DOES A CHOCOLATE A DAY KEEP THE DOCTOR AWAY?
Ryan Bradley, ND, MPH May, 2007
With rare exception, we love chocolate. For those that don’t love chocolate, this is usually due to lack of practice than true distaste. Recent studies have suggested chocolate may actually have health benefits, which is difficult to believe for some of us and certainly convenient for others who just need the slightest excuse. However, what is “chocolate” and what are the health properties attributed to it? Why is chocolate so appealing? Why do I crave it? And is there a balance between the reported health benefits and the health risks it may cause in some populations such as people with diabetes who carefully watch their sugar and fat intake? I hope this article helps to illuminate some of what we know about chocolate, its health benefits and gives some special recommendations for those with diabetes.
What is Chocolate?
Chocolate is derived from the fermented and cooked beans of the cacao tree (Theobroma cacao) and was originally produced in Central America and Mexico. In the United States, chocolate varieties include dark, milk, and white chocolate. All varieties contain cacao butter, the fat derived from the cacao bean, then added sugar, and often vanilla. Milk chocolate contains dairy and often pure milk fat plus cacao solids or liquor. Dark chocolate contains less or no dairy and a higher cacao concentration. White chocolate contains no cacao solids or liquor and only cacao butter.
The description above is really only the beginning of the complex and majestic food we call chocolate! The main ingredients of chocolate tell us very little about the reactions - and health benefits - stored inside this mysterious and treasured food. Inside the cacao solids are the following complex molecules that are highly active in our bodies:
Several major bioactive amines, including the now well-known neurotransmitter serotonin, but also dopamine, phenylethylamine, tyramine, and histamine.
Serotonin and dopamine are potent antidepressant compounds and are also involved with reward pathways in the brain. Chocolate appears to be a stimulant of reward pathways similar to cigarettes or other drugs, leading to our cravings.
Phenyethylamine (PEA) is also involved in pleasure pathways in the brain and creates a sense of bliss and may reduce pain. PEA is released when two people fall in love, thus reinforcing the appropriateness of chocolate on Valentine’s Day!
Tyramine and histamine are two amino acids that act on blood vessels and the heart. Histamine causes dilation, or opening, of vessels, while . Many people are very responsive to these compounds leading to headaches and allergy symptoms.
Compounds in a class called methylxanthines, including caffeine and theobromine[1, 2] which are both stimulants. Caffeine is well known, but theobromine is an interesting compound because it stimulates airway opening and also stimulates the heart.
Interestingly chocolate also contains fatty compounds similar to THC, the potent, intoxicating ingredient in the herb marijuana (chocolate does not contain THC, but may make the receptors in our brains more responsive to the THC-like compounds we produce on our own!)[1].
Last, but not least, chocolate contains potent antioxidant compounds called polyphenols, a class of compounds also found in other protective foods like red wine and green tea. It appears that the polyphenols are responsible for many of the cardiovascular and metabolic health benefits of chocolate. You have heard great things reported about other foods rich in polyphenols - namely red wine, dark colored berries, cinnamon and green tea - and chocolate (or technically cacao) is no exception.
Chocolate Research
Several studies now suggest cacao-derived polyphenols reduce blood pressure, improve insulin sensitivity, increase total antioxidant capacity, protect LDL cholesterol (“bad” cholesterol) from oxidation and raise HDL cholesterol.
Among the earliest published clinical studies of chocolate was a brief report by Taubert et al. in the Journal of the American Medical Association in 2003[3]. Taubert and colleagues gave 100g dark chocolate or 90g white chocolate to 13 elderly volunteers with isolated hypertension for 14 days. Significant results included reductions in both systolic (the top number) and diastolic (the bottom number) blood pressures by 5.1 and 1.8 points respectively. The study by Taubert et al. did not observe changes to LDL or HDL cholesterol.
Further studies in high blood pressure were conducted by Grassi et al. who administered 100g dark chocolate (containing 88mg polyphenols) or 90 g of white chocolate to 20 people with essential hypertension[4]. After 15 days he observed an 8.5 point reduction in systolic blood pressure (the top number) and an improvement in insulin sensitivity. Interestingly, only dark chocolate produced these effects suggesting the polyphenols were responsible.
In a second study performed in healthy humans in 2005, Grassi et al. found a similar improvement in insulin sensitivity, and also found an increase in total antioxidant capacity, a reduction in LDL cholesterol oxidation and a minor increase in HDL cholesterol[5].
Results suggesting chocolate increases HDL cholesterol are further corroborated by the findings of Murso et al. in 2004 where they administered 75g of dark chocolate, polyphenol-enriched dark chocolate or white chocolate to 45 healthy volunteers for 3 weeks. Positive findings include an increase in HDL cholesterol and a reduction in a marker of LDL oxidation[6].
Earlier studies also support the notion that chocolate reduces LDL oxidation. Wang et al. administered increasing doses (27, 53, and 80 g) of chocolate to humans and observed dose-dependent reductions in lipid oxidation markers and dose-dependent increases in antioxidant polyphenols[7]. Similarly, in 2001, when the research team of Wan et al. added 22g cacao powder plus 16g dark chocolate to the average American diet, they found reductions in LDL oxidation and increases in total antioxidant capacity measured by ORAC[8].
Milk Chocolate vs. Dark Chocolate
So far, all of the studies described have investigated dark chocolate and compared it to white chocolate, so what about milk chocolate? Well, so far most signs suggest milk chocolate just does not have all the same benefits. For example, Serafini et al. administered 100g dark chocolate, 100g dark chocolate with added milk, or 100g of milk chocolate to 12 healthy adults [9]. Milk added to the dark chocolate and the milk chocolate produced significantly lower absorption of the polyphenols and therefore did not increase total antioxidant capacity in the blood to the same degree as the dark chocolate alone.
