Chocolate, a Healthy Treat
By Roberta Lee, MD . Dr. Lee is the Medical Director at Continuum Center for Health and Healing, Beth Israel Medical Center, in New York, NY; she reports no consultant, stockholder, speaker's bureau, research, or other financial relationships with companies having ties to this field of study.
Of all the confections that have universal appeal, it's chocolate that usually tops the list. Americans consume more than 3.1 billion pounds of chocolate each year or roughly 11.7 pounds per person per year.1 Surprising as it may seem, Americans are not the highest consumers of chocolatethat distinction is credited to Switzerland, where each person on average consumes 22.3 pounds a year.2
In the past, chocolate was thought to worsen acne, increase dental decay, and worsen migraine headaches. While some of these things may still be true, new reports evaluating chocolate's effect on blood pressure and cardiovascular health are quite promising. This article will discuss recent studies showing the beneficial effects of chocolate.
Chocolate, produced from the seeds of Theobroma cacao, comes from a tropical tree whose name translates from Latin to "Food of the Gods." The name given to this tree by Linneaus signifies its importance to the Mesoamerican cultures who first used cacao. At one point, Theobroma cacao was so important in Mayan and Aztec cultures that it was used as a form of currency.
Theobroma cacao is divided into three major types: criollo, forestero, and trinitario. The trinitario group is derived from a mix of the criollo and forestero groups. Theobroma cacao grows within a tropical band that extends 20° north or south of the equator. The trees require partial shade and thrive in a hot and humid climate. The plants are pollinated by small midges, but 60% of the flowers fail to be pollinated.3 Usually trees do not produce fruit until they reach 5 years of age. Dispersion of the seed is facilitated by the sweet pulp surrounding the seeds, which attracts many animals that gnaw open the pods. To increase land production, cacao has been intercropped with other trees of economic value such as bananas, rubber, oil palm, or coconut.4
The seeds (also referred to as beans) are harvested initially from yellow or red pods growing directly on the stems and branches of the tree. Each pod bears 30-40 seeds each, depending on the variety. Once harvested, each pod is hulled to free up the seeds that are embedded in a white pulp. Over a 3-7 day period the seeds are "fermented," a process that reflects decay of the pulp as it separates from the seed. The final part of this process requires drying, usually in the sun, and during this time the seeds change from purple to brown. It takes 400 seeds or 40 pods to produce a pound of chocolate!5
Pharmacological Effects
The secret of chocolate's great appeal may be the result of a number of psychoactive compounds found in this beloved confection: the biogenic amines, methyl-xanthines, and cannabinoid-like fatty acids.
Biogenic Amines. Two biogenic amines are found in chocolate: tyramine and phenylethylamine (PEA). These are known to have sympathomimetic effects similar to nicotine. Both nicotine and the biogenic amines stimulate dopamine release in the brain. PEA is "heterogeneously distributed within the central nervous system" and acts as a neuromodulator of brain synapses.6 Several studies have suggested that it is an important modulator of mood. PEA and L-phenylalanine, the amino acid precursor to PEA, have been shown to improve certain types of depression.7 Some have suggested that the cravings for chocolate may be partially due to the biogenic amines found in chocolate (0.4-6.6 µg/g). Consequently, individuals consuming chocolate may be attempting to "self medicate" for these deficiencies.8 Opponents to this theory of amine-deficient chocolate cravings argue that PEA is too rapidly metabolized in the body to make this plausible. Within 5-10 minutes, PEA is metabolized by monoamine oxidase-β and aldehyde dehydrogenase to phenylacetic acid.8 Furthermore, PEA and tyramine are also found in other foods, such as cheeses and sausages, with similar or higher concentrations, yet they do not produce cravings in as large a number of people. In addition, many experts suggest that the consumption of PEA or tyramine does not ensure systemic circulation.9
Many substances with psychoactive properties share a similar chemical structure to phenylethylamine. An example of this is 3,4 methylenedioxymethamphetamine (MDMA), otherwise known as "ecstasy." Both are amphetamine analogs and act as stimulants facilitating increased catecholamine/serotonin levels. A case series of seven individualsheavy users of MDMA who took from 200 doses to as much as 2,000 dosesshowed a correlation between intense chocolate cravings and chocolate binges during associated depression following MDMA use.10 It is interesting that MDMA has been associated with low serotonin levels (5-HT) and 5-HT2 receptor degeneration. The investigators suggested that the specific preference for chocolate in these heavy MDMA users was due to the high PEA and tyramine content in the chocolate and "although not conclusive the association deserves further study."10
