People who have the lowest levels of vitamin D in their blood have an increased risk of death compared to those with the highest levels, a new study says.
In a study of more than 3,200 men and women, Austrian researchers found that subjects who had the lowest levels of vitamin D in their blood were about two times more likely to die of any cause compared to subjects who had the highest levels of vitamin D.
Vitamin D levels among study subjects were divided into quartiles. Study subjects with the lowest vitamin D levels had a median level of 19 nanomoles per litre and the second lowest had a median level of 33.2 nanomoles per litre. Subjects in the highest quartile had a median vitamin D level of 70.9 nanomoles per litre.
The findings are published in the June 23 edition of the Archives of Internal Medicine.
Vitamin D is emerging as a super vitamin in health studies around the world. Recent research has shown that people who have high levels of it in their blood have a reduced risk of developing illnesses ranging from diabetes to prostate cancer.
The primary way that people get vitamin D is via sunlight. The human body synthesizes vitamin D after the sun hits the skin. However, it can be obtained from some foods and from dietary supplements.
Figures included with the study indicate that 50 per cent of adults in North America do not have adequate levels of vitamin D. The recommended minimum level of vitamin D in the blood is between 50 and 75 nanomoles per litre.
The researchers said that the next step is to study if vitamin D has a direct impact on lowering the risk of death.
Abstract:
Independent Association of Low Serum 25-Hydroxyvitamin D and 1,25 Dihydroxyvitamin D Levels With All-Cause and Cardiovascular Mortality
Harald Dobnig, MD; Stefan Pilz, MD; Hubert Scharnagl, PhD; Wilfried Renner, PhD; Ursula Seelhorst, MA; Britta Wellnitz, LLD; Ju� rgen Kinkeldei, DEng; Bernhard O. Boehm, MD; Gisela Weihrauch, MSc; Winfried Maerz, MD
Background: In cross-sectional studies, low serum levels of 25-hydroxyvitamin D are associated with higher prevalence of cardiovascular risk factors and disease. This study aimed to determine whether endogenous 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels are related to all-cause and cardiovascular mortality.
Methods: Prospective cohort study of 3258 consecutive male and female patients (mean [SD] age, 62 [10] years) scheduled for coronary angiography at a single tertiary center. We formed quartiles according to 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels within each month of blood drawings. The main outcome measures were all-cause and cardiovascular deaths.
Results: During a median follow-up period of 7.7 years, 737 patients (22.6%) died, including 463 deaths from cardiovascular causes. Multivariate-adjusted hazard ratios (HRs) for patients in the lower two 25-hydroxyvitamin D quartiles (median, 7.6 and 13.3 ng/mL [to convert 25-hydroxyvitamin D levels to nanomoles per liter, multiply by 2.496]) were higher for allcause mortality (HR, 2.08; 95% confidence interval [CI], 1.60-2.70; and HR, 1.53; 95% CI, 1.17-2.01; respectively) and for cardiovascular mortality (HR, 2.22; 95% CI, 1.57-3.13; and HR, 1.82; 95% CI, 1.29-2.58; respectively) compared with patients in the highest 25-hydroxyvitamin D quartile (median, 28.4 ng/mL). Similar results were obtained for patients in the lowest 1,25-dihydroxyvitamin D quartile. These effects were independent of coronary artery disease, physical activity level, Charlson Comorbidity Index, variables of mineral metabolism, and New York Heart Association functional class. Low 25-hydroxyvitamin D levels were significantly correlated with variables of inflammation (C-reactive protein and interleukin 6 levels), oxidative burden (serum phospholipid and glutathione levels), and cell adhesion (vascular cell adhesion molecule 1 and intercellular adhesion molecule 1 levels).
Conclusions: Low 25-hydroxyvitamin D and 1,25- dihydroxyvitamin D levels are independently associated with all-cause and cardiovascular mortality. A causal relationship has yet to be proved by intervention trials using vitamin D.
