Researchers have known for years that broccoli is a rich source of anti-oxidants, vitamins and fiber that may protect against cancer, study leader Dipak K. Das and colleagues said.

Das and colleagues gave broccoli extract to lab rats for one month and measured its effects on the rats' heart muscle.

The study, published in the Journal of Agricultural and Food Chemistry, found that compared to a control group of rats that ate a regular diet, the broccoli-fed animals had improved heart function and less heart muscle damage when deprived of oxygen.

Broccoli's heart-healthy effects are likely due to its high concentrations of certain substances that seem to boost levels of a heart-protective protein called thioredoxin, the researchers said in a statement.