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Dietary supplements: prevalence of use in the New Zealand population.

Article Excerpt
Abstract

Objective: To determine prevalence of dietary supplement use in New Zealand and to describe types of supplements used.

Design: Secondary data analysis of two cross-sectional national surveys.

Subjects: In total, 3275 children aged 5-14 years, 4636 adults aged 15+ years.

Setting: Homes throughout New Zealand.

Main outcome measures: Prevalence data over 24 hours (children and adults) and over previous year (adults only), type of supplements consumed, pattern of dietary supplement use.

Results: Adults (24.2%) were more likely than children (5.4%) to consume any dietary supplement in the previous 24 hours. Over the previous year 59% of adults had consumed at least one supplement. Adult females were more frequent consumers than males both in the previous year (67.6%, 50.4%) and in the previous 24 hours (30.5%, 17.8%). Multivitamins and minerals were the type most frequently consumed by adults (19.8%) and children (2.1%). Older adults, compared with younger adults, are more likely to consume supplements daily and less likely to consume an individual supplement for a limited time.

Conclusions: The prevalence of use of dietary supplements of a population differs markedly depending on the duration of the period over which use of a supplement is recalled. In New Zealand adults, prevalence of use was 2.4 times higher recalling some use over the previous year, than when recalling use in the previous 24 hours. Use varied by age for adults and by ethnicity among adults and children.

Key words: dietary supplement, epidemiology, minerals, New Zealand, prevalence, questionnaire, vitamins.

INTRODUCTION

Foods may no longer be the sole source of nutrients, with nutrients sourced from both foods (frequently including those fortified with specific nutrients) and dietary supplements. (1) The term 'dietary supplements' once analogous with vitamins and minerals, is now used to include botanical supplements such as echinacea, various forms of garlic and a variety of physiologically active compounds derived from foods or other biological material. Although there has been a worldwide trend of an increase in the prevalence of dietary supplement use, (2-4) the necessity for and cost and safety of dietary supplements continues to be debated. (5)

The measurement and assessment of dietary supplement intake is an area with no international agreement, with little consistency in types of supplements specified, duration of time period of use, level of frequency of data collected and amounts consumed. The personal interview method in the home has been reviewed by Radimer who concluded that this was the best method of dietary-supplement data collection. (5) The time span pertaining to the period over which dietary supplement intake data are obtained will affect prevalence rates. Supplement use can be sporadic, irregular or regular and an individual may vary their supplement intake from month to month or week to week. (6) Information on supplement use 'over the previous year' will give higher prevalence rates than estimating prevalence based on consumption in 'the previous 24 hours' or 'in the previous week'. (4,7) This impact of the duration of the period over which prevalence rate is assessed can make comparisons between studies difficult.

Data for adults aged 15+years from the 1997 National Nutrition Survey (NNS97) (8) and for children aged 5-14 years from the 2002 Children's Nutrition Survey (CNS02) (9) were collected using the personal interview method, and provide the first opportunity to determine the prevalence of dietary supplement use in the New Zealand (NZ) population, and to describe the types of supplements used. Moreover, the questions used in the adult survey enable a comparison of prevalence rates, depending on whether data...

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