Health Benefits of Chocolate
Cocoa, the primary ingredient in chocolate, is the term for the dried and fully fermented fatty seed from the fruit of a cocoa tree, Theobroma cacao. The cocoa plant was likely first cultivated in circa 400 A.D. in the Mayan empire. They, however, did not utilize cocoa for its taste, but rather for the analeptic and revitalizing effects of xocolatl (fig. 1), a combination of ground, dried cocoa beans that were dissolved in water, cinnamon, and pepper. Cocoa beans became of such great value that they were used as currency in the Mayan and Aztec empires, where they were stored in safes beside gold and other invaluable stones1. Today, cocoa liquor, often referred to as “percent cacao” on packaging, is the most utilized ingredient in chocolate making. It is a paste made from ground, roasted, shelled, and fermented cocoa beans, otherwise known as nibs. In order to be classified as dark chocolate, chocolate must contain be at least 35% cocoa liquor by weight.
The chemical and physical properties of chocolate are mainly the results of cocoa butter. Cocoa butter is yellow in color and contains three primary triglycerides with oleic acid: POP (20%), POSt (40%), and StOSt (25%) (fig. 2). POP, POSt and StOSt are abbreviations for the triglycerides that make up cocoa butter. They can also be added to cocoa to make chocolate using cocoa butter substitutes, such as illipe butter, Borneo tallow, palm kernel oil, shea butter, and the kernel oil of a mango, among many others. Cocoa butter is brittle below 20 degrees Celsius, soft between 30 and 32 degrees Celsius, and melts at 940 to 97o Fahrenheit, or just barely below body temperature1. This is the chemical attribute responsible for chocolate’s characteristic melting-in-the-mouth experience.
Cocoa butter is a mixture of monounsaturated and saturated fatty acids. Oleic acid dominates the monounsaturated fraction, while the saturated fatty acids are primarily comprised of palmitic (fig. 3a) and stearic acid (fig. 3b). Generally, saturated fatty acids are associated with higher risks for coronary heart disease, as they have been shown to elevate total cholesterol and LDL. Stearic acid is, in a sense, an anomaly because it has not been found to elevate serum lipid levels to the same extent as other saturated fatty acids, such as myristic or palmitic acid. Cocoa butter has a relatively high lipid content, but since roughly 35% of the lipid content is stearic acid, it is thought to be nonatherogenic and to exert a neutral cholestrerolemic response in humans, meaning it does neither raises nor lowers cholesterol. Other organic components include carbohydrates (starch, cellulose, sucrose, glucose), pectose groups (pectose, pectin, pectic acid), vegetable acids, amides (asparagin), and extractives (chlorophyll, tannin, alkaloids). The inorganic components are mostly salts of several metals, namely potassium, calcium, magnesium, iron, and calcium.15
Several minerals necessary for optimal vascular function are also present in the cocoa bean. Magnesium, copper, potassium, and calcium are all present in relatively high concentrations in cocoa and they have all been linked to reduced risk of hypertension and atherosclerosis3, an inflammatory disease that involves a chronic injury to the endothelial lining of the blood vessel and the subsequent succession of inflammation and bodily responses18. Dark chocolate has 36 mg of magnesium, a cofactor in protein synthesis, muscle relaxation, and energy production, per serving, which is 9% of the daily recommended allowance. It reduces stress by hindering the release of cortisol, a predominant stress hormone10. This is thought to be one of the primary reasons people have stronger chocolate cravings in times of particular stress. Dark chocolate also serves as a major source of dietary copper in the American diet, providing 31% of the daily recommended value per serving. Copper is necessary for iron transport, glucose metabolism, infant growth, and brain development. Deficiency can potentially lead to, among other diseases, glucose intolerance, inflammation, hypertension, and myocardial hypertrophy3. Dark chocolate contains 1.90 mg of iron per serving, equating to 25% of the daily recommended value. Iron is found in human red blood cells called hemoglobin, which is vital in catalyzing the transfer of the oxygen in blood from lungs to other tissues7. This mineral content elucidates how highly processed chocolate with absurdly high sugar concentrations give chocolate a bad reputation, but in reality, the foundational components are actually quite healthy.
