Vitamin D is essential for the body to absorb calcium from food and aids the flow of calcium between bones and the blood. Adequate levels of Vitamin D are therefore important for helping to maintain healthy bones.

The sun’s ultraviolet radiation (UVR) is the best natural source of Vitamin D however it’s also the biggest cause of skin cancer.

To try and balance these effects of UVR, public health guidelines have been developed.

The guidelines state that during the hot months of the year (September to April) a few minutes of UVR exposure on face, hands and arms (or less than 15% of the skin surface) at mid-morning or mid-afternoon on most days of the week is enough time to make 1000 International Units (IU) of Vitamin D.

For the cooler months (May to August) between two and three hours spread across the week is required. For people with dark skin, during both summer and winter, three to six times this amount of sun exposure is required to ensure adequate Vitamin D levels.

Office workers across the Melbourne CBD were recruited to test the efficacy of these guidelines. Each person completed a detailed questionnaire and diary listing their sun exposure over two weeks in summer (February/March) and again in winter (August).

Vitamin D levels in the blood are inadequate when they fall below 50nmol/L. For the average office worker who followed the sun exposure recommendations during summer the average blood level of Vitamin D was 67nmol/L. But in winter, the average of those people following the recommendations was only 42nmol/L.

Implications

Staying sun safe during summer still provides enough sun exposure to generate more than adequate levels of Vitamin D. However in winter most office workers in the Melbourne CBD are failing to get enough sun exposure to meet the minimum Vitamin D requirements.

During these colder months, particular effort is needed to get outside and catch a few moments ofthe sun’s rays. Getting out when possible at lunch, taking a walk or sitting in the cool winter’s sun for a few extra minutes could help.

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Last Reviewed: 04/10/2019

© Norman Swan Medical Communications.



References

Kimlin M et al. Are the current Australian sun exposure guidelines effective in maintaining adequate levels of 25 hydroxyvitamin D? Journal of Steroid Biochemistry and Molecular Biology 2016;155:264- 270.