1. A healthy diet is usually not enough to achieve vitamin D sufficiency.
A recent survey found that 47% of the UK adult population have low vitamin D (less than 40nmol/l).1
From October to April, 90% of the UK lies above the latitude that permits adequate exposure to sunlight necessary for vitamin D synthesis.
And a healthy diet is usually not enough to achieve vitamin D sufficiency, as few foods contain substantial amounts of vitamin D – the most significant dietary sources are oily fish and cod liver oil.
2. Be aware of which patients are at high risk of vitamin D deficiency.2
People with pigmented skin are at high risk, as are the elderly, who spend more time indoors, and obese patients, who metabolise vitamin D differently. Other at-risk groups include patients with fat malabsorption syndromes and nephrotic syndrome,
patients who have had bariatric surgery, and patients taking anticonvulsants and antiretrovirals.
3. Look for the typical signs of vitamin D deficiency.
Children with profound vitamin D deficiency present with the classical skeletal deformities of rickets. Osteomalacia in adults usually presents with pain in the ribs, hips, pelvis, thighs and feet. Severe muscle weakness and hypotonia may be a prominent feature.
These patients have a definite indication for treatment. In the absence of bone disease, low vitamin D levels have been associated with non-musculoskeletal conditions such as cardiovascular disease, diabetes, cancer and multiple sclerosis.3 But a causal relationship hasn't been established and it is not known if vitamin D treatment alters the prognosis of these conditions.
4. To assess vitamin D status, measure 25hydroxyvitamin D levels.
Vitamin D status is most reliably determined by assay of serum 25(OH)D. Parathyroid hormone is only raised in a proportion of patients with vitamin D deficiency and cannot be used as a surrogate for 25(OH)D. Vitamin D deficiency is defined as a 25(OH)D below 50nmol/l.4 Patients with symptomatic osteomalacia or rickets usually have a 25(OH)D less than 25nmol/l.
5. Treat with a loading dose followed by a maintenance regimen.
Vitamin D deficiency is treated with oral calciferol in the bioequivalent forms of either ergocalciferol (vitamin D2, from yeast) or cholecalciferol (vitamin D3, from fish or lanolin).
Loading therapy replenishes vitamin D stores – then patients are continued on a lower maintenance dose.
Adults can be treated with 20,000-50,000IU of vitamin D2 or vitamin D3 once a week for eight weeks, or its equivalent of 2,000-6,000IU of vitamin D2 or vitamin D3 daily, followed
by maintenance therapy of 1,000-2,000IU daily.
6. In children with rickets, consider treating the rest of the family, too.
It is likely that other family members of a child with rickets will also be vitamin D deficient, and a maintenance dose of calciferol is recommended for them, too.3
7. Resolution of biochemical and skeletal abnormalities may take a long time.
A relatively rapid biochemical response to supplementation is seen in children, with normalisation of alkaline phosphatase levels within three months. But skeletal lesions take longer to heal.
It may take a year for alkaline phosphatase and parathyroid hormone levels to fall into the reference range in adults.3
8. Adult patients will need to take supplements for the rest of their lives.
Given that few adults have reversible risk factors for vitamin D deficiency, assume that vitamin D supplements should be given lifelong, or at least lifelong during winter months.
9. Avoid calcium and vitamin D combinations.
Avoid giving combined calcium and vitamin D preparations long term because the
calcium component is not usually necessary and reduces compliance. But in children, calcium supplementation (50mg per kg a day) is advised during the first weeks of therapy.3
10. Parenteral doses of vitamin D can be given in adults with severe malabsorption.
An intramuscular dose of 300,000IU calciferol monthly for three months followed by the same dose once or twice a year is an alternative to oral supplements in adults with severe malabsorption.
But recently, intermittent treatment with a high calciferol dose was shown to be associated with falls and fractures among elderly patients.5 So it is wise to reserve parenteral or oral high intermittent calciferol doses for patients who do not tolerate the oral, continuous low-dose supplements.
Professor Pierre-Marc Bouloux is professor of endocrinology at The London Clinic and lead consultant in endocrinology and diabetes at the Royal Free NHS Trust, Hampstead
Dr Aikaterini Theodoraki is a research fellow in endocrinology at the Royal Free NHS Trust, Hampstead
References
1 Hyppönen E and Power C. Hypovitaminosis D in British adults at age 45: nationwide cohort study of dietary and lifestyle predictors.
Am J Clin Nutr 2007;85:860-8
2 Holick M, Binkley N, Bischoff-Ferrari H et al. Evaluation, treatment and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2011;96:1911-30
3 Pearce S and Cheetham T. Diagnosis and management of vitamin D deficiency. BMJ 2010;340:b5664
4 Ross A, Manson J, Abrams S et al. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know. J Clin Endocrinol Metab 2011;96:53-8
5 Sanders KM, Stuart AL, Williamson EJ et al. Annual high-dose oral vitamin D and falls and fractures in older women. JAMA 2010;303:1815-22
