Nutritional status