Just in time for Valentine's Day, arguably one of the more candy-centric holidays, a new study by Japanese scientists will give choco-holics a reason to cheer: chocolate -- specifically dark chocolate -- is good for your cholesterol.

In the study, published in the Journal of Agricultural and Food Chemistry, Midori Natsume, Ph.D., and colleagues note studies have shown cocoa, the main ingredient in chocolate, appears to reduce the risk of heart disease by boosting levels of high-density lipoprotein (HDL), or "good" cholesterol, and decreasing levels of low-density lipoprotein (LDL), or "bad" cholesterol.

Credit for those heart-healthy effects goes to a cadre of antioxidant compounds in cocoa called polyphenols, which are particularly abundant in dark chocolate.

Just as those heart-shaped boxes of chocolates gets mouths watering, polyphenols rev up the activity of certain proteins, including proteins that attach to the genetic material DNA in ways that boost HDL levels.

How they work

Until now, however, nobody knew exactly how the polyphenols in cocoa orchestrated those beneficial effects.

The scientists analyzed the effects of cocoa polyphenols on cholesterol using cultures of human liver and intestinal cells. They focused on the production of apolipoprotein A1 (ApoA1), a protein that is the major component of "good" cholesterol, and apolipoprotein B (ApoB), the main component of "bad" cholesterol.

What they discovered was cocoa polyphenols increased ApoA1 levels and decreased ApoB levels in both the liver and intestine.

Additionally, the scientists discovered the polyphenols seem to work by enhancing the activity of so-called sterol regulatory element binding proteins (SREBPs).

SREBPs attach to the genetic material DNA and activate genes that boost ApoA1 levels, increasing "good" cholesterol. The scientists also found polyphenols appear to increase the activity of LDL receptors, proteins that help lower "bad" cholesterol levels.

Mental health aid

Chocolate can get beneficial for your mental health, too.

A study published in 2009 in the Journal of Proteome Research found eating about an ounce and a-half of dark chocolate a day for two weeks reduced levels of stress hormones in people who felt highly stressed.

“The study provides strong evidence that a daily consumption of 40 grams [1.4 ounces] during a period of two weeks is sufficient to modify the metabolism of healthy human volunteers,” the study authors said.

So go ahead -- indulge in some dark chocolate this Valentine’s Day. Your head and your heart might thank you.