Chocolate is a product manufactured with cocoa as the major ingredient. Consumption of chocolate is not advised by the health-conscious group of society. Over concerned mothers restrict their children from eating chocolate to avoid dental caries and the nutritionist recommends abstinence from chocolate to avoid obesity. They are correct, however, if chocolates are consumed with controlled portion size, cocoa is one of the health friendly foods.
Cocoa has a golden past
Long ago, the beneficial effects of cocoa had been recognized and its medicinal values are well documented in Europe between 16th and early 20th century. Greek meaning of Theobroma cacao is “food for the Gods” and cocoa was used by the priest in curing many diseases like angina and heart pain.
Cocoa is rich in polyphenols especially flavonoids which have high antioxidant capacity. It is reported that cocoa contains about 6 – 8% of polyphenols on dry weight basis. The health benefits of cocoa and chocolate are attributed to these flavonoids. Cocoa has higher flavonoids than tea and red wine. High concentration of flavonoids increases their benefits in many heath related disorders ranging from heart disease, cancer, stroke, insulin dependent disorders, vascular diseases and many more.
Detailed scientific explanation and research references for the health benefit of Chocolate & Cocoa Products
Among different naturally present polyphenols, cocoa beans especially cocoa powders are rich in a subclass of polyphenolics known as flavonoids. The basic chemical structure of a flavonoid consists of two aromatic rings linked via an oxygenated heterocyclic structure. Procyanidins (also called pro-anthocyanidin) are the major flavonoids in cocoa and their concentration is more than those present in blueberry and cranberry on a dry weight basis. It is oligomer and polymer of (+)- catechin and (-)-epicatechin. Flavonoids have capacity to transfer electrons free radicals and chelate metal catalysts. These flavonoids can also activate antioxidant enzymes, reduce alpha-tocopherol radicals, and inhibit oxidases. Being strong antioxidant, these flavonoids scavenge the free radicals which otherwise attack cellular DNA, proteins, lipids causing cellular damage and several pathological complexities. These properties of flavonoids explain their importance in biological system such as the ability to scavenge superoxide radicals and hydroxyl radicals, reduce lipid peroxyl radicals and inhibit lipid peroxidation. The antioxidant activity is attributed to the presence of a catechol group in the B-ring of many flavonoids while phenol groups present in flavanols provide hydrophilic character to these molecules and support an antioxidant effect in aqueous domains. Flavonoids also prevent lipid oxidation caused by initiators that act in the hydrophobic region of the lipid bilayer. According to a hypothesis, polyphenol get adsorbed to membranes by associating with the polar head group of phospholipids. This restricts the entry of oxidants to the bilayer.
Effect of cocoa processing on flavonoids
During primary and secondary processing of cocoa, flavan-3-ol undergoes chemical changes. Fermentation decreases the flavan-3-ol concentration and roasting and alkalization also have effect on final concentration of flavon-3-ol. Genetic makeup of cocoa can also bring about differences in the concentration of flavonoids.
Following table shows the content of polyphenols in different cocoa products as reported in few literatures. There is difference in the results and it may be attributed to difference in sample and in method adopted for analysis.
|Waterhouse et al., 1996
|Vinson et al., 1999
|Adamson et al., 1999
|Arts et al., 1999
|Richelle et al., 1999
Most common CVDs are atherosclerosis and thrombosis. Endothelial dysfunction, inflammatory response, modified lipids and lipoproteins, and activated platelets are associated with these diseases. Many studies report that the food rich in flavonoids or antioxidants helps in decreasing the risk of CVDs. Many reviews are available substantiating the fact that consumption of cocoa products are beneficial in terms of cardiovascular protection. Flavonoids which are strong antioxidants have a special property of scavenging reactive oxygen species (ROS) i.e. free radicals and reactive nitrogen species. The free radicals (i.e. ROS) generated during lipid oxidation are responsible for CVDs. They are strongly associated with hypertension, diabetes, smoking and other factors affecting CVDs. Several studies have been carried out to examine the antioxidant properties of dark chocolate taking adult humans as subjects, cocoa powder and cocoa drink. Even the cocoa leaves have shown to have antioxidant property like that of green tea. One of the research papers shows that scientists extracted antioxidant from cocoa husk by supercritical CO2 extraction thus, utilizing one of the byproducts of the cocoa processing industry.
