The health benefits of broccoli and related vegetables may come in part from a chemical known as sulforaphane, which appears to activate a specific heart-protecting protein, according to a study conducted by researchers from Imperial College, London and published in the journal Arteriosclerosis, Thrombosis and Vascular Biology.

“We know that vegetables are clearly good for you, but surprisingly the molecular mechanisms of why they are good for you have remained unknown for many years,” said researcher Paul Evans of the United Kingdom’s National Heart and Lung Institute. “This study provides a possible explanation for how green vegetable consumption can promote a healthy heart.”

Researchers carried out their tests directly on the chemical sulforaphane, which occurs naturally in vegetables in the family Brassicaceae, also known as cruciferous vegetables. In addition to broccoli, the cruciferous vegetables include maca, cabbage, cauliflower, radish, turnip, mustard greens and watercress.

Sulforaphane was found to increase the activity of the protein Nrf2, which is known to be inactive in areas of the cardiovascular system that are predisposed to plaque buildup. In these areas, which include bends and branches in blood vessels, blood flow is slowed or even disrupted entirely.

“What our study showed was that sulforaphane can protect those regions by switching on the Nrf2,” Evans said.

“These fascinating findings provide a possible mechanism by which eating vegetables protects against heart disease,” said Peter Weissberg of the British Heart Foundation, which funded the study. “As well as adding evidence to support the importance of eating ‘five-a-day’, the biochemistry revealed in this research could lead to more targeted dietary or medical approaches to prevent or lessen disease that leads to heart attacks and strokes.”

Because the study was carried out using pure sulforaphane, the researchers plan to repeat it in a way that closer approximates consumption of actual broccoli.

“We now need to go and test this with broccoli smoothies, as it were, and compare that with the effect of purified sulforaphane,” Evans said.