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I always had a poor view of the healthfulness of chocolate, but recently I came across an 8fact image which says otherwise:

Eating dark chocolate every day reduces the risk of heart disease by one third #8fact

Is it true that eating dark chocolate reduces the risk of heart diseases by one third?

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    Chocolate, coffee and red wine: three foods that always have alternating stories of healthfulness and harm published in the papers each week, because the improve some risks and worsen some others, and are correlated (not causally) with many others still. – Oddthinking♦ Oct 16 '14 at 5:07
  • Vox: The chocolate science hype machine – user22865 Jan 17 '18 at 12:49
  • related – De Novo Jan 7 at 19:13
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In several studies, chocolate consumption was associated with decreased risk of heart disease. Association does not already mean the cause-effect relationship, though.

The supposedly beneficial nutrients in chocolate are flavonoids, which are found in higher amounts in dark than in milk chocolate.

  1. PubMed Central (2012)

    Cocoa and particularly dark chocolate are rich in flavonoids and recent studies have demonstrated blood pressure lowering effects of dark chocolate....consumption of chocolate is inversely related with prevalent coronary heart disease in a general population.

  2. The American Journal of Clinical Nutrition (2008)

    The acute ingestion of both solid dark chocolate and liquid cocoa improved endothelial function and lowered blood pressure in overweight adults.

  3. The American Journal of Nutrition (2005)

    Dark, but not white, chocolate decreases blood pressure and improves insulin sensitivity in healthy persons.

In other studies, no effect of chocolate on heart disease was identified:

  1. The American Journal of Clinical Nutrition (2000)

    ...chocolate specifically was not shown to affect risk of coronary heart disease.

  2. The American Journal of Clinical Nutrition (2008)

    This investigation failed to support the predicted beneficial effects of short-term dark chocolate and cocoa consumption on any of the neuropsychological or cardiovascular health-related variables.

or insufficient evidence:

  1. PubMed Central (2006)

    ...flavonoids are likely protective against coronary heart disease mortality. The highest priority now is to conduct larger randomized trials to definitively investigate the impact of chocolate consumption on long-term cardiovascular outcomes.

  2. Cochrane Summaries (Meta-analysis of 20 studies, 2012)

    the effect of cocoa products on blood pressure in adults when consumed daily for a minimum of two weeks...a small but statistically significant blood pressure reducing effect of -2.8 mm Hg systolic and -2.2 mm Hg diastolic...more trials are required.

My conclusion: When the effects of dark chocolate in some studies seem to be small and of questionable clinical significance (a relatively small drop--2.8 mm Hg--of blood pressure) and inconsistent (no benefits in some studies), for me, there is insufficient evidence about the beneficial effects of dark chocolate on heart disease.

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    Cochrane is actually publishing a review of the other studies (it combines the results in an overall picture). You should mention that -- it's the most reputable resource you present by far. – Sklivvz Oct 16 '14 at 8:29
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    The conclusion of the Cochrane review says "more trials are required." So , obviously, Cochrane researchers themselves are aware their findings are "insufficient evidence." Also they say... "statistically significant" blood pressure reducing effect of -2.8 mm Hg systolic and -2.2 mm Hg diastolic..."Statistically significant" still does not mean "clinically significant." – Jan Oct 16 '14 at 8:53
  • I agree: you should specify that their position pretty much represents the scientific consensus and that some other articles are simply preliminary evidence. Presenting context and explaining which evidence is more valid is a key aspect of this site -- or at least of its top quality answers. – Sklivvz Oct 16 '14 at 11:51
  • The Cochrane review deals only with cocoa products and high blood pressure and not with other types of cardiovascular disease. I searched the topic by "chocolate" and "dark chocolate" keywords. If I search by "flavonoids," I again get mixed (does/not work) results. And if I search by "antioxidants," nothing seems to work. – Jan Oct 16 '14 at 12:44

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