A. LDL oxidation
It is of general conception that chocolate consumption increases the cholesterol level. This is because of the high saturated fatty acid content of chocolate. However, major fatty acid is stearic acid (~30% of fatty acids), which is neutral to LDL cholesterol. So, through clinical studies it has been reported that chocolate consumption has no effect on serum total and LDL cholesterol. Substantiating the positive effect of cocoa and chocolate on human health, reported that these products increase the serum concentration of HDL cholesterol by 4%. Effect of cocoa products on serum HDL cholesterol level has also been studied and it is reported an increase in serum HDL cholesterol and decrease in lipid oxidation. In a clinical study, it was found that, daily intake of cocoa powder has been shown to decrease the susceptibly of LDL to oxidation.
B. Blood Pressure
Few literatures report that there is no effect on blood pressure by the consumption of cocoa products. However, many later researches contradict the previous reports. Involvement of nitric oxide (NO) has been reported in vascular modulation and blood pressure. The angiotensin system is present in endothelial cells which are being controlled by NO Production. Angiotensin converting enzymes (ACE) of angiotensin system converts angiotensin I to angiotensin II and also inhibits bradykinin, vasodilator peptides. So the basic aim in lowering the blood pressure is to inhibit the angiotensin converting enzymes. One of the studies explained the probable mechanism of action of flavanoids in lowering the blood pressure. In this study, it is reported that flavonoids act as angiotensin I converting enzyme inhibitor thereby lowering the blood pressure. One paper explains the inhibitory effects of cocoa, tea and wine on the ACE. The study shows that these flavonoid-rich foods were capable of inhibiting ACE and concluded that this property was attributed to the presence of phenolic compounds and flavanols. Thus, not only the isolated procyanidins rather the flavanoid-rich foods are also capable of inhibiting ACE and thus, lowering blood pressure.
Nitric oxide plays an important role in human circulatory system. It acts as vasodilator and helps in circulation of blood to the vital organs of the body. Synthesis of NO in body takes place through two synthase– one by endothelial nitric oxide synthase (NOS) and other by inducible nitric oxide synthase (iNOS) in macrophages. Surprisingly, cocoa has been found to stimulate NOS and depress iNOS. Both of these effects on cocoa have been found to have beneficial effect on human health. Decrease in NO level leads to endothelial dysfunction which further leads to atherosclerosis. On the other hand due to strong vasodilating action, increase in NO produced by inflammatory cells which leads to septic shock in septicemic patients. Prostacyclins and leukotrienes (combined known as eicosanoids) are vasodilators and vasoconstrictors respectively. In one the studies, it is found that there is decrease in plasma leukotrienes and prostacyclins ratio in high-flavonoid chocolate fed subjects. Thus, this balance of eicosanoids not only helps in vasodilation but also control platelet aggregation and result in anti-inflammatory profile. One research also reported relationship between (-)-epicatechin and the flavanol-rich cocoa on the vascular function of human beings.
Many literatures are available explaining the effect of chocolate products on vasodilation. It is reported that endothelium dependent relaxation of vessels was increased when isolated rabbit aorata was exposed to cocoa extract (10-7 to 10-5 mol/L). The effect of cocoa beverages on healthy adult showed increase in vasodilation. It has been reported that the ingestion of cocoa rich in flavanol by a human with diminished endothelial function restores plasma NO. Similar work has also been done on healthy adults with dark chocolate as flavonoid source
Thrombosis and platelet aggregation
There are different theories to explain the mode of action of these flavonoids on suppressing the platelet activity. Superoxide anions have been reported to participate in platelet. These super oxide ions interact with nitric oxide (an antithrombotic factor) to form active nitrogen species which promote platelet aggregation. It is reported that increase in consumption of flavonoids decreased superoxide release, and increased platelet derived nitric oxide production thus, preventing the platelet aggregation. In another theory, it is said that catechin and quercetin synergistically inhibit platelet hydrogen peroxide production and it is related to some changes in eicosanoid metabolism. Later Kris-Etherton and Keen (2002) supported it by reporting that flavonoids increase the production of prostacyclin (an eicosanoid) which is the inhibitor of platelet aggregation.
Effects of cocoa on blood glucose level
Blood glucose level is one of the important parameters to indicate the health status of a person. Diabetes is due to high oxidative stress and it can be overcome by proper antioxidants in the diet. As discussed earlier cocoa is rich in polyphenols which are strong antioxidants. In of the studies, it is reported that Malaysian cocoa extract may be able to reduce hyperglycaemia and hypercholesterolemia thus, decreasing the risk of diabetes. This study reports reduction in glucose level when subjects were fed with 1, 2 and 3% cocoa extracts.
