Dark Chocolate: Health Benefits and How Much

Dark chocolate is one of the few treats with genuine health research behind it. The benefits come from cocoa flavanols — and they are modest. A small square is a better choice than milk chocolate, but it's still a treat.

What the research shows

• Blood pressure: a Cochrane review of controlled trials found that cocoa flavanols lowered blood pressure slightly — on average about 2–3 mmHg systolic, more in people with hypertension.
• Blood vessels: flavanols increase nitric oxide, which helps arteries relax and improves blood flow.
• Heart health: in the large COSMOS trial, a cocoa flavanol supplement did not significantly reduce total cardiovascular events, though cardiovascular deaths were lower — promising but not proof.
• Mood and brain: some studies suggest small benefits for memory in older adults with poor diets; evidence is limited.

Why "dark" matters

Flavanols are in the cocoa solids. The higher the cocoa percentage (70% or more), the more flavanols and the less sugar. Milk chocolate and white chocolate contain few or none. "Dutch-processed" (alkalized) cocoa loses much of its flavanol content.

The downsides

• Calories: about 170 calories and 12 g of fat per ounce (28 g).
• Sugar: even 70% chocolate contains some.
• Heavy metals: tests have found lead and cadmium in some dark chocolate brands. Eating it in moderation and varying brands keeps exposure low; this matters more for children and during pregnancy.
• Caffeine and theobromine can disturb sleep in sensitive people.

A sensible portion

About 1 ounce (20–30 g, a few squares) of 70%+ dark chocolate a few times a week fits into a healthy diet. Unsweetened cocoa powder in oatmeal or yogurt is a lower-sugar way to get flavanols.

More foods with blood pressure benefits: 5 Foods That Help Lower Blood Pressure