Older Adults Who Spend More Time Outdoors in Summer and Have Higher Dietary Vitamin D Than Younger Adults Can Present at Least as High Vitamin D Status: A Pilot Study.

Oktawia Borecka,Joanne E Osman,Mark D Farrar,Lesley E Rhodes,Ann R Webb

doi:10.3390/ijerph18073364

Abstract

Vitamin D3 can be produced by exposing skin to UVB radiation or sourced through dietary products. It is often stated that vitamin D status declines in older adults, yet little is known about differences in current-day lifestyle and dietary behaviours influencing vitamin D outcomes in younger (18–40 years old) and older adults (65–89 years old). Our objectives were to perform a pilot study to compare sun exposure behaviours, i.e., time spent outdoors, holiday behaviour and use of sunscreen/clothing, and dietary vitamin D intake, in young and older adults in the UK, together with assessment of their vitamin D status. A total of 13 young and 11 older volunteers completed a four-page questionnaire to assess sun exposure and photoprotective behaviour and an eleven-page one-week vitamin D diet diary, alongside their plasma 25(OH)D measurement. It was found that the older group tended to spend more time outdoors during the working week in summer, to take more summer and winter holidays each year, take longer winter holidays and have similar sunscreen use when compared to younger adults. Older adults had a significantly higher daily dietary intake of vitamin D (4.0 μg) than young adults (2.4 μg). Mean winter 25(OH)D concentration was higher in older (56.9 nmol/L) than in young adults (43.2 nmol/L), but there was no statistical difference between the groups. Contrary to common assumptions, in this study, older adults had sun exposure and dietary behaviours conferring a vitamin D status at least as good as that of younger adults.

Highlights

IntroductionVitamin D is essential for calcium homeostasis, which sustains a healthy musculoskeletal system
The discrepancy between our results and the traditional view that older adults have low vitamin D status can be explained by differences in the populations being tested; in the past, institutionalised and frail older adults were often recruited
Our data show that healthy 65+ year olds spend more time outdoors in summer than working-age adults and have more outdoor hobbies. They go on holiday more often, which when travelling to high sun exposure destinations would boost their vitamin D status. While both groups’ oral intake of vitamin D was below the Reference Nutrient Intake (RNI) of 10 ug/day [2], the dietary vitamin D intake of the older adults (4.0 μg) we studied was significantly higher than that of the younger group (2.4 μg)

Summary

Introduction

Vitamin D is essential for calcium homeostasis, which sustains a healthy musculoskeletal system. Exposure to sunlight allows for the production of vitamin D in human skin. UVB radiation initiates the conversion of the skin precursor 7-dehydrocholesterol (7DHC) to previtamin D and metabolites further down the pathway, such as 25-hydroxyvitamin D (25(OH)D) and 1,25-dihydroxyvitamin D (1,25(OH)2D). Serum 25(OH)D concentration is used to assess vitamin D status of a person [1]. It is estimated that 25(OH)D levels below

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