Dark Chocolates and the Heart

Dark Chocolates and the Heart

Are dark chocolates good for the heart?

A study published in Circulation suggests that eating dark chocolate can improve coronary vasomotion and reduce platelet reactivity [1].

Dark chocolates which contain 70% cocoa have lots of flavonoids – potent antioxidants which helps to overcome the oxidative stress. They also decrease the activation of blood platelets responsible for thrombosis.

High oxidative stress and limited availability of antioxidants can cause endothelial damage in the arteries, leading to increased chances for a thrombosis.

Flavonoid rich dark chocolate has the potential for a beneficial effect on graft atherosclerosis and hence this study in heart transplant recipients.

They compared the effect of flavonoid rich dark chocolate with cocoa free control chocolate on coronary vascular and platelet function in 22 heart transplant recipients in a double blind randomized study.

Coronary vasomotion was evaluated by quantitative coronary angiography and cold pressor test before and 2 hours after ingestion of 40 g dark chocolate or control.

Two hours after ingestion of flavonoid rich dark chocolate, coronary diameter increased from a mean of 2.36 mm to 2.51 mm (about 6%). Platelet adhesion also decreased in dark chocolate group while it was unchanged in the control group.

A subsequent editorial which appeared in the Lancet warns us about jumping in for dark chocolate without due considerations [2].

They pointed out that some manufacturers may remove flavanols because of the bitter taste and darken the chocolate. Flavanol content may not be there on the label as well.

They also highlighted the need to balance the calorie content of diet as chocolates have significant calorie content. Traditional way of healthy balanced diet low in sugar, salt and fat and rich in fresh fruit and vegetables was suggested by the article.


  1. Flammer AJ, Hermann F, Sudano I, Spieker L, Hermann M, Cooper KA, Serafini M, Lüscher TF, Ruschitzka F, Noll G, Corti R. Dark chocolate improves coronary vasomotion and reduces platelet reactivity. Circulation. 2007 Nov 20;116(21):2376-82.
  2. The devil in the dark chocolate. Lancet. 2007 Dec 22;370(9605):2070.