Methylxanthines. Methylxanthines, another group of stimulating compounds found in chocolate, are competitive inhibitors of adenosine. Adenosine is released after prolonged wakefulness and facilitates sleepiness.11 Thus, consumption of chocolate much like consumption of coffee, can stave off sleepiness. Of the three kinds of methylxanthines contained in chocolate (theobromine, caffeine, and theophylline), theobromine is predominant. One ounce of bittersweet chocolate contains 5-10 mg caffeine compared to an 8 ounce cup of coffee containing approximately 150 mg of caffeine. Further strengthening the stimulant effect, caffeine enhances catecholamine release, which intensifies wakefulness of theobromine.12 All three compounds are absorbed readily in the gastrointestinal tract. In addition, the methyl-xanthines are lipid-soluble and easily cross the placenta in pregnancy and the blood-brain barrier.13
Cannabinoid-Like Fatty Acids. The brain makes several substances called endocannabinoids. These are neurotransmitter-like substances that create euphoria, disinhibition, relaxation, and increased appetite.11 The endocannabinoids (arachidonoylethanolamide, otherwise known as anandamide and 2-arachidonoylglycerol [2-AG]) bind to cannabinoid receptors such as the CB 1 receptors in the brain. Tetrahydrocannabinol or THC, the active ingredient of marijuana (Cannabis sativa), likewise engages this same receptor. Release of the endocannabinoids also activates the mesolimbic dopamine system, catalyzing dopamine release in the nucleus accumbens.14 This activation is thought to influence cannabinoid tolerance and reward (the reward system is part of the brain that is activated by both natural and artificial chemicals, like addictive drugs).11,15 N-acylethanolamine, an anandamide-like compound found in chocolate,16 either acts directly at the cannabinoid sites or potentiates anandamide by preventing its breakdown. Those challenging the hypothesis of increased CNS cannabinoid receptor stimulation when chocolate is eaten feel that there is insufficient systemic absorption and activity within the CNS.
Chocolate and Behavior
Beyond the psychoactive components, are there other factors that contribute to the satisfaction one has when savoring a bite of chocolate? To address this question of which constituents of chocolate satisfy chocolate cravings, Michner and Rozin observed individuals who were known to have longstanding chocolate cravings.17 Once a week they were given one of six treatments: a chocolate bar, capsules containing the same amount of chocolate contained in the chocolate bar, placebo containing flour with the same amount of calories as the cocoa bar, a bar of white chocolate, white chocolate plus capsules containing the cocoa powder, or nothing. (For those unfamiliar with white chocolate, it is cocoa butter and flavorings without cocoa mass and contains no flavonoids.) When the subjects experienced the cravings they would open the box and consume what was offered and rate the amount of satisfaction noted from that particular choice. The results showed that the chocolate bar had the highest ability to satisfy the cravings. To a much lesser extent the white chocolate showed some ability to satisfy the craving, but the pills had a similar effect to taking nothing. The investigators concluded that it was the sensory experience rather than the pharmacologic factors driving the cravings.
Hormonal influences in chocolate cravings have also been evaluated. Some studies have suggested that there is a link between chocolate and the menstrual cycle. A questionnaire was distributed to 1,000 male and female college undergraduates evaluating choice of foods in cravings. Ninety-seven percent of the women and 68% of the men reported cravings. Thirty-two percent of the women linked their cravings to their menstrual cycle.18 However, another study looking at cravings of sweets or chocolate in subjects given progesterone, alprazolam, or placebo from the third week of the menstrual cycle until the second day of the actual onset of menses, showed that neither the progesterone or alprazolam reduced either craving.19 Participants were women in the Premenstrual Syndrome Program at the University of Pennsylvania between the ages of 18-45. It is interesting to note that the role of progesterone and its influence on mood has been evaluated with conflicting results. Some studies have indicated that it has a mildly sedating effect20 while others have suggested that progesterone may actually cause a negative mood.21
Antioxidants and Nutrients
Chocolate is rich in a variety of micronutrients including potassium, iron, magnesium, zinc, and copper (see Table). According to the U.K. Ministry of Agriculture, Fisheries, and Food (MAFF), chocolate has more iron than most vegetables (10.5 mg/100 g).13 It was shown in a three-day dietary record study that chocolate is a major source of dietary copper in the North American diet.22 Similarly, in Australia, sources of dietary copper among younger women were derived primarily from refined grains, beef, dairy, and chocolate. In addition, in a recent study of patients receiving long-term enteral nutrition with a documented copper deficiency, 30-45 g of Hershey's pure cocoa (with copper content 3.8 mg/100 g cocoa) was given for 40 days with a successful increase in copper levels.23