Cocoa contains several polyphenolic compounds; dark chocolate has up to 50 mg of polyphenols per gram!3 These act as antioxidants, so they prevent oxygen from binding with other substances, most notably fat. The basic structure of a flavonoid is a C6-C3-C6 backbone with two armomatic rings. They are distinguished from one another by their respective degrees of hydroxylation21. Single servings of cocoa products can contain more procyanidins than the amount consumed by the average American per day. Dark chocolate, in particular, is especially rich in flavonoids—specifically, flavanols, or flavan-3-ols, containing nearly triple the flavanol-rich cocoa solids compared to milk chocolate6 (fig. 4). Flavonoids are also found in tea, red wine, blueberries, apples, pears, cherries, and several types of nuts19. So far, the majority of studies have been conducted on the effects of chocolate intake and increased flavanol levels on the cardiovascular system, skin, cholesterol concentrations, and neurotransmitter release of anandamide and serotonin2. These flavanols are responsible for the bitter taste of cocoa since they form complexes with proteins in saliva. The primary flavanols in cocoa are epicatechin, catechin, and procyanidins, which contribute the majority of cocoa products’ antioxidant activity. These have denoted a plethora of effects on the central nervous system and its processes, with evidence mounting on its ability to shield from neurodegradation by decreasing neuroinflammation3. Chronic inflammation in the brain’s glial cells can effectuate gradual neural degeneration, leading to the onset of Parkinson’s disease, Alzheimer’s disease, and the neural injuries that are strongly associated with recurrent strokes. The structure of catechin (fig. 5) mirrors the structure of kinase inhibitors that possess anti-inflammatory effects on these glial cells. The increased velocity of blood flow in the middle cerebral artery has also been observed as a result of flavanol consumption, imparting evidence to the potential for protection against dementia and stroke3, as several studies have shown a link between a reduction in cerebral blood flow and the development of Alzheimer’s and depression with a significant increase occurring during remission14. A 2011 study showed that women who raised their cocoa consumption by 50 grams per week reduced their risk of cerebral infarction by 12%, hemorrhagic stroke by 27%, and total risk of stroke by 14%. In another study examining 37,000 Swedish men, it was found that those who consumed at least 1.8 ounces of chocolate per day were 17% less likely to have a stroke than their counterparts who did not do so22. These results are indisputably precursory and further research is required to ascertain the neuroprotective of the flavanols in cocoa products, but there is considerable potential for some significant health benefits.
Effect of Chocolate Components on Consumers
Elderly individuals with mild to moderate cognitive impairment, in particular, experience the most manifest effects of cocoa flavanol consumption. In a study examining cognitive function in response to cocoa flavanols, 90 elderly people with mild cognitive impairment were randomly grouped into one of three groups—a high flavanol group, who drank roughly 990 milligrams of cocoa flavanols per day for 8 weeks; an intermediate flavanol group (520 milligrams); and a low flavanol group (45 milligrams). When given two separate Trail Making Tests, the high and intermediate flavanols finished significantly faster than the low flavanol group. Verbal fluency test scores were also markedly better in the group given the highest flavanol concentration compared to their two counterparts17. This is likely an effect of the aforementioned increase in cerebral blood flow, but the data is significant in that it suggests that regular cocoa flavanol consumption can have a promising role in treating or slowing down the progression of cerebrovascular ischemic syndromes, such as dementia and stroke.
An individual’s memory is also improved through the consumption of cocoa enriched by flavonoids, which have a significant effect on cerebral blood flow. For brain function to be at its optimum level, cerebral blood flow must be maintained in order to aid in the unabating supplying of oxygen and glucose to neurons8. Increased blood flow to gray matter in the brain and other changes to regional blood flow in response to chocolate have been exhibited in fMRI studies. This fosters the growth of new blood vessels—angiogenesis– and of new nerve cells in the hippocampus, an essential region for memory processing. Epicatechin, an isomer of catechin, (fig. 5) triggers extracellular signal regulated kinase and cyclic AMP response element binding protein (CREB) (fig. 6) activation in cortical neurons, thereby augmenting the degree of CREB-regulated gene expression that is involved in the genesis of long-term memory3. Flavanols also enhance memory by interacting with several cell signaling pathways, most notably mitogen-activated protein, extracellular-signal-regulated, and phosphoinositide 3-kinase signaling cascades. These signaling cascades initiate gene expression and synthesis of proteins that are critical for prolonging long-term potentiation12, a key factor in the retention of memories.
There is also growing evidence to underpin the psychoactive effects of the flavanols and methylxanthine compounds that are present in cocoa products. The effects of cocoa flavanols on cognitive performance, anxiety, and mental fatigue through extended periods of mental demand were tested in a study on 30 individuals. The control group was given a beverage with 46 milligrams of total flavanols, while the experimental groups were given 520 or 994 milligrams. Both experimental groups exhibited notably elevated cognitive performance and diminished mental fatigue in comparison to the control group4. The exact mechanisms that underlie these effects remain unknown, but presumably, they may be associated with cocoa flavanols’ aforementioned effects on blood flow.
Cocoa also contains theobromine, a methylxanthine compound, that is present in chocolate at about 2-3% by weight. It is found in differing amounts in coffee, tea, and kola nuts, but chocolate is the most plenteous known source of it5. Theobromine has antioxidant activity that parallels that of caffeine with only slightly less stimulating effects on the central nervous system3 as a result of the missing methyl group in theobromine (fig. 7). While caffeine and theobromine are similar in the sense that they are both methylxanthines, the degree of their physiological effect differs, presumably because of the different half-lives—theobromine has a much longer half-life than caffeine13. The primary mechanisms of its effect on mood and alertness are its ability to inhibit phosphodiesterases and block adenosine receptors. Adenosine is an intermediate metabolite and a neuroregulatory messenger molecule of the central nervous system. The physiology of the brain is contingent upon deviations in adenosine concentrations, which impact adenosine receptors inside the neurons. The blockage of the specific receptors is what allows for the energy boost typically associated with caffeine and theobromine consumption, making them antagonists of adenosine receptors13. This underscores how chocolate’s perceived ability to boost mood has a scientific basis.
