Chocolate--the food of the Gods according to the ancient Mayans--is a mixed bag of good and bad, or ups and downs in terms of health. This article reviews the cultivation and uses of the products of the cacao tree (Theobrorna cacao), the processing and production of chocolate and other cocoa products, and the chemical composition and content of the cocoa bean. Chocolate as a food and confection focuses on nutritional and phytochemical content and unique hedonic qualities. Data are presented concerning consumption, chocolate craving, and the relation of chocolate intake to a variety of diseases affecting various body systems.

THE CACAO TREE (THEOBROMA CACAO)

The cacao tree has been known for 4000 years and cultivated for 1000 years.[1] It is indigenous to tropical Central and South America, originating in tropical rain forests of the Amazon or Orinoco basin in South America and later moving to Mexico and Costa Rica. Cacao now is cultivated in a zone 20 [degrees] north and south of the equator, in the West Indies, Brazil, Venezuela, West Africa (Ghana, the Ivory Coast, and Nigeria), Madagascar, Sri Lanka, the Philippines and Malaysia, and even in the United States (Hawaii, Fig. 1). The Mayans and Aztecs of Mexico believed that the God of Agriculture provided the cacao seed from Paradise.

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The word "chocolate" is derived from the Aztec "xocoatl" meaning bitter drink.[2] Montezuma used the beverage in religion and the beans as currency--100 beans were the value of one slave. The beans were also used in calculations. Cacao as a beverage was brought to Spain when Cortes delivered beans to the Emperor between 1502 and 1528. The Spaniards added sugar and cinnamon and heated the brew to improve the taste of the otherwise bitter Aztec drink and kept the beverage a secret for about a century. Cocoa subsequently was introduced to France, and by 1657, into England and the North American colonies of the Dutch and English. In 1765, Baker founded their chocolate company in Massachusetts.

WHAT IS IN THE COCOA BEAN?

The cacao tree takes 7 years to mature and produces for 20 years. The colorful cocoa pod ripens in about 6 months with a pulp that is sweet and citrus-like (Fig. 2). The seeds (beans) are bitter because of their alkaloid (methylxanthines) content, and fermentation is necessary to acquire the chocolate flavor. The cocoa bean is about 31% fat, 14% carbohydrate and 9% protein, rich in the amino acids tryptophan, phenylatanine, and tyrosine that are norepinephrine and dopamine precursors. The 400 chemicals that have been identified in the cocoa bean include: polyphenols (6%) including pyrazines, quinoxolines, oxazolines, pyrroles (tannins), pyridines, and the fiavonol proanthocyanidin; the amphetamine-like phenylethylamine; the methylxanthines theobromine (2%) and caffeine (1%); and 2% salts and 1% acids. The polyphenols explain why chocolate does not become rancid without refrigeration, despite its high fat content. Similar chemicals are found in red wine, grapes, tea, onions, apples, and citrus fruits; their consumption has been related to decreased risk of cardiovascular disease or cancer.

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MAKING AND EATING CHOCOLATE

Chocolate production is unique. A cacao tree yields 50 to 60 pods. The ripe, melon-like cocoa pods are cut by hand, and the 20 to 40 beans per pod are removed by hand. The beans undergo a two-phase fermentation for 4 to 6 days followed by drying in the sun for 5 to 7 days. The dried beans are usually shipped to foreign cocoa plants where they are roasted for 40 minutes at 100 [degrees] C to 220 [degrees] C to enhance the flavor. The shell is removed to yield the cocoa nib. The nib is milled by a mechanized process that was introduced during the Industrial Revolution. This made chocolate more available to persons other than the aristocrats and nobility. The resultant cocoa mass or chocolate liquor is solid and bitter. A process invented by the Dutch Van Houten in 1828, termed "pressing," separates the 45% cocoa solids or flaky cocoa powder (17% fat, 2.6% theobromine, 0.2% caffeine) from the remaining 55% golden stable cocoa butter. This separation facilitated the creation of "eating chocolate" that added ingredients such as fruits and nuts to the solids. The chocolate bar was invented in the United States in 1831. Hershey started business around 1900. Sugar and dry milk solids were added to the cocoa solids to produce milk chocolate in the Swiss process introduced by Nestle in 1875. Roller refining of chocolate for 72 hours reduces particle size to a premium 10 [micro]m to 12 [micro]m, and tempering controls crystal formation. Extra cocoa butter can be added, and a stirring or conching process, introduced by Lindt, improves smoothness and melting. Alkali is usually added to cocoa to increase solubility and neutralize acids, making the flavor milder.

