Winter &
Vitamin D Deficiency

Health implications of vitamin D deficiency

Vitamin D deficiency is of concern as it can lead to a variety of health conditions including the loss of bone density, which can contribute to osteoporosis and fractures in adults and rickets in infants and children. Low levels of vitamin D have also been found in association with other health conditions, such as cardiovascular disease, diabetes, immune system diseases, microbial and respiratory diseases, cognitive impairment in older adults, mental health and cancer.

Target vitamin D levels

The international recommendations for adequate vitamin D levels vary, but based on a review of current literature and recently published recommendations ^{1, 2} Clinical Labs suggests that adequate vitamin D status is a serum level equal to, or greater than, 50 nmol/L at the end of winter. This level should be 10-20 nmol/L higher at the end of summer to allow for seasonal decrease.

This figure is based on the level below which parathyroid hormone concentrations begin to rise and the risk of fractures increases.

As for all tests, Australian Clinical Labs’ pathologists and scientists will continue to evaluate current literature and our target range may change as new evidence emerges.

Who to test

Vitamin D testing should be ordered for patients at risk of vitamin D deficiency, including:

• Housebound people - including the sick and disabled
• Elderly in high care
• People with darker skin
• People who cover their skin due to religious or cultural reasons
• People who regularly avoid the sun
• People who work indoors

Also patients with:

• Signs, symptoms and/or planned treatment of osteoporosis or osteomalacia
• Increased alkaline phosphatase with otherwise normal LFTs
• Hyperparathyroidism, hypo- or hypercalcaemia or hypophosphataemia
• Malabsorption (i.e. CF, IBD, coeliac, etc)
• Medications known to decrease vitamin D levels (i.e. anticonvulsants)
• CRF and transplant recipients

Vitamin D testing

Vitamin D testing at Clinical Labs measures the concentration of total 25-hydroxyvitamin D (25-OHD) in a patient’s serum. The report will also include previous test results, for comparison (if applicable), and suggested cut points to define sufficient, deficient and severely deficient vitamin D levels.

Treatment

To ensure adequate levels of vitamin D are maintained throughout the year, the following sun exposure times (mins per day) are recommended for 1/3MED for moderate fair skin, at either 10am or 2pm daily.³

If patients are unable, for a variety of reasons, to gain the required amount of sun exposure for vitamin D production, supplementation may be required.

A maintenance dose of up to 1000 IU/day may be adequate, however some individuals will require higher doses. Severe vitamin D deficiency (serum level <20 nmol/L) may require 3000-5000 IU/day for 6-12 weeks.

Supplements should be vitamin D3. Adequate dietary calcium is also required, at least 1g/day and up to 1.3g/day, for older adults. Many patients will require supplementation to achieve this amount.

Note: Calcium supplements are best taken before sleep to ensure maximum absorption and suppression of peak bone turnover which usually occurs between approximately 2am and 3am.

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