Various studies have reported on vitamin C as well as other antioxidant vitamins and their effects on blood vessels.

In a study conducted by German researchers and published in the American Heart Association's (AHA) journal "Circulation" on July 1, 1996, the researchers found that vitamin C helps to absorb some of the damaging chemicals (called free radicals) in cigarette smoke that cause damage to the arterial wall.

The researchers compared blood flow in the arms of 10 healthy male non-smokers and 10 male chronic smokers. They found that the blood vessels in chronic smokers were more constricted. When a chemical was added to their blood to relax and widen the vessels, the response was limited. However, when vitamin C was injected into the same artery, it greatly improved the dilation effect.

The scientists suggest that vitamin C helps improve the ability of the thin layer of cells in the artery called the endothelium to function properly (i.e., either narrow or widen). They further note that vitamin C may protect against biochemical changes in LDL cholesterol (the "bad cholesterol) that cause it to be deposited in artery walls (a process called atherosclerosis).

In two other studies, reported at the annual AHA scientific sessions in New Orleans on November 12, 1996, researchers studied the effects of vitamins C and E on arteries. The first study, led by Dr. Henry Ting of Brigham and Women's Hospital in Boston, measured blood flow in 12 people with normal cholesterol (averaging 180 mg/dl) and 12 people with high cholesterol (averaging 280 mg/dl). The researchers took blood-flow measurements before and after injecting vitamin C into the artery in the forearm. They found that vitamin C improved the blood flow and widened blood vessels in the people with high cholesterol but had no effect on the people with normal cholesterol levels.

In another study led by Dr. Gary Plotnick at the University of Maryland Medical center in Baltimore, the researchers gave 20 adults with normal cholesterol levels (between 133 and 200 mg/dl) a 900 calorie meal that was at least 50% saturated fat. They then took timed blood flow measurements using a device that temporarily halted blood flow in order to see the extent the artery relaxed and widened to allow blood to flow. They found that after 4 hours, the subjects' arteries had only widened by 8%, half of what was expected by the researchers. However, as they predicted, when the subjects took vitamins E and C with their meals, the blood vessels widened by 18% after the four hour period.

The scientists believe that these antioxidant vitamins may help treat the effects of a high fat diet. However, the reader should note that these researchers have not conclusively determined the benefits of antioxidant vitamins and the AHA does not recommend the use of antioxidant vitamin supplements until more information is known.