The types of chocolate in the United States are regulated by the Food and Drug Administration. Types include: bitter, the chocolate liquor to which vanilla may be added; bittersweet, 35% (by weight) chocolate liquor with cocoa butter and sugar added (Fig. 1); and semisweet (chips) also containing 35% chocolate liquor and 27% cocoa butter; sweet chocolate, 15% chocolate liquor; milk chocolate (Swiss) with 10% chocolate liquor, 12% milk solids, condensed or whole milk, and 3% milk fat. White chocolate lacks cocoa powder and its chemicals. The terminology and the use of the word "chocolate" recently has become a source of friction in Europe and the United States in marketing and labeling consumer products with ingredients and percentages. Substitution of other fats for cocoa butter and changing proportions of ingredients have led to arguments among producers and countries that currently are unresolved. Chocolate products must contain materials from the cocoa bean to which sugar and milk can be added. Chocolate must have only cocoa butter (plus a small amount of dairy butter); otherwise terms such as "confectionery coating" are used.

Chocolate as a food is ingested primarily as a cocoa beverage or as chocolate used in a variety of confections and candies, desserts, snacks, and treats, such as chocolate bars, mixed with other candies, coatings for ice cream bars, etc. Chocolate syrup and toppings, mousses and puddings, and baked goods contain chocolate and cocoa butter but also may contain butterfat or other saturated fat (tropical vegetable oils), so it is important to read the labels to ascertain the ingredients.

The United States leads the world in import and production of chocolate candy, with the population consuming, on average, 10 lb of products per person, approximately one-third of which are chocolate. Highest percentage consumption occurs in 16- to 19-year-olds and women between 40 and 49 years. The highest amount in grams per day of chocolate candy is consumed by 12- to 19-year-old males and 30- to 39-year-old women (~3 oz/day). Most of this chocolate is not eaten as solid chocolate but as "panned, enrobed, molded" chocolate, ie, candies and coatings. The Swiss, however, outdo Americans by eating an average of 22 lb of products per year per person--after all, they invented milk chocolate!

CHOCOLATE AS A FAT

Overall, chocolate intake only accounts for about 1% of the total fat intake in the United States according to data from the 1987-1998 National Food Consumption Survey. This should be compared with deriving 30% of dietary fat from meats, 22% from grains (in crackers, cookies, cakes, and pies) and 20% from milk and dairy products. The fat in chocolate, cocoa butter, is high in saturated fat (60%), about half of which is stearic acid.[3] Cocoa butter has more stearate than any other common edible fat or oil (Fig. 3). Cocoa butter is a vegetable fat; therefore, it does not contain cholesterol. Milk chocolate, with added milk fat, is a source of cholesterol. The saturated fat content of common fats and oils (Fig. 3) shows that palm kernel and coconut oils are the highest in saturated fat, with cocoa butter ranked third. If the content of the long chain saturated fatty acids of 12 to 16 carbon chain length are ranked, cocoa butter moves to sixth place, below palm oil, butter oil, and beef tallow and resembles chicken fat. Whatever the fatty acid composition, favorable or not to cardiovascular risk, the calories, 9 kcal/g, are the same for all fats, so chocolate, especially versions highest in fat, is a high-calorie food. For example, a 3-lb box of chocolates yields 6900 kcal.

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EFFECTS ON BLOOD LIPIDS

In contrast to other saturated fats, in controlled feeding trials in humans, cocoa butter results in significantly lower levels of serum total and low-density lipoprotein (LDL) cholesterol compared with butter or beef fat, but it is not as hypolipidemic as olive oil (Fig. 4). Stearic acid has been termed a "neutral" fatty acid in terms of any effects on raising serum cholesterol or LDL cholesterol.[4] This lack of effect may be due, in part, to its poorer digestibility and lesser absorption in comparison to other long chain fatty acids. Stearate may, however, raise the levels of serum triglycerides and decrease levels of high-density lipoprotein (HDL) cholesterol, resulting in no net change in the ratio of LDL:HDL cholesterol. There are data also indicating that stearic acid increases the levels of Lp(a), a highly atherogenic variant of LDL, and increases the levels of fibrinogen, perhaps adversely affecting coagulation. At the present time, it is not clear whether stearic acid is prothrombogenic, in part because data in animal models may not be applicable to humans and no intervention trials have been undertaken.

