There are four types of natural fat, saturated, mono-unsaturated and polyunsaturated and, less commonly, natural transfats; we also have unnatural transfats which are sadly far too common.
All natural sources of fat contain a mix of saturated, mono-unsaturated and polyunsaturated, just in different proportions.
This means that the fat on meat is not all saturated, and nor is all the fat in sunflower oil polyunsaturated. This is shown in the picture, left, by Xyzzy n.
Also, have a look at picture at the end of this brief article to see more examples of what foods contain what proportions of the fats.
All fats are made of chains of carbon with attached hydrogen atoms, and some oxygen. A carbon atom has four available bonds (think of them like hands) which can attach to other carbon atoms or hydrogen atoms.
When all the available bonds are attached to other carbon atoms or hydrogen atoms (like clasping hands), we say that fat is saturated. That’s all it means.
Saturated fats, because all their available bonds are used up, are stable fats – you can see this is the stylised diagram of myristic acid, left.
Foods high in saturated fats (such as butter or the fat in meat) are solid at room temperature. Because they are stable, they are ideal for cooking with.
Once inside our bodies, as well as providing us with energy, saturated fats (and there are many types) have many uses.
These fats have one bond left unused; you will be familiar with olive oil which is high in monounsaturates. Oils high monounsaturated fats, like olive oil, are generally liquid at room temperature and solid in the fridge. They are fine for cooking a low to medium temperatures and have a range of uses in our bodies.
These fats have two or more unused bonds; they remain liquid even when refrigerated because they are ‘bendy’ or flexible – see the picture, left:
Polyunsaturated fats are unstable, spoiling with heat and light. These oils are found mainly in seeds, such as sunflower, flax and pumpkin seeds, and these are the ones the health authorities have been telling us to cook with… and thereby helping us add to bad health! Why’s that? Well:
Producing these oils on a commercial basis is done by chemical means (I won’t spoil your breakfast, but feel free to look up how), so they are stripped of much of their nutritional value;
Cooking with these oils at anything other than a very low temperature denatures them so they turn into harmful transfats;
Eating so much of these oils means we eat too many pro-inflammatory omega 6 fatty acids in proportion to anti-inflammatory omega 3 fatty acids (found mainly in oily fish and flax) which is bad for our health.
Eating a diet high in polyunsaturated fats helps contribute to a bad blood profile, heart problems and other health problems (including obesity), especially if you are eating a diet high in starchy and sugary carbohydrates too.
We do need some omega 6 fatty acids (as we can’t make them in our bodies), but these can be supplied through eating whole vegetables and fresh seeds.
We get natural transfats in some foods like butter – they have a role to play and are not harmful. BUT a different, harmful sort of transfat is created through hydrogenation of oils to make them solid and, you may be surprised to learn, saturated. They are used in margarines/spreads and in processed foods; they are also produced when we overheat unsaturated oils, particularly when frying.
These cause all sorts of havoc in your cells and you need to be doing all you can to avoid them.
Why are oils hydrogenated? They last a long time, so the foods which contain them (often too with sugars) have a good ‘shelf life’, and are cheap to make.