Coffee, Tea, Cocoa and Risk of Stroke

The author reviewed the association between coffee, tea, cocoa and stroke.

Polyphenols are abundant micronutrients in our diet, and evidence for their role in the prevention of degenerative diseases such as cancer and cardiovascular diseases is emerging. The polyphenols in coffee, tea and cocoa may reduce the risk of stroke through multiple mechanisms, in particular by lowering blood pressure and cholesterol, having anti-inflammatory effects and through improving insulin sensitivity.

This review summarizes the available evidence on the potential role of coffee, tea and cocoa in the prevention of stroke.

This review analyzed results from previous studies of coffee, tea, cocoa and risk of stroke.

The cardiovascular effects of coffee drinking depend in part on coffee preparation method and the characteristics of the individual. In a study of individuals with high blood pressure, intake of 200-300 mg caffeine (1.5 – 2 cups coffee) produced an average rise of 8.1 mmHg in systolic blood pressure (pressure when the heart is contracting) and 5.8 mmHg in diastolic blood pressure (pressure when the heart is filling/relaxing) in the first hour after drink ingestion, which lasted for greater than or equal to 3 hours. However, in another study of coffee consumption in mainly healthy participants with normal blood pressure, no significant change in blood pressure was found.

In the past, coffee was seen as a risk factor for cardiovascular disease. However, a study of coffee consumption and stroke in 402,260 U.S. participants found that in men, compared to no coffee consumption, the risk of stroke was reduced by 1% for those drinking one or less cups per day and reduced by 16% in those drinking 2-3 cups per day. In women, compared to no coffee consumption, the risk of stroke was increased by 15% for 1 or less cups per day while the risk of stroke was reduced by 7% for those drinking 2-3 cups per day.

In an analysis of 14 studies of green or black tea consumption and stroke, an increase of tea consumption by 3 cups per day was associated with a 13% reduced risk of stroke. The association was similar for men and women but green tea was associated with a 17% reduction while black tea was associated with a 9% reduced risk. Tea is believed to achieve this through positive effects on blood pressure, cholesterol and blood glucose concentrations.

Several controlled studies have found that flavanols (a compound released from cocoa) present in cocoa may improve platelet function. In a study of 5 trials, it was estimated that intake of 100 mg of flavanols induces a 3-11% reduction in platelet aggregation. Platelet aggregation can result in blood clots, leading to stroke. In an analysis of 5 studies, those in the highest category of chocolate consumption had a 19% lower risk of stroke compared to those in the lowest category of chocolate consumption. There was a 14% reduced risk of stroke for a 50-g per week increase in chocolate consumption.

The author stated that current evidence indicated beneficial effects of green and black tea as well as chocolate on cardiovascular health, and that tea and chocolate consumption may reduce the risk of stroke.