Thursday, May 31, 2012

Vitamin D and HDL Cholesterol

Vitamin D and HDL cholesterol  
                  Normal Vitamin D levels seem to have a positive effect on HDL. 
This may be an important association  but will require more research to fully evaluate the mechanism  and the effect of taking Vitamin D supplements on cardiovascular risk reduction. I have attached portions of two articles that will provide more detail if you are interested. I have  high lighted areas of interest to this discussion.


Circulating 25-Hydroxyvitamin D Concentrations Are Correlated With Cardiometabolic Risk Among American Black and White Adolescents Living in a Year-Round Sunny Climate
Samip Parikh MBBS, De-huang Guo MD, Norman K. Pollock PHD, Karen Petty PHD, Jigar Bhagatwala MBBS, Bernard Gutin PHD, Chris Houk MD, Haidong Zhu MD, Yanbin Dong MD
http://dx.doi.org/10.2337/dc11-1944

The NHANES 2001–2004 analyses including children and adolescents aged 1 to 21 years showed that 25(OD)D deficiency (<15 ng/mL) was associated with HDL cholesterol levels as compared with 25(OH)D levels ≥30 ng/mL (6). The assay-adjusted 25(OH)D data from NHANES 2001–2006 in adolescents aged 12–19 years found that 25(OH)D was directly related to HDL cholesterol (7). In addition, Rajakumar et al. (28) reported that in 237 black and white children (mean ± SD: 12.7 ± 2.2 years), plasma 25(OH)D was positively associated with HDL cholesterol. In theory, vitamin D could affect lipid levels directly, e.g., vitamin D is thought to be essential for maintaining adequate levels of apolipoprotein A-I, a major component of HDL cholesterol (29,30). In addition, the indirect effects of vitamin D on lipids could be through PTH or calcium balance. Furthermore, vitamin D might improve insulin secretion and insulin sensitivity, thereby indirectly influencing lipid metabolism (31). Our results demonstrated that 25(OH)D was positively correlated with HDL cholesterol independent of adiposity (i.e., %BF), which requires carefully controlled interventional and other experimental studies to further understand the observation.
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Prog Lipid Res. 2011 Oct;50(4):303-12. Epub 2011 May 27.

Vitamin D and metabolic health with special reference to the effect of vitamin D on serum lipids.

Source

Endocrinology Research Group, Institute of Clinical Medicine, University of Tromsø, and Medical Clinic, University Hospital of North Norway, 9038 Tromsø, Norway. rolf.jorde@unn.no

Abstract

Considering that the vitamin D receptor as well as the 1-α-hydroxylase enzyme that converts 25-hydroxyvitamin D (25(OH)D) to its active form 1,25-dihydroxyvitamin D have been found in tissues throughout the body, it is likely that vitamin D is important for more than the calcium balance. Accordingly, low serum levels of 25(OH)D have been associated with mortality, cardiovascular disease, type 2 diabetes, hypertension and obesity. Low serum levels of 25(OH)D have also been associated with an unfavourable lipid profile, which could possible explain the relation with cardiovascular disease and mortality. However, the relation between vitamin D and lipids have so far received little attention and is therefore the main focus of the present review. A PubMed search identified 22 cross-sectional studies where serum levels of 25(OH)D and lipids were related and that included a minimum of 500 subjects, and 10 placebo-controlled double-blind intervention studies with vitamin D where more than 50 subjects were included. In all the cross-sectional studies serum 25(OH)D was positively associated with high-density lipoprotein cholesterol (HDL-C) resulting in a favourable low-density lipoprotein cholesterol (LDL-C) (or total cholesterol) to HDL-C ratio. There was also a uniform agreement between studies on a negative relation between serum 25(OH)D and triglycerides (TG). On the other hand, the intervention studies gave divergent results, with some showing a positive and some a negative effect of vitamin D supplementation. However, none of the intervention studies were specifically designed for evaluating the relation between vitamin D and lipids, none had hyperlipemia as an inclusion criterion, and none were sufficiently powered. In only one study was a significant effect seen with an 8% (0.28 mmol/L) increase in serum LDL-C and a 16% (0.22 mmol/L) decrease in serum TG in those given vitamin D as compared to the placebo group. Accordingly, the effect of vitamin D supplementation on serum lipids is at present uncertain. Considering the numerous other promising vitamins and minerals that when properly tested have been disappointing, one should wait for the results of forthcoming vitamin D intervention studies before drawing conclusions on potential beneficial effects of vitamin D.
Copyright © 2011 Elsevier Ltd. All rights reserved.

Have fun, Be smart and talk to your doctor about Vitamin D
David Calder,MD
vitamin D and blood pressure tomorrow

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Your comments and questions are appreciated. David Calder,MD