by Craig Weatherby
The findings of the first-ever comprehensive evidence review support the widely held hypothesis that vitamin D protects cardiovascular health.
They come as little surprise, given the steady stream of epidemiological (diet-health) studies that link higher vitamin D blood levels to better heart health.
And the results should encourage funding of the large, controlled clinical trials needed to prove whether vitamin D affects the risk of cardiovascular disease, heart attacks, and heart-related deaths.
The encouraging background
Since 2006 we've reported on a half-dozen epidemiological studies that associate higher vitamin D blood levels with lower heart risks … and, in many cases, with lower diabetes and kidney risks as well.
For example, see “Vitamin D Lack Linked to Diabetes and Heart Risks” and “Vitamin D May Reduce Heart Attack Risk.”
(To see them all, search our newsletter archive for “vitamin d” and then use your browser's find function to search the archive page for “heart”.)
Importantly, scientists continue to uncover new physiological explanations for the statistical links found so far between vitamin D and cardiovascular health (Artaza JN et al. 2009).
Higher vitamin D blood levels are associated with improvements in cardiac function and with reductions in at least six risk factors for atherosclerosis and cardiovascular disease: inflammation, hypertension, excess growth of cardiac fibroblast cells, diabetes, arterial calcification, and arterial thickness.
Conversely, low blood levels of vitamin D are associated with three key risk factors for diabetes and heart disease: obesity, insulin resistance, and systemic inflammation.
And vitamin D appears to play a direct, hormone-like role in cardiovascular health, since vitamin D receptors are found in three kinds of cells critical to it: heart muscle cells, vascular smooth muscle cells, and endothelial (artery lining) cells.
British meta-analysis supports vitamin D for cardiovascular health
In this new study, researchers from Britain's University of Warwick performed the first ever systematic review (“meta-analysis”) of all studies that have investigated people's vitamin D blood levels and the presence or absence of so-called “cardio-metabolic” disorders (Parker J et al. 2010).
Cardio-metabolic disorders include metabolic syndrome—a cluster of signs associated with diabetes and cardiovascular disease (CVD)—as well as CVD and diabetes themselves.
The UK team's analysis encompassed all 28 studies found in the scientific literature, most published since 2004. These involved 99,745 participants, including men and women from a variety of ethnic groups.
No data from clinical trials was included, because none was available (See our comment about this lack, below).
Compared to participants with the lowest blood levels of vitamin D, people with the highest blood levels were 33 percent less likely to have CVD, 55 percent less likely to have type 2 diabetes, and 51 percent less likely to have metabolic syndrome.
Overall, the volunteers with the highest blood levels were 43 percent less likely to have any of these cardio-metabolic disorders.
As they wrote, “If the relationship proves to be causal, interventions targeting vitamin D deficiency in adult populations could potentially slow the current epidemics of cardio-metabolic disorders” (Parker J et al. 2010).
However, only well-designed clinical trials can prove a cause-effect relation between a drug or nutrient and any health condition.
Since nutrients cannot be made into patented, highly profitable products, drug companies have no incentive to test them.
This is why we should all write our Congresspersons to request far more funding for clinical trials to test the effects of promising nutrients against major diseases.
- Artaza JN, Mehrotra R, Norris KC. Vitamin D and the cardiovascular system. Clin J Am Soc Nephrol. 2009 Sep;4(9):1515-22. Epub 2009 Aug 20. Review.
- Gouni-Berthold I, Krone W, Berthold HK. Vitamin D and cardiovascular disease. Curr Vasc Pharmacol. 2009 Jul;7(3):414-22. Review.
- Judd SE, Tangpricha V. Vitamin D deficiency and risk for cardiovascular disease. Am J Med Sci. 2009 Jul;338(1):40-4. Review.
- Parker J, Hashmi O, Dutton D, Mavrodaris A, Stranges S, Kandala NB, Clarke A, Franco OH. Levels of vitamin D and cardiometabolic disorders: Systematic review and meta-analysis. Maturitas. 2010 Mar;65(3):225-236. Epub 2009 Dec 23.