This is a sequel to one of my previous posts:
A recent study looked at various hormonal and metabolic changes associated with consuming chocolate. In this case, 30 people were given 40 g of dark chocolate daily for 2 weeks. The authors conclude that the chocolate consumption was responsible for reducing metabolic changes associated with stress, including cortisol and catecholamine excretion.
Weaknesses of the study include its brief, non-randomized, non-blinded nature (mind you, many of us would not easily be fooled by a placebo chocolate substitute!). And I see that the study is associated with the "Nestle Research Centre" in Switzerland. While I am pleased to know that a large chocolate company has a "research centre," I do have to wonder if there could be a higher risk of bias at play.
Here's a link to the abstract:
In the meantime, there is a variety of evidence out there that chocolate consumption in moderation is good for your health, in a variety of ways.
However, one concerning issue I just learned about has to do with lead contamination in cocoa and chocolate products. Lead is a heavy metal poison which should not have any presence in the diet. It can have widespread toxicity, particularly affecting the nervous system, through either acute or chronic exposure. The issue of lead in chocolate is discussed in mainstream research, such as by Rankin & Flegal (references:http://www.ncbi.nlm.nih.gov/pubmed/16757407, http://www.ncbi.nlm.nih.gov/pubmed/16203244). Based on some of this research, it may be true that raw, unprocessed cocoa nibs have no significant lead contamination, rather the lead in some cocoa and chocolate products may be the result of industrial processing.
Hopefully, manufacturers can address this issue, so that we can be reassured about safety, and so that we can get on with the enjoyment of one of life's great pleasures, knowing that it, in moderation, may also be good for psychological and medical health.