In fact, high levels of one type of vitamin E -- known as gamma-tocopherol -- may actually increase the risk.
Because these chemicals are antioxidants, it has been thought that they may protect against the formation of plaque that can block arteries, by preventing the oxidation of LDL ("bad") cholesterol. Although several studies have examined the link between beta-carotene and heart disease, relatively few have looked at the effects of other so-called carotenoids.
To look into the question, Dr. Jing Ma from Harvard University in Boston, and others, turned to the Physicians' Health Study, which began in 1982 and followed participants for up to 13 years. The researchers compared the levels of carotenoids and tocopherols in the blood of 531 men who later had a heart attack with those of a control group of 531 similar men who did not have a heart attack.
Blood levels of five major carotenoids were measured, as well as levels of retinol, alpha- tocopherol and gamma-tocopherol.
"Based on the antioxidant hypothesis, we expected people with high levels of these compounds to be at low risk for developing heart disease," Dr. Ma told.
"But, this is not what we found."
Overall, there were was no evidence that the carotenoids or tocopherols protected against heart attacks, the team reports in the American Heart Association's journal, Circulation.
However, among current and former smokers, higher levels of beta-carotene did lower the risk of a heart attack.
On the other hand, high gamma-tocopherol levels were actually linked to an increased risk. But gamma-tocopherol itself may not actually be harmful, Ma noted. "Gamma-tocopherol may simply represent a marker for trans-fat intake," which is known to up the risk for heart disease.
"These findings should not discourage people from eating fruits and vegetables, as there are probably other components present that protect against heart disease," she stressed. "The bulk of evidence still supports a beneficial effect for eating such foods."