# Is dark chocolate good for you? The nutrition, the trials and the heavy metals

Dark chocolate has a healthy reputation, and some of it is earned. Here’s what an ounce really gives you, what the biggest cocoa trial found, what tests turned up about lead and cadmium, and how to pick a bar.

Source: https://nourishandstrong.com/is-dark-chocolate-good-for-you
Published: 2026-11-08
Updated: 2026-11-08
By: the Nourish & Strong team
General information, not medical advice.

**The short answer:** dark chocolate can be good for you in small amounts, as a treat with a few real perks. An ounce of 70% to 85% dark chocolate has 3 grams of fiber, 19% of the Daily Value for iron and 170 calories, USDA data show. Cocoa lowered blood pressure by about 2 points in trials, but it also brings sugar, saturated fat and traces of lead and cadmium.

Cocoa beans are rich in plant compounds called flavanols, which help blood vessels relax, Harvard’s Nutrition Source explains. Dark chocolate has more cocoa solids than milk chocolate, so it has more flavanols. How much benefit reaches you depends on the bar, the amount and what else you eat that day.

## Is dark chocolate good for you?

Dark chocolate is good for you in the sense that it carries more fiber and minerals than most sweets, and less sugar the darker it gets. The cacao percentage changes almost everything. Here’s one ounce (28 grams, about a third of a typical bar) of each type, from USDA FoodData Central:

| Per 1 oz (28 g) | Milk chocolate | Dark, 45% to 59% | Dark, 60% to 69% | Dark, 70% to 85% |
| --- | --- | --- | --- | --- |
| Calories | 152 | 155 | 164 | 170 |
| Sugars | 14.6 g | 13.6 g | 10.4 g | 6.8 g |
| Fiber | 1.0 g | 2.0 g | 2.3 g | 3.1 g |
| Saturated fat | 5.2 g | 5.2 g | 6.2 g | 6.9 g |
| Iron | 0.7 mg (4% DV) | 2.3 mg (13% DV) | 1.8 mg (10% DV) | 3.4 mg (19% DV) |
| Magnesium | 18 mg (4% DV) | 41 mg (10% DV) | 50 mg (12% DV) | 65 mg (15% DV) |
| Caffeine | 6 mg | 12 mg | 24 mg | 23 mg |

Source: USDA FoodData Central (SR Legacy). Percent Daily Values use the FDA’s Daily Values of 18 mg for iron and 420 mg for magnesium. Brands vary, so check your own label.

Two things stand out. Going from milk chocolate to a 70% to 85% bar cuts the sugar by more than half and triples the fiber. The calories barely move, because fat rises as sugar falls. Saturated fat climbs too: an ounce of the darkest bar has about a third of the FDA’s 20-gram Daily Value.

## How much dark chocolate should you eat a day?

There’s no official amount of dark chocolate to eat a day, but about 1 ounce is a sensible ceiling. Harvard’s Nutrition Source suggests keeping to an ounce a day, partly because of heavy metals. Consumer Reports goes further and suggests a serving a few days a week rather than every day.

Less may be enough. Harvard notes that observational studies linked about 6 grams a day, one or two small squares, with lower heart disease risk. Those studies show a link and can’t prove cause.

Sugar is the other reason to keep it small. The American Heart Association suggests no more than about 6 teaspoons (24 grams) of added sugar a day for most women and 9 teaspoons (36 grams) for most men, as Harvard summarizes it. An ounce of 70% to 85% chocolate uses up 6.8 grams of that. An ounce of milk chocolate uses 14.6. If you’re keeping an eye on your blood sugar, our guide to [normal blood sugar levels](https://nourishandstrong.com/normal-blood-sugar-levels) explains the numbers to watch.

## Is dark chocolate good for your heart?

Dark chocolate may help your heart a little, mainly through blood pressure, but the strongest trial didn’t prove it prevents heart attacks or strokes. The research comes in two parts.

**Blood pressure.** A Cochrane review of 35 trials with 1,804 mostly healthy adults found flavanol-rich cocoa lowered blood pressure by about 1.8/1.8 mm Hg over 2 to 18 weeks. The reviewers rated the evidence moderate. Our guide to [foods that lower blood pressure](https://nourishandstrong.com/foods-that-lower-blood-pressure) puts that next to foods with bigger effects, and [how to lower blood pressure](https://nourishandstrong.com/how-to-lower-blood-pressure) covers the rest.

**Heart attacks and strokes.** The COSMOS trial gave 21,442 older US adults either a cocoa extract capsule with 500 mg of flavanols a day or a placebo, for a median of 3.6 years. Published in 2022, it found:

- Total cardiovascular events were 10% lower with cocoa extract, but that result wasn’t statistically significant (410 events vs 456).
- Deaths from cardiovascular disease were 27% lower, a secondary result.
- There were no safety concerns.

