Critical vitamin D blood levels in older adults identified

According to new research from the US, the risk of diseases, such as hip fractures, heart attacks and cancer, increases when the blood concentration of vitamin D falls below 20 ng/milliliter or 50 nmol/liter.

In order to investigate how much vitamin D needs to be circulating in the blood in to lower the risk of a major medical event, such as a heart attack, hip fracture, diagnosis of cancer, or death, researchers measured the 25-hydroxy-vitamin D concentrations in blood samples of 1,621 Caucasian adults aged 65
and older (1). Over a period of about 11 years, the researchers looked at the association between each individual’s 25(OH)D test results and the time that the first defined medical event occurred. Based on a statistical analysis, it was concluded that the risk of these disease events rose when the concentration of
25(OH)D fell below 20 nanogramms/milliliter or 50 nanomol/liter. The association of low 25(OH)D blood concentrations with the risk of major disease events varied with the season: the vitamin D levels ran highest in the summer and lowest in the winter; levels in autumn were generally higher than those in spring.

The researchers commented that these results provided support to the threshold level recently recommen-ded by the US Institute of Medicine. This target level for adults was considerably lower than those set by other expert panels. The vitamin D threshold amount has become controversial, as several scientific societies set different targets. Season-specific targets for 25(OH)D blood concentrations may be more appropriate than a static target when evaluating a patient’s health risk. Sun exposure presents a tricky situation because people have to protect themselves from skin cancer and other sun damage. Additional dietary vitamin D intake is therefore recommended to reach adequate blood levels, the scientists said.

1. de Boer I. H. et al. Serum 25-Hydroxyvitamin D Concentration and Risk for Major Clinical Disease Events in a Community-Based Population of Older Adults. Ann Intern Med. 2012; 156:627–634.