Even if we don't follow the most healthful diet ourselves, most of us generally know which foods are good for us, and which foods aren't.

For example, you'd have to admit steamed broccoli is good for you, even if you don't like it very much. Nachos with cheese sauce, well you know that's unhealthy. Chocolate tastes so good it's got to be bad for you, right? Not completely, as we'll find out .

Consider the chocolate bar. This is a high fat food, much like a stick of butter, but with a crucial advantage. If you took a stick of butter out of your refrigerator and left in on a shelf for two months, it would go rancid. If you did the same thing with a chocolate bar, the chocolate would be fine.

This is because cocoa, which chocolate is made from, is rich with chemicals called flavonoids. When a food goes rancid, its fat breaks apart by a process called oxidation. Flavonoids are antioxidants, which means they hinder oxidation, keeping the chocolate from going rancid on the shelf.

Inside your body, antioxidants have beneficial effects too. For one, they slow down the decay of fatty chemicals called LDLs. When LDLs decay, they leave behind a dangerous plaque in your arteries. By slowing that decay, the flavonoids in a chocolate bar are actually working to make you healthier. However, unfortunately, the fat in that same chocolate bar is working harder to make you unhealthy.

If there were a tug of war between a chocolate bar's fat and its flavonoids, the fat would win every time. Still if you're looking for an excuse to eat that occasional chocolate treat, just remember those flavonoids and munch away.