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Recently, analogous to red wine and other flavonoid-containing foods, cocoa has been shown to have antioxidant properties with regard to LDL, similar to vitamin E.[5,6] A cup of hot chocolate containing two tablespoons of cocoa, and a 1.5-oz piece of milk chocolate (41g) have 146 mg and 105 mg total phenol respectively, compared with 210 mg in 140 ml red wine. The extracted cocoa phenols inhibited LDL oxidation by 75%; the authors concluded that "the pleasant pairing of red wine and dark chocolate could have synergistic advantages beyond their complementary tastes."[5] Before recommending chocolate to heart disease patients, these in vitro effects should be demonstrated in vivo, and heart disease rates should be examined in relation to chocolate/cocoa intake. In a follow-up study, similar to red wine, oxidation of LDL with cocoa prolonged the oxidation lag time of LDL in a concentration-dependent manner.[6] Volunteers then consumed 35 g dilipidated cocoa, and LDL oxidation was measured in blood samples taken before and 2 and 4 hours after consuming the cocoa. LDL oxidation lag time was prolonged significantly (p < 0.005) at 2 hours. These results reinforce the recommendation of allowing moderate chocolate consumption for patients at risk of atherosclerosis or with coronary heart disease.

WHAT IS OK

The bottom line on chocolate as a food suggests that two to three chocolate bars per week, 1.5 oz each, or a daily cup of cocoa with added skim milk, should be acceptable in the usual diet. Dark chocolate is preferable to the sweeter varieties, because it contains less fat, and cocoa is better in terms of calories and fat, because it contains 10% to 22% fat compared with 58% in chocolate. Equivalent in calories to the chocolate candy bar are: 2 pats of butter, 1 oz processed American cheese, 2 oz hamburger, and 3 cups of buttered popcorn, all containing cholesterol. Other equivalent snacks in terms of calories are: 1 oz pretzels and a 12-oz soft drink, or 1 bag of potato chips and the 12-oz soft drink. The consumer can choose from among these. Chocolate can serve as an occasional snack for diabetics and can be part of a Step 1 cholesterol-lowering diet.

Why does chocolate taste so good? It has a unique "mouth feel" with melt-away behavior, a creamy texture, and a puzzling food flavor and aroma, the latter coming from some 30 to 50 chemical compounds. Chocolate literally melts in your mouth, with cocoa butter liquefying abruptly at just above usual room temperature and completing the phase transition at body temperature (Fig. 5).

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CHOCOLATE AND HEALTH AND DISEASE

Chocolate has been associated with a large variety of postulated adverse effects on health and bodily functions and diseases (Table 1). These run the gamut from acne to premenstrual syndrome (PMS). For most of these medical problems, the association is weak, and many have been ruled out by properly designed investigation. Others remain as relatively minor problems for the population, although potentially serious for the affected individual. Chocolate has been used as a medicinal remedy over the years, and a treatise recommended chocolate for many diseases, citing it as a cure for Cardinal Richelieu's ills.

Table 1. Chocolate and diseases:
Medical maligning?

Acne                         Diabetes mellitus
Affective disorders          Heartburn
Allergy                      Immune function
Blood clotting               Infection
Blood lipids and
  heart disease              Kidney stones
Cancer                       Migraine headaches
Dental caries
  and plaque                 Premenstrual syndrome

This list represents disorders for which references have been published in recent years.

Chocolate Craving

The effects of chocolate on behavior and mood may be involved in the etiology of chocolate craving, the most common craving in North America that affects 40% of women (more at the time of menstruation) and 15% of men. Craving is related to the aroma, independent of sweetness, texture, and calories. It presumably relates to the content of phenylethylamine, an amphetamine-like substance that selectively increases tryptophan uptake by the brain.[7] This results in increased brain levels of 5-hydroxytryptamine, a dopamine precursor. Dopamine has been postulated as the inducer of feelings of "pleasure." Phenylethylamine also has been implicated in the aphrodisiac qualities of chocolate, and proposed as the mediator of the "falling in love" emotion, perhaps equivalent to orgasm (assuming these responses are biochemical in origin). Montezuma was said to have drunk a golden goblet of cacao beverage prior to entering his harem where he encountered a new partner every night.

