|
A few years ago, who would have thought that the food pyramid recommended by many agencies would be shaken? Now, many health care professionals have stopped suggesting that people base their diets on carbohydrates and have lifted the taboo on several fatty foods. Chocolate, one of the world's most widespread passions, has traditionally occupied the top of the pyramid, meaning that it is the least recommended food type.1 Research data published recently, however, may force us to reconsider this negative view about chocolate, especially dark chocolate. Before recommending dark chocolate to their patients, pharmacists should look at both the benefits and health hazards resulting from chocolate consumption.
If people were to consume pure cocoa, it would be easier to assess the positive and negative effects of ingredients found in cocoa beans. However, most people consume processed chocolate, with less desirable ingredients such as added sugar, corn syrup, milk fats, and hydrogenated oils.
Chemical Constituents
Hundreds of chemicals in cocoa beans have been identified, including polyphenols, pyrazines, quinoxalines, oxazolines, pyrroles (tannins), pyridines, flavonol proanthocyanidins, and phenylethylamine. The methylxanthines, which make up roughly 3% of the cocoa bean and consist of two thirds theobromine and one third caffeine, give cocoa its bitter taste and stimulative effect.2 Because of their theobromine content, methylxanthines act as myocardial stimulants, diuretics, coronary dilators, and smooth muscle relaxants.
The origin of the cocoa bean and treatments such as fermenting and roasting can also affect its chemical composition. The characteristic components of chocolate liquor, which is formed by grinding cocoa beans, are polyphenols such as gallic acid and catechin and their derivatives: theogallin, gallocatechin, epiatechin, and epigallocatechin.3 Separated cocoa butter, extracted from chocolate liquor, is mainly a mixture of triglycerides.
Cocoa beans are also composed of polar lipids (making up 1% to 2% of the cocoa bean), containing two thirds glycolipids and one third phospholipids, and phytosterols, which are found in concentrations of 1.8 to 2 mg/g and are composed of sitosterol (50% to 70%), stigmasterol (20% to 30%), and camposterol (5% to 9%). Cocoa butter contains mainly beta- and gamma-tocopherols in the range of 150 to 250 mg/g. The fatty acid composition of triglycerides is characteristically high in saturated and monounsaturated fatty acid (20% to 30% palmitic acid, 16:0 [16 refers to carbon chain length, 0 refers to zero bound]; 30% to 35% stearic acid, 18:0; and 30% to 35% oleic acid, 18:1; as a minor component 2% to 4% linoleic acid, 18:2; and < 0.3% linolenic acid, 18:3).4
Physiological Activity and Therapeutic Use
Cocoa and chocolate products have been delicacies for the wealthy for centuries and are today for all classes. Chemical evidence proves that the Mayans consumed a cacao beverage as early as 600 bc.5 When the Aztecs took over Central America, the cocoa bean was used not only for drinks but also as currency. Spaniard Hernando Cortez brought the first cocoa to Europe, sparking chocolate's reputation as an exquisite food for the well-to-do everywhere. Recently, health food stores have been stocking specialty chocolate products, some with high fiber and cocoa content and others that are low in sugar and milk fat. In pharmacy, chocolate flavoring may be used to mask the bitter taste of certain drugs.
Current knowledge of the pharmacology of pure cocoa includes its positive effects on lipid metabolism, which include a general lipoxygenase-inhibition of flavonols and procyanidins, as well as an inhibitory effect on nicotinamide adeninine dinucleotide phosphatedependent lipid peroxidation. In vitro studies further pinpointed the differential inhibitory effect of epicatechin and its low-molecular procyanidins on human 5-lipoxygenase, which may contribute to a putative anti-inflammatory effect of cocoa products.6
Animal and human studies have shown that orally administered cacao liquor polyphenols increase the resistance of low-density lipoproteins (LDL) to oxidation.7,8 The comparison of antioxidant activity of commonly consumed polyphenolic beverages (coffee, cocoa, and tea) indicates that cocoa powder infusion in a concentration range of 1.5% to 3.3% inhibits LDL oxidation as effectively as or better than green tea.9 Epidemiological studies have suggested that regular consumption of tea, especially green tea, would reduce LDL oxidation in vivo in humans, resulting in an inverse association of the tea consumption with cardiovascular disease. The list of other protective mechanisms of green tea may include an anti-inflammatory effect, antiplatelet activity, promotion of normal endothelial function, and blocking expression of cellular adhesion molecules. It is likely that eating dark chocolate would afford the same protection against cardiovascular diseases as green tea.
