Health effects of chocolate
The health effects of chocolate are the possible positive and negative effects on health of eating chocolate.

Unconstrained consumption of large quantities of any energy-rich food, such as chocolate, without a corresponding increase in activity, increases the risk of obesity. Raw chocolate is high in cocoa butter, a fat removed during chocolate refining, then added back in varying proportions during  manufacturing. Manufacturers may add other fats, sugars, and powdered milk as well.

Although considerable research has been conducted to evaluate the potential health benefits of consuming chocolate, there are insufficient studies to confirm any effect and no medical or regulatory authority has approved any health claim.

History

Theobroma cacao, the cacao tree, produces seeds containing flavanols. The seeds have been used to make beverages for some 2000 years in Aztec, Olmec, and Maya civilizations in central and south America. The drinks were ascribed a wide variety of curative and stimulant properties, unsupported by experimental evidence. In the 19th century, chocolate as a solid was invented, and milk and sugar were added to create milk chocolate, high in fat and sugar. Doubtful research, sometimes funded by the chocolate industry, has at times made suggestions of possible health benefits for these products.

Research

Acne
Overall evidence is insufficient to determine the relationship between chocolate consumption and acne. One preliminary study concluded that in males who are prone to acne, eating chocolate increases the severity of acne. Various studies point not to chocolate, but to the high glycemic nature of certain foods, like sugar, corn syrup, and other simple carbohydrates, as potential causes of acne, along with other possible dietary factors.

Addiction
Food, including chocolate, is not typically viewed as addictive. Some people, however, may want or crave chocolate, leading to a self-described term, chocoholic.

Weight gain
The effect of chocolate on body weight is unclear. A concern is that excessive consumption of chocolate may promote high calorie intake and weight gain, a risk factor for many diseases, including cardiovascular disease. As a consequence, consuming large quantities of dark chocolate in an attempt to protect against cardiovascular disease is likely to add excessive calories and induce weight gain.

Mood
By some popular myths, chocolate is considered to be a mood enhancer, such as by increasing sex drive or stimulating cognition, but there is little scientific evidence that such effects are consistent among all chocolate consumers. If mood improvement from eating chocolate occurs, there is not enough research to indicate whether it results from the favorable flavor or from the stimulant effects of its constituents, such as caffeine, theobromine, or their parent molecule, methylxanthine.

Heart and blood vessels
Reviews support a short-term effect of lowering blood pressure by consuming cocoa products, but there is no evidence of long-term cardiovascular health benefit. While daily consumption of cocoa flavanols (minimum dose of 200 mg) appears to benefit platelet and vascular function, there is no good evidence to support an effect on heart attacks or strokes.

Lead content
Although research suggests that even low levels of lead in the body may be harmful to children, it is unlikely that chocolate consumption in small amounts causes lead poisoning. Some studies have shown that lead may bind to cocoa shells and contamination may occur during the manufacturing process. One study showed the mean lead level in milk chocolate candy bars was 0.027 µg lead per gram of candy; another study found that some chocolate purchased at U.S. supermarkets contained up to 0.965  µg per gram, close to the international (voluntary) standard limit for lead in cocoa powder or beans, which is 1 µg of lead per gram. In 2006, the U.S. FDA lowered by one-fifth the amount of lead permissible in candy, but compliance is only voluntary. Studies concluded that "children, who are big consumers of chocolates, may be at risk of exceeding the daily limit of lead; whereas one 10 g cube of dark chocolate may contain as much as 20% of the daily lead oral limit. Moreover chocolate may not be the only source of lead in their nutrition" and "chocolate might be a significant source of Cd and Pb ingestion, particularly for children."

Polyphenol and theobromine content
Chocolate contains polyphenols, especially flavan-3-ols (catechins) and flavonoids which are under study for their potential effects in the body. The following table shows the content of phenolics, flavonoids and theobromine in three different types of chocolate.

Other animals

In sufficient amounts, the theobromine found in chocolate is toxic to animals such as cats, dogs, horses, parrots, and small rodents because they are unable to metabolise the chemical effectively. If animals are fed chocolate, the theobromine may remain in the circulation for up to 20 hours, possibly causing epileptic seizures, heart attacks, internal bleeding, and eventually death. Medical treatment performed by a veterinarian involves inducing vomiting within two hours of ingestion and administration of benzodiazepines or barbiturates for seizures, antiarrhythmics for heart arrhythmias, and fluid diuresis.

A typical  dog will normally experience great intestinal distress after eating less than  of dark chocolate, but will not necessarily experience bradycardia or tachycardia unless it eats at least a half a kilogram (1.1 lb) of milk chocolate. Dark chocolate has 2 to 5 times more theobromine and thus is more dangerous to dogs. According to the Merck Veterinary Manual, approximately 1.3  grams of baker's chocolate per kilogram of a dog's body weight (0.02  oz/lb) is sufficient to cause symptoms of toxicity. For example, a typical  baker's chocolate bar would be enough to bring about symptoms in a  dog. Of course, baking chocolate is rarely consumed directly due to its unpleasant taste, but other dark chocolates' canine toxicities may be extrapolated based on this figure. Given access, dogs frequently consume chocolate at toxic levels because they like the taste of chocolate products and are capable of finding and eating quantities much larger than typical human servings. There are reports that mulch made from cacao bean shells is dangerous to dogs and livestock.