Vitamin D is a steroid hormone and a component of a complex endocrine pathway sometimes called 'vitamin D endocrine system' (Medscape, 2012). 1 in 4 individuals will develop COPD during their lifetime (Lancet, 2011).Serum 25-hydroxyvitamin D (25-OHD) levels were measured in 414 (ex)-smokers older than 50 years and the link between vitamin D status and presence of COPD was assessed. The rs7041 and rs4588 variants in the vitamin D-binding gene (GC) were genotyped and their effects on 25-OHD levels were tested.
In patients with COPD, 25-OHD levels correlated significantly with forced expiratory volume in 1 s (FEV1).
Compared with 31% of the smokers with normal lung function, as many as 60% and 77% of patients with GOLD (Global Initiative for Obstructive Lung Disease) stage 3 and 4 exhibited deficient 25-OHD levels lower than 20 ng/ml.
25-OHD levels were reduced by 25% in homozygous carriers of the rs7041 at-risk allele.
76% and 100% of patients with GOLD stage 3 and 4 homozygous for the rs7041 allele exhibited 25-OHD levels lower than 20 ng/ml.
Vitamin D deficiency occurs frequently in COPD and correlates with severity of COPD. The data warrant vitamin D supplementation in patients with severe COPD, especially in those carrying at-risk rs7041 variants.
Despite this circumstantial evidence, a recent trial of vitamin D replacement in patients with COPD did not show a reduction in exacerbations unless the patients had a severe vitamin D deficiency.
Vitamin D deficiency occurs frequently in COPD and correlates with severity of COPD. The data warrant vitamin D supplementation in patients with severe COPD, especially in those carrying at-risk rs7041 variants.
Despite this circumstantial evidence, a recent trial of vitamin D replacement in patients with COPD did not show a reduction in exacerbations unless the patients had a severe vitamin D deficiency.
References:
Vitamin D deficiency is highly prevalent in COPD and correlates with variants in the vitamin D-binding gene. Thorax 2010;65:215-220 doi:10.1136/thx.2009.120659.
http://thorax.bmj.com/content/65/3/215.short
A vitamin D3 dosage of 800 IU/d increased serum 25-(OH)D levels to greater than 50 nmol/L in 97.5% of women http://bit.ly/GzBCcA
A vitamin D3 dosage of 800 IU/d increased serum 25-(OH)D levels to greater than 50 nmol/L in 97.5% of women http://bit.ly/GzBCcA
Image source: Lungs, Wikipedia, public domain.
