Dark Chocolate—‘Tis the Season of the Guilty Superfood

Dark chocolate, defined as 70% or greater cocoa mass, is a guilty pleasure or a potent superfood, depending on your perspective. Cocoa, known in herbal medicine as Theobroma cacao L., is high in a type of antioxidants called flavonoids; the specific group of these molecules as found in dark chocolate is among the most potent antioxidants in vivo, that is, when consumed by humans or animal studies.^[1] In studies, researchers feed subjects a set amount, usually 20–50 g of dark chocolate, and then draw blood samples to measure changes in actual antioxidant capacity in the blood. Measured in this way, the antioxidant capacity of dark chocolate rivals foods such as berries and fruits.

Nutritional Value

In addition to antioxidants, cocoa is rich in trace minerals. Analysis of dark-chocolate products shows that it is a good source of magnesium (roughly 250 mg per 100 g chocolate) and iron (10 mg per 100 g), as well as up to 3.5 mg zinc and 100 mcg selenium in 90% dark chocolate.^[2]

Metabolic Health

Dark chocolate possesses a host of intriguing metabolic benefits, including lowering blood glucose, elevating HDL (good cholesterol), lowering blood pressure, preventing cholesterol oxidation (which is thought to contribute to atherosclerosis), and improving vascular function.^[3][4][5][6] A 2016 meta-analysis published in the Journal of Nutrition found that cocoa flavonol intake ranging from 166 to 2110 mg per day was associated with improved insulin sensitivity and cholesterol profile.^[7] Cocoa consumption reduced fasting insulin by 2.33 µIU/mL; this shows that cells are better able to employ insulin to use blood glucose for energy. Cocoa is also recognized to decrease levels of a specific compound (C-reactive protein) responsible for causing inflammation (by 0.83 mg/dL). Although these numbers may appear small, they actually represent notable improvements, especially when considering that they are induced by the addition of a single dietary agent.

Theobromine, another component in dark chocolate, is thought to be responsible for reducing the “stickiness” of blood—that is, platelet aggregation—thereby reducing the risk of blood-clot formation.^[8] The 2016 meta-analysis also found that cocoa flavonols decreased a marker of “stickiness” called vascular cell adhesion molecule 1.^[7]

Exercise Capacity

Dark chocolate has been shown to improve exercise capacity and alter muscle structure.^[9][10] A study of 20 otherwise healthy, sedentary individuals randomized them to receive 20 g dark chocolate per day for three months or placebo. Researchers found that treatment with dark chocolate resulted in a 17% increase of V_O₂ max—a measurement of oxygen uptake within the lungs—as well as maximum work (watts) achieved, while there were no changes with placebo.^[9] Dark chocolate increases levels of specific proteins in their active forms that benefit skeletal-muscle structure. This improves strength and smooth-muscle tone to benefit posture and balance. It also increases levels of reduced glutathione within skeletal muscles, which acts as a critical intracellular antioxidant.

In patients with peripheral artery disease (PAD), associated with smoking as well as diabetes, consumption of 40 g dark chocolate decreased markers of oxidative stress (NO_x) and increased maximal walking distance by 11% and maximal walking time by 15%.^[10]

Mood Benefits

Perhaps not so surprisingly, dark chocolate also has documented benefits on mood and mental health. Studies have shown that consumption of flavonol-rich dark chocolate blunted the stress response, including the production of inflammatory cytokines and stress hormones, in men undergoing acute psychosocial stress.^[11] Another study found that consumption of cocoa polyphenols significantly improved mood, with subjects reporting improved “calmness” and “contentedness.”^[12]

One study found that consumption of flavonol-rich chocolate counteracted some of the detrimental effects of sleep deprivation.^[13] While sleep deprivation resulted in increased blood pressure, poorer vascular compliance, and poorer working memory, these effects were significantly mitigated when the women consumed flavonol-rich chocolate.

…Taken with a Grain of Salt

While dark chocolate is associated with many health benefits, a small number of prone individuals may exhibit detrimental effects. For instance, the caffeine content in dark chocolate may lead to overstimulation in some; others may experience aggravation of symptoms such as acid reflux or skin reactions such as eczema. Dark chocolate is also drying to the throat, and persons prone to throat problems such as sore throat or laryngitis may need to lay off if you are feeling run down.

Finally, keep in mind that although rich in antioxidants, dark chocolate is also rich in calories; 30 g or about three squares of Lindt 70% contains 180 calories! You can also reap the benefits of this plant in homemade hot-chocolate beverage made using real cocoa (rather than the commercially available, sugar-loaded hot-chocolate powders). Add a small amount of honey for sweetness. Enjoy this superfood in moderation!

1. da Silva Medeiros, N., et al. “Total phenolic content and antioxidant activity of different types of chocolate, milk, semisweet, dark, and soy, in cerebral cortex, hippocampus, and cerebellum of Wistar rats.” Biochemistry Research International. Vol. 2015 (2015): 294659.
2. Cinquanta, L., et al. “Mineral essential elements for nutrition in different chocolate products.” International Journal of Food Sciences and Nutrition. Vol. 67, No. 7 (2016): 773–778.
3. Almoosawi, S., et al. “The effect of polyphenol-rich dark chocolate on fasting capillary whole blood glucose, total cholesterol, blood pressure and glucocorticoids in healthy overweight and obese subjects.” The British Journal of Nutrition. Vol. 103, No. 6 (2010): 842–850.
4. Grassi, D., et al. “Blood pressure is reduced and insulin sensitivity increased in glucose-intolerant, hypertensive subjects after 15 days of consuming high-polyphenol dark chocolate.” The Journal of Nutrition. Vol. 138, No. 9 (2008): 1671–1676.
5. Mursu, J., et al. “Dark chocolate consumption increases HDL cholesterol concentration and chocolate fatty acids may inhibit lipid peroxidation in healthy humans.” Free Radical Biology & Medicine. Vol. 37, No. 9 (2004): 1351–1359.
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7. Lin, X., et al. “Cocoa flavanol intake and biomarkers for cardiometabolic health: A systematic review and meta-analysis of randomized controlled trials.” The Journal of Nutrition. Vol. 146, No. 11 (2016): 2325–2333.
8. Rull, G., et al. “Effects of high flavanol dark chocolate on cardiovascular function and platelet aggregation.” Vascular Pharmacology. Vol. 71 (2015): 70–78.
9. Taub, P.R., et al. “Beneficial effects of dark chocolate on exercise capacity in sedentary subjects: Underlying mechanisms. A double blind, randomized, placebo controlled trial.” Food & Function. Vol. 7, No. 9 (2016): 3686–3693.
10. Loffredo, L., et al. “Dark chocolate acutely improves walking autonomy in patients with peripheral artery disease.” Journal of the American Heart Association. Vol. 3, No. 4 (2014). pii: e001072.
11. Kuebler, U., et al. “Dark chocolate attenuates intracellular pro-inflammatory reactivity to acute psychosocial stress in men: A randomized controlled trial.” Brain, Behavior, and Immunity. Vol. 57 (2016): 200–208.
12. Pase, M.P., et al. “Cocoa polyphenols enhance positive mood states but not cognitive performance: A randomized, placebo-controlled trial.” Journal of Psychopharmacology. Vol. 27, No. 5 (2013): 451–458.
13. Grassi, D., et al. “Flavanol-rich chocolate acutely improves arterial function and working memory performance counteracting the effects of sleep deprivation in healthy individuals.” Journal of Hypertension. Vol. 34, No. 7 (2016): 1298–1308.