Vitamin D supplements contain either vitamin D2 or D3. However, the market penetration of vitamin D2 is constantly shrinking and in many countries, such as Germany, Italy, and Australia vitamin D2 supplements have almost completely disappeared. In addition, it appears that vitamin D2 is less potent than vitamin D3. A meta-regression analysis by Cranney et al. provided good evidence that supplements can increase serum 25(OH)D in a dose dependent manner (1). According to this analysis supplementation of 100 IU of vitamin D3 will increase the serum 25(OH)D concentrations by 1 – 2 nmol/L. This suggests that doses of 400-800 IU daily may be inadequate to prevent vitamin D deficiency in at-risk individuals. It should be considered that treatment effects may vary depending on the 25(OH)D level at baseline. Individuals with lower 25(OH)D baseline levels are likely to show a greater response to supplementation. There are only a few trials that examined the effect of vitamin D on 25(OH)D in children or adolescents with daily doses ranging from 200 to 2,000 IU of vitamin D3 and 400 IU of vitamin D2. Although data are limited, 400 IU of vitamin D2 appears to reliably correct vitamin D deficiency in infants.
Vitamin D supplementation – what dose is required
To avoid vitamin D deficiency the required daily intake of vitamin D from dietary sources and supplementation to prevent deficiency is at least 600 IU (15 µg) per day for those aged <70 years, and 800 IU (20 µg) per day for those aged > 70 years. Individuals in high-risk groups or with substantial sun avoidance may require higher doses. A different approach needs to be taken in patients with known vitamin D deficiency. All current guidelines recommend an initial loading phase where higher doses are given for 6-12 weeks. As the individual response to vitamin D supplementation varies widely a control measurement of the serum 25(OH)D level is prudent. Once an adequate 25(OH)D level has been restored the daily dose should be reduced to a maintenance dose between 800 to 2,000 IU per day (2).
Vitamin D supplementation and bone health in infants, children, and pregnant women
In breastfed babies vitamin D supply depends on the mothers’ vitamin D status and can be improved by supplementing the mother (3). The recommended daily intake is 300 IU for children up to 6 months of age and increases to 400 IU for older children. It has been estimated that a daily intake of 400 IU is adequate in children during the first year of life. After the age of 1 year a higher dose of 600 IU is recommended (4). Higher amounts may be needed in children with limited sun exposure or during winter time. Current guidelines recommend the administration of 600 IU per day in pregnant women (4).
1. Cranney A, Horsley T, O'Donnell S, Weiler H, Puil L, Ooi D et al. Effectiveness and safety of vitamin D in relation to bone health. Evid Rep Technol Assess (Full Rep) 2007;1-235.
2. Nowson CA, McGrath JJ, Ebeling PR, Haikerwal A, Daly RM, Sanders KM et al. Vitamin D and health in adults in Australia and New Zealand: a position statement. Med J Aust 2012;196:686-7.
3. Wagner CL, Taylor SN, Johnson DD, Hollis BW. The role of vitamin D in pregnancy and lactation: emerging concepts. Womens Health (Lond Engl ) 2012;8:323-40.
4. Ross AC, Manson JE, Abrams SA, Aloia JF, Brannon PM, Clinton SK et al. The 2011 Dietary Reference Intakes for Calcium and Vitamin D: what dietetics practitioners need to know. J Am Diet Assoc 2011;111:524-7.