Objective: To examine the use of vitamin, mineral and herbal supplements in patients attending family practice clinics.
Design: A prospective 1-year cohort study.
Setting: Sixteen family practices in Calgary.
Participants: One hundred and eighteen patients (more than 18 years of age) were initially interviewed; 12 patients were lost to follow-up.
Main outcome measures: Number and type of supplements used, duration of use, sources of patient information, beliefs about supplement efficacy and safety, reporting use to physicians, costs and changes in pattern of use over 1 year.
Results: Supplement use was unrelated to age, but more women (73%) used supplements than men (44%). Relative to age, more patients younger than 50 years believed supplements were safer than prescription medications (82% v. 43%, p = 0.0005). Younger patients were less likely than those over 50 years old to have received supplement information from physicians (10% v. 37%, p = 0.0008) and were less compliant than older patients with manufacturers' recommended dosages (p = 0.02). Whereas 74% of those over the age of 50 years informed their physician that they used supplements, only 30% of younger patients did so (p = 0.0006). At 1-year follow-up, the number of supplements taken per patient increased (p < 0.05), and there was a tendency for more patients to take supplements (61% v. 70%, p = NS).
Conclusions: The majority of patients attending family practices in Calgary use vitamin, mineral or herbal supplements, and monitoring of supplement use by health care professionals is minimal. Young patients, in particular, tend not to report their use of supplements. They also believe the supplements are safer and more effective than prescription medications and obtain information from nonmedical sources. Physicians should enhance patient understanding of these products and include supplement use in all medical histories. In particular, younger patients require more reliable information on supplements.