In the newest in a line of studies showing the potential value of vitamin D, new research from Johns Hopkins University shows that not getting enough of the so-called "sunshine vitamin" may increase the risk of early death by more than a quarter.
Researchers used data from the Third National Health and Nutrition Examination Survey and looked at people's vitamin D levels and then death from various causes. While the risk of death for people with low vitamin D from any single cause was only slightly elevated, the broader picture showed a 26 percent increase in death rates.
"[Low] vitamin D levels seem to confer an increased risk of dying from any cause," said Dr. Erin Michos, a cardiologist at Johns Hopkins, and one of the lead investigators of the study.
She said that the study showed an association between low vitamin D and death from heart disease, and said further study may reveal vitamin D to be a sign of impending heart disease.
"We think we have additional evidence to consider adding vitamin D deficiency as a distinct and separate risk factor for death from cardiovascular disease, putting it alongside much better known and understood risk factors, such as age, gender, family history, smoking, high blood cholesterol levels, high blood pressure, lack of exercise, obesity and diabetes," Michos said.
The study was published in this week's issue of the Archives of Internal Medicine.
But the study's researchers and others were quick to say that the study provides absolutely no evidence for now that taking vitamin D can reduce the risk of heart disease.
"Before we tell all Americans out there that this will definitely prevent heart attack, we need some clinical trials," Michos said.
Some took it a step further and questioned whether low vitamin D levels can even be considered a risk factor at all at this point.
"A relative increase in risk of death of 26 percent is not trivial, but not huge, either," said Dr. David Katz, director of the prevention research center at Yale University School of Medicine.
"Consider that being physically active, not smoking, and eating well could reduce the risk of premature death by as much as 80 percent," said Katz. "We would not want people to get the impression that a vitamin D supplement is a panacea. The findings are by no means that significant."
Others strongly agreed.
"It can't be considered a risk factor with the strength of cholesterol and hypertension until further studies are done," said Dr. Melvyn Rubenfire, the director of preventive cardiology at the University of Michigan.
But Rubenfire did not dismiss the importance of adequate vitamin D intake.
"I do encourage patients with CAD and other risk factors to be sure they have both adequate calcium and vitamin D, particularly those that use sun block," he said.
In fact, use of sunscreen in response to concerns about melanoma was cited by a number of physicians as a reason why many Americans are below advisable levels of vitamin D.
"I have been checking vitamin D studies in my patients for the last year and a half, and I have been astounded by the number of patients [with healthy lifestyles] that are 'D'- deficient," said Dr. Sandra Fryhofer, a clinical associate professor of medicine at Emory University School of Medicine.
"I have a relatively 'compliant' patient population. I advise sunscreen to prevent skin cancer [and wrinkles]. For the most part, my patients listen. But sunscreen with an SPF factor of 8 or more (and I recommend at least SPF 30 or higher) reduces the skin's ability to produce vitamin D by 95 percent. So, the amount of dietary vitamin D that was enough in the past may not be enough now that we are protecting our skin [and trying to prevent skin cancer]."
Many doctors cite the importance of vitamin D because of the relatively high levels of deficiency among Americans. A 2005 study from Drew University and UCLA showed that more than 41 percent of men and 53 percent of women had mildly or severely deficient levels of vitamin D.
Getting Up D Levels
And while vitamin D's impact on heart disease remains unclear, doctors recognize that its intake has other important benefits.
This new study adds to the mounting evidence that vitamin D deficiency is epidemic and that higher doses are needed," said Joanne Shearer, the director of food and nutrition services at Avera Heart Hospital in Sioux Falls, S.D.
"I would favor screening for vitamin D deficiency as we screen for blood sugar, cholesterol, blood pressure, etc. There are so many medical conditions that are now associated with vitamin D deficiency, that it seems like a prudent public health measure to take. Vitamin D screening and treatment is relatively inexpensive, versus the cost of treating the disease associated with vitamin D deficiency."
So, how should Americans make up the deficits in vitamin D?
"It would certainly be prudent to recommend daily consumption of low-fat and fat-free milk, and to educate people about other sources," said diet expert Keith-Thomas Ayoob of the Albert Einstein College of Medicine. "Fatty fish (salmon, mackerel, sardines, etc.) are loaded with vitamin D, for example."
Why Is This Vitamin Different?
Dr. James O'Keefe, a cardiologist at the Mid America Heart Institute in Kansas City, Mo., said that while studies like these only present preliminary findings, vitamin D may prove to be a bit more important than other vitamins taken as supplements.
He noted that the latest study's findings were unclear because many of the risk factors for heart disease, like obesity, can actually cause a deficiency in vitamin D. So, it may be a marker rather than an agent.
"It might just be a marker, but unlike the other vitamins, it's a hormone," O'Keefe said, referring to the fact that vitamin D is actually produced by the human body -- from being out in the sun, for example.
The problem, he said, is that many people have deficiencies in the vitamin that can be easily diagnosed and corrected. While surpluses of vitamins will often have no effect, getting a deficient vitamin up to speed will, as in the case of British sailors who avoided scurvy by eating limes.
And those chronic deficiencies are why people should monitor vitamin D levels, according to O'Keefe.
"People should know their vitamin D. Measure it. If it's abnormal, treat it," he said.
And, in addition to eating fish or taking a daily dose of the less popular cod liver oil, O'Keefe said that some sunshine should be a part of everyone's regimen.
"We're not designed to be moles; we're designed to be outdoor creatures," he said. "Prudent sun exposure not only feels good, it's good for vitamin D levels."