Use of dietary supplements in Denmark is associated with health and former smoking

OBJECTIVES: To describe the use of dietary supplements in a group of Danish adults and to investigate the differences between users and non-users with respect to age, gender, health and lifestyle factors.

DESIGN: Cross-sectional study in two Danish cities.

SETTING: The Danish Investigation on Iodine Intake and Thyroid Diseases, 1997-1998.

SUBJECTS: Participants were 3707 women (selected age groups between 18 and 65 years) and 942 men (60-65 years). Participation rate was 50%. Supplement data were collected in a personal interview. Data on education, smoking, alcohol intake, physical activity, use of medication and self-perceived health were derived from a self-administered questionnaire. Multiple logistic regression was used for the statistical analysis.

RESULTS: Participants were asked about all kinds of supplements, ranging from products containing vitamins and minerals, to fish oils and products of herbal origin. On average 59% reported use of some kind of dietary supplement. Most common were combined multivitamin/mineral products (48%) followed by single vitamin C products (10%). Twelve per cent used three or more different supplements. Supplement use was strongly associated with age and gender, being highest among elderly women (78%). Ex-smokers were more likely to use supplements than subjects who had never smoked (odds ratio (OR) 1.36, 95% confidence interval (CI) 1.09-1.76). Supplement use was more likely among subjects who had many days of illness 95% CI 1.12-1.66) and among users of medication 95% CI 1.04-1.42). Subjects who perceived their health as poor were more likely to use supplements other than just a multivitamin/mineral tablet 95% CI 1.31-3.77).

CONCLUSIONS: Use of dietary supplements was related to age, gender and smoking, but also to poor self-perceived health status and absence from work. This indicates that a group of people use supplements as a form of self-medication.