Dark chocolate and stroke risk in women

A weekly intake of a minimum 45 grams (1.6 ounces) of chocolate containing at least 30% of cocoa, or dark chocolate, is linked to a lower stroke incidence in women, showed a study.

The study was led by Susanna C. Larsson, PhD, of Division of Nutritional Epidemiology, National Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.

“We followed 33,000 women over the course of 10 years, and we found that those who ate most chocolate had a much lower risk – 20 per cent lower – of suffering a stroke,” she said.

The study, performed by Susanna Larsson, Jarmo Virtamo, and Alicja Wolk, was published in the Journal of the American College of Cardiology.

In 1997, 33,372 women, age 49 to 83 years, were enrolled and followed up around 10.4 years. The subjects completed questionnaires about their diet and lifestyle.

There were 1,549 strokes over the following ten years, 1,200 cerebral infarctions (a blood vessel in the brain is blocked, starving an area of the brain of blood), 224 hemorrhagic strokes (bleeding in the brain), and 125 unspecified strokes. Among the persons with more 45 grams (1.6 ounces) dark chocolate intake per week, there were 2.5 strokes per 1,000 women per year. In the same time there were 7.8 strokes per 1,000 women among those with less than 8.9 grams (0.31 ounces) a week intake. A stronger association, not explained yet, was observed for hemorrhagic stroke than for cerebral infarction (ischemic stroke). Only women with chocolate consumption around 66.5 g (2.35 ounces)/week had a significantly reduced risk of stroke. The study does not point out the type of chocolate eaten by the women, but mention that in the 1990s around 90% of chocolate in Sweden was milk chocolate, containing about 30% cocoa solids.

“Cocoa contains flavonoids, which have antioxidant properties and can suppress oxidation of low-density lipoprotein which can cause cardiovascular disease,” said Professor Larsson.

In the United States there are around 800,000 strokes every year. Among them, one of six dies and lots remain disabled. Antihypertensive drugs (medicine to lower high blood pressure), quitting smoking, adequate exercise, and healthy diet are the remedies doctors recommend. The chocolate, even dark chocolate, is not included.

The beneficial effects of dark chocolate on human health were highlighted over the years.

There are data which show that dark chocolate might be beneficial to the cardiovascular system (heart and blood vessels). Dark chocolate has been shown to reduce systolic and diastolic blood pressure in mild high blood pressure cases. Dark chocolate also has been demonstrated to improve endothelial and platelet function (preventing blood clots, chest pain and heart attack) and to ameliorate insulin resistance. Flavonoids contained in dark chocolate have strong antioxidant activity and can prevent the oxidation of low-density lipoprotein cholesterol (bad cholesterol), lowering the risk of atherosclerosis (stiff and clogged arteries).

Mary Engler of the University of California, San Francisco, and colleagues, found that around 45 grams (1.6 ounces) a day of dark chocolate can keep blood vessel elastic and healthy. The dark chocolate (high-cocoa content) contains epicatechin. Epicatechin is a particularly active plant flavonoid. Flavonoids prevent cholesterol from gathering in blood vessels and reduce the risk of blood clots. The study used Dove dark chocolate for two weeks and was published in the Journal of the American College of Nutrition. Mary Engler previously reported the results at the 2002 Scientific Sessions of the American Heart Association and at the Experimental Biology 2003 meeting.

Another study published in the Journal of Proteome Research and conducted by researchers at the Nestle Research Center in Lausanne, Switzerland, showed that eating about 40 grams (1.4 ounces) of dark chocolate a day for two weeks reduce stress. Half of the chocolate was eaten mid-morning and the other half was eaten mid-afternoon. The scientists found that high levels of stress hormone, cortisol, and the fight-or-flight hormones (catecholamines, adrenaline) present in highly stressed, anxious people were reduce by dark chocolate. Dark chocolate partially normalized stress-related differences in energy metabolism and microbial activity in the gut (microbiota).

Regarding the amount of anti-oxidants, dark chocolate and cocoa are better than pomegranate, cranberry, or blueberry juice, fruit powder mixes, a study conducted by the Hershey Company has showed. Polyphenols, organic molecules contained in dark chocolate, could maintain arteries smooth and lower risk of heart disease.

A study published in the Journal of Agricultural and Food Chemistry showed cocoa powder, baking chocolate and dark chocolate have between 14.1 to 18.5 micrograms of resveratrol (antioxidant) per serving (average California red wine contains 832 micrograms per glass).

Dark chocolate with minimum 60-85% cocoa content could prevent sunburns, showed an experiment conducted by researchers from Laval University in Quebec City (Canada) among women with sensitive skin. They ate three squares of dark chocolate a day for twelve weeks. The polyphenol ensure good oxygenation and blood supply to the skin surface, which could explain the protective effect of cocoa.

Cambridge University researchers have demonstrated that regular consumption of dark chocolate could reduce the risk of heart disease by a third. Other study said dark chocolate could be as good as exercise for human health.

Researchers from the United Kingdom and Colombia made a meta-analysis on 7 studies (the link between chocolate and  heart disease) that included 114,009 people. The results were released in the British Medical Journal. Dark chocolate could lower heart disease and stroke by 37%.

On the other hand, over-eating sweets and chocolate, even dark chocolate, might have no or opposite effects.

Chocolate contains a lot of sugar and fat, and caffeine. The persons with diabetes, other metabolic diseases, prone to irregular heartbeats, palpitation or high blood pressure, have to be very careful concerning the chocolate intake. They should read the product label and the ingredients.

“Previous research has suggested that dark chocolate can increase levels of good cholesterol and decrease blood pressure, both of which can reduce your risk of stroke. However, it’s very hard to say whether this is true of all types of chocolate and it’s difficult to determine whether the reduced stroke incidence found in this study is directly linked to the amount of chocolate consumed. A lot more research is needed,” said Dr Sharlin Ahmed, of The Stroke Association.

“Given the observational design of the study, findings of this study cannot prove that it’s chocolate that lowers the risk of stroke. Chocolate should be consumed in moderation as it is high in calories, fat and sugar. As dark chocolate contains more cocoa and less sugar than milk chocolate, consumption of dark chocolate would be more beneficial,” wrote Professor Larsson.

“It’s important to keep findings like these in context. These findings don’t mean that people need to exchange chocolate for broccoli in their diet. Chocolate does have antioxidants, and antioxidants are beneficial for your health. They can help make your arteries more flexible and they can help you resist the oxidation of cholesterol. But, what if they had tried this study with apple skins or grapes? There’s an upside and a downside to everything. I don’t think people should eat all the chocolate they can, but some chocolate in moderation can have some benefit,” said Dr. Nieca Goldberg, cardiologist, of the NYU Langone Medical Center in New York City.

Like in more other situations the moderation is the key. However, more studies are required to specify the exactly percent of cocoa (Theobroma cacao seeds) content in the dark chocolate needed to stroke or heart disease prevention, and also the effect on male’s health.