Vitamin D is hormone that plays an important role in the modulation of the immune system and in calcium homeostasis. Vitamin D is produced naturally in the body by the action of UV light on the skin, or can be consumed in the diet. Evidence suggests that in winter months at higher latitudes, large proportions of the population do not receive adequate sun exposure to produce optimum 25-hydroxyvitamin D levels. As a result, many people develop vitamin D insufficiency that is increasingly being linked to diabetes, arthritis, multiple sclerosis, cancer and cardiovascular disease. The link between coronary heart failure (CHF) and vitamin D insufficiency is not established. However, in recent years scientific understanding of CHF has shifted away from an isolated haemodynamic view to one of a chronic neurohormonal one, characterised by the release of inflammatory cytokines.
To investigate the role of Vitamin D in the pathophysiology of CHF, researchers1 fed 123 patients with CHF either 50 µg of vitamin D3 and 500 mg of calcium, or a placebo plus 500 mg calcium every day for 9 months. The results demonstrated that 25-hydroxyvitamin D (a good marker for vitamin D status) increased by 26.8 ng/L in the treatment group compared to 3.6 ng/L in the control group. Parathyroid hormone (PTH) fell significantly in the treatment group by 14 %, but increased 11 % in the control group. Interleukin-10 (IL-10; a cytokine able to suppress inflammation) levels decreased by 43 % in the treatment group, but did not change in the control group. In contrast tumour necrosis factor alpha (TNF-α; a cytokine increasingly implicated in the development of CHF) levels did not differ significantly in the treatment group, but increased by 12 % in the control group.
These results support a role for vitamin D insufficiency in the development of CHF, probably through modulation of inflammatory pathways. In particular, vitamin D supplementation is able to suppress the release of TNF-α, but stimulate the release of IL-10. This supports previous studies that suggest that vitamin D plays a role in modulation of inflammation. Not only was vitamin D able to suppress inflammation, but was able to decrease levels of PTH, a hormone associated with adverse cardiac function. Many people do not have adequate levels of 25-hydroxyvitamin D because of too little sun exposure. For people in higher latitude during the winter and autumn months it is recommended that vitamin D3 supplements are used to maintain proper blood levels. Optimum levels of 25-hydroxyvitamin D are currently recommended to be ≈50 ng/L or 125 nmol/L.
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