Originally vitamin D was understood to be required for optimal bone health, deficiency of which could lead to osteomalacia in adults and rickets in children. Little more attention was paid to vitamin D status once fortification of foods resulted in the almost total eradication of known deficiency diseases. However, in recent decades vitamin D research has uncovered further information that suggests that vitamin D and its active metabolites 25-hydroxtvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)2D] are involved in a number of major physiological roles including regulation of the insulin hormonal system and immunity. This is unsurprising, because vitamin D is not a vitamin at all, but a steroid hormone related to cholesterol. Vitamin D therefore is able to bind to DNA in the nucleus of cells and regulate gene expression. Recently, epidemiological research has suggested that vitamin D status is related to certain cardiovascular risk factors.
Analysis1 of the serum levels 25(OH)D in 292 postmenopausal women (aged 50 to 79 years) has been reported to show associations between vitamin D status and the risk of developing cardiovascular disease. As has been shown previously, circulating 25(OH)D was inversely associated with adiposity and waist to hip ratios. Both central adiposity and an increased waist to hip ratio are established risk factors for cardiovascular disease. Inverse association between 25(OH)D and serum triglyceride levels, and the triglyceride to high density lipoprotein (HDL) cholesterol ratio were also reported. Comparison of the tertile with the highest 25(OH)D (≥52nmol/L) with the tertile with the lowest 25(OH)D (<35nmol/L) revealed a 28% increase in the likely of developing metabolic syndrome as 25(OH)D levels dropped. This increase in risk between the top and bottom tertiles remained significant even after adjustment for body mass index.
These results suggest that 25(OH)D concentrations in healthy postmenopausal women are inversely associated with a number of known risk factors for cardiovascular disease. This supports previous data that shows that poor vitamin D status, typified by low levels of 25(OH)D, is involved in the development of diabetes, insulin resistance and metabolic syndrome. This group of diseases is increasingly being seen as a group of connected disorders that results from metabolic disruption to the insulin hormonal system and increases the risk of cardiovascular disease. Poor vitamin D status is now fairly well established as being associated with increased adiposity which may relate to the lipid soluble nature of the vitamin D causing sequestration into fat cells and reducing circulating levels. This may then adversely affect insulin function which disrupts the lipid profiles of the individuals and leads to insulin resistance and increases risk of diabetes and metabolic syndrome.
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