Health benefits: Forget spinach, the real nutritional star of the cartoon Popeye should have been Olive Oyl. Olive oil protects against heart disease by keeping 'bad' (LDL) cholesterol levels in check, raising the quantity of good (HDL) cholesterol. And olive oil contains more monounsaturated fatty acids than any other natural oil. It's so easy on the digestion that it even has a beneficial, calming effect on stomach ulcers.
Health downsides: Heat olive oil to smoking point (about 200ºC) and, like other oils, it turns nasty. Not only does olive oil lose its flavour, the structure of fatty acid chains within it is altered, potentially making it less healthy.
How to get the best health benefits: "The good news is that it’s difficult to heat olive oil to such a high level as to render it dangerous, but heating will diminish its benefits," says registered nutritionist Carina Norris. So use it on salads, add to cooked mashed potato or drizzle over risotto. And if you’re wondering whether to opt for standard, virgin or extra virgin olive oil, go for extra if you can. Although there isn’t a huge amount of nutritional difference between the different types (extra virgin contains more antioxidants), the main difference is in the superior flavour.
Health benefits: You can heat sunflower oil to 246ºC before it smokes, making it ideal for frying.
Health downsides: Sunflower oil low in saturated fats, which is good, but also low in monounsaturates and high in polyunsaturates, which isn’t so good. Polyunsaturates, which lower both our ‘good’ and ‘bad’ cholesterol levels, are found in many foods so we tend to get enough of them while monounsaturates, which lower the ‘bad’ without decreasing the ‘good’, are less common but are better for our cholesterol levels, and so are far more important.
How to get the best health benefits: Reserve sunflower oil oil for frying – but be aware that normal frying renders food less nutritious than stir-frying, steaming or grilling. "The higher the temperature and the longer the food stays at that heat, the more nutrients you lose," says Norris.
Health benefits: "Like its Mediterranean cousin olive oil, avocado oil is rich in monounsaturated fats but it’s even lower in saturated fats – an added bonus," says Norris. But it’s not just good for eating, you can use it on your skin too. Avocado oil is soaked with vitamin E and helps soften the skin, reducing the appearance of wrinkles.
Health downsides: Like most vegetable fats, this delicious oil oxidises when exposed to bright light - and changing its chemical composition can make it taste bad. Keep your avocado oil hidden in a dark place.
How to get the best health benefits: Avocado oil has a higher smoke point than olive oil, so is a good bet for cooking. And its flavour is more delicate than that of olive oil so you needn’t worry about it overpowering a dish.
Pumpkin seed oil
Health benefits: Aside from being rich in omega-3 and 6, pumpkin seed oil also contains helpful quantities of zinc too, essential for a healthy immune and reproductive system. Preliminary studies on animals have found pumpkin seeds to help alleviate the inflammation caused by arthritis too.
Health downsides: Heating this oil doesn’t impair its flavour but it will impair its nutritional value.
How to get the best health benefits: Pumpkin seed oil has a distinctive dark-green colour making it ideal as a finishing touch to a risotto or mashed potato – simply drizzle on in a circular motion to create a great-looking dish.
Health benefits: Grapeseed oil is ideal for low-fat diets because it creates a film more easily than other oils – spreading itself more thinly over a salad, for example. Grapeseed oil is less volatile than many other vegetable oils and so can be used for frying. It’s also used in a lot of cosmetic products and is an excellent skin moisturiser.
Health downsides: Grapeseed oil is not high in monounsaturated fats, so isn’t as heart-healthy as olive or avocado oil, for example.
How to get the best health benefits: Flavour is grapeseed oil’s downfall – it doesn’t have much. So add herbs to your bottle (rosemary, thyme, garlic or chilli) to give it extra kick and drizzle over salad.
Health benefits: All nut-based oils are low in saturated fats. Choose walnut for extra omega-3; almond and hazelnut for added vitamin E (great for skin and hair), and a good helping of monounsaturated fats.
Health downsides: Heating nut oils can alter their flavour, so chefs tend to use these delicious – and expensive! – liquids as you would a herb or spice.
How to get the best health benefits: Drizzle on top of vegetables for a nutty finish; on toast with cinnamon and a sprinkle of sugar; or in a salad.
Flaxseed (or linseed) oil
Health benefits: "Linseed oil is a rich source of the omega-3 alpha-linolenic acid, which can help prevent heart attacks and stroke," says Norris. The oil is also an excellent source of omega-6 fatty acids and its alpha-linolenic acid helps prevent stroke and skin problems such as acne.
Health downsides: Don’t swap your sardines for seeds just yet. Although flaxseeds contain six times more omega-3 than the equivalent quantity of most fish oils, the omega-3s in flaxseeds is in a form that’s much harder for the body to use than that in fish oil.
And be aware that this oil just can’t stand the heat – it can even change its chemical structure when exposed even to warm room temperatures. Keep it in the fridge and use it only on salads. For added benefit, sprinkle a handful of seeds in your porridge or cereal
How to get the best health benefits: Don’t be fooled into thinking that a bottle of linseed oil from your local DIY shop is the same as that from your healthfood supermarket – it’s either heat-treated or has chemicals added, so won’t be nearly as tasty on your salad!
Health benefits: Taken from the safflower seed, safflower oil is flavourless and contains an omega-6 fatty acid called linoleic acid. And, say researchers, it could prove as useful a tool as omega-3 in the fight against heart disease.
Health downsides: "We don’t yet know all we need to about omega-6 fatty acids," says Professor. Martha Belury, lead study author from Ohio State University, US. "Some research was done in the 60s and omega-6s were found to improve cardiovascular health in men, but little or no research was done into the mechanisms that made this happen. Now, because of public interest in omega-3s, funding research concerning omega-6s is very difficult. But I firmly believe there’s more to be learned and we’re working on it."
How to get the best health benefits: There are two kinds of safflower oil available. Monounsaturated safflower oil can tolerate high temperatures and so can be used in hot dishes, but polyunsaturated safflower oil should not be used for cooking. Instead, use it in salad dressings and sauces.