Recently, investigators have extracted several Nacylethanolamines (arachidonyl, linoleoyl, and oleoyl) from cocoa powder.[8] Anandamide (the arachidonyl amine) is a brain lipid that binds to cannabinoid receptors with high affinity and mimics the psychoactive effects of plant-derived cannabinoid drugs; it may be an endogenous cannabinoid neurotransmitter or neuromodulator. These compounds were not found in white chocolate that contains only cocoa butter and milk, nor in brewed espresso coffee. The oleoyl and linoleoyl derivatives inhibit the breakdown of anandamide, thus indirectly mimicking cannabinoids. The investigators have not determined if the amine content in cocoa powder is sufficient to have biological activity. Cannabinoid drugs heighten sensitivity and produce euphoria. Thus these compounds may intensify the sensory properties of chocolate essential to craving, or interact with the methylxanthines in chocolate to produce transient feelings of well-being. Theobromine has caffeine-like properties, but the caffeine content of chocolate is low (6 mg/oz), equivalent to that in a cup of decaffeinated coffee. Methylxanthines are competitive antagonists of adenosine receptors. Theobromine acts as a myocardial stimulant, diuretic, smooth muscle relaxant, and dilator of coronary arteries. Theobromine content is highest in baking chocolate and cocoa and lower in sweet and milk chocolate and chocolate syrup.

Women with eating disorders may be "chocolate addicts." Studies in these self-described addicts have shown no improvement in depression, relaxation, or feeling content after eating chocolate--rather, the women felt guilty![9] Some 30% of psychiatric patients with mood disorders consume chocolate, a figure not dissimilar from the general public. Chocolate interacts with monoaminoxidase inhibitor medications used in treating some psychiatric disorders. The response induced is similar to tyramine-containing foods, such as hard cheeses, and may elevate blood pressure. This effect may be exacerbated by combining chocolate and these other foods (yeast products, dry sausage, corned beef, broad beans, sauerkraut). Any of these foods may potentially trigger a carcinoid syndrome reaction (flushing, diarrhea, bronchospasm, heart valve abnormalities that are the result of excessive serotonin secretion by carcinoid tumors).

Migraine

Chocolate long has been viewed as triggering attacks of migraine headaches. In 16% of migraineurs studied, headache was precipitated by chocolate or cheese.[10] The combination of cheese and chocolate nearly always produced a headache. The same subjects developed headache after drinking red wine or beer or with the combination of alcohol and stress. Tension headaches were unrelated to chocolate intake. Chocolate also has been associated with the prevalence of PMS and has been found to increase PMS in women with more severe symptoms.

Toxicity

Toxic effects of chocolate are inconsequential. Over the years, infection with Salmonella, Yersinia, or Listeria have been reported, from contaminated confections or chocolate milk. A 2-year study in rats fed cocoa powder (57-74 mg/kg body weight/day) corresponding to 50 times the 90th percentile of United States intake, showed no adverse effect on reproduction nor any dominant lethal mutations.[11] Survival was not affected. Abnormalities noted were reversible testicular atrophy at the highest dose with aspermatogenesis, myocarditis, interstitial fibrosis, hydronephrosis, and renal microcalcification. Benign mammary gland fibroadenoma incidence was increased to 24% compared with 16% in controls, but there was no evidence of carcinogenicity.

In terms of tumor potential, caffeine is a promoter of the carcinogen dimethylbenzanthrene-induced mammary cancer. Methylxanthine intake may be associated with fibrocystic disease of the breast. Polyphenols (tannins) have been associated with increased risk of esophageal cancer. The LD50 of theobromine in rats is 1g/kg body weight.

