Have you ever wondered if dark chocolate is actually heart-healthy? According to many news reports, dark chocolate appears to have many properties to help combat heart disease (1). Can this actually be true or is it media hype?
Antioxidants
Antioxidant is actually a very a broad term referring to hundreds of substances, most notably vitamin C, vitamin E, beta-carotene, vitamin A, lycopene, selenium, lutein and polyphenols. It is found in many foods such as berries, beans, and nuts (2-4). An inevitable byproduct from normal bodily processes (such as digestion and respiration) and environmental contaminants (such as cigarette smoke) is the formation of free radicals. Free radicals are highly unstable molecules that cause “oxidative stress,” which can damage cells and may play a role in many diseases such as Alzheimer’s disease, diabetes, cancer and cardiovascular disease (4). In some studies antioxidants have been shown to counteract free radicals, however, the evidence is mixed (3,4).
The cocoa bean is rich in antioxidant flavonoids (a subclass of polyphenols) (1). Flavonoids are found exclusively in plants and serve to help protect the plant from environmental toxins, microbes, and fungi, along with helping repair damage. Flavonoids have garnered much attention recently and are best known for their possible medicinal purposes such as fighting atherosclerosis, high cholesterol, and certain types of cancers.
Flavonols are the main type of flavonoid found in the cocoa bean (1). Flavonols have antioxidant properties and may serve a role in lowering LDL (bad) cholesterol and improving blood flow to the brain and heart (1).
What Does the Science Say?
There is a lot of anecdotal evidence claiming a flavonoid-rich diet may reduce the risk of cardiovascular disease, inflammation, and high blood pressure. But does research support these claims? Let’s take a closer look at some of the science.
Mennen, et al., performed a cross-sectional analysis on 1,289 women and 1,005 men and found a high consumption of flavonoids “may lower cardiovascular risk through their antioxidant capacity” (5).
Engler et al., states, “Increasing evidence from experimental and clinical studies using cocoa-derived products and chocolate suggest an important role for these high-flavanol-containing foods in heart and vascular protection” (6).
A review by Schneider et al., determined chocolate rich in flavonols can improve endothelial function (lining of blood vessels) and is good for overall cardiovascular health (7).
Allen et al., performed a double-blind, placebo-controlled, cross-over study evaluating the efficacy of dark chocolate on cardiovascular health (i.e., cholesterol, blood pressure). A total of 49 adults completed the study, and the results indicate a low-fat diet in conjunction with dark chocolate consumption may lower cholesterol and improve blood pressure (8).
Hooper et al., found favorable acute and chronic effects of cocoa on blood pressure and flow-mediated dilatation (improved blood flow) and minor favorable effects on LDL and HDL cholesterol (9).
Nogueira et al., performed a clinical trial on overweight hypertensive patients and concluded that dark chocolate high in polyphenols improves endothelial function, however there were no significant changes in blood pressure, blood lipid profile, or percentage of body fat (10).
Lastly, a meta-analysis performed by Ried et al., concluded that flavonol-rich chocolate may lower blood pressure slightly (2-3 mm Hg). However, more long-term random control trials are necessary to determine long-term effects (11).
Take Home Message
As the research indicates, the flavonoids found in the cocoa bean are likely beneficial for your overall cardiovascular health, but science is still trying to determine the extent.
Before running to the convenience store to buy a chocolate bar, it is important to understand that not all forms of chocolate are equal. Most commercial chocolates are heavily processed to improve taste (cocoa is very bitter and pungent). During this processing many of the flavonols are lost (1). It is believed most dark chocolate products have more flavonols retained during processing than milk chocolate; however, it depends on the manufacturing process. But for now, if you desire a piece of chocolate, dark chocolate appears to be your best choice for health.
It is important to note that the optimum beneficial quantity of dark chocolate has not been determined. Cleveland Clinic recommends a moderate portion (one ounce) a few times per week along with other flavonoid-rich foods (i.e., berries, apples, red wine and tea) (1).
References
- Cleveland Clinic. Heart Health Benefits of Chocolate. http://my.clevelandclinic.org/heart/prevention/nutrition/food-choices/benefits-of-chocolate.aspx. Accessed February 3, 2014.
- WebMD. 20 Common Foods with the Most Antioxidants. http://www.webmd.com/food-recipes/20-common-foods-most-antioxidants. Accessed January 29, 2014.
- National Center for Complementary and Alternative Medicine (NCCAM). Antioxidant and Health: An Introduction. http://nccam.nih.gov/health/antioxidants/introduction.htm. Accessed January 29, 2014.
- Harvard School of Public Health. Antioxidants: Beyond the Hype. http://www.hsph.harvard.edu/nutritionsource/antioxidants/. Accessed January 29, 2014.
- Mennen LI, Sapinho D, de Bree A, Arnault N, Bertrais S, Galan P, Hercberg S. Consumption of foods rich in flavonoids is related to a decreased cardiovascular risk in apparently healthy French women. J Nutr. 2004 Apr;134(4):923-6.
- Engler MB, Engler MM. The emerging role of flavonoid-rich cocoa and chocolate in cardiovascular health and disease. Nutr Rev. 2006 Mar;64(3):109-18.
- Schneider, C, Strawbridge E. Chocolate and cardiovascular health. Integrative Medicine. 2012 Oct;15(10):109.
- Allen RR, Carson L, Kwik-Uribe C, Evans EM, Erdman JW Jr. Daily consumption of a dark chocolate containing flavanols and added sterol esters affects cardiovascular risk factors in a normotensive population with elevated cholesterol. J Nutr. 2008 Apr;138(4):725-31.
- Hooper L, Kay C, Abdelhamid A, Kroon PA, Cohn JS, Rimm EB, Cassidy A. Effects of chocolate, cocoa, and flavan-3-ols on cardiovascular health: a systematic review and meta-analysis of randomized trials. Am J Clin Nutr. 2012 Mar;95(3):740-51.
- Nogueira Lde P, Knibel MP, Torres MR, Nogueira Neto JF, Sanjuliani AF. Consumption of high-polyphenol dark chocolate improves endothelial function in individuals with stage 1 hypertension and excess body weight. Int J Hypertens. 2012;2012:147321.
- Ried K, Sullivan TR, Fakler P, Frank OR, Stocks NP. Effect of cocoa on blood pressure. Cochrane Database Syst Rev. 2012 Aug 15;8:CD008893. doi: 10.1002/14651858.CD008893.pub2.