Adequate Vitamin D Intake
During the summer, the human body is able to produce its much-needed vitamin D with the help of UVB light. The sun is an important source of vitamin D, also in Finland. The photochemical production of vitamin D is decreased during the summer months, as people cover themselves too much due to fears of developing skin cancer. Likewise, if one wears sunscreen or is only exposed to sunlight after the end of the workday, very little vitamin D is produced through the skin. In the northern parts of Finland, the production of vitamin D in the skin stops completely in the fall, as the necessary UVB rays no longer penetrate the atmosphere.
We receive small amounts of vitamin D from the food we eat, for example from fish, mushrooms and dairy products which have been fortified with vitamin D. Nevertheless, the human body gets most of its vitamin D through exposure of skin to sunlight.
The starting point for vitamin D dosage should be the serum level of vitamin D, which should preferably range from 80 to 125 nmol/l. This level of intake is supported by evidence-based scientific reviews.
In order to reach the optimal level, most adults have to use a 50 μg vitamin D supplement from September to May. Those who avoid sun exposure during summertime, the elderly and the hospitalized need a vitamin D supplement throughout the year.
A person’s size also determines the level of adequate intake. A daily intake of 35 μg may be sufficient for small and thin individuals. However, larger and notably obese individuals may need 75 μg or even 100 μg of vitamin D daily.
When adhering to these recommendations, use of vitamin D is very safe. For example, the European Food Safety Authority (EFSA) considers 100 μg per day as the tolerable upper intake level of vitamin D (EFSA).
Nevertheless, there is considerable individual variation in dose-response. Therefore, it is recommended that each individual has the adequacy of her or his vitamin D intake checked at a medical center at least every few years. Even without any tests, an adult can safely use 50 μg of vitamin D daily.
Bischoff-Ferrari HA, et al. Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes. Am J Clin Nutr. 2006 Jul;84(1):18-28.
EFSA. Scientific Opinion on the Tolerable Upper Intake Level of vitamin D. EFSA Journal 2012;10(7):2813.
Finravinto 2012 -tutkimus — The National FINDIET 2012 Survey. THL 2013.
Lagunova Z, et al. The dependency of vitamin D status on body mass index, gender, age and season. Anticancer Res. 2009 Sep;29(9):3713-20.