Additional Benefits
An additional cardiometabolic health benefit of dark chocolate appears to be a reduction platelet aggregation, or clotting tendency, of the blood. When blood clots, or thrombi, form prematurely they can become dislodged causing a stroke or heart attack. Typically aspirin or other anticoagulant medications, like warfarin, are taken to “thin the blood” or reduce this stickiness.
However, according to the results of a randomized trial by Innes et al. in 2003, dark chocolate polyphenols may also reduce platelet aggregation[10]. The beneficial effects of dark chocolate were not seen with milk or white chocolate, once again suggesting the dark polyphenols are critically important to this action. The anticoagulant effects of chocolate received additional support by the findings of the GeneSTAR trial[11]. GeneSTAR is intended to study genetic differences in the cardioprotective effects of aspirin, however the study also stumbled onto a protective effect of chocolate. About 140 people refused to eliminate chocolate from their diets while participating in the study and so the investigators followed this group separately. They discovered chocolate eaters had slowed blood clotting compared to others. Although the protective effect of chocolate was approximately 1/10th of aspirin, the main action appears to be the same.
Not all studies of chocolate have shown positive changes in markers of cardiovascular or metabolic health. Farouque et al. administered a chocolate polyphenol-rich beverage or placebo to 40 people with known heart disease in a randomized fashion for six weeks[12]. No changes in vascular function were observed, nor were any differences in cellular adhesion molecules (a strong marker of atherosclerosis).
Reported cardiometabolic benefits of dark chocolate:
Improves blood pressure
Improves insulin sensitivity
Increases HDL (“good”) cholesterol
Reduces oxidation of LDL (“bad”) cholesterol
Increases total antioxidant capacity
Reduces coagulation of the blood
Chocolate as Treatment?
Although dark chocolate appears to have consistent benefits for cardiometabolic risk factors it is premature to consider it a “treatment” but rather as a part of a heart healthy diet rich in vegetables, whole foods and other polyphenol-rich ingredients. That said, it appears that even small quantities of dark chocolate have health benefits and should be consumed without guilt. There are a few important caveats to consider:
Only eat dark chocolate. So far, the vast majority of the health effects of chocolate are only found in dark chocolate. Milk and white chocolates retain all the sugar and fat, but without the healthful polyphenols.
Be careful with high doses of chocolate if you take anticoagulant medications like warfarin, Plavix, or high-dose aspirin (especially if you bruise easily on aspirin). Although poorly studied, there is evidence of a possible interaction between dark chocolate and these medications and laboratory monitoring should occur if you start eating dark chocolate or cacao regularly.
If you have diabetes, the sugar in chocolate still counts towards your total carbohydrate intake. However, very low sugar chocolates are available, and although bitter at first it is an acquired taste.
Few studies have been performed on people with diabetes, and therefore little is known about health benefits of chocolate in this population. In fact, insulin sensitivity has only been studied in people without diabetes.
Hopefully in the future, larger studies will test whether chocolate really is beneficial to long-term cardiovascular health. As if we needed more reasons to enjoy dark chocolate…
REFERENCES
1. Bruinsma, K. and D.L. Taren, Chocolate: food or drug? J Am Diet Assoc, 1999. 99(10): p. 1249-56.
2. Pastore, P., et al., Determination of biogenic amines in chocolate by ion chromatographic separation and pulsed integrated amperometric detection with implemented wave-form at Au disposable electrode. J Chromatogr A, 2005. 1098(1-2): p. 111-5.
3. Taubert, D., et al., Chocolate and blood pressure in elderly individuals with isolated systolic hypertension. Jama, 2003. 290(8): p. 1029-30.
4. Grassi, D., et al., Cocoa reduces blood pressure and insulin resistance and improves endothelium-dependent vasodilation in hypertensives. Hypertension, 2005. 46(2): p. 398-405.
5. Grassi, D., et al., Short-term administration of dark chocolate is followed by a significant increase in insulin sensitivity and a decrease in blood pressure in healthy persons. Am J Clin Nutr, 2005. 81(3): p. 611-4.
6. Mursu, J., et al., Dark chocolate consumption increases HDL cholesterol concentration and chocolate fatty acids may inhibit lipid peroxidation in healthy humans. Free Radic Biol Med, 2004. 37(9): p. 1351-9.
7. Wang, J.F., et al., A dose-response effect from chocolate consumption on plasma epicatechin and oxidative damage. J Nutr, 2000. 130(8S Suppl): p. 2115S-9S.
8. Wan, Y., et al., Effects of cocoa powder and dark chocolate on LDL oxidative susceptibility and prostaglandin concentrations in humans. Am J Clin Nutr, 2001. 74(5): p. 596-602.
9. Serafini, M., et al., Plasma antioxidants from chocolate. Nature, 2003. 424(6952): p. 1013.
10. Innes, A.J., et al., Dark chocolate inhibits platelet aggregation in healthy volunteers. Platelets, 2003. 14(5): p. 325-7.
11. Unknown. Abstract 4101. American Heart Association Scientific Sessions. 2006.
12. Farouque, H.M., et al., Acute and chronic effects of flavanol-rich cocoa on vascular function in subjects with coronary artery disease: a randomized double-blind placebo-controlled study. Clin Sci (Lond), 2006. 111(1): p. 71-80.