Knowing which fats and oils are healthy and which ones should be avoided can be confusing. Add to that the complication that heat can seriously damage some fats, knowing what to use when can be really tricky.
Firstly, let’s establish the 3 main types of fat:
The much maligned saturated fats like butter, goose fat and coconut oil are not nearly as bad as we have been led to believe. We need some saturated fat in the diet for certain biological functions and they are much healthier than cheap cooking oils that are often thought to healthy – confused? More on this below.
Saturated fats, being saturated means they don’t oxidise and damage when heated making them great for cooking with. Saturated fats should be restricted in the diet, but some saturated fat, especially products from grass-fed cows and extra virgin coconut oil are very healthy. Ghee (clarified butter) is also a good option for cooking. These can all be used for low to medium heat frying and baking. Goose fat is lower in saturated fat than butter and has a good amount of a very healthy monounsaturated fat called oleic acid (also very high in coconut oil), which had lots of health benefits. It is renown for making great roast potatoes and is safe to use for this kind of high-heat cooking.
Refined polyunsaturated fats are the most commonly used for cooking. They include generic vegetable oil, which is usually a mix of oils often including soy bean oil; sunflower, corn, grapeseed and pumpkin seed. These fats are healthy in their original state however, because they turn rancid very easily when exposed to heat, light and oxygen these oils are put through a highly mechanized process involving heat and chemicals to deoderize (removing the smell of rancid fat) and bleach them. This process changes the chemical structure making them more stable and therefore more suitable as cooking oils but far, far less healthy. Many people believe these cheap cooking oils are considerably more damaging than saturated fats.
Unrefined, cold-pressed polyunsaturated fats can be found in some supermarkets and health food shops. They are more expensive, should always be in dark glass bottles and have a stronger flavour which can be a good or a bad thing, depending on what you’re using it for. These oils are super healthy but spoil and go rancid easily when heated and exposed to light and oxygen.
Monounsaturated fats are well known as having many health benefits. Olive oil is probably the best known monounsaturated with extra virgin olive oil being the healthiest as it the least processed and cold-pressed. Only buy extra virgin olive oil in dark glass bottles as it is very light sensitive.
Virgin olive oil is less expensive and more stable but lacks some of the health benefits of extra virgin. Extra virgin olive oil has the strongest flavour so is not always appropriate for dishes with a delicate flavour. As a base for salad dressings extra virgin olive oil is ideal.
Sesame and peanut (ground nut) oil are healthy options as they are also largely monounsaturated as is rapeseed but this oil has a mixed reputation due to rapeseed crops being highly genetically modified.
There is one area of complete consensus when it comes to fats – that trans fats are bad, bad, bad. I have blogged about this before so I will keep it brief:
These are plant-based oils that are put through a process using heat and chemicals to create a more stable, less volatile product and to make them solid at room temperature making them much less prone to spoiling and significantly extending the shelf-life of products the are put in to. These altered fats are added to baked goods, ready meals, snack foods etc.
However, there is a high cost. The healthy fat as was, becomes a trans-fat, either hydrogenated or partially hydrogenated. This means the fat is chemically altered and is no longer a healthy fat. These fats are unrecognizable by the human body and have been identified as posing several serious health issues. Many countries have banned the use of trans fats. The UK government is talking about it but as yet has not done so.
When it comes to which fats to cook with, different oils react to heat in various ways. This comes down to the smoking point of the oil. The healthier the oil, the lower the smoking point meaning it will start to smoke and therefore become damaged at a lower heat.
All unrefined, cold pressed polyunsaturated oils have a low smoke point so should be used only for light sautéing, for salad dressing or for dressing foods once cooked. The most vulnerable to heat is flax seed oil and should never be heated Just to complicate things, olive oil has various smoke points: the better quality, the lower the smoke point. Good quality extra virgin olive oil has a low – medium smoke point.
Medium smoke point oils good for pan frying and baking include walnut, sesame, pumpkin, virgin olive oil, unrefined peanut (groundnut) and butter. High smoke point oils, suitable for deep-frying, barbequing and high heat pan-frying include refined oils like rapeseed, sunflower, corn, peanut oil and safflower (although not healthy options) and, of course, goose fat, coconut oil and Ghee. As healthy saturated fats these last three are stable when heated and are highly recommended.
Hope this clarifies (hee hee) things a little.