Vitamin D deficiency causes rickets, osteomalacia, muscle weakness, and muscle cramps and might be associated with falls and fractures. The prevalence of vitamin D deficiency is high in the Netherlands. The Dutch Health Council advises exposure of the face, neck, and hands to sunlight for 15–30 minutes/day when the sun is at its highest. All young children up to 4 years of age and all people older than 70 years should take a vitamin D supplement. Women older than 50 years, people with a dark skin, and people with limited exposure to sunlight are advised to take extra vitamin D for preventive purposes, although there is no strong evidence to support this recommendation. For general practitioners, the most important patient groups are elderly patients with malabsorption, liver disease, kidney disease, or an increased fracture risk and people who attend their GP with symptoms possibly associated with vitamin D deficiency. Because of the limited accuracy of many vitamin D assays and the high risk of incidental findings, routine vitamin D testing is not advocated. The Dutch Health Council advises supplementation with 10 microg vitamin D/day for people younger than 70 years and 20 microg/day for people older than 70 years; however, this is not always sufficient because of problems with adherence. Vitamin D can be taken daily but also periodically, once every 3 months. The maximum daily dose is 100 microg/day. Two studies have reported possible adverse effects with a single supplement of 7500 microg and 12,500 microg, respectively. If there are symptoms of vitamin D deficiency, a loading dose might be beneficial in order to achieve adequate blood levels as soon as possible. A regimen of 250 microg/day for 10 days or 625 microg/week for 6-8 weeks appears to be safe for this purpose.
Elders PJM. Vitamin D supplementation. Huisarts Wet 2015;58(3):156-9.