Immune Function

The polyphenols in chocolate that have antioxidant function may modulate immune function measured in humans in vitro,[12] Cacao liquor polyphenols were prepared by extracting and concentrating defatted cacao liquor to obtain 50% polyphenols. Cacao liquor polyphenols (100 [micro]g/ml) were noted to have an effect on lymphocyte and granulocyte functions, inhibiting reactive oxygen species (oxygen radicals and hydrogen peroxide) from activated granulocytes and lymphocytes. The extract inhibited lymphocyte proliferation and immunoglobulin production in response to mitogen, in part due to decreased production of interleukin-2 by T lymphocytes. The effect was similar to that observed with vitamin E or citrus flavonoids like quercetin.

Allergy

Allergy to chocolate has been observed, most commonly in workers in confectionery plants where 31% were noted to have immediate wheal skin reactions to skin prick with cocoa, with 6% reacting to cocoa beans and 12% to chocolate.[13] Occupational asthma has been reported with IgE-dependent responses and immediate asthmatic allergic reactions of sneezing, rhinorrhea, wheezing, hives, severe headache, nausea, and cramps induced by a specific inhalation challenge. It is not clear which proteins are responsible, although a similar protein pattern was obtained in cocoa bean sheath, the internal bean content, and cocoa powder. Sporadic allergic reactions usually occur in children and are outgrown.

Other Disorders

There is no evidence that chocolate causes acne, and a usual diet is more dental plaque-promoting than a chocolate-skim milk diet. Kidney stone formation may be enhanced by chocolate; ingestion of a 100-g chocolate bar increased oxalate excretion threefold and also increased calcium excretion, similar to sucrose. Because these changes may favor urolithiasis, stone-prone subjects should avoid chocolate, and to minimize urolithiasis, it is advisable to drink a lot of water if chocolate is eaten. Heartburn is common after eating chocolate, and the lower esophageal sphincter relaxes after chocolate, with more gastric acid reflux noted in the esophagus. Thus, it is recommended that patients with esophagitis avoid chocolate.

CONCLUSIONS

Chocolate is a unique food that can be enjoyed in the diet in moderation both as a beverage and as a snack. Although high in calories because of its high fat content, the high stearate percentage makes this vegetable fat relatively innocuous in terms of atherogenic potential. The unique chemicals in the cocoa bean have a variety of effects on brain function and may act as antioxidants. For most of us, chocolate is not an inducer or exacerbator of disease or adverse symptoms. So--Enjoy!

The author thanks Mary P. Glode, M. D., University of Colorado Health Science Center, Denver, CO, and Penny Kris-Etherton, Ph.D., Pennsylvania State University, State College, PA, for references provided.

REFERENCES

[1.] Young AM. The chocolate tree: a natural history of cacao. Washington, D.C.: Smithsonian Institution Press; 1994.

[2.] Young G. Chocolate: food of the gods. National Geographic 1984;166:665-86.

[3.] Pearson TA, guest scientific editor. Stearic acid: a unique saturated fatty acid. Am J Clin Nutr 1994;60(6S): 983S-1072S.

[4.] Kris-Etherton PM, Yu S. Individual fatty acid effects on plasma lipids and lipoproteins: human studies. Am J Clin Nutr 1997;65:1628S--44S.

[5.] Waterhouse AL, Shirely JR, Donovan JL. Antioxidants in chocolate. Lancet 1996;348:834.

[6.] Kondo K, Hirano R, Matsumoto A, Igarashi O, Itakkura H. Inhibition of LDL oxidation by cocoa. Lancet 1996; 348:1514.

[7.] Rozin P, Levine E, Stoess C. Chocolate craving and liking. Appetite 1991;17:199-212.

[8.] DiTomaso E, Meltrame M, Plomelli D. Brain cannabinoids in chocolate. Nature 1996;382:677--8.

[9.] Macdiarmid HI, Hetherington MM. Mood modulation by food: an exploration of affect and cravings in `chocolate addicts'. Br J Clin Psychol 1995;35:129-38.

[10.] Peatfield RC. Relationships between food, wine, and beer-precipitated migrainous headaches. Headache 1995;35:355-7.

[11.] Tarka SM Jr, Morrissey RB, Apgar JL, Hostetler KS, Shively CA. Chronic toxicity/carcinogenicity studies of cocoa powder in rats. Food Chem Toxicol 1991;29: 7-19.

[12.] Sanbongi C, Suzuki N, Sakane T. Polyphenols in chocolate, which have antioxidant activity, modulate immune functions in humans in vitro. Cell Immunol 1997;177: 129-36.