Dark chocolate, sometimes touted as a "super food," is rich in antioxidants. Antioxidants are important to cellular health, generally, and are key to immune function, which appears to be particularly sensitive to the antioxidant-oxidant balance in cells. Direct evidence for chocolate's antioxidant effects on the immune system, however, is slim.
Antioxidants in Chocolate
Antioxidants are part of the body's defense system against free radicals, charged molecules that cause damage by reacting with cell membranes, proteins, DNA and other cell components. Many compounds have antioxidant properties including vitamins, such as vitamin C and vitamin E; minerals, such as zinc and selenium; and other compounds such as beta-carotene and flavonoids. Chocolate, together with tea, red wine, and many fruits and vegetables, contains flavonoids, which have antioxidant properties. A review of chocolate's properties in "Chemistry Central Journal," reported that chocolate, depending on its post-processing cocoa content, is one of the most concentrated sources of dietary antioxidants known.
Antioxidants and the Immune System
According to a report in "Nutrition & Metabolism," there is substantial evidence for the health benefits of flavonoids in cardiovascular disease. However, there is little direct evidence that chocolate's flavonoids protect the immune system. However, the speculation is that because antioxidants are key to a well functioning immune system, and chocolate is particularly rich in antioxidants, it therefore is protective of the immune system.
It is clear that the antioxidant-oxidant balance in immune cells is important to their function. A review in "American Journal of Clinical Nutrition" noted this balance is critical not only to the integrity of the cell membranes, proteins and nucleic acids but for cell communication as well. Cells of the immune system, which appear to be particularly sensitive to the antioxidant-oxidant balance, show oxidative stress and poorer immune function when this balance is disrupted. The authors note that immune cells tend to have higher concentrations of antioxidant nutrients than other cells, and deficiencies in a range of antioxidants could compromise immune function.
Research
The only direct research on the link between chocolate and immune function comes from research in animals. In 2008, researchers reported in the "Journal of Nutritional Biochemistry" that rats fed cocoa-enriched diets showed increased activity in intestinal immune responses for both antibodies and T-helper cells.
Broadly, research shows that dietary antioxidants are needed to maintain the immune response across all age groups. Researchers in the "Journal of Clinical Nutrition" reviewed the literature on the impact of dietary antioxidants on immune function in the elderly. In general, the immune function among elderly subjects is less responsive with signs of oxidative stress. However, research supplementing their diets with various antioxidants showed boosts to their immune systems. Although flavonoids were not included in this review, the role of antioxidants in immune function supports speculation that chocolate's flavonoids might also positively affect immune function.
Considerations
Direct evidence of chocolate boosting immune function is meager but research does show a strong relationship between antioxidants and immune function. Before you reach for that chocolate bar, however, consider that most chocolate undergoes processing---fermenting, roasting, dilution---that strips away much its antioxidant activity. The best options are dark chocolate with a high cocoa content without a lot of additives that either dilute the chocolate or add calories.
References
- "Chemistry Central Journal": Cacao Seeds Are a "Super Fruit": A Comparative Analysis of Various Fruit Powders and Products: Stephen J Crozier, et al: 2011.
- "Nutrition and Metabloism": Chocolate and Prevention of Cardiovascular Disease: A Systematic Review: Eric L Ding, et al: 2006.
- "American Journal of Clinical Nutrition": Antioxidants and Immune Function in Aged Persons: Overview of Present Evidence: Simin Nikbin Meydani, et al; 1995.
- "Journal of Nutritional Biochemistry": Intestinal Immune System of Young Rats Influenced by Cocoa-Enriched Diet: Emma Ramiro-Puig, et al: 2008.