Since cocoa and chocolate are high in flavonoids, they were an obvious choice for acute feeding studies, which have demonstrated increased plasma antioxidant capacity, and reduced platelet reactivity.10 Dutch scientists carried out a clinical trial in which 70 subjects with primary hypercholesterolemia ate three servings of phytosterol-enriched chocolate (1.8 g phytosterols) per day for four weeks. Plasma totals and LDL cholesterol levels were significantly reduced by 6.4% and 10.3%, respectively. However, triglyceride and high-density lipoprotein levels were not affected. While intestinal cholesterol absorption decreased, researchers observed an elevated level of lathosterol concentration, indicating increased endogenous cholesterol synthesis in response to decreased absorption.11 These findings indicate that dietary chocolate enriched with phytosterols can be used as a functional food to help reduce coronary heart disease risk for people with mild hypercholesterolemia.
Anticarcinogenic Properties: It is generally accepted that flavonols and procyanidins may have anticarcinogenic activities. The anticarcinogenic effects of polyphenols have been extensively examined, and researchers have found that the polyphenol components of green tea, grapes, and berries may possess chemopreventive properties. The mechanisms of antimutagenesis and anticarcinogenesis by which tea polyphenols act include modulation of extracellular and intracellular metabolic and proliferative processes.12,13 However, much less is known regarding whether cocoa powder polyphenols have similar activities. Recent studies using cocoa powder and extracts with differing amounts of flavonols and related procyanidin oligomers showed growth inhibition on human colonic adenocarcinoma in vitro.14
Antioxidant Properties: Oxygen free radicals have been implicated as a major cause of DNA damage. There is evidence that cocoa liquor polyphenols are effective in preventing the damaging chemical reaction by scavenging active oxygen radicals.15,16 In vitro biological activity of polyphenols has been proven, but the in vivo activity depends on the amount of polyphenols reaching the target cells or the amount of biochemical compounds in the active chemical form surviving the digestion process. Cocoa procyanidins appear to be remarkably stable; most ingested procyanidins are absorbed in active form and available for metabolism.17 Clinical studies have shown that both the oligomeric and monomeric units of procyanidins favorably affect cardiovascular health and that they can reach their targets as early as 30 minutes after the consumption of flavonol-rich cocoa beverages.18
Chocolate Cravings
Dietetic professionals are aware of the reality of chocolate cravings. Chocolate contains many biologically active constituents that potentially influence different sections of the brain that control behavioral and psychological actions.19,20
Regional cerebral flow was studied in subjects who ate chocolate beyond satiety. The scientists observed modulation in cortical chemosensory areas, indicating that taste and smell are important for processing the internal and motivational state. The results supported the hypothesis that there are two separate motivational systems: a coordinating approach and an avoidance behavior.20
Chocolate cravings have been associated with certain drug-induced neuroses, which indicate the presence of a pharmacologically active substance in chocolate. Scientists have targeted primarily the methylxanthines, which act as competitive antagonists on adenosine receptors. They have found an endogenous cannabinoid compound called anandamide, which is present in microsomes found in the brains of rats.21 Anandamide (N-arachidonylethanolamine) is a brain lipid that mimics the effects of plant-derived cannabinoid drugs. It is also released by neurons and is rapidly hydrolyzed by amidohydrolase enzymes.22 Other fatty acid derivatives of ethanolamine, which is found in cocoa beans, do not activate brain cannabinoid receptors but can raise anandamide levels since they inhibit anandamide breakdown.22
Research has demonstrated that women are more susceptible to cravings than men are and that chocolate cravings may be associated with the menstrual cycle. Cravings have been correlated with negative moods, and eating chocolate relieves cravings that are independent from hunger.23 Researchers have found several explanations for the craving phenomenon. It may originate from a need for complex carbohydrate consumption (ie, the sugar content of chocolate), which increases the availability of the amino acid tryptophan, the precursor of serotonin. However, the texture, smell, and taste of chocolate, as well as the pleasure-causing anandamides chocolate contains, also cause chocolate cravings.
