Why do women use dietary supplements? The use of the theory of planned behaviour to explore beliefs about their use

Dietary supplements use is increasing, despite the lack of evidence to sugg est they are needed to meet dietary deficiency in the majority of people. R easons for consuming dietary supplements are likely to be complex, combinin g social, psychologic al, knowledge and economic factors. The Theory of Pla nned Behaviour (TPB) is a widely used model of social cognition, which has recently been applied to the nutrition field. It was used in a questionnair e, along with a number of additional measures, to explore dietary supplemen t use in a cohort of women. Data from 303 questionnaires were included in t he analysis. The results showed that intentions were the major predictor of dietary supplement use. Health value and susceptibility to illness were al so significant predictors of dietary supplement use (total of 82.9% of resp ondents correctly classified as users or non-users). Intentions themselves were most strongly predicted by attitude, with 70% of variance explained by attitude, subjective norms and perceived behavioural control. Other signif icant predictors of intentions were control beliefs, normative beliefs and health value. Beliefs underlying dietary supplement use revealed difference s between supplement users and non-users in relation to the notion that tak ing dietary supplements acts as an insurance against possible ill-health, w ith supplement users believing more strongly than nonusers that taking diet ary supplements would stop them getting ill and help them to be healthy. Bo th users and non-users of supplements also perceived the media, in the form of books and magazines, to be a powerful influence on a person's decision to use supplements. The findings of this study highlight the potential of t he TPB in exploring supplement-taking behaviour, while throwing light on th e factors influencing an individual's motivations to use dietary supplement s. (C) 2001 Elsevier Science Ltd. All rights reserved.