The authors called for more research. Keep in mind that COSMOS used a capsule and didn’t test chocolate. The Cochrane trials gave 30 to 1,218 mg of flavanols a day, in 1.4 to 105 grams of cocoa products. Getting high doses from chocolate bars would also mean a lot of sugar and calories.

## Does dark chocolate have heavy metals?

Yes, dark chocolate usually has small amounts of lead and cadmium. Consumer Reports found both metals in every bar and product it tested, in two rounds of testing.

| Consumer Reports test | What was tested | Above CR’s level of concern |
| --- | --- | --- |
| December 2022 | 28 dark chocolate bars | 23 bars for lead or cadmium at 1 oz a day; 5 for both |
| October 2023 | 48 chocolate products in 7 categories | 16 of 48 overall |
| October 2023, dark bars | 7 bars | 5 of 7 |
| October 2023, milk chocolate bars | 5 bars | 0 of 5 |
| October 2023, hot chocolate mixes | 6 mixes | 4 of 6, for lead |
| October 2023, cocoa powder | Several powders | 2 high in lead, none high in cadmium |

Source: Consumer Reports, December 15, 2022 and October 25, 2023. CR measured against California’s limits of 0.5 micrograms of lead and 4.1 micrograms of cadmium a day, which it calls the most protective available. There are no federal limits for most foods, so these results compare products with each other. They don’t show a bar breaks the law. The FDA told CR that chocolate is a minor source of these metals internationally.

Where the metals come from matters. Cadmium is taken up from the soil as the tree grows, and CR found it tends to rise with cacao percentage. Lead gets onto the beans after harvest, from dust while they dry in the sun. Organic bars weren’t safer in CR’s 2022 tests, and a 2024 study CR reported on found organic products tended to have higher levels.

The risk is greatest for pregnant people and young children, CR says, because the metals can affect brain development. If that’s your household, keep dark chocolate small and occasional.

## Does dark chocolate have caffeine?

Yes, dark chocolate has caffeine, about 12 to 24 mg per ounce depending on the cacao percentage, USDA data show. An 8-ounce cup of coffee has 100 to 200 mg, Harvard notes. Milk chocolate has about 6 mg, and a tablespoon of unsweetened cocoa powder about 12 mg. For most adults, the FDA cites 400 mg a day as an amount not generally linked with harmful effects.

If you’re sensitive, a few squares after dinner could still matter. Our guide on [how long caffeine lasts](https://nourishandstrong.com/how-long-does-caffeine-last) explains why timing counts, and [are energy drinks bad for your heart](https://nourishandstrong.com/are-energy-drinks-bad-for-your-heart) shows how much bigger other sources are.

## What dark chocolate is healthiest?

The healthiest dark chocolate is a bar with a high cacao percentage, little added sugar, a short ingredient list and lower tested levels of heavy metals. Here’s how to choose in the store:

- **Look for 70% or higher.** Harvard suggests 70% for the most flavanols, and the table above shows sugar dropping as the percentage rises.
- **Read the Added Sugars line.** Compare bars per ounce. Lower is better.
- **Scan the ingredients.** Harvard says lower-quality bars may add butterfat, vegetable oils, or artificial colors or flavors. A short list is easier to judge.
- **Watch for "processed with alkali."** This Dutch processing smooths the taste but strips flavanols. In one lab survey, natural cocoa powder averaged 34.6 mg of flavanols per gram and heavily alkalized powder 3.9 mg.
- **Check test results.** Consumer Reports publishes which products tested lower. If you can’t find yours, CR suggests a slightly lower percentage, such as 70% over 80%, because cadmium tends to rise with cacao. That isn’t foolproof.
- **Switch brands now and then,** CR advises, so one high-metal product isn’t your only source.

Natural unsweetened cocoa powder is another option. A tablespoon has 12 calories, 2 grams of fiber and almost no sugar, USDA data show. Stir it into yogurt or oatmeal, or try the cocoa bites and mousse in our [healthy Christmas treats](https://nourishandstrong.com/healthy-christmas-treats).

## Your next step

Look at the bar in your cupboard. Note the cacao percentage and the added sugar per ounce, and compare it with the table above. Then break off one ounce, put the rest away and enjoy it slowly with fruit or nuts. If you’re weighing other sweet swaps, our guide to [whether honey is healthier than sugar](https://nourishandstrong.com/is-honey-healthier-than-sugar) runs the same numbers for honey. For more desserts built on fruit, The Banana Book has 60 simple recipes.

