How much vitamin D do I need?
Vitamin D is a unique vitamin, since adequate levels are usually maintained through exposure to sunlight. If exposure to sunlight is sufficient, dietary vitamin D can be considered unnecessary.
Current food supplies and patterns of eating also make it virtually impossible to obtain enough vitamin D from dietary sources alone. 1
Most people can produce enough vitamin D for their body’s needs through regular daily activity with incidental exposure to the sun. In summer, this equates to a few minutes of sunlight on the face, arms and hands or equivalent area of skin, on either side of peak UV periods (midday), on most days of the week.
In winter in areas such as the southern parts of Australia, UV radiation levels are less intense. This means that people may need as much as two to three hours of sunlight exposure to the face, arms and hands, or equivalent area of skin, spread over the course of the week. 2 In the winter months, people also spend more time indoors and wear more clothing due to colder temperatures. For this reason, vitamin D deficiency is usually more common in winter.1
If the level of sun exposure required to maintain vitamin D levels is not possible, oral supplementation may be necessary. In summer, sun protection measures, such as limiting sun exposure, wearing protective clothing and hats, and the use of sunscreen means that vitamin D production is reduced even in Australia’s warm climate. The application of sunscreen with a sun protection factor as low as ten reduces UVB radiation necessary for vitamin D synthesis by 90%. 3
The current Nutrient Reference Values for Australia and New Zealand for vitamin D are as follows: 1
- Children (boys and girls 1-18 years old): 5.0 mcg/day
- Adults (men and women 19- 50 years old): 5.0 mcg/day
- Elderly adults (men and women 51- 70 yrs): 10.0 mcg/day
- Elderly adults (men and women > 70 yrs): 15 mcg/day
Sunlight exposure and environmental factors vary widely between individuals, which makes vitamin D requirements difficult to assess. If you are concerned about your vitamin D status and whether you may need a supplement, speak to your doctor. They will be able to conduct a simple blood test and recommend the level of oral supplementation that is required.