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Dark Chocolate and Cocoa as Food: Research, Sugar and Metals

What trials and cohort studies found about dark chocolate and cocoa foods, how they differ from cocoa-extract supplements, and the sugar, caffeine and cadmium points to know.

Content last updated . This page has not been medically reviewed.

Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.

Overview

Cocoa comes from the seeds of Theobroma cacao L. [1] Chocolate and cocoa powder contain flavanols (a group of plant compounds), caffeine, fat and, in most chocolate, sugar. This page is about cocoa and dark chocolate as foods. Cacao as an ingredient (nibs, butter, powders) is in Cacao and Cocoa.

Food or extract matters. A trial of a cocoa-extract capsule is not evidence about a chocolate bar, and the amount of flavanols in a bar varies. Keep the two apart as you read.

What the research shows

QuestionWhat the source foundStrength of evidencePopulation and form studied
Blood pressureA Cochrane review of 35 randomized trials found a small drop with flavanol-rich cocoa products (systolic -1.76 mmHg, diastolic -1.76 mmHg), mainly in trials of 2 to 18 weeks. The reviewers rated the evidence moderate quality, and found no significant difference in people with normal blood pressure. [2]Promising but limitedMainly healthy adults; cocoa products and chocolate vs low-flavanol or flavanol-free controls
Blood fatsA meta-analysis of 10 trials (320 people, 2 to 12 weeks) found lower LDL and total cholesterol with dark chocolate or cocoa products, and no clear effect on HDL or triglycerides. [3]Promising but limitedDark chocolate or flavanol-rich cocoa in short trials
Cardiometabolic markersA 2024 meta-analysis of 31 trials of cocoa extract or dark chocolate with at least 70% cocoa found no effect on weight, waist, triglycerides, HDL or HbA1c, but lower total and LDL cholesterol, fasting glucose and blood pressure. [4]Promising but limited; biomarkers, not clinical outcomesAdults; extract and chocolate combined
Heart events, extractIn the COSMOS trial (21,442 older US adults), a cocoa-extract supplement did not significantly reduce total cardiovascular events but reduced cardiovascular death by 27%. [5]Mixed; supplement, not foodAdults 60 or 65 and over; 500 mg flavanols a day as a capsule, median 3.6 years
Chocolate and deathsA cohort study of 27,111 men plus an updated meta-analysis linked more chocolate with lower mortality. The intake came from food questionnaires. [6]Observational association, not proofMainly men; chocolate types mixed

Cocoa trials measure changes in blood pressure and cholesterol numbers; none of the sources above show that eating chocolate prevents heart disease. Proper evidence not found (searched PubMed for randomized trials of chocolate bars against heart attack or stroke) for such trials. The Cochrane reviewers also noted that excluding trials with industry-employed authors gave a slightly smaller effect. [2]

Sugar, fat, caffeine and metals

  • Sugar and fat: the trials above tested set amounts of flavanol-rich cocoa products, so a typical sweet bar may not be the same exposure. Dark chocolate contains saturated fat and is a source of calories. [3] See Added Sugars, Sodium and Saturated Fat on Labels.
  • Caffeine: the NHS lists less than 25 mg in a 50 g bar of plain dark chocolate and less than 10 mg in the same size of plain milk chocolate. [7] Official limits are on Caffeine in Foods and Drinks.
  • Metals: a study of 155 milk and dark chocolates from the Serbian market found cadmium between 0.010 and 0.29 mg/kg; weekly intakes were below tolerable limits for all samples, but in some samples reached about 61% to 64% of the limit for toddlers and other children. [8] That is one country and one study. The topic is covered in Heavy Metals and Contaminants in Food.
  • Allergy and other points: chocolate may carry milk, nut or soy ingredients; read labels. [9]
  • Medicines and pregnancy: not described in the sources we read for chocolate as food beyond caffeine. Ask a pharmacist or clinician.

Related

Coffee · Polyphenols and Flavonoids in Foods · Cacao and Cocoa

Frequently asked questions

Is dark chocolate good for you?

Short trials found small improvements in blood pressure and cholesterol numbers, and cohort studies link chocolate with lower mortality, but these results do not show it prevents disease. [2][3][6]

How much dark chocolate should I eat?

Sources we read do not give a recommended amount of chocolate. Trials used set amounts of cocoa products or extracts, which varied widely (the Cochrane trials used 1.4 to 105 g of cocoa products a day). [2] Ask your clinician or dietitian.

Is cocoa powder or a cocoa supplement better than chocolate?

No head-to-head comparison was found. The large COSMOS trial tested a capsule, not food. [5]

Does dark chocolate contain caffeine?

Yes, but less than coffee; the NHS lists under 25 mg in a 50 g bar of plain dark chocolate. [7]

Does chocolate contain heavy metals?

One study of chocolates on the Serbian market found cadmium in all samples, below tolerable weekly limits overall. [8] Read Heavy Metals and Contaminants in Food.

References
  1. GBIF Secretariat. GBIF Backbone Taxonomy species match for Camellia sinensis (L.) Kuntze, Theobroma cacao L., Coffea arabica L. and Coffea canephora Pierre ex A.Froehner (all status ACCEPTED, exact match). Read 2026-10-23.
  2. Effect of cocoa on blood pressure (Cochrane review). Cochrane Database Syst Rev 2017. PMID 28439881. Read 2026-10-23.
  3. Effects of cocoa products/dark chocolate on serum lipids: a meta-analysis. Eur J Clin Nutr 2011. PMID 21559039. Read 2026-10-23.
  4. Effects of Cocoa Consumption on Cardiometabolic Risk Markers: Meta-Analysis of Randomized Controlled Trials. Nutrients 2024. PMID 38931273. Read 2026-10-23.
  5. Effect of cocoa flavanol supplementation for the prevention of cardiovascular disease events: the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) randomized clinical trial. Am J Clin Nutr 2022. PMID 35294962. Read 2026-10-23.
  6. Relationship between chocolate consumption and overall and cause-specific mortality, systematic review and updated meta-analysis. Eur J Epidemiol 2022. PMID 35460393. Read 2026-10-23.
  7. NHS (UK). Foods to avoid in pregnancy. Last reviewed 15 June 2026. Read 2026-10-23.
  8. Impact of Chocolate Cadmium on Vulnerable Populations in Serbia. Foods 2024. PMID 39796308. Read 2026-10-23.
  9. U.S. Food and Drug Administration. Food Allergies. Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.