A new study reported in the May 2000 issue of the Journal of the American College of Cardiology suggests that very high doses of supplemental vitamin C cannot reverse established blood vessel abnormalities in smokers.

Cigarette smoking increases the risk of heart disease in a number of ways. One aspect of arterial function that worsens with smoking is dilation or widening of the arteries when blood flow through them is increased. Smokers’ arteries are more likely to develop atherosclerosis (fatty deposits) and become less elastic than arteries of nonsmokers. This lack of arterial dilation could lead to diminished blood flow to the heart. If it continues, a heart attack might result. This is an important early factor in the development of cardiac problems.

Because smokers often have lower-than-normal levels of antioxidant vitamins, such as vitamin C, in their blood, it has been suggested that increasing the intake of such vitamins might help prevent some smoking-related problems, such as impaired arterial dilation. Some smokers hope that by taking extra vitamin C they can reduce their risk of smoking-related heart trouble. But recent research does not support this theory.

To measure arterial function, researchers use a blood pressure cuff to compress the subjects’ brachial arteries, which are large arteries in the upper arm. They then released the pressure. Normal response to such manipulation is a dilation of the artery after the pressure is removed — the dilation was measured by an ultrasound technique, which provided an image of the artery.

Researchers from the Heart Research Institute of Australia and the University of Turku, Finland, studied the arterial dilation of 20 healthy smokers (average age 36 years) — eight men and 12 women. Arteries of participants were studied first before taking any supplements, and then two hours after taking 2 grams of vitamin C or an inactive compound (a placebo). Then, they took either 1 gram of vitamin C or an identical placebo every day for eight weeks. Subjects did not know whether they were receiving vitamin C or a placebo.

Two hours after the initial dose of vitamin C, the investigators found that the dilation of arteries was significantly increased (that is, more normal) compared to dilation after the placebo treatment.

However, after eight weeks of high-dose vitamin C supplementation, there was no difference between the arterial responses of smokers who had taken vitamin C supplements and their response when they took the inactive pills.

The authors interpreted these results as indicating that even long-term, high-dose vitamin C supplementation does not normalize the chronic arterial dysfunction that accompanies cigarette smoking. They noted that “smoking remains the major modifiable risk factor for vascular disease,” and that any benefit of vitamin C supplementation was very short lived. They stated that their study “discourages the daily use of vitamin C for vascular protection in smokers.”

“In fact,” said Dr. Victor Herbert of the Mount Sinai Medical School in New York City, “vitamin C supplements promote atherosclerosis by converting LDL cholesterol to the harmful form that deposits in arteries.” Herbert, a scientific advisor to the American Council on Science and Health, points out that, “all antioxidants soak up destructive free radicals in some circumstances and generate them in others. Cigarette smoke, for example, causes vitamin C to generate free radicals.”

It should be noted that the level of vitamin C supplementation in this study (1 gram or 1,000 milligrams) was quite high compared to the dietary amount recommended for healthy adults, which is 75 milligrams per day.

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