A link has been discovered between higher serum vitamin D levels and lower plasma cholesterol levels in primary school children, according to new research from the University of Eastern Finland. Children whose serum 25-hydroxyvitamin D levels exceeded 80 nmol/l had lower plasma total and low-density lipoprotein (LDL) cholesterol levels than children whose serum 25-hydroxyvitamin D levels were below 50 nmol/l, which is often regarded as a threshold value for vitamin D sufficiency. 25-hydroxyvitamin D is the major circulating form of vitamin D. The findings were reported in one of the leading journals of endocrinology, the Journal of Clinical Endocrinology and Metabolism. Vitamin D is well known as being an essential vitamin for bone metabolism, and low serum 25(OH)D levels increase the risk of rickets, osteomalacia, and osteopenia.
Vitamin D may also improve plasma lipid levels and have a beneficial impact on other risk factors of cardiovascular diseases. However, evidence on these other health effects of vitamin D is still scarce and partially conflicting, and therefore not a sufficient basis for giving recommendations. Lifestyle factors, such as healthy diet, physical activity, and spending time outdoors in the sun leading to the production of vitamin D in the skin, may be linked to both higher serum vitamin D levels and lower plasma lipid levels. The researchers found that the link between higher serum vitamin D levels and lower plasma cholesterol levels was independent of body adiposity, dietary factors, physical activity, parental education, and day length prior to blood sampling. Moreover, hereditary factors that have previously been linked to serum vitamin D levels did not modify the observed association. More research is needed to uncover the reasons behind the inverse association of serum vitamin D with plasma lipid levels. Vitamin D is synthesised endogenously in the skin in the presence of UV-radiation from the sun. However, in northern latitudes, the exposure to sunlight alone is inadequate to maintain sufficient serum 25(OH)D levels, especially during the winter. The new findings provide support for the importance of following recommendations for vitamin D intake, which vary from country to country. The most important dietary sources of vitamin D are vitamin D fortified products such as dairy products and spreads, and fish. In addition to the dietary intake, taking a vitamin D supplement is also recommended for the general population in several countries where there are limited sunny days. The recommended use of vitamin D supplements varies a lot among these countries (mostly 5-50 µg/d, corresponding to 200-2000 IU/d) depending on age group and other factors.