By Michael F. Richman, MD, FACS, FCCP
In the October 18, 2011 issue of the Journal of the American College of Cardiology, Dr. Susanna Larsson of the National Institute of Environmental Medicine in Stockholm, Sweden stated in a news release that women who ate up to two bars of chocolate per week showed a significantly reduced risk of stroke. Those women who ate up to a half of a bar or even smaller amounts also had a reduction in the stroke rate.
The study included 33,372 women who were asked to report how often and how much chocolate and other foods they consumed over the course of a year. Investigators listed the women into categories ranging from those who never ate chocolate to those who indulged three or more times a week and examined the risk of stroke over a mean follow-up of 10 years, adjusting for major risk factors associated with stroke. Women who reported having been diagnosed with hypertension did not show any significant benefit; however, those without hypertension and higher chocolate consumption seemed to show a decrease in strokes. The researchers identified 1549 strokes in their study.
I know this sounds great to chocolate lovers, but there’s a problem with the way the study was conducted. The gold standard of any trial is to have what is called level 1 evidence. This means that the study was randomized, blinded to the researchers, controlled, and resulted in a statistically significant primary endpoint. An example of this would be a study comparing two drugs or a drug versus a placebo in which neither the patient nor the investigator knew what the patients were being given. The study is rigorously controlled and the goal of the study (primary endpoint) is clearly reached with statistical significance. This study did not appear to follow such strict standards.
First, the women were given a food frequency questionnaire and from this these wonderful results were reported. I don’t remember what I ate yesterday let alone keeping track of everything for an entire year. Then, a statistician was brought in to adjust the data and was somehow able to exclude anything else that may impact stroke rates. The result is a study saying that Swedish women who ate a certain amount of chocolate had lower stroke rates than those who did not. The association between chocolate consumption and stroke was stronger the higher the concentration of cocoa in the chocolate.
So, what are the health properties of chocolate? Researchers have long thought that cocoa, the main ingredient in chocolate, may have cardiovascular benefits due to the flavonoids in cocoa and their antioxidant properties. Antioxidants protect the body from damage caused by free radicals and can suppress oxidation of low-density lipoprotein particles, which are the carriers of the bad cholesterol in the blood. Dark chocolate consumption has also been shown to reduce blood pressure, which is a major risk factor for stroke, but the data is limited at best.
Now the question from chocoholics is: how much should one eat? Chocolate, and especially chocolate bars, are high in sugar, fat and calories and should therefore be consumed in moderation if at all. Dark chocolate, with a concentration of greater than 50% cocoa, is usually lower in sugar and has higher flavonoid content. Indulgence in chocolate in moderation remains a reasonable approach to satisfy a craving. Eating a healthy diet, controlling blood pressure and cholesterol levels, and modifying other risk factors for stroke is the best approach for now.