Cocoa flavanoids and cancers
The high content of polyphenols in cocoa renders it a wide spectrum in terms of disease control and valuable health benefits. Apart from CVD, diabetes and inflammatory diseases cocoa has been proved to be beneficial against many other diseases. One paper talks about the anti-proliferative properties of flavanols and procyanidins from cocoa extracts on human colon cancer cells. Their results are strongly supporting the fact that cocoa flavanoids are potent anti-proliferative substances. These polyphenols cause non-apoptotic cell death and block G2/M phase of the cell cycle thus affecting the cell cycle. This blockade is caused due to the inhibition of polyamine biosynthesis which gets increased in cancer. It is also reported that the efficiency of the polyphenols as anti-proliferative and anti-tumoural substance depends on the degree of polymerization.
Reactive oxygen species (ROS) are one of the important causes of the cancer. The ROS cause the DNA mutation. Food rich in flavanoids (antioxidants) can control the ROS thus, preventing any harmful effect of the same. In few reports, it was found that cocoa liquor was capable of reducing mutagenic activity of heterocyclic amines.
Neuroprotective effects of cocoa
Neuroprotective effects of flavanoids against the neuronal deficits associated with aging or age-related neurodegenerative diseases are being substantiated by many epidemiological studies. The mechanism of neuroprotective action of flavonoids has been studied. Through cellular studies, it is explained that epicatechin prevents neuronal cell death caused by oxidized low-density lipoprotein-induced oxidative stress. Reactive oxygen species also participate in neural diseases. During such diseases over production of ROS takes place, leading to a massive destruction of neurons and trophic cells. Thus, the use of antioxidants can be very much useful in controlling such cellular damage. Cerebrovascular health and flavanoid rich foods like cocoa have been studied by many workers. They reported that these compounds increase the cerebral blood flow by stimulating eNO synthase activities. McCarty (2006) reported the effect of flavanoid rich cocoa and other foods on the controlling of Alzheimers disease. Still lot of work is yet to be done to understand the effect of cocoa on the neural protection.
Other health benefits of cocoa
Aging is one of the chronic diseases which every living being has to suffer without fail. Lot of researches are going on to control this unavoidable truth. There are many theories of aging. Some explains the biological process of aging in terms of muscular change, cell damage, gene activation leading to aging-related physiological changes. Other found oxidative protein change in cerebral cortex and cerebellum in aged mice. Involvement of free radicals and decrease in the activity of antioxidant enzymes (superoxide dismutase, glutathione and catalase) were reported in all the cases. Thus, total attention is being driven to naturally occurring antioxidants like flavanoids and other polyphenols. As we have discussed a lot about the antioxidant properties of cocoa we can think of its enormous potential in fighting against aging and the aging related complications. It is reported the cocoa rich flavanols can reverse the endothelial dysfunction of human aging via NO.
One of the papers shows the effect of cocoa extract on alcohol induced liver damage and it is concluded that flavanoids present in cocoa can prevent the early alcohol induced liver injury. Alcohol oxidative stress is extensive. Alcohol consumption causes the formation of the α-hydroxyethyl free radical in vivo. It directly damages proteins and small molecules. Thus, its prevention can be done by the use of suitable antioxidants. Thus, increased dietary intake of flavonoids which are exceptionally efficient antioxidants and radical scavengers can be used as the liver protectors.
There is even good news for smokers. It is reported that the cocoa can have vascular health benefits in smokers. It is so because the oral ingestion of a flavanol-rich cocoa increases the circulating pool of bioactive NO and endothelium-dependent vasodilation.
Beneficial effect of cocoa related to curing of secretory diarrhea has been studied. It isreported that these flavanoids can inhibit cystic fibrosis transmembrane conductance regulator (CFTR)- mediated chloride transport across human colon epithelia. Escherichia coli and Vibrio cholerae are the two major microbes responsible for secretory diarrhea. The enterotoxins produced by these organisms activate the secretion of Cl– and inhibit the absorption of Na+ across the membranes of enterocytes which leads to massive fluid loss into lumen of gut. CFTR plays an important role in this process and acts as the major Cl– channel in human intestines. So, blocking of CFTR can inhibit water and salt loss during diarrhea.
Adam, W. B., Hardy, P., Nierenstein, M. 1931. The catechin of the cocoa beans. J. Amer. Chem. Soc. 53, 727-728.
Adamson, G. E., Lazarus, S. A., Mitchell, A. E., Prior, R. L., Cao, G., Jacobs, P. H., Kremers, B. G., Hammerstone, J. F., Rucker, R. B., Schmitz, H. H. 1999. HPLC method for the quantification of procyanidins in cocoa and chocolate samples and correlation to total antioxidant capacity. J. Agric. Food Chem. 47, 4184-4188.
Amin, I., Faizul, H. A., Azli, R. 2004. Effect of cocoa powder extract on plasma glucose levels. Nutr. Food Sci. 34, 116-121.
