Antioxidant flavonoids and other phytonutrients in dark chocolate are thought possibly to improve health, primarily through reduction in cardiovascular diseases such as heart attacks and strokes.
In terms of a medicinal agent, we have not been sure of the therapeutic “dose.” A recent study out of Italy provides a clue.
Researchers at Catholic University, Campobasso, Italy, surveyed residents in southern Italy regarding chocolate intake and measured their C-reactive protein (CRP) levels. CRP is a marker of inflammation and a predictor of coronary artery disease such as heart attacks. Generally, higher levels of CRP are associated with higher risk of heart attacks. If you have a choice, go for lower levels of CRP.
Participants in the study were selected by simple random sampling from city hall registries and were at least 35 years old. Researchers were looking for healthy people, so the following were excluded from the study: those who reported known cardiovascular disease, eating a special diet, or on drug therapy for high blood pressure, diabetes, or adverse blood lipids. Twenty percent of initial recruits refused to participate. Of the 10,994 initial recruits, 4,849 men and women made it into the final study.
Of the 4,849 subjects, two subgroups were identified: 1) a control group of 1,317 (27%) who never ate any type of chocolate, and 2) a test group of 824 (17%) subjects who regularly ate dark chocolate only.
Interviewers administered questionnaires to the subjects to document clinical and personal information such as dietary habits, socioeconomic status, physical activity, medical history, risk factors for cardiovascular disaese and tumors, family history of cardiovascular disease, drug use, etc.
Regarding chocolate consumption, participants were asked about frequency – daily, weekly, or monthly – of a “standard dose” (20 grams) and about type of chocolate: milk, dark, nut chocolate, or any type. Someone eating more than one type of chocolate was classified as “any type.”
Other measurements: blood pressure, weight, height, waist circumference, blood glucose, serum lipids (various cholesterols and triglycerides), and high-sensitivity C-reactive protein.
Age-adjusted CRP levels were lower in dark chocolate users (1.13 mg/L) than in the nonconsumers of chocolate (1.30 mg/L).
Dark chocolate eaters were divided into thirds: the lowest third of average consumption, the middle third, and the highest third. The lowest third ate under 19 grams per week. The middle third ate between 19 and 47 grams per week. The highest third ate over47 grams per week. The chocolate-related reduction in CRP was lost in people who were in the highest third (or tertile), i.e., eating more than 47 grams a week or 20 grams every three days. People in the lowest tertile of dark chocolate consumption had a CRP reduction the same as the middle third.
Systolic blood pressure in dark chocolate consumers was 3 mmHg lower than the pressure in nonconsumers. No difference in diastolic pressures.
The researchers cite two clinical trials that investigated the effect of cocoa on markers of inflammation but did not find any association. They wonder if those studies enrolled too few participants, or whether the relatively high doses of chocolate masked the effect. In the present study, the lowering of CRP was seen in consumption of up to 20 grams every three days, but seemed to disappear at higher doses.
The authors write that:
“. . . regular intake of small amounts of dark chocolate . . . consumption should have no harmful effect on anthropometric variables such as BMI [body mass index] and waist:hip ratio and can be viewed as a promising behavioural approach to lower, in a quite pleaseant way, cardiovascular risk factors at a general popoulation level.” And . . .
“According to data reported in apparently healthy American men and women, ranges of serum CRP measured in our nonchocolate consumer population would belong to a “moderate” risk estimate quintile, whereas the ranges found in dark chocolate consumers would beclassified as a “mild” risk estimate. For the decrease in serum CRP values from moderate to mild quintile, the relative risk of suffering a future cardiovascular event would apparently decrease by 26% in men and 33% in women.”
The authors are careful to point out that this study does not prove that low-dose dark chocolate lowers CRP levels. It’s an association. “Additional studies are necessary to explain the mechanisms linking dark chocolate consumption and regulation of serum CRP concentrations.”
The healthy dose of dark chocolate may be quite small: no more than 20 grams every three days, and perhaps quite a bit less. This is not much by U.S. standards. The serving size listed on many bars in the U.S. is 40 grams. Forty grams has about 100 calories. Twenty grams twice a week translates to 6 calories a day.
The authors of this study don’t address whether 40 grams a week would be just as healthy as 80 grams every two weeks.
Eating more, on average, than 20 grams every three days may entirely wipe out the healthy effects. This effect is like wine’s: a little is probably good for you, too much is either neutral or harmful.
I’m sorry to be so wishy-washy on this issue, but that’s the state of the science today. The study at hand may help us optimize dark chocolate’s effect on C-reactive protein. But dark chocolate’s other healthy effects may require other doses, higher or lower.
The next step is to take 20,000 middle-aged people, give half of them various doses of scheduled dark chocolate, give the other half placebos, then record rates of diseases and death over the next 10 years. Who would pay for this multi-million dollar study? Either government or chocolate manufacturers.
-Steve Parker, M.D.
Reference: Di Giuseppe, Romina, et al. Regular Consumption of Dark Chocolate Is Associated with Low Serum Concentrations of C-Reactive Protein in a Healthy Italian Population. Journal of Nutrition, , 138 (2008): 1,939-1,945.