[Relationship between vitamin D deficiency and metabolic syndrome]

Vitamin D deficiency and metabolic syndrome are 2 very common health problems in the Spanish population. It has been suggested that patients with metabolic syndrome may be vitamin D deficient more often than subjects without it and that low vitamin D levels may predispose to metabolic syndrome development. However, the results of prospective and intervention studies have been different and such relationship remains unclear. We assessed the relationship between 25-hydroxyvitamin D levels and the prevalence and incidence of metabolic syndrome.

We undertook a population-based cohort study in Spain. At baseline (1996-1998), 1,226 subjects were evaluated. Follow-up visits were performed in 2002-2004 and 2005-2007.At baseline and follow-up, participants underwent an interview and a standardized clinical examination with an oral glucose tolerance test in those subjects without known diabetes. At the second visit, 25-hydroxyvitamin D levels and intact parathyroid hormone levels were measured.

The prevalence of metabolic syndrome at the second and third visit was 29.4 and 42.5%, respectively. Mean levels of 25-hydroxyvitamin D were lower in subjects with metabolic syndrome: 21.7 (6.21) vs 23.35 (6.29) ng/ml, P<.001.The prevalence of vitamin D deficiency (25-hydroxyvitamin D<20 ng/ml) at the second evaluation was 34.7%, with significant differences between subjects with and without metabolic syndrome(34.6 vs 26.5%, P<.01). Men with vitamin D deficiency had more frequently hypertension and metabolic syndrome than men with normal levels. Women with vitamin D deficiency had more frequently hyperglycemia, hypertension, increased waist circumference and hypertriglyceridemia. In a prospective study, 25-hydroxyvitamin D values<20 ng/ml were not significantly associated with an increased risk of developing metabolic syndrome in the next 5 years (odds ratio 0,99, 95% confidence interval 0.57-1.7, P=.97) after adjusting by sex and age.

Vitamin D deficiency is associated with an increased prevalence but not with an increased incidence of metabolic syndrome.