Danish study links low levels of vitamin D to higher risks of heart attack and early death
By Craig Weatherby
Until recently, vitamin D was an overlooked nutrient … an oversight that likely harmed public health.
When it comes to bone health, it's become clear that maintaining adequate vitamin D levels is more important than taking big doses of calcium.
But numerous population studies link lack of vitamin D to higher risk for infections, various cancers, and certain auto-immune disorders … findings that fit with vitamin D's broad, hormone-like effects in the body.
Most recently, several population studies – and a few clinical trials – linked low vitamin D levels to a higher risk of heart attack, arteriosclerosis, and angina (Danik JS et al. 2012; Pilz S et al. 2012).
Other studies show that vitamin D deficiency may increase blood pressure, which raises the risk of heart attack. Heart disease is the most common cause of adult death, according to the World Health Organization (WHO), which estimates that it kills at least 17 million people annually.
For our coverage of some of the prior research, see “Vitamin D Lack Raises Heart-Death Risk”, “Vitamin D Linked Closely to Heart Health” … and other articles in the Vitamin D & Heart Health and Vitamin D & Metabolic Health sections of our News Archive.
The connection between low vitamin D levels and heightened risk of heart disease seen in population studies must be confirmed by clinical trials … a number of which are now underway.
But it can't hurt – and would help overall health – to use diet and supplements to ensure adequate levels. (See our sidebar, “Fish fit the vitamin D bill; Sockeye salmon stand out”.)
Now, Danish researchers have affirmed the heart-health role of vitamin D in the largest study to date, which used blood tests to determine people's vitamin D status … as opposed to very rough estimates based on diet/lifestyle questionnaires.
Danish study supports heart-vitamin D link
The new analysis relied on data from 10,170 Danes who participated in the Copenhagen City Heart Study in the early 1980's, and provided blood samples as part of that study.
The authors of the new study measured the vitamin D levels in those samples, and compared those levels to the participants' health records over the ensuing 29 years (Brøndum-Jacobsen P et al. 2012).
The results of that comparison linked low levels of vitamin D with markedly higher risks of heart attack, heart disease, and early death.
Low blood levels of vitamin D were linked to these increased risks:
Ischemic heart disease (IHD) is characterized by reduced blood supply to the heart muscle, usually due to coronary artery disease caused by atherosclerosis (clogged arteries).
The risk of IHD rises with age, smoking, eating meat, high levels of certain kinds of cholesterol, diabetes, and high blood pressure.
The scientists compared people whose vitamin D levels fell in the bottom five percent – less than 15 nmol/L (6 ng/mL) – to those whose vitamin D levels exceeded 50 nmol/L (20 ng/mL).
(The U.S. Institute of Medicine recommends a minimum blood level of 50 nmol/L, but leading researchers recommend higher levels … see our sidebar, “Vitamin D: Recommended RDAs and blood levels”.)
The higher risks remained after the results were adjusted to account for several factors that can influence the level of vitamin D and the risk of heart disease and death.
As co-author Børge Nordestgaard said, “… we can ascertain that there is a strong statistical correlation between a low level of vitamin D and high risk of heart disease and early death. The explanation may be that a low level of vitamin D directly leads to heart disease and death.” (UC 2012)
Of course, no population study can prove a cause-effect relationship, which he noted: “However, it is also possible that vitamin deficiency is a marker for poor health generally.” (UC 2012)
Dr. Nordestgaard noted that sun exposure is the primary source of vitamin D, but cautioned against overdoing it:
“The cheapest and easiest way to get enough vitamin D is to let the sun shine on your skin at regular intervals. There is plenty of evidence that sunshine is good, but it is also important to avoid getting sunburned, which increases the risk of skin cancer.” (UC 2012)
Companion evidence review affirms vitamin D's heart role
Additionally, the Danish group performed a “meta-analysis” in which they reviewed 35 prior studies on vitamin D and heart health (Brøndum-Jacobsen P et al. 2012).
Their meta-analysis covered 18 studies investigating the risk of ischemic heart disease and 17 studies looking at vitamin D and early death.
The Danish team compared people who fell in the lowest quartile (one-quarter) of vitamin D blood levels to those in the highest quartile.
The results showed that the risk of ischemic heart disease and early death rose by 39 percent and 46 percent respectively, for those in the lowest quartile versus those in the highest quartile of vitamin D status.
Given the accumulating evidence linking vitamin D to heart health, one would seem foolish not to take steps to ensure adequate intakes and blood levels.
Brøndum-Jacobsen P, Benn M, Jensen GB, Nordestgaard BG. 25-Hydroxyvitamin D Levels and Risk of Ischemic Heart Disease, Myocardial Infarction, and Early Death: Population-Based Study and Meta-Analyses of 18 and 17 Studies. Arterioscler Thromb Vasc Biol. 2012 Aug 30. [Epub ahead of print] Danik JS, Manson JE. Vitamin d and cardiovascular disease. Curr Treat Options Cardiovasc Med. 2012 Aug;14(4):414-24. Pilz S, Kienreich K, Tomaschitz A, Lerchbaum E, Meinitzer A, März W, Zittermann A, Dekker JM. Vitamin D and cardiovascular disease: update and outlook. Scand J Clin Lab Invest Suppl. 2012 Apr;243:83-91. Review. University of Copenhagen (UC). Vitamin D deficiency increases risk of heart disease. September 24, 2012. Accessed at http://news.ku.dk/all_news/2012/2012.9/vitamin-d-deficiency-increases-risk-of-heart-disease/
Vitamin D: The latest
RDAs and blood levels
In 2010, the U.S. Institute of Medicine's expert committee established higher RDAs and safe intake limits for vitamin D:
The Tolerable Upper Intake Level—the safe intake limit—for adults doubled, from 2,000 IU to 4,000 IU per day.
When it came to setting adequate blood levels of vitamin D, the IOM report retained the prior recommended minimum, which is 20 nanograms per milliliter (ng/mL).
However, leading researcher Michael F. Holick, Ph.D., M.D., of Boston University Medical Center says the evidence supports keeping vitamin D levels above 30 ng/mL (75 nmol/L).
Fish fit the vitamin D bill;
Sockeye salmon stand out
In addition to getting vitamin D from supplements, certain fish rank among the very few substantial food sources of vitamin D, far outranking milk and other D-fortified foods.
Among fish, wild sockeye Salmon rank as the richest source, with a single 3.5 ounce serving surpassing the US RDA of 600 IU by about 15 percent:
Vitamin D per 3.5 oz serving*
*For our full test results, click here.