As a personal trainer in London, my clients often ask me for tips on healthy eating. One question which came up recently was: “Which oils are best for cooking with, health-wise?”
The best oils for cooking are the ones which are more stable at high temperatures, and also are the least processed.
Generally, the higher the content of polyunsaturated fats in an oil, the less stable it is at high temperatures, so you need to choose oils with higher saturated and monounsaturated fat content. This is counter-intuitive, because polyunsaturated fats (omega 3 and omega 6) are generally regarded as “healthy fats” which is true, except when they’re heated.
Extra Virgin Olive Oil
This is one of the best oils for cooking, as it is not chemically processed and fairly heat-resistant. Olive oil is 14% saturated fat, 75% monounsaturated fat, and just 11% polyunsaturated fat.
Olive oil doesn’t oxidise easily, which means that the fats don’t break down when heated. As a result, fewer harmful oxidised compounds are created when olive oil is used in cooking. The higher degree of saturation, the more stable the oil in its chemical structure when heated. Monounsaturated fats are far more stable than polyunsaturated fats, so olive oil is great for cooking with.
As with all oils, don’t re-heat food containing olive oil, as this can degrade the fats in the oil and cause oxidisation and the resulting harmful compounds.
Beware of olive pomace oil, a much lower grade of olive oil than extra virgin olive oil.
Whereas extra virgin is extracted naturally from the first press of olives, olive pomace oil is extracted from the remaining olive pulp left over from the first press. Solvents are used to chemically extract the remaining oil from this pulp, and the British Food Standards Agency has warned that contaminants caused by the chemical extraction process may have carcinogenic properties.
The Spanish government went further, imposing a temporary ban on olive pomace oil until more had been learned about PAHs (polycyclic aromatic hydrocarbons), the main contaminant in olive pomace oil. Now they have allowed it back into the market, but with legal restrictions on the maximum amount of PAHs.
It is very tempting, when you see the high price of extra virgin olive oil, to choose the big 5 litre carton of Olive Pomace Oil Blend (a 50/50 blend of olive pomace oil and canola oil) in the supermarkets, which is cheaper than a small bottle of olive oil. The price difference is for a reason, as the quality of the oil and the health effects are very different too.
Another oil that is ideal for cooking with is coconut oil, but use sparingly. This oil is over 90% saturated fat, which makes it more stable and therefore highly heat-resistant. Another plus is the chemical-free processing of this oil. In addition, coconut oil is rich in lauric acid, which has strong anti-pathogen properties. Coconut oil is also great for healthy skin, nails and hair.
Cooking Oils to Avoid
Sunflower oil is high in omega 6 polyunsaturated fats, which makes it one of the worst for cooking. Omega 6 fatty acids are essential fatty acids, but only healthy in small quantities and best eaten cold and uncooked in their natural state, such as in nuts & seeds.
Flaxseed oil is also terrible for cooking, being high in omega 3 polyunsaturated fatty acids. When consumed cold and uncooked and in small quantities, omega 3 is essential for health. When cooked at high heat, its chemical structure breaks down (oxidises) and releases harmful compounds. When you eat fatty fish, rich in omega 3, the cooking process does not break down the fat to the same extent that heating polyunsaturated oil to a high heat does, so the omega 3 in cooked fish is healthy to eat.
Avocado cooking oil is also bad for cooking, mainly because it undergoes a chemical refining process with solvents and heat to manufacture the oil from avocados. Raw avocados, in contrast are very good for you, as is extra virgin avocado oil used as a salad-dressing, because it is cold-pressed and no solvents are used in its production.
Canola oil (also known as rapeseed oil) is not the worst oil for cooking with, but still has a fairly high percentage of polyunsaturated fats at 28%, with a lower percentage of saturated fats (7%) and 65% monounsaturated fats. Canola oil derives its name from the country where most of it is produced: Canada, which has thousands of acres of rapeseed fields in full bloom in the summer. Those fields of yellow flowers are also abundant in parts of rural England, where the rapeseed plant is cultivated for its oil.
Regardless of the oil used, health experts recommend you avoid deep-fat frying, because of the large amount of fat absorbed into the food being fried. Worst of all is deep-fried food where the oil has been re-heated many times, such as in fish & chip shops, which results in the oil becoming increasingly toxic.
The Best Cooking Pans
When you cook with oil, choose a pan which isn’t coated with Teflon. Marketed for its non-stick properties, Teflon has the major health disadvantage of releasing chemical particles which have been linked to Alzheimers and certain cancers. So use stainless-steel, cast-iron or ceramic pans instead.
Although it’s not an oil, it’s worth a quick mention. Butter is great for cooking with, and also tastes delicious. Butter is processed naturally, with no chemicals, and it’s rich in vitamins A, B12, E and K2. It’s high in saturated fat (68%), the rest being monounsaturated fat (28%) and zero polyunsaturated fats. This makes the fats in butter very stable at high heat. Just make sure you use it in moderation.
(Dominic Londesborough is a personal trainer in London and an online nutrition coach.)