Why vegetable oils aren't the answer
It seems such a simple question. Yet just how confusing can one subject be? Everyone has a different answer – including different ‘experts’ on the topic. So just what is the healthiest cooking oil?
Each oil attempts to market itself as the healthiest: rapeseed, avocado, ‘untoasted’ sesame – with such strong marketing messages how can consumers really know what we should be using to cook with? Chefs recommend cooking oils that give most (or least) flavour to the food, and favour refined oils that can be heated to high temperatures. Add to this a smattering of perplexing jargon about stability, smoke points and woefully confusing messages about saturated and polyunsaturated fats, and it’s easy to see why most of us really have no idea what to use.
At home, the oil I cook with most is olive oil; I admit that my olive oil collection is now becoming a bit of an obsession – including unfiltered, cold pressed oils from several different countries as well as those I use for cooking. Next on my list are coconut oil, organic butter and ghee (clarified butter) and occasionally use goose fat and sesame oil. I would use avocado oil but it’s expensive and more importantly I find it hard to locate.
The rest of my oils – cold-pressed, unrefined walnut, cobnut, British rapeseed and pumpkin seed (to name a few) adorn the shelves next to my various olive oils. I love using these for drizzling over cooked foods, as dressings or in hummus-type dips.
In an attempt to demystify the world of healthy cooking oils, here’s what we think:
Animal Fats: butter, ghee, lard, duck and goose fat – these ‘stable’
animal fats are best for cooking – they can be heated to high temperatures without chemically altering. But should we be eating them? Well here’s the thing: for years we’ve been told to reduce saturated fat due to the risk of cardiovascular disease. Yet recent research has finally done a u-turn on saturated fat, concluding that ‘saturated fat isn’t the issue’ (but sugar may be!). In addition butter provides Vitamin A in the form of retinol (so for those who genetically don’t convert beta-carotene to Vitamin A well, butter is an important Vitamin A source). We’ve started to make our own ghee at home – it can be used for high heat cooking but from a nutritional point of view is a great source of butyrate – a short chain fatty acid that is extremely beneficial to the digestive system.
Coconut Oil is a ‘must have’ in the kitchen cupboard – a tasty,
plant-based saturated fat, very stable and fab to cook with – on the stove, in curries, smoothies and in bakes. Although technically a saturated fat, coconut is rich in medium chain fatty acids – which are used by the liver for energy instead of being stored as fat. Coconut also has antimicrobial properties so is great for the immune system. Unless you buy refined coconut oil, it does taste (obviously) of coconut – so it’s not great in every meal.
Olive Oil, a monounsaturated fat and component of the healthy ‘Mediterranean’ diet has been shown in research to reduce heart disease risk. It’s not as stable as saturated, but is still good for cooking albeit at slightly lower temperatures. Extra-virgin olive oil (EVO) is cold pressed, higher polyphenol (antioxidant) and studies show that this is the oil to eat for most of the health benefits (a couple of tablespoons a day). Contrary to popular belief, EVO can be heated to nearly the same temperature as ‘normal’ olive oil. But if you cook with EVO know that it will lose some of the beneficial antioxidant properties the longer you cook with it and the higher the temperature. So I do cook with my cheaper bottles of EVO but keep the temperature low (well under 160°C) or the time short. If I’m sautéing I don’t heat the oil by itself for long – adding the food (e.g. onions) will quickly lower the temperature.
Vegetable oils shouldn’t be used for cooking. They include sunflower, safflower, corn, rice bran, groundnut, rapeseed (canola) as well as most seed and nut oils (with the exception of avocado or macadamia which are mostly monounsaturated). Rapeseed has a high monounsaturated fat content (which is good) but also a larger proportion of the easily oxidised polyunsaturated fats than olive oil does – so I keep cold-pressed rapeseed oil for dressings and mayo instead.
Vegetable oils are unstable fats – chemically changing (oxidising) very easily. The smoke point of an oil is where it changes chemically, releasing carcinogenic compounds. But crucially – oils oxidise, and become damaging to our health, at lower temperatures than the smoke point; the ‘smoke point’ that is so often quoted isn’t the most important factor in whether to cook with an oil – instead it’s the oxidisation factor. Oxidised oils damage the body and it’s the ‘unstable’ polyunsaturated oils that oxidise most easily, particularly with heat.
Yet ironically these are the very oils – cheap and easily available, that we are told are healthy. For years we were told to ditch butter and use margarine or sunflower oil for cooking. Now we know better – at home – but they’re still used in processed foods, for deep-frying in fast food outlets and for potato crisps (it makes no difference that they’re ‘hand cooked’ in sunflower oil) and margarines. Not only do fast food outlets use the unstable oils but they heat them repeatedly – the worst possible combination. The more an oil is reheated, the worse it becomes.
The only seed oil I cook with occasionally is a little (ideally unrefined) sesame oil for the flavour it adds. Research suggests that it is the only nut or seed oil with a particular polyphenol (sesamol) that actually protects the oil from oxidation at high temperatures. So for stir-fries, I start off with stable coconut oil (or I steam fry with a little water) and add sesame oil for a minute at the end – or simply drizzle it over noodles.
The final big issue with vegetable oils is that they are usually refined. The refined, light coloured, low flavoured oils in the supermarket have a higher smoke point, so are favoured by chefs. Do we care I hear you say? Well, think about it. Some oils are not so easy to extract (have you tried to get oil from a sunflower seed or rapeseed?) so heat and/or chemicals are normally used. We know with high temperatures that polyunsaturated fats oxidise and go rancid. They smell bad and look unappetising. So after extraction, these oils need to be bleached and ‘deodorised’ to get rid of the smell and make them look better. But the high temperature refining process itself is likely to have already oxidised some of the fats, as well as lowering beneficial polyphenol content. Add to this the chemicals involved and refined oils don’t really top my list of oils I’d like to eat.
It’s no wonder we’re confused….. but stick with butter, olive oil, ghee and coconut oil for cooking – and you won’t go far wrong.
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