Which fat does what?
Polyunsaturates, saturates, monunsaturates, essential fatty acids – so what's good and what's not? In other words, what constitutes good fats, which can contribute to a healthy diet, and which ones have the potential to raise your cholesterol and increase the risk of heart disease? Here’s what you need to know.
Saturated and trans fats
Let’s look at saturated fats first. Because these raise levels of LDL or ‘bad’ cholesterol, saturated fats contribute to the risk of heart disease and stroke. They’re commonly found in many manufactured and packaged foods, including deep-fried takeaways, commercially baked cakes, biscuits, pastries and pies as well as fatty snack foods. But dairy foods, such as butter and regular-fat milk and cheese, and meat also contain saturated fat, so it’s important to choose low-fat dairy products and leaner cuts of meat.
And remember that coconut milk and cream, as well as coconut oil, also contain saturated fat. According to the Dietitians Association of Australia, despite being popular with some eating ‘trends’, the current evidence shows that coconut oil doesn’t stack up against healthy unsaturated fats, like those found in olive oil.The Heart Foundation agrees saying that, like butter, coconut oil is something to use only sometimes and in small amounts.
Trans fats are rare in nature, but are created during the manufacturing process of foods or from superheating oils and fats during food production. So deep-fried foods, commercial cakes and biscuits and pies and pastries tend to contain higher levels of trans fats. Because they act like saturated fats in the body, they tend to raise levels of LDL cholesterol. However, unlike saturated fats, they also lower HDL cholesterol so are likely to be even more damaging.
Cholesterol actually plays several essential roles in the body, including producing hormones, like oestrogen and testosterone, helping your body produce vitamin D and building the structure of cell membranes. But, even so, having high levels of the wrong type of cholesterol circulating in your blood increases your risk of heart disease.
The ‘wrong’ type is LDL or ‘bad’ cholesterol, which contributes to blocked arteries and therefore the risk of heart disease. On the flip side, HDL, or ‘good’ cholesterol helps protect the arteries from the build up of fatty deposits.
Although food manufacturers have latched on to the idea that the cholesterol in food is the main cause of heart disease, so advertise products as being cholesterol free, it’s actually eating large amounts of foods that contain saturated and trans fats that has the most influence on blood cholesterol levels.
Polyunsaturates and monounsaturates
These fats tend to lower LDL blood cholesterol when they replace saturated fats in the diet, with polyunsaturated fat believed to have a slightly greater impact than the monounsaturated variety.
Sources of polyunsaturated fat include fish, linseed and chia seeds, pine nuts, walnuts and brazil nuts, as well as vegetable oils like soybean, sunflower, safflower and canola oil – as well as margarine spreads made from those oils.
Sources of monounsaturated fat include avocados, almonds, hazelnuts and cashews, and olive and canola oils.
It’s important to remember that unsaturated fats are healthy fats and are an important part of a healthy diet.
A quick guide to buying and storing oils:
- Stick to single oils, rather than blends.
- Check the best-before dates and choose smaller bottles to ensure the oils are always fresh.
- Choose dark glass bottles or tins, which mean the oils will be better preserved.
- Store away from heat sources and bright lights when you get them home.