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Analyses Performed


190 analytical tests on 11 best-selling dark chocolates in the United States.
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Must-see Statistic


All products failed at least one of four heavy metal screenings for arsenic, cadmium, lead, and mercury.
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Unconventional Wisdom


Products measured caffeine levels ranging from 16 mg/serving to 42 mg/serving.

Testing Summary

Labdoor analyzed 11 best-selling dark chocolates for theobromine, caffeine, flavonoids, phenylethylamine, nutrition, and heavy metal (arsenic, cadmium, lead, mercury) contamination.

Of the 11 products tested, eight reported a claim for % cacao. Based on our estimates, we concluded that those eight products met their % cacao claims. All but one product exceeded 170 kcal/serving, the recommended calories in a "sweet snack" based on US federal health data. All products exceeded the "sweet snack" recommendation for sugar of 4.25 g/serving1,2,3. About a third of the products measured more than 10% of the daily value for iron for most adults in a single serving. On average, products recorded 30 mg/serving of caffeine, 283 mg/serving of theobromine, a mild stimulant8, and 154 mg/serving of flavonoids, compounds that might help with chronic disease prevention9.

All products failed at least one of four heavy metal screening for arsenic, cadmium, lead, and mercury4. Only one product recorded any additives that were listed in CSPI's (Center for Science in the Public Interest) list of additives to "avoid"5.


Label Accuracy

Small bottle with magnifying glass Based on our best estimates, the eight products that reported % cacao had the % cacao they claimed.

Eight of 11 products in this testing batch reported a claim for % cacao, either on product labels or after we contacted their manufacturers. We concluded that based on our best estimates, those eight products met their label claims for % cacao.

Because cacao is a mixture of ingredients and different processing methods affect this composition, a standard for testing % cacao has not yet been established. We estimated % cacao using the following methods:

First, we used published research to build a statistical model of how theobromine content relates to cacao content (line fit was 0.85 R-squared), and then we estimated % cacao from there using our own measured theobromine values6. Secondly, we estimated cacao content by subtracting out weights of all other ingredients from each product's total serving size weight assuming FDA labelling rules7. Estimates from these two methods were averaged to provide a final estimation of the product's % cacao within a range of error, and this was compared to label claims, if available.


Product Purity

Microscope All products passed screenings for arsenic, cadmium, lead, and mercury.

All products failed at least one of four heavy metal screenings for arsenic, cadmium, lead, and mercury. Four products failed both cadmium and lead screenings. Three products measured more than double the California Proposition 65 MADL (Maximum Allowable Dose Level) for safe daily cadmium consumption in a single serving. California Proposition 65 publishes proposed and established limits for safe consumption of heavy metals in a full day. A product passes heavy metal screenings if its heavy metal levels in one serving do not meet or exceed those daily limits4.


Nutritional Value

Fruits Products measured 4% to 50% of the daily value (DV) for iron for most adults in one serving.

Based on data from federal health organizations, a "sweet snack" for an adult typically consists of at least 8.5% of a day's worth of fiber (1.7 g), protein (2.4 g), and vitamins and minerals (based on NIH recommendations2), as well as no more than 8.5% of a day's worth of calories (170 kcal), fat (6.6 g), saturated fat (1.9 g), carbohydrates (25.5 mg), sugar (4.25 g), sodium (108 mg), or cholesterol (25.5 mg)1,3.

Overall, products measured an average of 218 kcal/serving, ranging from 170 kcal/serving in Cadbury Royal Dark to 290 kcal/serving in Trader Joe's Dark Chocolate. In addition, products measured an average of 18 g of sugar per serving, ranging from 10 g/serving in Ghirardelli Twilight Delight Intense Dark to 24 g/serving in M&M's Dark Chocolate Candies. All but one product met the "sweet snack" recommendation for iron in one serving. Godiva 72% Cacao Dark Chocolate Bar had the most iron, measuring 61 % of the daily value for iron for most adults in a single serving2.


Ingredient Safety

Caution sign Only one product recorded any additives listed on CSPI's list of additives to "avoid".

Products were penalized for additives based on the Center for Science in the Public Interest (CSPI)'s safety ratings for additives. Only one product recorded any additives on CSPI's "avoid" list. M&M's Dark Chocolate Candies recorded artificial food dyes linked to adverse health effects like behavioral problems in children and allergic reactions5.


Projected Efficacy

Line with arrow going up Products measured an average of 154 mg of flavonoids per serving.

CAFFEINE: Products measured an average of 30 mg of caffeine per serving. For scoring purposes, caffeine measurements were compared to caffeine in half a cup of coffee, which has about 48 g8.

THEOBROMINE: Products measured an average of 283 mg of theobromine per serving. Theobromine is a precursor of caffeine and a mild stimulant. For scoring purposes, theobromine measurements were compared to theobromine in 100% pure eating chocolate, which has about 518 mg per 100 g of chocolate6.

FLAVONOIDS: Products measured an average of 154 mg of flavonoids per serving. The class of compounds known as polyphenols, which includes flavonoids, has been found in several research studies to contribute to the prevention of chronic diseases like cardiovascular disease, cancers, and osteoporosis. For scoring purposes, flavonoid measurements were compared to flavonoids in 100% pure eating chocolate, which has about 103 mg per 100 g of chocolate9.

PHENYLETHYLAMINE (PEA): Products measured an average of 0.7 mg of PEA per serving. PEA is a mood-enhancing compound that is quickly broken down into inactive components upon consumption10,11. After extensive research, we've concluded that there isn't enough evidence yet for an effective dosing recommendation for PEA in humans.


Sources

  • 1ODPHP. (2016). Scientific Report of the 2015 Dietary Guidelines Advisory Committee.
  • 2NIH. (2017). Dietary Supplement Fact Sheets.
  • 3WHO. (2015). Guideline: Sugars Intake in Adults and Children.
  • 4OEHHA. (2016). Proposition 65.
  • 5CSPI. (2016). Chemical Cuisine.
  • 6USDA. (2017). Nutrient Lists - Theobromine.
  • 7FDA. (2016). CFR - Code of Federal Regulations Title 21.
  • 8Ludwig IA, et al. (2014). Variations in caffeine and chlorogenic acid contents of coffees: what are we drinking?. Food & Function. 5:1718-1726.
  • 9Engler MB, et al. (2003). Flavonoid-Rich Dark Chocolate Improves Endothelial Function and Increases Plasma Epicatechin Concentrations in Healthy Adults. Journal of the American College of Nutrition. 3:197-204.
  • 10Janssen PA, et al. (1999). Does phenylethylamine act as an endogenous amphetamine in some patients?. Int J Neuropsychopharmacol. 2(3):229-240.
  • 11Irsfeld M, et al. (2013). B-phenylethylamine, a small molecule with a large impact. Webmedcentral. 4(9):pii4409.