Made from the seeds of cocoa tree, dark chocolate has been shown in clinical studies to improve health and lower the risk of heart disease.

Here are the nutritional facts. A 50 gram bar of dark chocolate with 80 per cent cocoa contains:

• Six grams of fibre,

• 35 per cent of the recommended daily amount for iron

• 30 per cent of the RDA for magnesium

• 45 per cent of the RDA for copper

• 50 per cent of the RDA for manganese.

It also has plenty of potassium, phosphorus, zinc and selenium.

In addition, the fat content of cocoa and dark chocolate is excellent, as these fats are mostly unsaturated.

Dark chocolate also contains stimulants such as caffeine and theobromine, but is unlikely to cause insomnia as the amount is very small compared with coffee.

Antioxidant effects

Dark chocolate is one of the best-known sources of antioxidants. It is loaded with organic compounds that are biologically active and function to fight free radicals.

The latter are molecules responsible for vessel and tissue damage and are incriminated in heart disease, brain decline and cancer development.

These favourable dark chocolate ingredients include polyphenols, flavonols and catechins, among others. ORAC, or oxygen radical absorbance capacity, is a laboratory measure of the antioxidant activity of foods.

While the biological relevance of this metric is questioned because it is done in a test tube and may not have the same effect in the body, it is worth mentioning that unprocessed cocoa beans are among the highest ORAC scoring foods, higher than blueberries and Acai berries.

These same antioxidants appear also to be highly protective against the oxidation of bad cholesterol or LDL. Once oxidised, LDL becomes very sticky and able to build vessel blockages or plaques (atherosclerosis). In a study of about 500 elderly men, cocoa was found to reduce the risk of cardiovascular death by a whopping 50 per cent over a 15-year period.

Another study revealed that eating chocolate two or more times per week lowered the risk of having calcified plaque in the arteries by 32 per cent.

These studies are, however, “observational” and can study an association but cannot prove for certain that it is a causal one ie that chocolate was responsible for the reduction in risk.

The flavonols in dark chocolate can also stimulate the endothelium or the lining of arteries, to produce Nitric Oxide.

One of the functions of NO is to send signals to the arteries to relax, which lowers resistance to blood flow and therefore reduces blood pressure.

Many but not all trials showed that cocoa and dark chocolate can improve hypertension, but the effect is usually mild.

Dark chocolate can also reduce insulin resistance, which is another common risk factor for many conditions like heart disease and diabetes.

Other beneficial effects

Dark chocolate may also boost the function of the brain. One study of healthy volunteers showed that regular consumption of high-flavonol cocoa improved blood flow to the brain, possibly slowing mental decline. It also enhances verbal fluency.

The bioactive compounds in dark chocolate may be good for the skin. The flavonols can protect against sun-induced damage and improve blood flow to the skin, resulting in an increase in skin density and hydration.

The minimal erythemal dose is the minimum amount of ultraviolet B rays, UVBs, required to cause redness in the skin, after 24 hours of sun exposure.

In one study of 30 people, the MED more than doubled after 12 weeks of consuming dark chocolate.

Are all types of chocolate healthy?

When cocoa is processed into chocolate products, it goes through several steps to reduce its rather bitter taste.

The more chocolate is processed, the more flavonols are lost. Most commercial chocolates are highly processed, but the best choices are dark chocolate over milk chocolate, and cocoa powder that has not undergone Dutch alkalisation (not treated to neutralise its natural acidity).

One should watch out for extra ingredients that can add lots of unhealthy extra fat and calories, such as marshmallow, refined sugar, artificial flavours, corn syrup.

So, for now, enjoy moderate portions of chocolate (eg one ounce) a few times per week, and do not forget to eat other flavonoidrich foods such as apples, red wine (also by moderation), tea, onions and berries.

• Joe Yammine is a cardiologist at Bermuda Hospitals Board. He trained at the State University of New York, Brown University and Brigham and Women’s Hospital. He holds five American Board certifications. He was in academic practice between 2007 and 2014, when he joined BHB. During his career in the US, he was awarded multiple teaching and patients’ care recognition awards. The information herein is not intended as medical advice nor as a substitute for professional medical opinion. Always seek the advice of your physician. You should never delay seeking medical advice, disregard medical advice or discontinue treatment because of any information in this article.