When we're sad and stressed, what do many of us do? We resort to chocolate. There's a long history of people using chocolate to make themselves happier, but the question still remains: is there a scientific basis behind it, or is the mood boosting ability of chocolate just an old wives' tale? Here are the facts on the chemical composition of chocolate and how it can affect our moods.

One of the things that could account for the satisfaction we feel upon eating a lot of chocolate is that it's so sweet and rich. Even dark chocolate has a high percentage of fat and sugar, and these properties stimulate the hypothalamus. The hypothalamus is the part of our brain responsible for pleasing sensations. When you eat chocolate to improve your mood, the sensations distract you from whatever's making you upset.

In addition, chocolate can affect the amount of serotonin in the brain. This chemical is known for having an effect on mood, and is regulated by many anti-depressants. While the effect of chocolate is far less than that of medical remedies for depression, it does have a noticeable one on the way serotonin is released.

Chocolate also contains substances called unsaturated N-acylethanoamines. These may be responsible for activation of cannabinoid receptors or an increase of endocannabinoid levels - some of the same effects that occur with marijuana consumption, but on a much smaller level. That could result in euphoric feelings and heightened sensitivity - possibly responsible for chocolate's reputation as an aphrodisiac.

One of the substances that makes unsweetened chocolate so bitter - theobromine - is similar to caffeine and theophylline. It, like those substances, is a stimulant. That means that consuming it could make you feel more alert and energetic, resulting in greater feelings of happiness. This chemical was first discovered in cacao beans in 1841 by a Russian chemist, but it wasn't until 1878 that it was isolated from those beans.

It's the primary alkaloid in cocoa powder and chocolate, with dark chocolate containing a lot and white chocolate containing only trace amounts. Theobromine also shows up in tea, kola nuts and guarana berries. Though it isn't addictive, it might be responsible for the feeling we refer to as being a "chocoholic", and has also been cited as one of the possible reasons some people consider chocolate to be an aphrodisiac.

Chemically, chocolate does have the ability to boost mood. However, to get much of an effect from these compounds, you'd have to eat a lot of chocolate. The fat and sugar content of this snack mean that it's not ready to be used to fight depression, but a little bit might help you cure the blues.

Let's just forget all the science for a moment though. I think most would say they are pretty happy while eating chocolate and after for a bit. Some things in life you don't need a scientific test for. Eating chocolate is one of those times. If it tastes good and makes you feel good then enjoy your chocolate.