## Quick questions

### Is dark chocolate high in iron?

Yes, dark chocolate is fairly high in iron for a sweet. One ounce of 70% to 85% dark chocolate has about 3.4 mg, or 19% of the FDA’s 18 mg Daily Value, according to USDA data. Milk chocolate has about 0.7 mg. That ounce also brings about 170 calories and 7 grams of sugars.

### Does dark chocolate have magnesium?

Yes, dark chocolate has magnesium. One ounce of 70% to 85% dark chocolate has about 65 mg, which is 15% of the FDA’s 420 mg Daily Value, USDA data show. Unsweetened cocoa powder has about 27 mg per tablespoon with almost no sugar, so it’s a lighter way to get some.

### Is dark chocolate good for high blood pressure?

Dark chocolate and cocoa may lower blood pressure slightly. A Cochrane review of 35 trials found flavanol-rich cocoa lowered it by about 1.8/1.8 mm Hg over 2 to 18 weeks, mostly in healthy adults. That’s a small effect, and many trials used flavanol-rich cocoa products rather than ordinary candy bars.

### Is organic dark chocolate lower in heavy metals?

No, organic dark chocolate isn’t reliably lower in heavy metals. Consumer Reports found organic bars weren’t safer in its 2022 tests, and a 2024 study it reported on found organic chocolate products tended to have higher levels. Choosing products with lower test results and varying brands helps more.

### Is dark chocolate healthier than milk chocolate?

Dark chocolate of 70% or more has less than half the sugar, three times the fiber and far more iron and magnesium than milk chocolate, USDA data show. Milk chocolate bars tested lower in lead and cadmium in Consumer Reports’ 2023 tests, though, so both are best kept small.

### Does dark chocolate have sugar?

Yes, most dark chocolate has added sugar. One ounce has about 6.8 grams of sugars at 70% to 85% cacao and 13.6 grams at 45% to 59%, according to USDA data. The higher the cacao percentage, the less room is left for sugar, so check the Added Sugars line on the label.

This article is general information, not medical advice. If you’re pregnant, feeding young children, or have a heart condition, high blood pressure or caffeine sensitivity, ask your doctor or dietitian how chocolate fits your diet. Don’t change any medicine without talking to your doctor.

## Sources

- [USDA FoodData Central. SR Legacy: Chocolate, dark, 45-59%, 60-69% and 70-85% cacao solids; Candies, milk chocolate; Cocoa, dry powder, unsweetened](https://fdc.nal.usda.gov/)
- [Harvard T.H. Chan School of Public Health, The Nutrition Source. Dark Chocolate](https://nutritionsource.hsph.harvard.edu/food-features/dark-chocolate/)
- [Harvard T.H. Chan School of Public Health, The Nutrition Source. Added Sugar](https://nutritionsource.hsph.harvard.edu/carbohydrates/added-sugar-in-the-diet/)
- [Sesso HD et al. Effect of cocoa flavanol supplementation for the prevention of cardiovascular disease events: the COSMOS randomized clinical trial. Am J Clin Nutr, 2022](https://doi.org/10.1093/ajcn/nqac055)
- [Ried K et al. Effect of cocoa on blood pressure. Cochrane Database of Systematic Reviews, 2017](https://doi.org/10.1002/14651858.CD008893.pub3)
- [Miller KB et al. Impact of alkalization on the antioxidant and flavanol content of commercial cocoa powders. J Agric Food Chem, 2008](https://doi.org/10.1021/jf801670p)
- [Consumer Reports. Lead and Cadmium Could Be in Your Dark Chocolate (December 15, 2022)](https://www.consumerreports.org/health/food-safety/lead-and-cadmium-in-dark-chocolate-a8480295550/)
- [Consumer Reports. A Third of Chocolate Products Are High in Heavy Metals, CR's Tests Find (October 25, 2023)](https://www.consumerreports.org/health/food-safety/a-third-of-chocolate-products-are-high-in-heavy-metals-a4844566398/)
- [Consumer Reports. Lead and Cadmium Are Common in Chocolate, Especially Organic (2024)](https://www.consumerreports.org/health/food-safety/lead-and-cadmium-are-common-in-chocolate-especially-organic-a1042224604/)
- [FDA. Spilling the Beans: How Much Caffeine Is Too Much?](https://www.fda.gov/consumers/consumer-updates/spilling-beans-how-much-caffeine-too-much)
- [FDA. Daily Value on the Nutrition and Supplement Facts Labels](https://www.fda.gov/food/nutrition-facts-label/daily-value-nutrition-and-supplement-facts-labels)