Good fats and bad fats

High fat food is likely to make us put on weight since it is also high in calories and thus can make us weight gain.  Being overweight increases our risk of type 2 diabetes, high blood pressure, strokes and heart attacks.  However not all fat is bad, nor does all fat raise our cholesterol. 

We need some fat in our diet since it helps us transport some vitamins around the body and provides essential nutrients such as essential fatty acids (EFA’s) which are thought to have a positive effect on the heart and immune system as well as having a key role in membrane structure. 

The easy way to remember which fat is good and which is bad is to remember that bad fats are generally solid at room temperature, whereas good fats are liquid at room temperature.

Saturated fats

These are the fats to avoid.  Saturated fats are generally found in products such as meat, cheese, butter, ice-cream, processed sweet food such as cakes and biscuits and coconut milk or cream.  These are known to raise bad cholesterol – LDL cholesterol which is linked to increased risks of development heart disease, strokes and type 2 diabetes.

Trans fats

Although these occur naturally in low levels in some meat and dairy products, they are mostly found in processed foods.  The food industry creates trans fats by turning a liquid oil into a solid in order to give products a longer shelf life and improve their texture and ‘mouth feel’.  Look out for ‘hydrogenated vegetable oil/fat’, ‘shortening’ or ‘partially hydrogenated vegetable oil/fat’ on food labels. 

Fried food is also a potential problem.  Try to avoid fried food you eat when you eat out since the oils they can be cooked in may also be hydrogenated (to make it more stable and hence reusable more times) and thus contain high levels of trans fats.  Similarly, don’t re-use oil at home since the repeated heating can create trans fats in it.

It is generally recommended that adults eat less than 5g per day.  However as a population we eat about half this amount since most food manufacturers have removed the hydrogenated vegetable oil from their products.  However, any food which is not in labelled packaging (like take away), or imported (and so not subject to UK food labelling regulations) may contain hidden trans fats.

So why are trans fats so bad for you? Not only do they raise levels of LDL ‘bad cholesterol’ but they also lower the levels of HDL ‘good cholesterol’ and so may cause even more damage than saturated fats.

Unsaturated fats

These are divided into 2 groups – polyunsaturated and monounsaturated fats which have potentially different effects on blood cholesterol.

Polyunsaturated fats tend to be liquid at room temperature and may help lower your total and LDL (bad) cholesterol, but may also lower your HDL (good) cholesterol.  They can be divided into omega-3 and omega 6 – both of which are important for heart health.  However, omega-3 helps to reduce inflammation (and so is important in helping all inflammatory conditions) and for good cognitive function.  Our bodies are able to make limited amounts of omega-3 from plant sources such as nuts and seeds, but the best source is oily fish such as salmon and mackerel. 

Monunsaturated fats also tend to be liquid at room temperature but are the healthiest fats of all since they too help lower total and LDL cholesterol, but unlike polyunsaturated fats they maintain levels of HDL (good cholesterol).  These have also been shown in research to help with control of blood sugar & insulin levels and so may be helpful in diabetes.

Find these in olives, olive oil and olive spreads, rapeseed oil and spread, avocado, peanuts, peanut oil and peanut butter.

References
Mayo Clinic Nutrition and healthy eating. Available at: http://www.mayoclinic.com/health/fat/NU00262 

NHS choices. High Cholesterol.  Available at: http://www.nhs.uk/conditions/Cholesterol/Pages/Introduction.aspx