A form of vitamin A common in carrots and many other fruits and vegetables appears to substantially reduce the risk of heart problems in people who already have coronary artery disease, researchers have found.

The findings, released last week at the American Heart Association annual meeting in Dallas, are still considered preliminary. But they raise the possibility that people whose heart arteries are already clogged may be able to ward off heart attacks and other cardiac problems by consuming the nutrient called beta carotene.

Charles Hennekens, who directed the study at Brigham and Women's Hospital in Boston, cautioned that the results will have to be confirmed by further research before anyone recommends that people eat carrots to save their hearts.

If the apparent connection between beta carotene and healthy hearts turns out to be true, however, it will add another element to the already strong association between diet and the heart.

Beta carotene, which the body changes into vitamin A, is the nutrient that gives fruits and vegetables their orange color. Especially good sources include carrots, sweet potatoes, peaches and cantaloupes.

The latest results were part of the Physicians' Health Study, a years-long project in which 22,000 male doctors have been randomly assigned to take beta carotene pills, aspirin, placebos or some combination of the three.

The aspirin results already have been released. They showed that taking an aspirin every other day reduces the risk of a first heart attack by 44 percent.

The beta carotene experiment was intended to see if the nutrient prevents cancer; this part of the study is scheduled to continue until 1995. However, the researchers have looked separately at the effect of beta carotene on 333 participants who already had evidence of coronary artery disease before the study began. All had suffered angina, chest pain resulting from obstructions in the arteries that feed the heart.

After six years of study, there were 10 heart attacks among the men who took beta carotene and 17 among those who took a placebo. Among men in this group who took both beta carotene and aspirin, there were no heart attacks at all.

Overall, those who took the 50-milligram beta carotene pills every other day experienced about half as many "major events" -- including heart attacks, strokes, cardiac arrest, bypass operations and angioplasty to open clogged arteries.

"Even if this turns out in future studies to be a benefit, it will still be an adjunct" to other strategies for reducing heart disease, such as lowering cholesterol and blood pressure and stopping smoking, Hennekens said.

The data so far suggests only that beta carotene will prevent further heart trouble in people who already have heart disease. The ongoing study with the rest of the physicians should answer whether it will also help people with healthy hearts and whether it will prevent cancer.

Just why this form of vitamin A might be good for the heart is unclear, but researchers speculate that it might work because it is an anti-oxidant. Vitamin A and some other nutrients remove a highly reactive form of oxygen that can damage tissue in the same way that oxygen causes iron to oxidize, or rust.