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Sweets are tasty, but refined sugar shouldn’t comprise a large part of our diet. Dark chocolate is promoted as a sweet with relative health benefits. Let’s think twice: what’s the evidence that dark chocolate is good for you? 

One of the potential benefits of dark chocolate is its relatively high content of antioxidants. Antioxidants can neutralize the free radicals (molecules that can damage cells) produced during natural metabolic processes, or when we are exposed to smoke, radiation, or other carcinogens (1). It is proposed that ingesting antioxidants can help protect against cardiovascular disease and cognitive decline (2,3).  

The idea that flavanols, the antioxidant agents in dark chocolate, reduce rates of cognitive decline has no support from adequately controlled and randomized experiments (4). The quality of the evidence used to support the claim that flavanols delay cognitive decline is low, such as uncontrolled cohort studies. For example, a study of just 17 participants claimed flavanols increase blood flow to the brain (an indirect outcome) (5).  

A large randomized trial with no placebo arm studied antioxidant supplementation beginning in 1998 and found that cognitive function was perhaps marginally improved over an 18-year period (6). But a placebo-controlled trial found that antioxidant-containing supplements did not protect against dementia (7). As is often the case, better quality evidence often contradicts the findings of less rigorous studies.   

Another claim for antioxidants is that they protect against cardiovascular disease. However, several large studies have shown no difference in cardiovascular outcomes between people taking antioxidant supplements and those taking placebos (8,9). After a careful look, it is questionable whether dark chocolate provides protection against cognitive decline or cardiovascular disease. However, that’s not to say it isn’t still a satisfying sweet! 

References:

1. Lobo V, Patil A, Phatak A, Chandra N. Free radicals, antioxidants and functional foods: Impact on human health. Pharmacogn Rev. 2010;4(8):118-126. doi:10.4103/0973-7847.70902 
2. A flavanol-rich diet may increase brain function. Harvard Health Publishing and Harvard Medical School. March 1, 2021. Accessed July 15, 2023. https://www.health.harvard.edu/mind-and-mood/a-flavanol-rich-diet-may-increase-brain-function 
3. Lobo V, Patil A, Phatak A, Chandra N. Free radicals, antioxidants and functional foods: Impact on human health. Pharmacogn Rev. 2010;4(8):118-126. doi:10.4103/0973-7847.70902 
4. A flavanol-rich diet may increase brain function. Harvard Health Publishing and Harvard Medical School. March 1, 2021. Accessed July 15, 2023. https://www.health.harvard.edu/mind-and-mood/a-flavanol-rich-diet-may-increase-brain-function 
5. Ullah A, Munir S, Badshah SL, et al. Important Flavonoids and Their Role as a Therapeutic Agent. Molecules. 2020;25(22):5243. Published 2020 Nov 11. doi:10.3390/molecules25225243 
6. Panche AN, Diwan AD, Chandra SR. Flavonoids: an overview. J Nutr Sci. 2016;5:e47. Published 2016 Dec 29. doi:10.1017/jns.2016.41 
7. Gratton, G., Weaver, S.R., Burley, C.V. et al. Dietary flavanols improve cerebral cortical oxygenation and cognition in healthy adults. Sci Rep 10, 19409 (2020). https://doi.org/10.1038/s41598-020-76160-9 
8. Grodstein F, Kang JH, Glynn RJ, Cook NR, Gaziano JM. A Randomized Trial of Beta Carotene Supplementation and Cognitive Function in Men: The Physicians’ Health Study II. Arch Intern Med. 2007;167(20):2184–2190. doi:10.1001/archinte.167.20.2184 
9. Kryscio RJ, Abner EL, Caban-Holt A, et al. Association of Antioxidant Supplement Use and Dementia in the Prevention of Alzheimer’s Disease by Vitamin E and Selenium Trial (PREADViSE). JAMA Neurol. 2017;74(5):567–573. doi:10.1001/jamaneurol.2016.5778 
10. Hennekens C., et al. Lack of Effect of Long-Term Supplementation with Beta Carotene on the Incidence of Malignant Neoplasms and Cardiovascular Disease. New England Journal of Medicine. 1996; 334:1145-1149. DOI: 10.1056/NEJM199605023341801 
11. Lee I, Cook NR, Gaziano JM, et al. Vitamin E in the Primary Prevention of Cardiovascular Disease and Cancer: The Women’s Health Study: A Randomized Controlled Trial. JAMA. 2005;294(1):56–65. doi:10.1001/jama.294.1.56 
12. https://www.mooringspark.org/news/the-health-benefits-of-dark-chocolate