Last reviewed on 12 September 2026.
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This page sets out what the trials found, how much dark chocolate is sensible, what the percentage on the wrapper means, and the less advertised side: sugar, calories, heavy metals and the people for whom chocolate causes trouble.
What is in dark chocolate that might be good for you?
The main candidates are cocoa flavanols, a group of plant compounds that includes epicatechin, present in the cocoa bean in larger amounts than in most foods. In studies they appear to help blood vessels relax and widen, which is the proposed route to lower blood pressure. Dark chocolate also contains magnesium, iron and fibre, because it is made from a seed. The catch is that flavanol content varies enormously between products. Fermentation, roasting and especially alkalising, the step that makes Dutch-process cocoa darker and milder, destroy a large share of them, and labels almost never state the amount.
Does dark chocolate lower blood pressure?
Slightly, yes. A Cochrane review of randomised trials found that cocoa products lowered blood pressure by about 2 mmHg on average compared with a placebo or a low-flavanol product, in trials lasting a few weeks to a few months. The effect appeared larger in people who already had raised blood pressure. Two mmHg is a real but small change, less than cutting down on salt usually achieves, and the trials did not show that it lasts for years or prevents strokes. Many used cocoa drinks or specially made high-flavanol products rather than ordinary chocolate. A high blood pressure diet chart covers changes with far larger effects.
Does dark chocolate protect the heart?
The best trial so far says not clearly. COSMOS, a large randomised trial in the United States, gave about 21,000 older adults either a cocoa extract supplement providing 500 mg of flavanols a day or a placebo, for a median of about three and a half years. The supplement did not significantly reduce total cardiovascular events, the trial's primary outcome. Deaths from cardiovascular causes were lower in the cocoa group, but that was a secondary finding, which counts as a signal for further research rather than proof. The trial deliberately used capsules, not chocolate, to keep sugar and fat out of the comparison.
Why is a chocolate bar not the same as cocoa flavanols?
Because a bar delivers its flavanols along with sugar, fat and calories, and sometimes delivers few flavanols at all. Matching the daily dose used in COSMOS from chocolate would typically take far more than any sensible portion, and because processing varies, even a large amount would not guarantee it. Observational studies that link chocolate eaters with less heart disease cannot separate the chocolate from everything else about people who eat it in moderation. The flavanols are plausible as a benefit. The bar is a treat that happens to carry some of them, and it should be judged as a treat.
What does 70 per cent on the wrapper mean?
It means 70 per cent of the bar's weight comes from the cocoa bean, as cocoa mass, cocoa solids and cocoa butter combined. Most of the remaining 30 per cent is sugar, with small amounts of emulsifier and flavouring. A 50 per cent bar is therefore roughly half sugar, and milk chocolate is typically lower still in cocoa and higher in sugar and milk solids. A higher percentage usually means less sugar and often more flavanols, though processing matters too. Check the ingredient list: cocoa mass should come first, and products that replace cocoa butter with other vegetable fats are best treated as confectionery.
Choosing and sizing a bar
The wrapper tells you most of what you need, if you read past the front of it.
Read the percentage
It is the share of the bar's weight that came from the cocoa bean. Most of the rest is sugar, so a 50 per cent bar is roughly half sugar.
Check the ingredient list
Cocoa mass should come first. A bar that replaces cocoa butter with other vegetable fats is confectionery, whatever the front says.
Set the portion before you open it
About 20 to 30 g, a few squares, giving roughly 120 to 170 kcal.
Count it into the day
Eaten daily, 30 g adds more than 1,000 kcal a week, enough to shift body weight over months if nothing else changes.
Vary what you buy
Lead and cadmium turned up in every bar in one published test, so rotating brands makes more sense than loyalty to one.
How much dark chocolate should you eat in a day?
