Harvard study links low blood levels of the “sunshine and seafood” vitamin to higher heart attack risk
by Craig Weatherby
The death of widely liked and admired NBC political newsman Tim Russert from coronary heart disease last week came as a complete surprise to his doctors.
He showed none of the symptoms that would normally lead to invasive tests that might have revealed his high degree of risk.
According to his doctors, Mr. Russert's autopsy revealed an enlarged heart and significant atherosclerosis (plaque buildup) of the left anterior descending coronary artery.
When the plaque in this artery burst, it threw off a fresh clot that blocked the artery. This blockage caused a heart attack, which simply means that heart muscle cells suffer from lack of oxygen and begin to die.
In turn, the heart attack caused a fatal ventricular arrhythmia, which was the immediate cause of death.
No single food or lifestyle factor can prevent all heart attacks or sudden cardiac deaths.
But a new epidemiological study adds possible heart protection to the fast-growing list of potential benefits associated with vitamin D.
Harvard study links higher vitamin D to reduced heart risk
Researchers from the Harvard School of Public Health reviewed the medical records and blood samples of 454 men between 40 and 75, selected from among 18,225 men who'd participated in the Health Professionals Follow-up Study.
At the outset of the original study, the participants had provided blood samples and completed questionnaires on diet and lifestyle factors.
The men selected for the new analysis had either died from heart disease or suffered a non-fatal heart attack during the first 10 years following their enrollment.
At the time they enrolled, all the men were free of diagnosed cardiovascular disease.
To conduct the new analysis, the Harvard team compared data from these 454 “cases” with data from 900 healthy “control” men with no history of heart disease (Giovannucci E et al. 2008).
Results indicate possible heart-protective effect of vitamin D
The Harvard team's analysis showed that during a decade of followup, men with low blood levels of vitamin D (15ng/mL) were more than twice as likely (i.e., 142 percent more likely) to have died from heart disease or suffered a heart attack, compared with men whose blood levels are considered sufficient, albeit far short of optimal (30ng/mL).
And even men with intermediate vitamin D levels (22.6-29.9 ng/mL) were 60 percent more likely to have died from heart disease or suffered a heart attack, compared to men with the higher levels (30ng/mL).
The data analysis that produced this result accounted for factors that could influence heart attack risk (e.g., omega-3 intake, family history of heart attack, high blood pressure or diabetes, body mass index, physical activity, cholesterol levels).
While these results were based on blood tests rather than far less unreliable measures of vitamin D levels such as food-intake surveys, it cannot prove that higher vitamin D levels produced the risk reduction.
But as the authors wrote, “…the amount of vitamin D required for optimal benefit may be much higher than would be provided by current recommendations (200-600 IU per day), especially in those with minimal sun exposure.”
“Thus, the present findings add further support that the current dietary requirements of vitamin D need to be increased to have an effect… substantially large enough for potential health benefits.”
In fact, two years ago, a team of experts—which included the lead author of the new analysis (Harvard professor Edward Giovannucci, M.D., Sc.D.)—concluded that optimal health requires a minimum vitamin D blood level of about 90 ng/mL, or three times the level considered “high” in the new Harvard analysis (Bischoff-Ferrari HA et al. 2006).
- Bischoff-Ferrari HA, Giovannucci E, Willett WC, Dietrich T, Dawson-Hughes B. Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes. Am J Clin Nutr. 2006 Jul;84(1):18-28. Review. Erratum in: Am J Clin Nutr. 2006 Nov;84(5):1253. dosage error in abstract. Am J Clin Nutr. 2007 Sep;86(3):809.
- Giovannucci E, Liu Y, Hollis BW, Rimm EB. 25-hydroxyvitamin D and risk of myocardial infarction in men: a prospective study. Arch Intern Med. 2008 Jun 9;168(11):1174-80.