Saturated and unsaturated fats

Michael loves pizza - especially with olive oil. But he's mystified that the oil is liquid while the cheese on the pizza has solidified. Let's dive into the pizza to examine this. Olive oil is a mixture of different fats. Here's one of the fat molecules.

Look at that fatty acid. It's rather crooked! When fatty acids are crooked like this, it makes each fat molecule take up more space. Compare to this fat molecule, where all the fatty acids are straight. The straight fatty acids can be packed together more densely than the crooked ones -- there are smaller gaps.

And when fat molecules are packed together like this, they sort of stick together, and that's what makes the fat take a solid form. Olive oil on the other hand, has fatty acids which are crooked. Thanks to that crookedness, the fatty acids don't pack together so tightly, so they don't attach to each other as much. That's what makes it liquid at room temperature. But, what is it then that makes the fatty acid so crooked?

Well, look here. A fatty acid is a long chain of carbon atoms, with hydrogen atoms surrounding them. And here, in straight fatty acids, the entire carbon chain is completely saturated with hydrogen atoms. There are two hydrogens attached to each carbon. Except the last one, where there are three.

As many as can fit there. Now compare to the crooked fatty acid. Here's two hydrogen atoms missing! And over here as well! Instead there's a double bond between the carbon atoms in those places.

So the crooked fatty acid is un-saturated. And since there are double bonds in several places, we call it poly-un-saturated. A fatty acid with only one double bond is mono un-saturated. It's enough that one of the fatty acids in the molecule has more than one double bond -- then the fat counts as poly-unsaturated. Oils with a lot of poly-unsaturated fat are fluid at room temperature, like corn oil or sunflower oil.

Now the pizza has cooled down, and the fat in the cheese has solidified. Most of the fatty acids in the cheese are straight, so they are tightly packed, and are solid at room temperature. Just like butter, and coconut oil. The entire chain of carbon atoms is saturated with hydrogen. Saturated fat.

Fats, in both plants and animals, are mixtures of saturated, mono-unsaturated and poly-unsaturated. In most cases, fat from animals contain a lot of saturated fat. Most of the fat in milk, butter, cheese, and ice-cream is saturated. But there are exceptions. The fat in fish and crayfish is to a large degree unsaturated.

Plants contain mostly unsaturated fats. Like olives, avocado, and different types of nut. But there are exceptions - most of the fat in coconut is saturated. So, why does this matter? Fat is fat, isn't it?

Well, your body reacts differently to different types of fat... The majority of scientists researching food and health agree that polyunsaturated fats are healthier than saturated, especially for your heart and blood vessels. But, more recently, some scientists have started to question this. They argue that saturated fats have a worse reputation than they deserve, and that they may even be good for us. Oh go on then, a little more olive oil on that pizza won't harm?