CORVALLIS, Ore. - Moderate daily supplements of vitamin C taken by people with coronary artery disease may be effective in improving the function of blood vessels, preventing the chest pains of unstable angina pectoris and reducing the risk of heart attack and stroke, new studies suggest.
The recently published research, funded by the National Institutes of Health, was conducted by collaborating scientists from the Linus Pauling Institute at Oregon State University and Dr. John F. Keaney, Jr., and Dr. Joseph A. Vita at the Boston University School of Medicine.
In three recent reports, these researchers have outlined how patients with a healthy level of vitamin C in their bloodstream - which was provided in one study by a daily 500 milligram supplement - had blood vessels with significantly improved "vasodilation," or the ability to relax and avoid dangerous constriction. Similar findings were also made with one prescription drug.
"These studies are providing a new perspective on heart disease," said Balz Frei, professor and director of the Linus Pauling Institute at OSU. "Atherosclerosis, or clogged arteries, are still a serious health concern, but they don't necessarily mean a person will suffer a heart attack or stroke. It appears there are also other key factors in the health of blood vessels, and they may be influenced by vitamin C."
In tracing the biological underpinnings of heart disease, Frei said, scientists are honing in on the ability of a naturally-produced compound in the body, nitric oxide, that helps relax blood vessels, inhibits the aggregation of platelets and the formation of blood clots, and decreases the risk of plaque rupture - all of which are relevant to actually having a heart attack or stroke.
Studies suggest that nitric oxide can be "inactivated" by superoxide radicals, which are the reactive oxygen compounds often present with high cholesterol levels. When nitric oxide availability is improved, it reduces the presence of unstable angina pectoris or the risk of coronary events linked to a higher level of heart attacks, experts say. This, in fact, is how nitroglycerin tablets work - they are often taken by patients to provide nitric oxide and relieve the symptoms of angina attacks.
And at least two other mechanisms which can help do that, Frei said, are healthy levels of vitamin C or use of a prescription drug which can increase levels of glutathione, also an antioxidant.
"Use of antioxidants such as vitamin C may not primarily act through inhibition or reduction of atherosclerotic lesions," Frei said. "We don't suggest that atherosclerosis is not a serious health concern, because it is. But it is not the only major factor relevant to actually having a heart attack."
Researchers became intrigued by that concept, Frei said, when it was found that some cholesterol-lowering drugs or the use of vitamin E supplements appeared beneficial to coronary patients even when the state of their blood vessels had not yet changed much.
"It's clear there's something more at work here than just scarred or clogged arteries," Frei said. "We now believe that preserving the biologic availability of nitric oxide is very important, and that antioxidant vitamins, especially vitamin C, can play a very important role in this."
Findings from some of the most recent work were published in the April, 1998, Journal of the American College of Cardiology. In the study of 149 patients, those with low levels of vitamin C were strongly correlated to a higher incidence of painful, unstable angina pectoris - even though there was no apparent difference in the level of artherosclerosis between patients with high or low vitamin C levels.
Another study published in March, 1998, in the Journal of Clinical Investigation found that a prescription drug which increases levels of glutathione can also improve blood vessel function, even though the underlying artherosclerosis is largely unchanged. And it's known that vitamin C can also help protect levels of glutathione.
And a third study, awaiting publication and presented recently at a professional conference in California, indicated that a 500 milligram daily supplement of vitamin C was enough to provide most of the benefits it had to offer in improving blood vessel function.
"With the issue of vasomotor dysfunction, we're basically finding that moderate supplements of vitamin C can soon restore the dilation characteristics of atherosclerotic blood vessels to those of healthy blood vessels," Frei said. "That's not the only risk factor for heart disease and stroke, but it appears to be an important one."
Based on the findings of this and other recent studies making similar findings, Frei said, any patient with unstable angina pectoris or coronary heart disease might be prudent to take up to a 500 milligram supplement of vitamin C daily. Many patients studied have inadequate levels of the vitamin.
A diet rich in fruits and fresh vegetables would be even better for this purpose, he said, because it would provide generous levels of vitamin C and many other health benefits as well. But there is no known health risk for people who wish to use 500 milligram daily vitamin C supplements, or even more, he said, and chances are there may be substantial benefits for the heart.