Precautions
Moderate consumption of dark chocolate does not pose any hazards. If the product's lipid components originate from cocoa butter and/or lecithin, which is composed of stearic acid, oleic acid, and palmitic acid, it has a fairly neutral effect on the lipid profile.24 Concern about high saturated fat content, especially stearic acid, may be unfounded since stearic triglycerides are not absorbed as well as other fats and are excreted in the feces.25 Milk chocolate, however, contains cholesterol and small amounts of other long-chain saturated fats that may adversely influence the lipid profile.
Chocolate is blamed for causing many adverse effects and for influencing bodily functions. Although chocolate has been blamed for causing acne and premenstrual syndrome, its association with these medical problems is weak or has not been established. However, there are a few conditions that have a real association with chocolate consumption. People with recurrant migraine headaches who are sensitive to cheese and red wine or who are undergoing stress will be affected by chocolate. Pregnant women and women attempting to conceive should restrict their consumption of caffeine-containing products. Those with high blood pressure, insomnia, asthma, heart problems, digestive problems, or elevated lipoprotein (a) levels should consult their physician before regularly including dark chocolate in their diets.3
Dosage
The beneficial effects of dark chocolate are typically seen at dosages normally consumed by humans (30 to 90 g/d). To benefit from chocolate, people who can afford the caloric intake from fat (10 to 35 g) can eat three to four bars (1.5 oz) per week of dark chocolate or have a daily cocoa drink with skim milk and a small amount of sugar. However, overweight or obese people should limit their chocolate intake. Too much chocolate consumption during pregnancy can be dangerous for fetuses since they have not developed the enzymatic setup for demethylation.26 Overdose, which can happen after consumption of more than 300 mg of caffeine and more than 300 mg of theobromine, can have negative effects on the central nervous system and can cause stomach irritation. (In fact, dogs can be lethally poisoned by eating enough chocolate to ingest 100 to 150 mg/kg of theobromine. Thus, chocolate should not be left within a dog's reach.)
Conclusion
There are many questions surrounding the benefits and risks of chocolate, which is a favorite food of people worldwide and a part of the regular diet in the United States. How frequently, in what quantity, and in what form can we enjoy cocoa products? Should the high saturated fat and caloric content associated with chocolate concern us? Can everyone eat chocolate and cocoa products without penalty?
Detailed multidisciplinary research on the effects of cocoa and chocolate has led scientists to several conclusions. Chocolate may lower the risk of LDL oxidation, and its high stearate levels are innocuous in terms of atherogenic potential. Additionally, cocoa or chocolate consumption may have a beneficial effect on eicosanoid synthesis and may shift prostacyclin levels, which reduces the risk of platelet aggregation, thrombosis, and vasoconstriction. Because dark chocolate is high in fiber and procyanidins, it may have a preventive effect on certain cancer development. However, more research needs to be done on the antiproliferative effects of cocoa polyphenols because their benefits have not been established in vivo. Dark chocolate and cocoa powder contain low amounts of anandamide and other N-acetylethanoamine derivatives (brain lipids that bind to cannabinoid receptors), which may be responsible for the feeling of pleasure people describe when they consume chocolate. These compounds may also be responsible for intensifying the sensory properties of chocolate that are essential to craving. Finally, because of its theobromine content, chocolate acts as a myocardial stimulant, a diuretic, a coronary dilator, and a smooth muscle relaxant.
The above points are characteristic of chocolate that has a high cocoa content (dark chocolate and pure cocoa powder). Milk chocolate, white chocolate, chocolate syrup, and other chocolate-containing products have few or no benefits, and their high sugar and milk fat content adversely influence their dietary impact.
REFERENCES
1. US Department of Agriculture, Center for Nutrition Policy and Promotion. The Food Guide Pyramid. Home and Garden Bulletin Number 252. Available at: www.usda.gov/cnpp/pyrabklt.pdf.
2. Feldman EB. Death by chocolate: facts and myths. Nutr Today. 1998;May-June. Available at: www.findarticles.com/cf_0/m0841/n3_v33/21181282/print.jhtml.
3. Luna F, Crouzillat D, Cirou L, Bucheli P. Chemical composition and flavor of Ecuadorian cocoa liquor. J Agric Food Chem. 2002;50:3527-3532.
4. Nacional de Chocolates. Industrial products: cocoa butter. Available at: www.chocolates.com.co/ingles/pi_boletin_03.htm.
