A new systematic review suggests higher chocolate consumption may be associated with a lower risk for incident stroke and stroke-related mortality….
Results of 2 prospective cohort studies showed, respectively, a 22% reduction in stroke risk for those who had 1 serving of chocolate per week and a 46% reduction in stroke mortality from weekly consumption of flavonoids in 50 g of chocolate vs no consumption. A third study showed no association between chocolate intake and stroke or death.
Senior author Gustavo Saposnik, MD, from St. Michael’s Hospital and the University of Toronto, Canada, stated that, “However, the number of studies looking at this relationship was small …we need more prospective studies that specifically identify the type of chocolate and the amount, including the amount of flavonoids included in the composition of the chocolate, to make more valid conclusions.”
Chocolate contains cocoa butter, flavonoids, carbohydrates, and vitamins. Previous studies, most of them epidemiological, have shown varying effects of chocolate consumption on the risk for cardiovascular disease, the researchers, with first author Sarah Sahib, BScCA, from McMaster University in Hamilton, Ontario, Canada, write. “Less is known about the risk of stroke in association with flavonoid intake,” they note.
To examine this association, the authors carried out a systematic review of studies published between 2001 and 2009, using search terms including flavonoids, flavanols, isoflavones, and anthocyanidins, as well as stroke and mortality.
“We found 88 publications, among them 3 prospective studies, and another retrospective study providing some information on the effect of chocolate consumption on the incident risk of stroke,” Dr. Saposnik said. “Two of these studies show a reduction in the incident risk of stroke, and the other 2 didn’t show any substantial difference.”
For example, of the 3 prospective studies, 1 found no association between flavonoid intake and the risk for stroke or death when 3% of catechin intake came from chocolate. However, a second study found a reduction in incident stroke for chocolate consumption once per week vs no consumption.
The third study looked at the association between flavonoid intake and stroke mortality and found a suggestion of protection against stroke mortality from 50 g of chocolate.
The authors conclude that further prospective studies are needed “to assess whether the benefit of chocolate-based flavonoid consumption truly lowers stroke risk, or whether the apparent benefit is biased by a healthy user effect.”
Still, there are varying types of chocolate, and the amounts that are required to affect stroke risk may bring a load of sugar and fats that may work counter to the beneficial effects. “50g of chocolate per day is a significant amount,” Dr. Saposnik notes.
Finally, large longitudinal studies are also expensive, and funding for them is scarce, which may explain why much of the evidence is coming from epidemiologic studies, he added. One alternative may be to conduct smaller studies, looking at the effects of consuming controlled amounts of chocolate on some intermediate biomarker of stroke risk.
American Academy of Neurology 62nd Annual Meeting. April 10-17, 2010. Published online February 11, 2009.