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.

Cross-sectional study in two Danish cities.

The Danish Investigation on Iodine Intake and Thyroid Diseases, 1997–1998.

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.

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 (OR = 1.37, 95% CI 1.12–1.66) and among users of medication (OR = 1.22, 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 (OR = 2.2, 95% CI 1.31–3.77).

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.