About 20 to 30 g, a few squares of a typical bar, is a sensible ceiling for regular eating. That portion gives roughly 120 to 170 kcal, because dark chocolate carries about 550 to 600 kcal per 100 g, most of it from cocoa butter and sugar. Eaten daily, 30 g adds more than 1,000 kcal a week, enough to shift body weight over months if nothing else changes. Treating it as a small, planned part of the day's food rather than an extra is what keeps it compatible with weight control. Many people find a 70 per cent bar harder to overeat than a milk one.
Is dark chocolate better than Indian sweets?
Calorie for calorie the difference is small, but it often wins on sugar and on portion. A 25 g serving of 70 per cent dark chocolate carries around 7 to 8 g of sugar, less than a typical piece of syrupy mithai, and its intensity makes a small amount satisfying. Its fat is mainly cocoa butter, which is largely saturated, though its main saturated fat, stearic acid, has a more neutral effect on blood cholesterol than most. The page on calories in Indian sweets gives figures for the sweets it is usually compared with. Neither is a health food, and both fit into a diet in small amounts.
Does dark chocolate contain lead and cadmium?
Many bars do, in small amounts. In a 2022 test, Consumer Reports, an American consumer organisation, measured lead and cadmium in 28 dark chocolate bars and found both metals in every one, with most exceeding a strict Californian safety benchmark for at least one metal at a daily portion of about 28 g. Cadmium is taken up from the soil by the cacao plant, while lead appears to settle on the beans as they dry outdoors. Those bars were sold in the United States, and comparable published testing for the Indian market is limited. The sensible response is moderation and variety, with extra restraint for children and during pregnancy.
How much caffeine is in dark chocolate?
Roughly 20 mg in a 25 g portion of 70 to 85 per cent chocolate, based on USDA figures of about 80 mg per 100 g. That is a fraction of a cup of brewed coffee but enough to register in sensitive people, particularly in the evening. Chocolate also contains theobromine, a milder stimulant related to caffeine, at about ten times the caffeine level. Together they can disturb sleep in some people when eaten late. The page on whether coffee is good or bad for you covers caffeine limits. Theobromine is also why chocolate is poisonous to dogs, even in fairly small amounts.
Can dark chocolate trigger migraines or acid reflux?
It can worsen reflux, and its link with migraine is weaker than its reputation. Chocolate relaxes the valve at the lower end of the oesophagus, which lets stomach acid rise, and it appears on most lists of reflux triggers alongside coffee, fatty meals and mint. For migraine, many sufferers name chocolate as a trigger, but controlled studies have mostly not confirmed it, and some researchers think the craving for sweet food is an early sign of an attack that has already begun. If you suspect a pattern, a food and symptom diary kept for a few weeks will tell you more than any list.
Is dark chocolate safe with diabetes, kidney stones or blood pressure tablets?
In small portions it usually fits a diabetic diet, and it deserves more thought with kidney stones. A few squares of 70 per cent chocolate carry modest sugar and cause a modest rise in blood glucose, while sugar-free bars are not automatically better and their sugar alcohols can upset the stomach. Cocoa is high in oxalate, so people who form calcium oxalate stones are often advised to limit it. Anyone on blood pressure tablets should not treat chocolate as a replacement for them or alter a dose because of it; the doctor who prescribed the medicine is the person to ask about any change.
Learning to read the claims on the wrapper
Cocoa is a textbook case of a real compound with a real mechanism, wrapped in marketing that runs well ahead of the trials. NNWA's Antioxidants and Phytochemicals course teaches that distinction through topics such as how antioxidants work, the phytochemical families, cooking and bioavailability, and myths and marketing. It is an intermediate course of three to four weeks. Learners pay 7,999 rupees, reduced from 11,999, or can spread the cost as 667 rupees a month, and they earn an NNWA certificate rather than a university qualification.
The honest summary
Dark chocolate's clearest benefit is a small, short-term fall in blood pressure from cocoa flavanols, around 2 mmHg. The largest trial of cocoa extract did not significantly cut cardiovascular events, and a bar delivers its flavanols with sugar, fat and calories. Choose 70 per cent or more, keep to 20 to 30 g, and vary what you buy given the heavy metal findings. Enjoy it as a food you like, which is reason enough, rather than as a medicine.