Antioxidants
The physical health benefits associated with chocolate ingestion are primarily derived from the antioxidants contained therein. Antioxidants keep cells from being damaged during oxidation, a normal process that occurs in all living beings but is toxic to living tissue. Oxidation is tightly regulated by the body, with antioxidants acting as buffering agents that neutralize the oxidative process. Antioxidants come in a wide variety of classifications; those found in chocolate are phenolics and flavonoids. The flavonoids in chocolate are mostly composed of the catechins, epicatechins, and to a lesser extent the anthocyanins.13 These are the same flavonoids found in red wine and tea (Camellia sinensis). Chocolate actually contains more catechins than tea.24 Dark chocolate contains 53.5 mg/100 g, whereas milk chocolate contains 15.9 mg/100 g and black tea 13.9 mg/100 g.25 However, unlike green tea, chocolate does not contain (-)epigallocatechin gallate (EGCG), which has been found to have the most beneficial effects of all the catechins, particularly in regard to anticarcinogenic activity.26
Antioxidant activity can be measured in specific units called oxygen radical absorbance capacity (ORAC) units per 100 g. Dark chocolate contains an order of magnitude more antioxidants when compared with other healthy foods such as blueberries, kale, and broccoli.27 Different types of chocolate contain different amounts of flavonoids. The flavonoid content is therefore directly dependent on the amount of cocoa mass present. Dark chocolate with 30-90% cocoa mass has more flavonoids than milk chocolate, which has 7-35% cocoa content. White chocolate with no cocoa mass, only cocoa butter, lacks any beneficial antioxidant effect. One study done at the University of Scranton found that 40 g of milk chocolate contained 300 mg of polyphenols,28 equivalent to five servings of fruits and vegetables or a glass of red wine.29
Cardiovascular Health Benefits
Chocolate has several reported cardiovascular health benefits. It has been found to lower "bad" cholesterol, or LDL, while leaving unchanged the "good" cholesterol, or HDL.30 The explanation for this reduction in LDL is linked to the high flavonoid content of chocolate. Arterial damage by LDL is mediated through an increase in oxidation and inflammation by the LDL particle as it becomes embedded in the inner lining of the artery (known as the endothelium). Over time this chemical reaction produces cholesterol plaque. In effect, the flavonoids serve as a source of further suppression of both inflammation and oxidation. In addition, platelet inhibition by chocolate was observed in a small study of 16 individuals given either 81 mg of aspirin, or cocoa, or aspirin plus cocoa.31 A significant reduction of blood pressure was also reported in several studies with chocolate use.32,33 The mechanism for reduction in blood pressure is attributed to the enhancement of nitric oxide-dependent relaxation of the endothelial lining of the arteries. Some have concern that the fat content found in the cocoa butter can have negative cardiovascular effects because of the predominance of stearic and oleic acids. However, recent findings suggest that stearic acid, which comprises one-third of the lipid content in chocolate, is cholesterol neutral.34
Conclusion
Chocolate has some promising data for health benefits and it may be effective in lowering cholesterol, reducing blood pressure, and adding valuable antioxidants in our diets. However, large trials are lacking and chocolate will need to be investigated further. Although chocolate can not be a substitute for fruits and vegetables, it seems reasonable to look upon this confection as a healthier treat. Based on the present evidence, one ounce of dark chocolate (65% cocoa or higher) would be a "therapeutic dose." However, chocolate enthusiasts should be aware that white chocolate, mostly comprised of cocoa butter without cocoa mass, has none of the health benefits discussed above as the cocoa mass contains all the antioxidants. Furthermore, those wishing to maximize health benefits should look for dark chocolate bars that do not contain partially hydrogenated oils as these oils have negative health benefits.
Recommendation
If there is any challenge to the enjoyment of this confection and its health benefits it would be chocolate's calorie density, which comes from its high fat content. Intake of cocoa in the form of a cocoa drink rather than as a chocolate bar will reduce both the calories and the fat content. A cocoa beverage using cocoa powder and made with skim milk has approximately 150 calories per cup. In contrast, a chocolate bar (50 g) has approximately 250 calories.35 Thus, enjoy that one ounce or 1/3 of a dark chocolate bar a day as a treatnot a meal!
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Lee R. Chocolate, a healthy treat. Altern Med Alert 2005;8(12):138-142.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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