No introductions are needed for this highly treasured food that dates back to 2000 BC. At that time, the Maya from Central America, the first connoisseurs of chocolate, drank it as a bitter fermented beverage mixed with spices or wine. Today, the long rows of chocolate squares sitting neatly on your store shelves are the end result of many steps that begin as a cacao pod, larger than the size of your hand. Seeds (or beans) are extracted from the pod and fermented, dried, and roasted into what we recognize as cocoa beans. The shells of the bean are then separated from the meat, or cocoa nibs. The nibs are ground into a liquid called chocolate liquor, and separated from the fatty portion, or cocoa butter. The liquor is further refined to produce the cocoa solids and chocolate that we eat. After removing the nibs, the cocoa bean is ground into cocoa powder that is used in baking or beverages.
Dark chocolate contains 50-90% cocoa solids, cocoa butter, and sugar, whereas milk chocolate contains anywhere from 10-50% cocoa solids, cocoa butter, milk in some form, and sugar. Though dark chocolate should not contain milk, there may be traces of milk from cross-contamination during processing, as the same machinery is often used to produce milk and dark chocolate. Lower quality chocolates may also add butter fat, vegetable oils, or artificial colors or flavors. White chocolate does not contain any cocoa solids and is made simply of cocoa butter, sugar, and milk.
Dark Chocolate and Health
Cocoa is rich in plant chemicals called flavanols that may help to protect the heart. Dark chocolate contains up to 2-3 times more flavanol-rich cocoa solids than milk chocolate. Flavanols have been shown to support the production of nitric oxide (NO) in the endolethium (the inner cell lining of blood vessels) that helps to relax the blood vessels and improve blood flow, thereby lowering blood pressure. [1,2] Flavanols in chocolate can increase insulin sensitivity in short term studies; in the long run this could reduce risk of diabetes. [3,4]
Observational studies support the benefits of cocoa flavanols. The link between blood pressure and high cocoa intake was described in a study of the Kuna Indians, an isolated tribe who live on the Caribbean Coast of Panama.  Hypertension was extremely uncommon in this group, even among older ages, and even with a dietary salt intake that is greater than most Western populations. When the Kuna migrated to urban environments and changed their diets, their rates of high blood pressure increased. Notably, their traditional intake of cocoa as a beverage was very high, at more than five cups daily of either home-grown or Colombian cocoa powder rich in flavanols. The urinary levels of flavanols in the island-dwelling Kuna were significantly higher and their rates of death from heart disease, cancer, and diabetes significantly lower than their counterparts living in urban centers.
Other observational studies suggest a link between high cocoa or chocolate intake of 6 grams daily (1-2 small squares) and a reduced risk of heart disease and mortality, possibly in part by reducing blood pressure and inflammation. [6,7]
Dark chocolate is high in calories (150-170 calories per ounce) and can contribute to weight gain if eaten in excess. However, chocolate, like nuts can induce satiety, so the longer term implications for weight control are not clear. It also contains a moderate amount of saturated fat, which can negatively affect blood lipid levels, though its heart-protective effects from flavanols appear to outweigh the risk. Choosing dark chocolate and eating modest quantities may offer the greatest health benefits.
Should I be concerned about heavy metals in dark chocolate?
Dark chocolate and cocoa powder sometimes contain small amounts of heavy metals like cadmium and lead, naturally found in soil, air, and water. Amounts of metals in these foods depend on the geographic region where the cocoa beans were harvested. Higher cadmium levels have been found in chocolate originating from Latin America compared with Africa (West Africa produces 75% of the world’s cocoa bean supply). [8,9] Lead contamination may occur during manufacturing if cocoa beans and chocolate products are exposed to air, water, or soil containing lead. 
Independent groups that have evaluated different samples of chocolate found that dark chocolate, which contains more cocoa solids, tends to contain more metals than milk chocolate. Also, organic brands do not necessarily contain less metals than non-organic chocolate, sometimes containing more.
Lead poses greater risks in children and the fetuses of pregnant woman. According to the U.S. Environmental Protection Agency, they absorb more lead than adults, and their brains and nervous systems are more sensitive to the damaging effects of lead. Lead exposure can lead to delayed growth, anemia, and behavior and learning problems. In fetuses and infants, lead can harm various organs and cause premature birth. Long-term lead and cadmium exposure in adults can negatively affect the kidneys and nervous system.
The Joint Food and Agriculture Organization/World Health Organization and the U.S. Food and Drug Administration conducted separate studies to assess dietary intakes of cadmium and lead from cocoa and chocolate products in children and adults, and found that these foods were not major sources of cadmium and lead in the diet.  Still, international efforts have been made to reduce metal contamination in cocoa and chocolate. These include establishing maximum levels for cadmium and lead in these foods, and publishing codes of practice for agricultural and manufacturing to prevent and reduce contamination in food.  Examples are:
- Avoiding the purchase of cocoa beans from regions with high cadmium levels
- Avoiding planting in regions with high cadmium
- Establishing quality assurance manufacturing practices that prevent lead contamination of cocoa beans
In January 2019, the European Commission implemented maximum limits for cadmium in cocoa and chocolate products, and denied access to products in European markets that did not meet these standards. The U.S. Food and Drug Administration also set maximum levels for lead in candy that includes chocolate.