Buijisse, B.; Feskens, E. J. M.; Kok, F. J.; Kromhout, D. 2006. Cocoa intake, blood pressure, and cardiovascular mortality. Arch. Intern. Med. 166, 411-417.
Engler, M. B., Engler, M. M. 2006. The emerging role of flavonoid-rich cocoa and chocolate in cardiovascular health and disease. Nutr. Rev. 64 (3), 109-118.
Fisher, N. D. L., Hughes, M., Gerhard-Herman, M., Hollenberg, N. K. 2003. Flavanol-rich cocoa induces nitric oxide dependent vasodilation in healthy humans. J. Hypertension. 21, 2281-2286.Fisher, N. D. L., Hughes, M., Hollenberg, N. K. 2004. Cocoa rich flavanols reverses the endothelial dysfunction of human aging via NO. Amer. J. Hypertension. Vol-17, No-5, Part 2.
Grassi, D., Lippi, C., Necozione, S., Desideri, G., Ferri, C, Croce, G., Valeri, L., Pasqualetti, P., Blumberg, J. B. 2005b. Cocoa reduces blood pressure and insulin resistance and improves endothelium-dependent vasodilation in hypertension. Hypertension. 46, 1-8.
Kenneth, B M., Stuart, D. A., Smith, N. L., Lee, C. Y., McHale, N. L., Flangan, J. A., Boxin Ou, Hurst, W. J. 2006. Antioxidant activity and polyphenol and procyanidin contents of selected commercially available cocoa- containing and chocolate Prod. in United States. J. Agric. Food Chem. 54, 4062-4068.
Liwei, Gu., House, S. E., Xianli Wu, Boxin Ou, Prior, R. L. 2006. Procyanidin and catechin and antioxidant capacity of cocoa and chocolate Prod.. J. Agric. Food Chem. 54, 4057-4061
Mursu, J., Voutilainen, S, Nurmi, T., et al. 2004. Dark chocolate consumption increases HDL cholesterol concentration and chocolate fatty acids may inhibit lipid peroxidation in healthy humans, Free Radical Bio. Med. 37, 1351-1359
Rein, D., Lotito, S., Holt, R. R., Keen, C. L., Schmitz, H. H., Fraga, C. G. 2000c. Epicatechin in human plasma: In vivo determination and effect of chocolate consumption on plasma oxidation status. J. Nutr. 130, 2109S-2114S.
Sanbongi, C., Suzuki, N., Tsuyoshi, S. 1997. Polyphenols in chocolate, which have antioxidant activity, modulate immune functions in humans in vitro. Cell. Immunol. 177, 129-136.
Schramm, D. D., Wang, J. F., Holt, R. R., Ensunsa, J. L., Gonsalves, J. L., Lazarus, S. A., et al. 2001. Chocolate procyanidins decrease the leukotriene –prostacyclin ratio in humans and human aortic endothelial cells. American J. Clin. Nutr. 73, 36– 40.
Sharma & Naidu, 2008. Science of cocoa processing, Jain Brothers, New Delhi
Steinberg, F. M., Holt, R. R., Schimtz, H. H., Keen, C. L. 2002. Cocoa procyanidin chain length not determine ability to protect LDL from oxidation when monomer units are controlled. J. Nutr. Biochem. 13, 645-652.
Steinberg, F. M., Bearden, M. M., Keen, C. L. 2003. Cocoa and chocolate flavonoids: Implications for cardiovascular health. J. Amer. Diet. Assoc. 215-223.
Vinson, J. A., Proch, J., Zubik, L. 1999. Phenol antioxidant quantity and quality in foods: cocoa, dark chocolate, and milk chocolate. J. Agric. Food Chem. 47, 4821-4824.
Virgili, F., Scaccini, C., Hopp.e, P. P., Kramer, K., Packer, L. Plant phenols and cardiovascular disease: antioxidants and cell modulators. In: Kramer, K., Hoppe, P. P., Packer, L. (Eds.) Nutraceuticals in health and disease prevention. Marcel Dekker. New York. pp. 187-215.
Wan, Y., Vinson, J., Etherton, T. D., Proch, J., Lazarrus, S. A., Kris-Etherton, P. M. Effects of cocoa powder and dark chocolate on LDL oxidative susceptibility and prostaglandin concentrations in humans. Amer. J. Clin. Nutr. 74, 596-602.
Wiswedel, I., Hisrsch, D., Krof, S., Gruening, M., Pfister, E., Schewe, T., Sies, H. 2004. Flavanol-rich cocoa drink lowers plasma F(2)-isoprostane concentrations in humans. Free Rad. Biol. Med. 37, 411-421.
Zumbe, A. 1998. Polyphenols in cocoa: are there health benefits? BNF Nutrition Bulletin. 23, 94-102.