What is the healthiest cooking oil?

Find out the best and worst oils to cook with

Wondering what is the healthiest cooking oil? Should you use coconut oil, olive oil or sunflower oil? And which oils are the healthiest?

Learn the difference between saturated and unsaturated fats, why trans fats are harmful for health and the importance of smoke points. Find out the best and worst oils to cook with.

The difference between saturated and unsaturated fats

There are two main types of dietary fats: saturated and unsaturated fats. Unsaturated fats are further categorised into monounsaturated fats and polyunsaturated fats. Each of these groups of fats has a unique chemical structure.

Saturated fats are saturated with hydrogen molecules, making them a more stable fat and solid at room temperature. They include:

  • Coconut oil
  • Butter/ ghee
  • Palm oil
  • Lard, cream, cheese
  • Meat

Unsaturated fats are liquid at room temperature and less stable as they contain fewer hydrogen molecules. Monounsaturated fats are considered more stable than polyunsaturated fats as they have a slightly different chemical structure. They also contain omega 7 and 9, whereas polyunsaturated fats are rich in omega 3 and 6.

Monounsaturated fats include:

  • Olive oil
  • Macadamia nut oil
  • Avocado oil
  • Rapeseed oil (canola)
  • Peanut oil
  • Safflower oil
  • Sesame oil
  • Nuts (except walnuts)
  • Sunflower seeds
  • Avocados

Polyunsaturated fats include:

  • Sunflower oil
  • Corn oil
  • Soybean oil
  • Cottonseed oil
  • Walnuts
  • Flaxseeds, chia seeds, pumpkin seeds
  • Cold water fish (salmon, trout, tuna, mackerel, sardines, herrings, anchovies)

What are trans fats?

Trans fats (also called trans fatty acids) are a type of unsaturated fat that are naturally found in some animal-derived foods like milk and meat. Artificially-produced trans fats are made by food manufacturers by adding hydrogen molecules to liquid vegetable oils to make them solid (a process called hydrogenation) and extend product shelf life. This type of trans fat is found in margarine, refined vegetable oils, baked products such as cookies, pies and cakes, and processed foods like doughnuts, fried chicken, microwave popcorn, crips, shortening, frozen pizza, mozzarella sticks and French fries.

Artificial trans fats are very harmful for your health and are linked to increased risk of heart disease, blood clot formation, insulin resistance and cancer. Trans fats stiffen cell membranes, making them prone to damage as it alters their protective action and increases permeability, allowing toxins to penetrate the cell.

Why the smoke point of oils matters

The smoke point of an oil is the temperature at which it starts to burn or smoke. Some oils have a high smoke point, whereas others have a much lower smoke point.

Dietary fats and oils are prone to rancidity, generating compounds which are highly detrimental to health. Oils are more prone to oxidation if they are:

  • High in polyunsaturated fats
  • Exposed to prolonged heat, light or oxygen
  • Naturally low in antioxidants.
  • Refined or heavily processed

Oxidation is a chemical reaction that occurs if a substance comes into contact with oxygen. An example of oxidation is an apple that goes brown when cut open and left out.

When an oil goes rancid, its odour and flavour become unpleasant. Oxidation can also lead to production of highly toxic compounds (such as malondialdehyde) that can cause cell damage and genetic mutation.

Frying foods in oil promotes free radical formation which causes damage to cells. Frying is best avoided or kept to a minimum.

Cooking oils: which one should you use?

The best oils for cooking depend on how you intend to use them – is it for a salad dressing, for frying or for lightly sautéing your food.

As saturated fats are considered more stable and less prone to oxidation/rancidity, they are better for cooking as they can tolerate being heated. They have a high smoke point and should be chosen for high temperature cooking.

Monounsaturated fats oxidise at higher temperatures; however, they can be used for low temperature cooking (like sautéing and stir-fries) due to the naturally-occurring antioxidants in these oils.

Polyunsaturated fats oxidise when heated and produce free radicals that damage cells. They should only be used in their raw, cold-pressed form for pouring over cooked or raw foods. These oils are best stored in dark-coloured bottles in the fridge or freezer as they can go rancid quickly and can be oxidised simply through direct light exposure.

The best oils for high temperature cooking:

  • Coconut oil
  • Butter
  • Ghee

The best oils for low temperature cooking: (not above 180°C)

  • Extra virgin olive oil
  • Avocado oil
  • Macadamia oil

The best oils for dressings or drizzling:

  • Flaxseed oil (cold-pressed)
  • Extra virgin olive oil (cold-pressed)
  • Walnut oil (unrefined, cold-pressed)

Refined oils to avoid:

  • Rapeseed oil (canola oil)
  • Safflower oil
  • Sunflower oil
  • Corn oil
  • Soybean oil
  • Cottonseed oil
  • Margarine
  • Vegetable oils

These refined oils are harmful for the body. During the refining process, the oils are often purified, treated and deodorised with toxic chemicals like bleach and hexane. They also oxidise easily during the refining process, making them go rancid and turn into trans fats.

Avoid unhealthy oils at all costs

There is much confusion around what oils are best to cook with as there are so many to choose from. Frying foods at high temperatures isn’t healthy, but if you do want to fry foods, it’s best to use a saturated fat like coconut oil. Avoid using highly refined oils and eating foods that contain trans fats. Cold-pressed oils like flaxseed oil and extra virgin olive oil are the healthiest oils when used as dressings or drizzled over foods (not heated). Familiarise yourself with the smoke points of oils to prevent burning or smoking oils.

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