by Craig Weatherby
Before the early 1990's, few researchers entertained the possibility that vitamin D might be important to heart health. We became aware of the prospect thanks to John Cannell, M.D., founder of the Vitamin D Council.
Recently, Dr. Cannell related the results of intriguing research, which prompted us to present this summary of his report and some other exciting findings on the subject.
Vitamin D was once considered important primarily in the context of bone health, and, more recently, as a strong anti-cancer agent.
But like a Polaroid photo, the image of vitamin D as an important heart-health player has developed slowly over the past two decades.
Let's review the evidence, starting with a landmark, overlooked study from 16 years ago, and ending with research released this month that illuminates how vitamin D helps keep human hearts healthy.
New Zealand study linked low vitamin D to higher heart risk
In 1990, Professor Robert Scragg of the University of Auckland published the startling discovery that heart attack victims had lower vitamin D levels than their healthy counterparts.
His team examined blood taken from 179 heart-attack patients within 12 hours of the onset of symptoms. For comparison, they examined blood taken on the same day from a group of healthy people (“controls”) who matched the heart patients in terms of age and gender distribution.
Dr. Scragg's group found that the heart-attack patients had significantly lower average vitamin D levels compared with the healthy controls: specifically, the cardiac cases had average levels of 32.0 nano moles per liter (nmol/L), versus 35.5 nmol/L in the blood from the healthy controls.
The risk of a heart attack was calculated as being 57 percent lower among the people whose vitamin D levels were equal to or above the median level measured, compared with subjects whose vitamin D levels were below the median.
As the team of “Kiwis” concluded, “These results provide support for the hypothesis that increased exposure to sunlight is protective against coronary heart disease.”
San Francisco finding echoes Auckland results
Further evidence linking low vitamin D levels to increased risk of heart disease came from the 2002 Asia Pacific Scientific Forum sponsored by the American Heart Association.
Paul Varosy, M.D. of the University of California at San Francisco led the study in women over age 65, some of whom were taking supplemental vitamin D.
As Dr. Varosy said, “Low blood levels of certain forms of vitamin D have been associated with increased risk of heart attacks, but to my knowledge no one has studied whether vitamin D supplements affect the risk of heart disease events … taking a simple multivitamin tablet is inexpensive, safe and common… [so] we thought it would make sense to address our question.”
His team enrolled 9,704 women ages 65 and older from a study of osteoporotic fractures:
- 4,268 women were taking supplemental vitamin D, mostly from multivitamin
- Vitamin D-calcium link may explain cardiac benefits
Two bad things happen when blood levels of vitamin D are low:
- Bones cannot absorb sufficient calcium.
- Calcium accumulates in artery walls and promotes formation of dangerous fatty plaques. The same processes that lead to calcium loss from bones may induce the accumulation of calcium in arteries, for unknown reasons.
- tablets containing 400 international units (IU): the US recommended daily allowance, which most experts agree should be 1,000 IU (Vieth R 2006).
- Another 733 women reported prior use of vitamin D supplements.
Significantly, given the mineral's key role in cardiac functions, the UC team reported that use of calcium supplements did not affect the results: “The protective effect of vitamin D supplement use was similar among women who never used calcium supplements… and among women who either currently or previously used calcium supplements.”
The researchers controlled for other possible confounding factors as well, including heart disease risk factors (diet, hereditary, and lifestyle), reported health status, and education.
Italians illuminate vitamin D's heart and diabetes benefits
As we've said, atherosclerosis is the build up of fatty plaques in arteries, and the break up of those plaques leads to the occlusions and clots that constitute the direct causes of heart attacks, heart failure, and strokes.
This month, a team led by Giovanni Targher, M.D. published exciting results concerning the vitamin D-heart link.
Using a standard measure called “carotid artery intimal thickness” , they found that low vitamin D blood levels were associated strongly with a greater degree of atherosclerosis (Targher G et al 2006).
Diabetes appears blunted by vitamin D
Earlier this year, the same team found vitamin D deficiencies in three out of five people diagnosed with type 2 diabetes (Cigolini M et al 2006).
They measured blood levels of vitamin D in 459 people diagnosed with type 2 diabetes and a control group of 459 comparable non-diabetic people.
The rate of vitamin D deficiency was 61 percent in the diabetics, versus only 43 percent in the non-diabetic controls. It is not surprising that both groups had relatively high rates of vitamin D deficiency, since most people, even in sunny countries, are deficient or borderline-deficient (Hochwald O et al 2004, Thomas MK et al 1998).
And, in line with the Italian's findings on artery health and vitamin D, the 31 percent of the diabetics with cardiovascular disease were very likely to also have low blood levels of vitamin D.
While these findings need confirmation via controlled clinical trials, it makes sense to ensure ample vitamin D intake right now. Think of it as a harmless heart-health measure that comes with bountiful bone-bolstering, cancer-curbing benefits.
- Cigolini M, Iagulli MP, Miconi V, Galiotto M, Lombardi S, Targher G. Serum 25-hydroxyvitamin D3 concentrations and prevalence of cardiovascular disease among type 2 diabetic patients. Diabetes Care. 2006 Mar;29(3):722-4.
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- Scragg R, Holdaway I, Jackson R, Lim T. Plasma 25-hydroxyvitamin D3 and its relation to physical activity and other heart disease risk factors in the general population. Ann Epidemiol. 1992 Sep;2(5):697-703.
- Scragg R, Jackson R, Holdaway IM, Lim T, Beaglehole R. Myocardial infarction is inversely associated with plasma 25-hydroxyvitamin D3 levels: a community-based study. Int J Epidemiol. 1990 Sep;19(3):559-63.
- Simpson RU, Weishaar RE. Involvement of 1,25-dihydroxyvitamin D3 in regulating myocardial calcium metabolism: physiological and pathological actions. Cell Calcium. 1988 Dec;9(5-6):285-92. Review.
- Targher G, Bertolini L, Padovani R, Zenari L, Scala L, Cigolini M, Arcaro G. Serum 25-hydroxyvitamin D3 concentrations and carotid artery intima-media thickness among type 2 diabetic patients. Clin Endocrinol (Oxf). 2006 Nov;65(5):593-597.
- Thomas MK, Lloyd-Jones DM, Thadhani RI, Shaw AC, Deraska DJ, Kitch BT, Vamvakas EC, Dick IM, Prince RL, Finkelstein JS. Hypovitaminosis D in medical inpatients. N Engl J Med. 1998 Mar 19;338(12):777-83.
- Varosy PD et al. Fracture and the Risk of Coronary Events in Women with Heart Disease. American Heart Association Asia Pacific Scientific Forum 2002. Abstract ID: 100267. Wednesday 4/24/2002.
- Varosy PD et al. Vitamin D Supplement Use and the Risk of Coronary Heart Disease Mortality in Older Women. American Heart Association Asia Pacific Scientific Forum 2002. Abstract ID: 100351. Tuesday 4/23/2002.
- Vieth R, Chan PC, MacFarlane GD. Efficacy and safety of vitamin D3 intake exceeding the lowest observed adverse effect level. Am J Clin Nutr. 2001 Feb;73(2):288-94.
- Vieth R. Critique of the considerations for establishing the tolerable upper intake level for vitamin D: critical need for revision upwards. J Nutr. 2006 Apr;136(4):1117-22.
- Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. Am J Clin Nutr. 1999 May;69(5):842-56. Review.