Polyunsaturated fats
This type of oil (e.g. sunflower oil) has lots of missing hydrogen molecules and therefore lots of bends in its chemical chain making it very VERY reactive. These oils are so reactive that when we eat them they are used almost exclusively for reactions in our bodies and very rarely for energy. Polyunsaturated fats are usually described as “Essential Fatty Acids” or EFA for short. They are often sold as supplements and are vital for the health of our hearts, nervous systems, joints and brains – in fat pretty much the entire body will benefit from regular consumption of EFA. The reason polyunsaturated oils are considered so healthy is because of all the fats, they are the most reactive.
No sooner have we eaten them they are whizzing around our bodies doing a myriad of useful functions. However, this reactivity is a double edged sword. Polyunsaturated fats are very easily damaged by heat, light and oxygen and should NEVER be heated. Heating polyunsaturated fats creates trans fats which are the true “bad boy” of the fat gang (more about trans fats in a moment). They should be consumed raw, in their cold pressed extra virgin form only and stored in a dark glass airtight bottle. They have a life span of around 4-8 weeks so should not be stored (even correctly) for longer than this to preserve their healthful properties.
As a side note – EFA are excellent anti-inflammatories. They can reduce the pain of some arthritic conditions very effectively. Cod liver oil has long been associated with healthy joints and is a great example of polyunsaturated oils doing an essential job. Around 30 – 40 % of our daily fat intake should be made up of polyunsaturated fats.
Trans fats
These nasty little critters are responsible for pretty much everything that saturated fats are wrongly blamed for. From heart disease to clogged arteries to the weak £ and global warming - it’s not saturated fats at fault but trans fats. (Okay – maybe the last two aren’t down to trans fats but it would be handy if we could blame them on something!)
Trans fats are “bent” unsaturated fats which have been straightened out artificially which causes great confusion in our body’s cells. In chemistry shape matters. Square pegs fit into square holes, round pegs into round holes. Trans fats are treated by the body as one thing when in fact they are something completely different. They end up going places they shouldn’t and block the healthy fats from doing their job. It’s as though a square peg has been jammed into a round hole and this means other fats consumed a) can’t do their healthy job and b) are now surplus to requirements and more likely to be stored around our middles.
Trans fats should be avoided at all costs. They’re not hard to dodge if you follow these simple guidelines…
- Don’t cook with polyunsaturated fats – use saturated fat or monounsaturated oils instead
- Avoid overheating monounsaturated fats – they do rancid easily
- Cut down on processed and takeaway foods – they often contain “hidden” trans fats
- Switch back to butter from margarine – there are no trans fats in butter!
- Avoid any food which has the word “hydrogenated” or “partially hydrogenated” listed on it’s ingredients
- Cut back on shop-bought pies and pastries – home made is best
- Keep your oils in dark glass airtight bottles
- Only buy extra virgin cold pressed oils.
So – to recap…never never NEVER (!!!) cook with polyunsaturated fats! Remember – saturated fats e.g. butter and lard are great for all types of cooking, monounsaturated fats e.g. olive oil are okay for short cooking times/lower temperatures but polyunsaturated fats, whilst healthy if consumed raw, are turned into trans fats at even low temperatures so don’t cook with them at all.
I hope from this you can see that not all fats are bad and that some are even very good for us so enjoy your fats (in moderation of course!) and could someone pass me the butter dish please?!
Patrick Dale
Read part 1 here http://www.ultra-fitmagazine.co.uk/?p=503
Read part 2 here http://www.ultra-fitmagazine.co.uk/?p=1120
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