Chocolate’s effects on the human brain can be attributed to the multitude of psychoactive compounds—namely serotonin, anandamides, and phenylethylamine– present. Serotonin (fig. 8a) is a neurotransmitter responsible for controlling mood and the substance behind chocolate’s perceived antidepressant effect1. Anandamides (fig. 8b) are endogenous cannabinoids produced naturally in the brain at very limited quantities. They stimulate and expand synapses in the brain, which facilitates the transmission of brain waves associated with positive emotion5, with “anand” translating to “bliss” in Sanskrit, thus making the eater feel momentarily happier and more energized. When produced naturally in the brain, anandamides are broken down rapidly so its effects are often not felt9. Certain chemicals in chocolate, however, have been shown to slow down the rate of anandamide breakdown, which allows its effects to be recognized. Phenylethylamines (fig. 8c) are neurotransmitters with a stimulant effect that are accountable for feelings of pleasure1. These three neurotransmitters work in conjunction to create the short-lived feelings of satisfaction and contentment in consumers, demonstrating how the emotions associated with eating chocolate can be boiled down to its chemical structure.
Aside from benefits to the brain and central nervous system, elements of cocoa structure can have distinctive effects on overall physiological function, aiding in the lowering of blood pressure, reduction in blood clots, and an increase in good cholesterol. The cardioprotective effects of flavonoids can be attributed to a series of properties, such as antioxidant and antiplatelet activity, immunoregulatory properties, and beneficial effects on the endothelium, or the inner cell lining of blood vessels. Flavanols have consistently been shown to enhance nitric oxide production in the endothelium, which improves blood flow by relaxing the blood vessels and subsequently lowering blood pressure6. Epicatechins improve vascular function, reduce blood pressure, improve insulin sensitivity, and reduce platelet activity3. In a study examining the effect of cocoa flavanol consumption and blood pressure, subjects with untreated essential hypertension received 6.3 grams of dark chocolate daily for 18 weeks. Over that time, researchers observed dependable and notable drops in both systolic and diastolic blood pressure11. Cholesterol is also affected by the flavanols in dark chocolate. In a study by researchers at Harvard University, dark chocolate was found to elicit a small decrease in LDL cholesterol and a significant jump in HDL cholesterol6. Cocoa flavanols have also been found to preclude blood clotting by moderating eicosanoid synthesis in endothelial cells. Eicosanoids perform similar to hormones, but they are lipid compounds. Eicosanoids significant to flavanols are prostacyclin (fig. 9a), which impedes blood clotting, and leukotrienes C4, D4, and E4 (fig. 9b), which play a role in vasoconstriction and inflammation. The flavanols present in cocoa have been found to induce a 32% increase in the levels of prostacyclin and 29% decrease in the levels of leukotriene18, 21. Hypothetically, this favorable ratio between the different eicosanoids should lead to the inhibition of blood clotting and a dramatic reduction in inflammation.
Dark Chocolate vs Overprocessed Chocolate
Human metabolism is affected by dark chocolate. In a 2009 study, consuming 40 grams of dark chocolate daily for an extended period of time was found to reduce the urinary excretion of cortisol and catecholamines. It also normalized differences related to stress in energy metabolism and activities in the gut microbiome. This provides compelling evidence that dark chocolate consumption is capable of modifying the metabolic capabilities of healthy humans by creating variations in their host and gut microbial metabolisms23.
The risk of developing cardiovascular disorders can also be mitigated through the consumption of flavanols. Psychosocial stress is a major risk factor in the promotion of cardiovascular diseases because the body’s hypothalamus-pituitary-adrenal axis and sympathetic nervous system stress responses are induced more rapidly in times of heightened anxiety20. This takes a massive toll on the heart and can eventually lead to a higher risk of developing cardiovascular diseases. Numerous animal studies, however, have shown that the administration of flavonoids could potentially protect from the unpropitious effects of stress by reducing the degree of the previously mentioned stress responses20. These findings, among others, indicate how flavanols play key roles in supporting many somatic functions to varying degrees in several different parts of the human body.
It is paramount to note that all of the aforementioned benefits likely cannot be extrapolated to chocolates with high sugar contents and excessive processing. The total flavanol concentration hinges on how the cocoa was handled post-harvest and what processing techniques were implemented. Cocoa powder that is alkali-processed is depleted of a majority of its flavanol content16. While a plethora of findings imply a cogent link between dark chocolate consumption and neurological and physiological benefits, these advantages can quickly be outweighed by the low nutritional values of many chocolates on the market today. These findings are also not justification to eat a diet composed solely or primarily of cocoa products, but rather an indication that, in moderation, chocolate—a food that people have deemed indubitably detrimental to individual health– can actually be quite the opposite and possess a growing list of neurological, psychological, and physiological advantages.