Chocolate/cocoa
Overview
Few natural products have been claimed to successfully treat as many disorders as chocolate. The modern concept of chocolate as food has overshadowed its traditional medicinal use, although recent trials have looked at evidence for some of its traditional uses. Chocolate is processed from the pod of the cacao plant. The earliest evidence for its medical use is in Mayan civilizations, and for most of its approximately 4000-year history, chocolate was consumed as a bitter drink referred to as the “drink of the Gods.” The traditional drink was mixed with water, vanilla, honey, chili peppers, and other spices. Important components in chocolate include flavonoids (antioxidants), cocoa butter, caffeine, theobromine, and phenylethylamine.
Chocolate has stimulating, anti-inflammatory, neuroprotective, and cardioprotective effects, and improves the bioavailability of nitric oxide, which can improve blood pressure and platelet function.50 Epicatechin (an antioxidant) in cocoa is primarily responsible for its favorable impact on vascular endothelium via its effect on both acute and chronic upregulation of nitric oxide production. Other cardiovascular effects are mediated by the anti-inflammatory effects of cocoa polyphenols, and modulated through the activity of NF-kappaB.51
Dark chocolate appears to have the greatest benefit, as milk binds to antioxidants in chocolate, making them unavailable. Therefore, milk chocolate is not a good antioxidant source. There is no specific amount of chocolate that is known to be ideal, but an average of one to 2 ounces per day is often used in studies.
Cardiovascular effects. Chocolate does contain saturated fat, but a comparative, double-blind study found that short-term use of cocoa powder lowered plasma low-density lipoprotein (LDL) cholesterol, oxidized LDL, and apo B concentrations, and the plasma high-density lipoprotein (HDL) cholesterol concentration increased, relative to baseline in the low-, middle-, and high-cocoa groups.52 A small randomized crossover trial without clinical outcomes indicated that chocolate may increase HDL cholesterol without increasing weight.53
A meta-analysis of short-term (2-12 weeks) treatment with dark chocolate/cocoa products showed reductions in LDL and total cholesterol, but no changes in HDL or triglycerides.54 Another meta-analysis of RCTs, however, showed no short-term effect of cocoa/chocolate on lipid concentrations.55 A randomized, placebo-controlled double-blind study of 62 patients with diabetes and hypertension showed that high polyphenol chocolate improved triglyceride levels.56
Multiple studies have shown that chocolate is associated with a reduction in cardiovascular risk.57-59 A best case scenario analysis using a Markov model to predict the long-term effectiveness and cost effectiveness of daily dark chocolate consumption in a population with metabolic syndrome at high risk of cardiovascular disease concluded that daily consumption of dark chocolate can reduce cardiovascular events by 85 per 10,000 population treated over 10 years. The study concluded that $42 could be cost effectively spent per person per year on prevention strategies using dark chocolate.59
In addition, a meta-analysis of 7 observational studies showed that high levels of chocolate consumption (any type) were associated with a 29% reduction in stroke compared with the lowest levels of chocolate intake.57 Results of a similar meta-analysis from Neurology in 2012 also suggested that moderate chocolate consumption (any type) may lower the risk of stroke.60
That said, 2 systematic reviews specifically relating to the risk of coronary heart disease and chocolate intake were inconclusive.61-62
Blood pressure (BP). An RCT published in JAMA indicates that inclusion of small amounts of polyphenol-rich dark chocolate as part of a usual diet efficiently reduced BP and improved the formation of vasodilative nitric oxide.63 A meta-analysis of 10 RCTs also showed mean BP change in the active cocoa treatment arms across all trials was -4.5 mm Hg (95% confidence interval (CI), -5.9 to -3.2; P<.001) for systolic BP and -2.5 mm Hg (95% CI, -3.9 to -1.2; P<.001) for diastolic BP.64
A Cochrane Review meta-analysis of 20 studies revealed a statistically significant BP-reducing effect of flavanol-rich cocoa products compared with control in short-term trials of 2 to 18 weeks' duration.65 Because studies have shown improvement in BP with chocolate intake, investigations into a role of chocolate in the prevention of preeclampsia have been undertaken. In some studies, chocolate intake was associated with reduced odds of preeclampsia and gestational hypertension.66,67
Diabetes. Chocolate may exert significant vascular protection because of its antioxidant properties and possible increase of nitric oxide bioavailability, which can influence glucose uptake. A small trial comparing the effects of either dark or white chocolate bars (which do not contain the polyphenols) showed improved BP and glucose and insulin responses to an oral glucose tolerance test in healthy subjects on dark chocolate, but not white chocolate.68 A comparison of chocolate consumption and risk of diabetes in the Physicians’ Health Study showed an inverse relationship between chocolate intake with incident disease, but this association appeared only to apply in younger and normal-body weight men after controlling for comprehensive lifestyles, including total energy consumption.69
Fatigue. The effect of chocolate on a person’s energy level has been noted for centuries.70 A small randomized trial showed improved energy levels in those treated with higher chocolate intakes. In a double-blind, randomized, clinical pilot crossover study, high cocoa liquor/polyphenol rich chocolate, reduced fatigue in subjects with chronic fatigue syndrome.71
Anxiety. A small randomized trial showed chocolate decreased anxiety in high-anxiety trait subjects and improved the anxiety level and the energy levels of low-anxiety trait participants.72
Eye effects. The literature presents conflicting evidence regarding the effect of flavonoids on patients with glaucoma and ocular hypertension. However, a meta-analysis showed that flavonoids have a promising role in improving visual function in patients with glaucoma and ocular hypertension, and appear to play a part in both improving and slowing the progression of visual field loss.73
Cognitive decline. Chocolate intake (any type) was associated with a lower risk of cognitive decline (RR = 0.59; 95% CI, 0.38-0.92) with the greatest benefit noted in those who averaged more than one chocolate bar or one tablespoon of cocoa powder per week. This protective effect was observed only among subjects with an average daily consumption of caffeine <75 mg (69% of the participants; RR = 0.50; 95% CI, 0.31-0.82).74
The bottom line
Chocolate with high cocoa content (dark chocolate) appears to be safe and beneficial as part of a healthy diet and lifestyle that includes exercise and stress reduction to decrease cardiovascular risk and may improve energy levels.
CORRESPONDENCE
Michael Malone, MD, Family and Community Medicine, Penn State College of Medicine, 500 University Drive, Hershey, PA 17033; malm0001@hotmail.com.