Is Dark Chocolate Actually Healthy? What the Evidence Says

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12 min read

Last updated October 24, 2026

Dark chocolate has the best publicist in the food world. For years it has been sold as the rare indulgence that is secretly medicine: good for your heart, your brain, your mood, your waistline. The original version of this article repeated ten of those claims, and some of them were true-ish, some were exaggerated past recognition, and a few were simply not supported by the studies cited for them. This rebuild grades every claim against the primary evidence, and it starts with the part the health halo leaves out: the lead and cadmium that Consumer Reports found in every bar it tested.

Last updated October 24, 2026: Rebuilt from the primary sources. The heavy metals evidence now leads; every benefit claim was graded against its actual study; claims the evidence could not carry (weight loss, skin protection, exercise performance, blood sugar) were removed; the product picks were re-decided from Consumer Reports’ own test tables; references were audited and the unrelated ones deleted.

This article is general information, not medical advice.

The Heavy Metals, First

In December 2022, Consumer Reports published laboratory tests of 28 dark chocolate bars. Every bar contained detectable lead and cadmium, both of which enter cacao from the soil and the environment. Measured against California’s Proposition 65 maximum allowable dose levels, 0.5 micrograms per day for lead and 4.1 micrograms for cadmium, scaled to a one-ounce serving, 23 of the 28 bars exceeded the level for at least one metal, and five were high in both. A second round in 2023, covering 48 chocolate products, found 16 over at least one level. This is not a fringe finding: a 2024 George Washington University study in Frontiers in Nutrition, covering 72 cocoa products across four testing years, found 43 percent exceeded the lead level and 35 percent the cadmium level, with organic products running higher in both.

Now the framing, in both directions, because this topic collects spin from both sides. California’s levels are warning triggers, set with large safety margins, and they are not federal safety limits: the FDA has no cadmium limit for chocolate and no chocolate-specific lead limit, and the GWU researchers found 97.2 percent of products below the FDA’s interim reference level for lead, with median metal levels below the California benchmarks. The GWU authors’ own conclusion was that a single serving may not pose any appreciable risk for the average person. The chocolate industry, through the National Confectioners Association, maintains that its products comply with California law under a settlement and that chocolate is safe to eat and can be enjoyed as treats. That settlement, reached with As You Sow in 2018, set its own concentration benchmarks by cacao content, tightening over time: for bars above 65 and up to 95 percent cacao, lead at 0.150 parts per million initially, dropping to 0.100, and cadmium at 0.450, dropping to 0.400.

Where does that leave a reader? Lead and cadmium are cumulative toxins with no nutritional upside, children and pregnancy raise the stakes, and frequency is the variable you control. Consumer Reports’ own guidance is the sane middle: treat dark chocolate as an occasional food, roughly an ounce at a time, favor the bars that test low, and be sparing or skip it entirely for young children and during pregnancy. The bars that tested low are named in the choosing section below, with their numbers.

Dogs and Chocolate: The Theobromine Warning

What the Evidence Actually Supports

Here is every benefit claim from the original article that survived contact with its own citations, graded. Two distinctions run through the whole table: whether the study fed people chocolate or a concentrated cocoa extract, and whether the outcome was a health event or a short-term measurement.

Four claims from the original ten did not survive and are not in the table, because a table would flatter them: weight loss (the trials show no advantage; one 18-week trial found identical loss in both groups), skin protection from the sun (shown only with specially made high-flavanol chocolate, not conventional bars), exercise performance (a single nine-person crossover study), and blood sugar benefits (no adequate evidence). They were the kind of claims that make a food sound like a supplement, and they are the reason this article needed rebuilding rather than refreshing.

COSMOS: The Big Trial, Read Honestly

The COcoa Supplement and Multivitamin Outcomes Study is the best evidence in this field, and it deserves its numbers stated plainly. It randomized 21,442 older adults to a cocoa extract providing 500 milligrams of flavanols a day, including 80 milligrams of epicatechin, or placebo, and followed them a median of 3.6 years. On the primary outcome, total cardiovascular events, the extract group came in at a hazard ratio of 0.90, a 10 percent lower rate that was not statistically significant (p = 0.11): the trial did not prove its main point. On a secondary outcome, death from cardiovascular disease, the ratio was 0.73, which was significant. And in the per-protocol analysis, counting only participants who actually took the extract as directed, the primary ratio improved to 0.85 and reached significance.

Both results belong in the article, which is why both are here: the intention-to-treat result is the trial’s official answer, and the per-protocol result is a genuine signal about consistent users, with the standard caveat that people who stick to a regimen differ from people who do not. And the distinction that outranks both: COSMOS tested capsules of concentrated extract. Nobody in it ate chocolate bars, and the flavanol dose it delivered is one a bar eater cannot reliably match, for the reason in the next section.

