Updated: Nov 16, 2018
A growing body of research has shown that cocoa and dark chocolate is beneficial to many aspects of health, particularly cardiovascular and brain health. The main contributors are the powerful antioxidant flavanols as well as theobromine and L-tryptophan. The cocoa polyphenolic compounds also has prebiotic effect which modulates gut bacteria and further enhances anti-inflammatory properties.
Cocoa is naturally rich in antioxidant polyphenols called flavanols. Polyphenols are natural compounds produced by plants in response to stress to help them adapt to their environment. When we consume polyphenol-rich plants, they can place a mild stress on our body cells via activation of sirtuin genes, mimicking the effect of caloric restriction and exercise. Health benefits of cocoa was early evident from the population of Kuna American Indians who had remarkably low rates of hypertension, obesity, diabetes, cancer and early deaths thanks to their high intake of locally made flavanol-rich cocoa beverage.
Cocoa flavanols have been shown to help regulate immune system and alleviate inflammatory conditions associated with allergies, asthma, arthritis and heart diseases. Regular and moderate consumption of dark chocolate (20g every 3 day) was shown to be inversely associated with low serum C-reactive protein, a marker of inflammation. Collectively, research suggests that cocoa with high polyphenol content could aid in the resolution of inflammatory response and, as a potent antioxidant, it can be a complementary anti-inflammatory therapy.
Interestingly, a study revealed that due to limited absorption of cocoa flavonoids in the small intestine, the anti-inflammatory benefits of cocoa and chocolate depend on the gut bacteria, bifidobacteria and lactobacilli, metabolising polyphenols into smaller anti-inflammatory compounds which could be easily absorbed into the bloodstream. Previous studies demonstrating that cocoa flavanols possess prebiotic effect which helps balance the gut microflora. A study showed that consumption of high dose cocoa flavanols (495mg) significantly increased the 'good' gut bacteria, Bifidobacterium and Lactobacillus, while the pathogenic Clostridia were radically decreased, along with reduction of the inflammation marker C-reactive protein. These findings implicate the bidirectional interaction of cocoa polyphenols and the gut bacteria which mimics the effect of prebiotics and probiotics. In other words, it appears that the health benefits of cocoa could be mediated via modulations of the gut microflora.
The flavanols in cocoa and dark chocolate may help prevent heart disease by lowering blood pressure and improving blood flow to the heart. One of the main mechanism lies on the stimulation of nitric oxide production by the endothelium causing relaxation of the arteries which lowers resistance to blood flow. In addition, cocoa flavanols increase the bioavailability of nitric oxide, which in turn affects insulin-stimulated glucose uptake and vascular tone. One study demonstrated that short-term consumption (15 days) of 100 g dark chocolate per day (containing 500 mg polyphenols) significantly increased insulin sensitivity and decreased blood pressure compared with white chocolate consumption in healthy individuals and in glucose-intolerant hypertensive subjects. Another study has confirmed the beneficial effect of dark chocolate on vascular function after moderate consumption (8g daily) of 70% dark chocolate for one month.
As a source of powerful antioxidants, cocoa may protect cells against oxidative damage and prevent oxidation of LDL cholesterol, which is another key mechanism for lowering the risk of cardiovascular diseases. In one study, consuming cocoa drink containing high polyphenolic compounds for 4 weeks reduced plasma LDL cholesterol and oxidised LDL concentration while the plasma HDL cholesterol increased. In addition, a meta-analysis (a combined results from multiple studies) revealed beneficial effects of cocoa and dark chocolate on total and LDL cholesterol whilst no significant effect on HDL and triglyceride. Interestingly, high polyphenols in cocoa may activate a specific gene pathway called the Nrf2 pathway enhancing antioxidant levels in the body, which promotes detoxification and reduces inflammation.
Cocoa has been shown to improve insulin sensitivity (i.e smaller amounts of insulin required to lower blood sugar levels) and, as a result, may help delay and prevent the onset of diabetes and prediabetes. A study in non-diabetic adults showed a significant increase in insulin sensitivity after consuming 20g polyphenol-rich dark chocolate (500mg) for 4 weeks. Moreover, research suggests that regular consumption of cocoa flavanols may promote healthy cognitive function possibly through improved insulin sensitivity. Consuming flavonoid rich cocoa (993 and 520 mg/d for 8 weeks) was shown to increase cognitive function in elderly individuals with mild cognitive impairment and improve age-related cognitive dysfunction in cognitively intact elderly subjects, along with improved insulin sensitivity, blood pressure and lipid peroxidation (degradation of fats by free radicals).
Cocoa may improve memory, attention span and cognition. One study demonstrated that a moderate dose (150mg for 5 days) of flavanol-rich cocoa can increase blood flow to the brain and a single acute dose of flavanol-rich cocoa (450mg flavanol) increased the cerebral blood flow to gray matter, suggesting the potential utilisation for the treatment of dementia and strokes. Neuroprotective and neuromodulatory properties of cocoa flavanols have been shown in numerous studies. The absorbed flavonoids accumulate in the brain regions, mainly the hippocampus involving in learning and memory and are believed to act on promoting neurogenesis (formation of new nerve cells), neuronal function and brain connectivity as well as improving blood flow and angiogenesis (blood vessel formation) in the brain and sensory system. Recent studies demonstrated that 250mg dose of cocoa flavanol improved minor cognitive performance acutely (same day) but not sub-chronically (4weeks) whereas a higher dose of 900mg cocoa flavanols was shown to enhance cognition in chronic intervention.
Cocoa may help regulate mood and lower depression. Consumption of a high dose cocoa polyphenol drink (500mg/d for 30 days) was shown to increase calmness and contentedness in healthy individuals. Cocoa also contains compounds such as methylxanthine compounds, caffeine and theobromine, with psycho-stimulant effect. Methylxanthines have been shown to exert health benefits mainly through blockade of adenosine receptors in the central nervous system enhancing arousal, mood and concentration levels. In addition, dark chocolate contains amino acid L-tryptophan, a precursor of dopamine and serotonin, the brain neurotransmitters which are responsible for mood regulation.
It is worth noting that different brands of cocoa may differ considerably in their nutritive value and health benefits. The higher percentage of cocoa in dark chocolate (70% or higher), the more flavonoids and less sugar. Moreover, the polyphenol content of cocoa and dark chocolate depends on the method of manufacturing. Alkalised or Dutch processed cocoa has reduced amounts of flavanols. Accordingly, minimally processed dark chocolate and raw cocoa would be the best option for maximal health benefit. High percentage of saturated fats and added sugar in cocoa products can also counteract the health benefits. The bottom line is to opt for the best quality cocoa and dark chocolate at least 70% cocoa mass and enjoy it in moderation.