Not all brands of dark chocolate are high in cadmium and lead. The links below show testing of various chocolate brands for heavy metal content. (Note: The Nutrition Source does not endorse specific brands, and the inclusion of branded products in these external resources does not constitute an endorsement.)
To reap the health benefits of dark chocolate while minimizing risk, choose brands tested lower in heavy metals and limit to one ounce a day. Those at higher risk for negative side effects such as children and those who are pregnant may wish to eat even smaller amounts and only occasionally.
Purchase and Storage
- Choose 70% dark chocolate or higher to obtain the most flavanols. Though keep in mind that the higher the percentage of cocoa solids, the greater the bitter flavor.
- Store in a cool dry area (65-70 F) in a tightly sealed container. Do not refrigerate, which can promote the chocolate to “bloom,” a whitish coating caused by sugar rising to the surface due to excess moisture. Bloom does not affect flavor but does not look appealing.
- If stored properly, dark chocolate will last up to two years.
- To melt: Dark chocolate should be heated gradually to prevent scorching. This may be done on a stove top on low heat or in a microwave oven on 50% power. Break chocolate into smaller pieces and place in pan or microwave to heat. Stir continually (or after each minute) to ensure even heating. Drizzle 1-2 tablespoons of melted dark chocolate over oatmeal, yogurt, or fresh fruit for an easy healthful snack.
- Serve a few squares of dark chocolate or chocolate curls with fresh fruit and nuts for an easy elegant dessert.
- Blend 1-2 tablespoons of unprocessed cocoa with one large frozen banana for a dairy-free version of chocolate ice cream.
- Because the bitter flavor increases with a higher percentage of cocoa solids, try taking a small piece and allowing it to melt slowly in your mouth. This technique may offer a different, more pleasurable experience than quickly chewing and swallowing the chocolate.
Did You Know?
- Cocoa is sometimes treated with alkali, or Dutch-processed, to improve the flavor and appearance. However this causes a significant loss of flavanols. Natural cocoa, found in the baking aisle, retains the most flavanols. 
- The higher percentage of cocoa solids, the higher the caffeine content. Two ounces of 70% dark chocolate contains about 50-60 mg caffeine. In comparison, an 8-ounce cup of coffee contains 100-200 milligrams of caffeine.
- If your chocolate has developed bloom, no need to throw it out! You can remove the bloom by melting the chocolate, stirring it well, and then allowing it to slowly cool back into a solid.
- Chocolate is derived from an intensive process of farming, harvesting, and transport, often employing less expensive labor or child labor overseas. “Fair-Trade” labeled chocolate certifies that the chocolate has been manufactured at a fair wage and with the exclusion of child labor.
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- Fisher ND, Hughes M, Gerhard-Herman M, Hollenberg NK. Flavanol-rich cocoa induces nitric-oxide-dependent vasodilation in healthy humans. J Hypertens. 2003;21:2281-6.
- Engler MB, Engler MM, Chen CY, et al. Flavonoid-rich dark chocolate improves endothelial function and increases plasma epicatechin concentrations in healthy adults. J Am Coll Nutr. 2004;23:197-204.
- Grassi D, Desideri G, Mai F, et al. Cocoa, glucose tolerance, and insulin signaling: cardiometabolic protection. J Agric Food Chem. 2015;63:9919-26.
- Hooper L, Kay C, Abdelhamid A, et al. 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;95:740-51.
- Hollenberg NK, Fisher ND, McCullough ML. Flavanols, the Kuna, cocoa consumption, and nitric oxide. J Am Soc Hypertens. 2009;3:105-12.
- Buijsse B, Feskens EJ, Kok FJ, Kromhout D. Cocoa intake, blood pressure, and cardiovascular mortality: the Zutphen Elderly Study. Arch Intern Med. 2006;166:411-7.
- Buijsse B, Weikert C, Drogan D, Bergmann M, Boeing H. Chocolate consumption in relation to blood pressure and risk of cardiovascular disease in German adults. Eur Heart J. 2010;31:1616-23.
- Abt E, Fong Sam J, Gray P, Robin LP. Cadmium and lead in cocoa powder and chocolate products in the US Market. Food Additives & Contaminants: Part B. 2018 Apr 3;11(2):92-102.
- Abt E, Robin LP. Perspective on cadmium and lead in cocoa and chocolate. Journal of agricultural and food chemistry. 2020 Apr 15;68(46):13008-15.
- Rankin CW, Nriagu JO, Aggarwal JK, Arowolo TA, Adebayo K, Flegal AR. Lead contamination in cocoa and cocoa products: isotopic evidence of global contamination. Environmental health perspectives. 2005 Oct;113(10):1344-8.
- Miller KB, Hurst WJ, Payne MJ, et al. Impact of alkalization on the antioxidant and flavanol content of commercial cocoa powders. J Agric Food Chem. 2008;56:8527-33.
Last reviewed March 2023
The contents of this website are for educational purposes and are not intended to offer personal medical advice. You should seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website. The Nutrition Source does not recommend or endorse any products.