A brief guide to cooking methods and cooking with fats

The cooking method we use can impact our food's nutrient value as well as its impact on our health. Here’s a nutritionist’s summary of the best and worst cooking methods, as well as some tips when it comes to cooking with oils and fats.

Tatiana Mazzocca
Tatiana Mazzocca
Saturday 14 January 2023

The best cooking methods are those that not only create delicious dishes but also retain a high amount of vitamins and nutrients in the food when cooked.

Some of the less favourable cooking methods are those that reduce the nutrient density of the cooked food, but also cause health damaging changes such as burning and blackening of the food; when this happens, compounds are created called heterocyclic amines or polycyclic aromatic hydrocarbons (PAHs), and these have been linked to cancers as they can initiate changes to DNA.

Keep reading for our review of safer and health promoting cooking methods. And importantly we have outlined at the bottom what fats are safe to use with heat and which fats are best drizzled on cold at the end.


Grilling, baking and roasting have the green light.

These cooking methods are overall very good and retain nutrients well, as long as we get the timing right - over baking or grilling to the point of blackening the food is not healthy.

Roasting vegetables, with a knob of butter, and a pinch of sea salt, can really bring out the flavour and increase the availability of nutrients such as beta carotene and lycopene (a carotenoid that can help reduce the risk of heart disease). The point at which to stop cooking with these methods is just before the food gets blackened or there is a lot of smoke circulating the oven (this smoke contains carcinogenic compounds).

Steam, don’t boil!

Many nutrients leach into the water when you boil your food, especially the water soluble vitamins C and B; one way to deal with this is to drink some of the water once you are finished.
However, a much superior way to lightly cooking vegetables is to steam them. Lightly steamed vegetables retain most of their nutrients - it's not possible for them to leach into the water given they do not come into contact with it (just the steam). Lightly steamed vegetables are possibly superior to raw veg too as they are easier to digest and therefore more nutrients gets absorbed.
Here is a great steamer option you can use straightaway on the hob.

Sauté, don’t fry:

Frying dehydrates vegetables and increases fat absorption, whilst decreasing nutrients available. Lightly sautéing vegetables keeps the nutrients and antioxidants in!

Stir-frying with coconut oil is a tasty way to prepare foods, such as vegetables, while also opting for a healthier cooking method.


The jury is still mixed on the pros and cons of microwaving. In theory, microwaving is a good cooking option as it uses little water and is very quick and therefore should maintain most nutrients. A pubmed study found no significant nutritional differences exist between foods prepared by conventional and microwave methods.

However, a study inSpain found that microwaving broccoli for 5 minutes reduces total flavonoid content by 97%, which is a significant loss of its health benefits.

Overall, it's likely a good option for many foods, and eating veg cooked by this method is definitely better than eating no veg at all, however, I would advise steaming foods when there is the option over a microwave, and saving the microwave when you want convenience and speed.

Slow cooking.

Slow cooking is one of the oldest cooking methods, and it’s making a comeback thanks to Slow Cooker pots, mimicking the old terracotta containers that were placed on stoves or fireplaces. This cooking method requires 4 to 8 hours and never exceeds 90 degrees Celsius. This way, all the nutrients are preserved and the food cooks slowly, remaining juicy and very soft.

Slow cooking is particularly recommended for cooking legumes, soups, potatoes, fish and meat main courses, and in the main it will retain the organoleptic properties (colour, texture, aroma and taste) of the food.

It is advised to choose ceramic slow cookers and not aluminium ones, as aluminium heats up fast and can react with acidic foods creating a toxic cooking environment.

Air Frying:

Air frying has become very popular recently. To summarise the pros and cons, this method requires less oil than traditional frying which is great if you want to reduce your fat intake. It's very quick and involves less washing up.

However, it can still overcook foods resulting in health damaging compounds, so it's important to get the timing right. It has been found to reduce the omega 3 content in oily fish. Read here for more information.

Overall, its a viable option if you want a healthier alternative to frying and you get the timing right. But roasting, grilling or steaming may be an easier option if you don't want any more equipment in your kitchen, and possibly these options may be favoured for cooking fish and meat.

What fats are safest to cook with?

The two properties which impact how healthy or toxic an oil is when heated are its smoke point and oxidative stability.

Generally speaking, the more saturated a fat the more stable it is when heated e.g. butter. The unsaturated oils, e.g. olive and nut oils, will become oxidised and produce free radicals at high temperatures; free radicals in the body can damage DNA and cells.

  • Given the above, it is therefore best to cook with butter, ghee and coconut oil.
  • Avoid heating olive oil and avocado oil - these are best drizzled on the food cold.

Ideally, when choosing olive oil, choose extra virgin olive oil for the most optimal nutrients.

Extra tips on how to maximise nutrient absorption when cooking:

  • Make sure to pair iron rich foods (beef, fish, lentils) with vitamin C rich foods (broccoli, lemon juice, parsley, bell peppers). This is especially needed if you are low in iron or anaemic, as the Vitamin C contained in them will enhance the absorption by as much as 70%!
  • In addition, make sure to avoid dairy products and teas too close to main meals containing iron as these nutrients (calcium and tannins) can decrease iron absorption. For example, avoid cheese on spaghetti bolognaise or opt for tofu with lentils instead of feta with a lentil salad.