A daily "tomato pill" can significantly improve the functioning of blood vessels in patients with heart disease, research has shown.
The findings suggest that a powerful antioxidant in tomatoes may contribute to the health benefits of a Mediterranean diet.
Participants in the study were given a supplement called Ateronon that contains seven milligrams of the tomato ingredient lycopene.
Of 36 patients with heart disease, those taking the pill every day for two months saw their blood vessels widen by 53%.
This was due to improved functioning of the endothelium, the inner wall cell lining of blood vessels, scientists believe.
The tomato pill had no effect on healthy volunteers whose blood vessels were already "normal".
Constriction of blood vessels reduces blood flow and is one of the main factors that can lead to heart attacks and strokes.
Lead scientist Dr Joseph Cheriyan, from Addenbrooke's Hospital and Cambridge University, said: "There's a wealth of research that suggests that the Mediterranean diet - which includes lycopene found in tomatoes and other fruit as a component - is good for our cardiovascular health. But so far, it's been a mystery what the underlying mechanisms could be.
"We've shown quite clearly that lycopene improves the function of blood vessels in cardiovascular disease patients. It reinforces the need for a healthy diet in people at risk from heart disease and stroke.
"A daily 'tomato pill' is not a substitute for other treatments, but may provide added benefits when taken alongside other medication. However, we cannot answer if this may reduce heart disease - this would need much larger trials to investigate outcomes more carefully."
Professor Jeremy Pearson, associate medical director at the British Heart Foundation, which helped to fund the study, said: "Impaired endothelial function is a known predictor of increased risk of future heart disease. Further work is needed to understand whether the beneficial effects seen in this small study translate into clinical benefit for at-risk patients."
Lycopene has been promoted for its anti-cancer properties, especially in relation to prostate cancer.
However, convincing evidence that the compound really can fight cancer in patients is lacking.