This is a summary and explanation of:
R. di Giuseppe et al. (2013). The Role of Dark Chocolate on Inflammation: A Bitter Taste for a Better Life. Chapter 27, 371-378.
Chocolate contains flavanols (catechins, epicatechins, and procyanidins), which are antioxidants. These antioxidants inhibit oxidation, which is a process that results in free radicals causing damage to cells, and has been linked to aging and cell disruption or cell death. It's a normal process within living organisms, but research has lead to the idea that one's current environment and diet may be speeding up this process. Diets high in antioxidants may slow down the rate of oxidation, which could also slow down the rate of cell disruption that leads to diseases such as stroke and heart attacks. It is currently a controversial area of research.
di Giuseppe et al. begins to explain what sort of chocolate is the most beneficial. Dark chocolate has a greater amount of these flavanols (antioxidants) than milk chocolate. The flavanols are contained in the dark, nonfat, solids of the cocoa bean, and so milk chocolate essentially dilutes the amount of polyphenols. In fact, it is believed that milk proteins may interfere with intestinal absorption. It's been observed that 200g of milk chocolate, or 100g of dark chocolate taken with 200 ml of full fat milk, both have reduced antioxidant capacity when ingested compared to just 100g of dark chocolate without milk (Serafini et al., 2003). Cocoa powder, which is the dark cocoa solid with much of the fat removed, has the highest flavanol content. However, dutched cocoa powder, which makes up nearly all the cocoa powder purchased in stores, has very little of the flavanols left, even less than dark chocolate itself. The alkalinization process that makes it "dutched" reduces the flavanol content.
Chocolate flavonoids as anti-inflammatory agents:
Engler et al. (2004) found that dark chocolate consumption increases blood plasma epicatechin, which helps with vasodilation. This in turn may help with cardiovascular disease, such as reducing risk of atherosclerosis (Wan et al., 2001). Atherosclerosis is the condition of plaque build up and vessel hardening, which reduces arterial blood flow and can lead to strokes and heart attacks.
Dark chocolate and platelets:
The anti-inflammatory effects of cocoa flavonoids can be measured by looking at platelet and endothelial cell activation. Platelets flow to sites of tissue damage and close open wounds to reduce and stop blood loss. However, they also add to the build up around damaged blood vessels; damage that free radicals may casually play a role in.
Atherosclerosis is an inflammatory disease. Platelets can enhance this thickening effect, and progress the atherosclerosis to the final development of arterial thrombosis.
Rein et al. (2000) observed a significant reduction in platelet microparticles 2-6 hours after ingesting flavonoid-rich cocoa beverage. It has also been shown to have an aspirin-like effect, inhibiting epinephrine-induced platelet function and activation (Pearson et al., 2002). Aspirin prevents platelets from building up and forming a clot, thinning the blood, which is beneficial to those at risk for blood clots.
Dark chocolate and eicosanoids:
Eicosanoids are metabolites that mediate the inflammatory processes. They send out signals to induce swelling, redness, and heat. Chocolate flavonoids may regulate the production of eicosanoids (Schramm et al., 2001), negatively affecting inflammation.
Dark chocolate and cytokines:
Cytokines are molecules that send messages out during times of immune response and stimulate the movement of cells towards sites of infection and trauma. They also interact with eicosanoids.
Chocolate flavanols (procyanidins) stimulate anti-inflammatory cytokines and control production of their pro-inflammatory counterparts. In a study on 25 healthy subjects, who ingested 36.9g of dark chocolate and 30.9g of cocoa powder drink for 6 weeks, reduced LDL oxidizability. Low-density lipoproteins, or LDL, have a greater risk of being oxidized by free radicals than HDL. Once LDL are oxidized, they become more reactive with the surrounding tissue, and can lead to blood vessel tissue damage. Once the tissue is damaged, it leads to inflammation in the area that leads to plaque build up and arterial wall hardening, thickening, and decreased blood flow.
Dark Chocolate and CRP:
C-reactive protein, or CRP, is used as a blood test marker for inflammation in the body. It is produced in the liver, and its levels will rise in response to inflammation. Flavonoid-rich foods (such as chocolate) have been shown to be inversely associated with CRP concentrations found in blood serum.
In a 1-week study of participants ingesting 100 g of dark chocolate, CRP levels in women (but not in men) were reduced by 23%. Platelet reactivity and LDL levels also decreased in all participants, with a rise in HDL levels.
di Giuseppe et al. (2008) compared 1317 subjects who ate no chocolate in the past year, with 824 subjects who ate dark chocolate regularly (median intake of 5.7 g dark chocolate per day), and found significant association between serum CRP and dark chocolate consumption. Dark chocolate consumers did somewhat have more healthy dietary habits (eating less meat, refined cereal, and alcohol), but adjustment for these and other factors didn't modify the association that dark chocolate eaters had lower CRP levels, but only slightly decreased the strength of the association. They also observed that consumers of up to one serving (20g) of dark chocolate every 3 days had serum CRP concentrations that were lower than both non-consumers and those who consumed more than 20g every 3 days, suggesting moderation.
di Giuseppe et al. suggest that small doses of dark chocolate could be more effective than higher doses. Since chocolate is high in fat, eating too much could increase total energy and saturated fatty acid intake, which could cancel out or decrease the protective effects of the polyphenols on inflammation.
Dark chocolate consumption, due to its flavanol content, is becoming associated with reducing inflammation, especially in regards to individuals with a high risk of cardiovascular disease. The flavanols, also classified as antioxidants, can interact with molecules and cell communication to decrease vascular inflammation. Although the benefits of chocolate, and even the benefits of antioxidants are still not fully understood and controversial, there appears to be some promise of their effect on reducing risk of cardiovascular disease. di Giuseppe et al. do note that moderation is key, with too much dark chocolate consumption possibly canceling out its benefits at a more moderate level of 5-7 g per day.