Predictors for cod-liver oil supplement use--the Norwegian Women and Cancer Study

To assess the use of cod-liver oil supplements among Norwegian women and to examine dietary, lifestyle, demographic, and health factors associated with use of this supplement.

Cross-sectional study.

The study is based on data from a food frequency questionnaire from 1998 answered by 37,226 women aged 41-55 y, who in 1991/1992 participated in the Norwegian component of the European Prospective Investigation into Cancer and Nutrition (EPIC). The Norwegian EPIC cohort was based on a random nation-wide sample of Norwegian women.

Cod-liver oil supplement use was reported by 44.7% of the participating women. Subjects with higher education, high physical activity level, and body mass index (BMI) in the normal range were more likely to use cod-liver oil supplements. Consumption did also increase with increased age as well as with increased reported consumption of fruits, vegetables, fatty fish, lean fish, and vitamin D (excluding the vitamin D contribution from cod-liver oil). Energy intake was higher among cod-liver oil users than nonusers. Whole-year daily users of cod-liver oil were also more likely to take other dietary supplements (OR=2.45, 95% CI: 2.28-2.62). Never smokers were more likely to use cod-liver oil supplements than current smokers.

Use of cod-liver oil is associated with several sociodemographic factors, self-reported health issues, and intake of fish, fruit, and vegetables. When assessing the relationship between cod-liver oil use and occurrence of chronic diseases potential confounders need to be considered. Cod-liver oil use seemed not to be matched with vitamin D needs. Thus, emphasis on assessing vitamin D status by measuring levels in blood should be investigated further, in particular, among people living in northern latitudes.