Fact Files : The Sunburnt Country – the increasing prevalence of Vitamin D deficiency

Julie Albrecht, Accredited Practising Dietitian

The increasing prevalence of the deficiency of the Sunshine Vitamin – Vitamin D, is somewhat of a paradox in our sun drenched country, with nearly a third of all men and women having a mild to moderate deficiency (1). There is a higher prevalence among the older population with nearly 50% of patients in aged care facilities surveyed having mild vitamin D deficiency (1).

A study undertaken in South East Queensland, measured the vitamin D level of 414 men and women with a mean age of 42 years. It found 23.4% had mild Vitamin D deficiency ( < 50 nmol/l) and 8 % had a moderate Vitamin D deficiency (< 24 nmol/l) (2).
Vitamin D deficiency impacts on the muscuoskeletal health of the individual, with severe deficiency resulting in osteomalacia in the adult and rickets in children (1). Milder forms of the deficiency result in secondary hyperparathyroidism and increased bone turnover and the increasing risk of osteoporosis (1). Proximal myopathy and muscle pain may also be part of this deficiency presentation (1). Vitamin D deficiency also impacts mental health - depression, immunity and autoimmunity, obesity and the progression of type II diabetes (1).

In Australia the major source of vitamin D is through sunlight exposure, with less vitamin D being synthesized in the elderly, veiled, dark skinned individuals and during the winter months (3). Research has demonstrated that on average a whole body exposure for 10 –1 5 minutes (1 minimal erythemal dose - 1 MED) in the midday sun is comparable to taking 15000 IU of vitamin D (3). On this basis the exposure of around 15% of our body surface, exposing our face, neck and arms, to around 1/3 MED, should provide approximately 1000IU (3). It is important to note the amount of sun exposure to produce 1/3 MED will vary dependent on the skin type, latitude, season and time of day (3). The table below will provide some useful guidance (3).

From a dietary perspective, Vitamin D is found in small quantities in a few foods, and it is estimated that most Australians’ consume 2 - 3 ug/day (< 100IU) of vitamin D daily (3). Food sources include sea salmon, herring, mackerel, liver, eggs and fortified foods such as margarine and some low fat milk (3).

The daily requirement for Vitamin D is 400 – 600 IU, with a larger dose being required to treat patients with deficiency (3). This higher level is necessary to ensure repletion of Vitamin D stores in the fat and muscle (3). As the body fat compartment is larger than plasma and extracellular fluid compartments, there will be a lag time before normalisation of serum 25-OHDlevels are realised (3). The treatment of Vitamin D deficiency is 3000 – 5000 IU per day for at least 6 – 12 weeks, followed by an ongoing treatment of 1000 IU daily (3, 4).

Taking into consideration our ongoing public health message of SLIP, SLOP, SLAP, it is now prudent that checking Vitamin D status should be monitored annually.

References

1. Ebeling, Peter., Editorials., Megadose therapy for vitamin D deficiency., MJA.,Volume 183., Number 1., 4th July 2005.
2. Editorials., Vitamin D deficiency in South East Queensland., MJA., Volume 174., 5th February 2001.
3. Working Group of the Australian and New Zealand Bone and Mineral Society, Endocrine Society of Australia and Osteoporosis Australia., Vitamin D and adult bone health in Australia and New Zealand: a position statement., MJA., Volume 182., Number5., 21 March 2005.
4. Diamond, T.D., Wo,K.W, Rohl, P.G., Meerkin, M., Annual intramuscular injection of a meagdose of cholecalciferol for treatment of vitamin D deficiency: efficacy and safety data., MJA., volume 183., Number 1., 4th July 2005.

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