Some of you appear to be confused by some about types of fat and 'fat' terminology is frequently misused. Hopefully these notes will help clarify the issue.
Fats in the Blood
There are a number of fats in our blood which doctors measure to assess our heart disease risk. These are sometimes known as lipids, and the most common ones are discussed below.
Cholesterol is a waxy fat, made naturally in our bodies by the liver, and is an essential part of living tissues. Too much cholesterol builds up on the walls of arteries which supply the heart (coronary arteries). If these deposits become too large clots are liable to form, cutting off blood flow through the vessel causing heart disease.
A high cholesterol level can be inherited but it can also be affected by lifestyle, especially through lack of exercise and a poor diet. A raised blood cholesterol level is a main risk factor for heart disease.
Your total cholesterol level can be divided into subfractions to give a more accurate reading of what is going on in your blood. The two main subfractions are:
- LDLs – this is 'bad' cholesterol and this level should be kept to a minimum
- HDLs – this is 'good' cholesterol as it denotes cholesterol which is being returned to the liver for disposal. This level should be high
The problem with total cholesterol (TC) level is that it masks the subfractions. You could have a fairly high TC but this is because HDLs are high, reducing heart disease risk. Nevertheless, if your TC is very high it is likely that your LDLs are also raised.
Triglycerides are another fat in our blood. Doctors commonly measure these, as a high figure also increases your risk of heart disease.
Fats in our Diet
Saturated fats generally come from animal sources such as meat and dairy produce, but are also found in some vegetable oils, margarines and processed foods. These fats should be kept to a minimum as they can be converted to cholesterol.
Polyunsaturated fats are abundant in sunflower and soya products. A high intake of these in proportion to total fat intake can help lower total cholesterol.
Monounsaturated fats are the favourable choice. These are very high in olive, rapeseed and avocado oils. Consuming more of these helps lower triglycerides, LDLs and total cholesterol, whilst keeping HDLs high.
Trans fats are found in hydrogenated oils and margarines and some confectionery. These should be avoided as can raise LDLs and reduce HDLs.
Omega-3 fats (w3s) are abundant in oily fish. Eat oily fish at least 3 times a week, as w3s help lower LDLs and triglycerides, whilst raising HDLs and helping to prevent clots forming. Oily fish include mackerel, sardines, pilchards, trout, and salmon.
Remember, all fats contain the same amount of calories. Aim to keep total fat intake reasonably low, especially if you want to lose body fat.