How to Choose a Bar

Start with the number that does not mean what you think. The percentage on a dark chocolate label is the share of cacao solids and cocoa butter, and it says nothing reliable about flavanol content, which is where the supported benefits live. EFSA’s authorized claim is built on 200 milligrams of cocoa flavanols a day, delivered by 2.5 grams of high-flavanol cocoa powder or 10 grams of high-flavanol dark chocolate. Ordinary bars vary enormously, and processing decides much of it: alkalizing cocoa, the Dutching that makes cocoa darker and milder, can strip around 90 percent of the flavanols, with natural cocoa powder carrying roughly 34.6 milligrams per gram against 3.9 in heavily alkalized powder. A gentle rule: high percentage plus minimal processing is the better bet, natural cocoa powder is the most reliable flavanol buy in the aisle, and no label percentage is a flavanol guarantee.

Then choose on the metals. In Consumer Reports’ December 2022 tests, the bars in its “Safer Choices” group came in below California’s warning levels for both metals, expressed here as percentages of those levels per ounce: Mast Organic Dark Chocolate 80% (lead 14%, cadmium 40%), Taza Deliciously Dark 70% (33% and 74%), Ghirardelli Intense Dark 86% (36% and 39%), Ghirardelli Intense Dark Twilight Delight 72% (61% and 96%), and Valrhona Abinao 85% (63% and 73%). The 72% Ghirardelli’s cadmium figure, at 96% of the warning level, is below the line rather than comfortably below it, and it is printed that way here on purpose. Two bars from the old version of this article are gone from the picks because the same tables disqualify them: Lindt Excellence 85% tested at 166% of the lead level, and the Hu bar tested in 2022 was among the highest in lead. Test results describe the bars tested, in that round, in December 2022; sourcing changes, and so can numbers.

Check Price on Amazon: Mast Organic Dark Chocolate 80% (6-pack)

Watchdog Approved

Winston’s Picks: the low-metal bars from Consumer Reports’ December 2022 tests.

Mast Organic Dark Chocolate 80%
The lowest combined metals in the 2022 tests: lead 14% and cadmium 40% of the California warning levels.

Taza Deliciously Dark 70%
Stone-ground and minimally processed: lead 33%, cadmium 74% in the same tests.

Ghirardelli Intense Dark 72% Twilight Delight
Lead 61%, cadmium 96%: below both warning levels, with the cadmium close to the line, as noted above.

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Professor Winston Wants to Know

Our resident watchdog is taking the temperature of the room.

After all that, where do you land on dark chocolate?

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After all that, where do you land on dark chocolate?

A square or two a dayAn occasional treat onlyI switched to cocoa or nibsOff it since the metals news

Cast your voteSee results

Want to say more? The comments below are open.

Questions Readers Ask

So is dark chocolate healthy or not?

It is a confection with a real but modest flavanol benefit and a real heavy metals cost. Eaten occasionally, in ounce portions, from bars that test low, it is a reasonable pleasure. Eaten daily by the barful on the theory that it is health food, it is a misunderstanding of the evidence.

Are the California warning levels the same as federal safety limits?

No. Proposition 65 levels (0.5 micrograms of lead and 4.1 micrograms of cadmium per day) are warning triggers with wide safety margins, the strictest benchmarks in the country. The FDA has no chocolate-specific lead limit and no cadmium limit for chocolate, and in the 2024 GWU study nearly all products fell below the FDA’s interim reference level for lead. Both sets of numbers are in this article because a reader deserves the strict yardstick and the federal context at once.

Is a higher cocoa percentage always better?

No. Percentage measures cacao content, not flavanols, and heavy processing, especially Dutching, can remove most of the flavanols from a high-percentage product. Higher percentage does mean less sugar, which is its own virtue, and it also means more theobromine and often more metal per ounce, which is why the dog warning and the metals table both scale with darkness.

How much chocolate is dangerous for a dog?

Less than most people think, and dark chocolate is the dangerous kind: mild signs start around 20 milligrams of theobromine per kilogram of body weight, and dark semisweet chocolate carries about 5.4 to 5.7 milligrams per gram. Call a veterinarian or ASPCA Poison Control at (888) 426-4435 as soon as you know a dog has eaten it; signs can take 6 to 12 hours to appear.

What about cocoa powder and nibs?

Natural, non-alkalized cocoa powder is the most concentrated reliable flavanol source in the grocery aisle (heavily Dutch-processed powder keeps only a fraction), and it carries no added sugar. The metals story follows the cacao, though, so powder is not a free pass, and dry cocoa powder is the most theobromine-dense product of all for dogs.

For the other half of the chocolate story, the taste half, see our essay on why American chocolate outshines Europe’s best. This article covered what chocolate does in the body; that one covers what it does on the tongue, and the two arguments are better read together.

Sources consulted for this rebuild include Consumer Reports’ dark chocolate tests (December 2022 and 2023), Sesso et al., the COSMOS trial, American Journal of Clinical Nutrition (2022), the George Washington University Frontiers in Nutrition study (2024), EFSA’s cocoa flavanol opinion (2012), the Cochrane review of cocoa and blood pressure, Jia et al. (2010), the As You Sow Proposition 65 settlement (2018), and the Merck Veterinary Manual’s chocolate poisoning reference.