5. Hurst WJ, Tarka SM Jr, Powis TG, et al. Archaeology: cacao usage by the earliest Maya civilization. Nature. 2002;418:289-290.
6. Schewe T, Kuhn H, Sies H. Flavonoids of cocoa inhibit recombinant human 5-lipoxygenase. J Nutr. 2002;132:1825-1829.
7. Osakabe N, Natsume M, Adachi T, et al. Effects of cacao liquor polyphenols on the susceptibility of low-density lipoprotein to oxidation in hypercholesterolemic rabbits. J Atheroscler Thromb. 2000;7:164-168.
8. Osakabe N, Baba S, Yasuda A, et al. Daily cocoa intake reduces the susceptibility of low-density lipoprotein to oxidation as demonstrated in healthy human volunteers. Free Radic Res. 2001;34:93-99.
9. Richelle M, Tavazzi I, Offord E. Comparison of the antioxidant activity of commonly consumed polyphenolic beverages (coffee, cocoa, and tea) prepared per cup serving. J Agric Food Chem. 2001;49:3438-3442.
10. Kris-Etherton PM, Keen CL. Evidence that the antioxidant flavonoids in tea and cocoa are beneficial for cardiovascular health. Curr Opin Lipidol. 2002;13:41-49.
11. De Graaf J, De Sauvage Nolting PR, Van Dam M, et al. Consumption of tall oil-derived phytosterols in a chocolate matrix significantly decreases plasma total and low-density lipoprotein-cholesterol levels. Br J Nutr. 2002;88:479-488.
12. Katiyar SK, Mukhtar H. Tea antioxidants in cancer chemoprevention. J Cell Biochem Suppl. 1997;27:59-67.
13. The review of natural products: green tea. Facts and Comparisons. 1999;Feb.
14. Carnesecchi S, Schneider Y, Lazarus SA, et al. Flavanols and procyanidins of cocoa and chocolate inhibit growth and polyamine biosynthesis of human colonic cancer cells. Cancer Lett. 2002;175:147-155.
15. Yamagishi M, Osakabe N, Takizawa T, et al. Cacao liquor polyphenols reduce oxidative stress without maintaining alpha-tocopherol levels in rats fed a vitamin Edeficient diet. Lipids. 2001;36:67-71.
16. Yamagishi M, Osakabe N, Natsume M, et al. Anticlastogenic activity of cacao: inhibitory effect of cacao liquor polyphenols against mitomycin Cinduced DNA damage. Food Chem Toxicol. 2001;39:1279-1283.
17. Rios LY, Bennett RN, Lazarus SA, et al. Cocoa procyanidins are stable during gastric transit in humans. Am J Clin Nutr. 2002;76:1106-1110.
18. Holt RR, Lazarus SA, Sullards MC, et al. Procyanidin dimer B2 [epicatechin-(4beta-8)-epicatechin] in human plasma after the consumption of flavanol-rich cocoa. Am J Clin Nutr. 2002;76:798-804.
19. Bruinsma K, Taren DL. Chocolate: food or drug? J Am Diet Assoc. 1999;99:1249-1256.
20. Small DM, Zatorre RJ, Dagher A, et al. Changes in brain activity related to eating chocolate: from pleasure to aversion. Brain. 2001;124(pt 9):1720-1733.
21. di Tomaso E, Beltramo M, Piomelli D. Brain cannabinoids in chocolate. Nature. 1996;382:677-678.
22. Desarnaud F, Cadas H, Piomelli D. Anandamide amidohydrolase activity in rat brain microsomes: identification and partial characterization. J Biol Chem. 1995;270:6030-6035.
23. Macdiarmid JI, Hetherington MM. Mood modulation by food: an exploration of affect and cravings in "chocolate addicts." Br J Clin Psychol. 1995;34:129-138.
24. Acu-Cell Analysis. Chocolate & cocoa: "healthy" benefits of negative health effects? Available at: www.acu-cell.com/choc.html.
25. Weisburger JH. Chemopreventive effects of cocoa polyphenols on chronic diseases. Exp Biol Med (Maywood). 2001;226:891-897.
26. Christian MS, Brent RL. Teratogen update: evaluation of the reproductive and developmental risks of caffeine. Teratology. 2001;64:51-78. |
