Vitamin D and living in northern latitudes--an endemic risk area for vitamin D deficiency.
OBJECTIVE
To review the current literature on the health effects of vitamin D, especially the effects on inhabitants living in the northern latitudes.


METHODS
Literature review.


METHODS
The scientific literature concerning health effects of vitamin D was reviewed and the current dietary recommendations for inhabitants living in northern latitudes were discussed.


RESULTS
Vitamin D is a steroid-structured hormone produced in the skin upon exposure to UVB-radiation or obtained from certain food products (for example, liver). Its production is mediated by the vitamin D receptor, which belongs to the nuclear receptor family, and exerts its function as a transcription factor regulating several target genes. Active metabolites of vitamin D play an important role in calcium and phosphate homeostasis. Deficiency of vitamin D results in diminished bone mineralization and an increased risk of fractures. In addition, vitamin D is connected to a variety of other diseases that include different cancer types, muscular weakness, hypertension, autoimmune diseases, multiple sclerosis, type 1 diabetes, schizophrenia and depression.


CONCLUSIONS
Vitamin D plays a fundamental role in calcium and phosphate homeostasis. A deficiency of vitamin D has been attributed to several diseases. Since its production in the skin depends on exposure to UVB-radiation via the sunlight, the level of vitamin D is of crucial importance for the health of inhabitants who live in the Nordic latitudes where there is diminished exposure to sunlight during the winter season. Therefore, fortification or supplementation of vitamin D is necessary for most of the people living in the northern latitudes during the winter season to maintain adequate levels of circulating 25(OH)D3 to maintain optimal body function and prevent diseases.
Huotari
Anne
A
A I Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland.
Herzig
Karl-Heinz
KH