August 29, 2012 — More evidence supports a link between chocolate consumption and reduced stroke risk.
A new study shows that men who consume the most chocolate have a 17% lower risk for stroke than those who consume the least. A meta-analysis included in the study showed an overall 19% decreased risk for stroke for the highest consumers of chocolate — male and female — compared with those who ate the least.
Although results "suggest that chocolate consumption is inversely associated with risk of stroke," further research is needed to confirm these findings before any recommendations about chocolate consumption can be given, according to the authors, led by Susanna C. Larsson, PhD, of the Division of Nutritional Epidemiology, National Institute for Health and Welfare, in Helsinki, Finland.
The study is published online August 29 in Neurology.
The study included 37,103 men from the Cohort of Swedish Men, a prospective study that began in 1997, when all men aged 45 to 79 years residing in 2 counties in central Sweden were asked to provide detailed information on diet and other lifestyle factors. Researchers assessed chocolate consumption using a self-administered food frequency questionnaire that included 96 foods and beverages.
For chocolate consumption, respondents could choose from 8 categories, ranging from never, to eating this confection 3 or more times per day. To determine consumption in grams, researchers multiplied the frequency of consumption by 4 age-specific portion sizes to arrive at quartiles of chocolate consumption: less than 12.0 g/week (0); 12.0 to 19.5 g/week (12.5); 19.8 to 51.3 g/week (38.4); and at least 51.8 g/week (62.9).
By linking the study population to the Swedish Hospital Discharge Register, researchers identified incident cases of stroke. They classified stroke events as cerebral infarction, intracerebral hemorrhage, subarachnoid hemorrhage, and unspecified stroke.
From 1998 to 2008, 1995 cases of first stroke were reported, including 1511 cerebral infarctions, 321 hemorrhagic strokes, and 163 unspecified strokes. Compared with men who had the lowest chocolate consumption, those who ate the most chocolate were younger on average but were less likely to be current smokers. They tended to be slightly leaner, and to consume more alcohol, red meat, fruits, and vegetables, but less fish.
After adjustment for several factors, including age, education, smoking status, body mass index, physical activity, aspirin use, history of hypertension, and atrial fibrillation, high chocolate consumption was associated with a statistically significant lower risk for total stroke.
Compared with men in the lowest quartile of consumption (0 g/week), those in the highest category (62.9 g/week) had a reduced risk for stroke of 17%. Results were similar for cerebral infarction and for hemorrhagic stroke.
Table. Stroke Risk With Highest vs No Chocolate Consumption
|Outcome||Relative Risk (RR)||95% Confidence Interval||P Value|
|Stroke||0.83||0.70 - 0.99||.08|
|Cerebral infarction||0.83||0.69 - 1.01||.14|
|Hemorrhagic stroke||0.84||0.56 - 1.25||.42|
Age-standardized incidence rates of stroke were 85 per 100,000 person-years for those consuming the least chocolate, and 73 per 100,000 person-years for those in the highest quartile.
In an analysis stratified by history of hypertension, an inverse relation between chocolate consumption and risk for total stroke was observed in men without hypertension (relative risk [RR], 0.76; 95% confidence interval [CI], 0.62 - 0.93), but not in men with a history of hypertension (RR, 1.04; 95% CI, 0.77 - 1.41; P for interaction = .04).
It is possible that the blood pressure–lowering effect of chocolate consumption helps explain the association in men without a history of hypertension; such men may have had normal blood pressure at baseline as the result of treatment for hypertension, say the authors.
Results were unchanged after additional adjustment for history of hypercholesterolemia.
The researchers also carried out a meta-analysis that included results from the current study as well as from 4 other prospective studies assessing the association between chocolate consumption and stroke risk. In this analysis, which included 4260 stroke cases, the overall RR for stroke for the highest vs lowest category of chocolate consumption was 0.81 (95% CI, 0.73 - 0.90), or a 19% reduction in risk.
A dose-response meta-analysis used the same methods.
Chocolate is a rich source of flavonoids that may protect against cardiovascular disease through antioxidant, antiplatelet, and anti-inflammatory effects. Flavonoids may also lower blood pressure, increase high-density lipoprotein (HDL) cholesterol, and improve endothelial function. Chocolate contains antioxidant-rich caffeine, albeit in low amounts.
One of the limitations of the study is that chocolate consumption was self-reported and was measured only at a single time point. Another is that information on the type of chocolate consumed was not available. As a result, any association with dark chocolate, previously linked to health benefits, could not be examined, but in general, about 90% of chocolate consumed in Sweden is milk chocolate, containing about 30% cocoa solids, they write.
The authors stress also that chocolate is high in sugar, saturated fat, and calories and should be consumed in moderation.
Reached for a comment, Gustavo Saposnik, MD, director of the Stroke Outcomes Research Center, and associate professor and clinician scientist in the Departments of Medicine (Neurology) and Health Policy, Management, and Evaluation, at St. Michael's Hospital, University of Toronto, in Ontario, Canada, said the present study confirms previous observations, including those of his own systematic review, that eating chocolate is associated with lower risk for stroke.
Results of his and his colleagues' review, presented at the American Academy of Neurology Meeting in 2010 and reported by Medscape Medical News at that time, showed that in one study, a 22% reduction in stroke risk was noted for participants who had a single serving of chocolate per week, and in another, a 46% reduction in stroke mortality resulted from weekly consumption of flavonoids in 50 g of chocolate vs no consumption. However, the number of studies looking at the relationship between chocolate consumption and stroke risk, and included in the analysis, was small.
Dr. Saposnik found it interesting that in the current study, even very low chocolate consumption (median, 62.9 g/week) was associated with a 17% stroke reduction.
He noted that the study was limited by the use of questionnaires that were not specifically intended to target the association between chocolate and risk for stroke. This, he said, could introduce potential risk for misclassification. As well, Dr. Saposnik said that the study provided limited information about the composition of the chocolate consumed.
For Dr. Saposnik, the strength of the study was the meta-analysis, which included results from 5 studies.
This study was supported by the Swedish Council for Working Life and Social Research, the Swedish Research Council/Committee for Infrastructure, and the Karolinska Institute. The authors have disclosed no relevant financial relationships.
Neurology. 2012;79:1223-1229. Published online August 29, 2012. Abstract
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