Ample evidence indicates that chocolate may have beneficial effects on the cardiovascular system. Chocolate consumption has been shown to reduce systolic and diastolic blood pressure in short-term randomized feeding trials (1), and has been demonstrated to improve endothelial and platelet function and to ameliorate insulin resistance (2). Moreover, flavonoids in chocolate possess strong antioxidant activity and can suppress oxidation of low-density lipoprotein cholesterol (3).
In the autumn of 1997, 39,227 women completed a questionnaire that included approximately 350 items concerning diet and other lifestyle factors (4). We excluded women with a missing national identification number, those with implausible values for total energy intake, and those with a history of cancer, stroke, coronary heart disease, or diabetes mellitus before baseline. That left 33,372 women, age 49 to 83 years, for analysis. The study was approved by the Ethical Review Board at the Karolinska Institutet (Stockholm, Sweden). Chocolate consumption was assessed using a self-administered food-frequency questionnaire. Women were asked to indicate how often on average they had consumed chocolate and 95 other foods during the previous year. There were 8 pre-defined consumption categories ranging from never to ≥3 times a day. In the 1990s, approximately 90% of chocolate consumption in Sweden was milk chocolate, containing approximately 30% cocoa solids (5).
Our findings are broadly consistent with those from previous smaller studies, which observed either a statistically significant (136 stroke cases) (6) or a nonsignificant (111 or 469 stroke cases) (5,7) inverse association between chocolate consumption and total stroke. In the present study, only women in the highest quartile of chocolate consumption (median 66.5 g/week) had a significantly reduced risk of stroke, suggesting that higher intakes are necessary for a potential protective effect. The reason for the stronger association observed for hemorrhagic stroke than for cerebral infarction is unclear.
In summary, results from this cohort of women suggest that a high chocolate consumption is associated with a lower risk of stroke.