The truth about cooking oils: The experts’ guide

Are seed oils really all that bad for you? What about coconut? Peta Bee asks the experts.

If you’re not sure which are the healthiest oils and fats to use in your cooking, you are not alone.

With conflicting studies being published as to which is best, along with heated debate on social media, it’s no surprise that we’re confused.

Seed oils such as sunflower, safflower and corn oil have recently come in for particular criticism, with influencers using the hashtags seedoils and seedoilfree branding them as unhealthy, even toxic, and blaming them for driving up rates of obesity and disease.

Donald Trump’s health secretary, Robert F Kennedy Jr, has suggested that Americans are being “unknowingly poisoned” by seed oils.

But experts aren’t convinced. This criticism of seed oils rests on their high content of omega-6 polyunsaturated fatty acids, including one called linoleic acid.

In theory, larger amounts of omega-6 fatty acids compared with lower levels of anti-inflammatory omega-3 fatty acids contribute to inflammation in the body that is linked to disease. However, according to Philip Calder, a professor in nutritional immunology at the University of Southampton, “it is a hypothetical argument” without scientific backing. “People have talked [online] about the fact that seed oils can be pro-inflammatory but there isn’t any evidence in humans that it is the case,” Calder says.

That’s not all.

There's conflicting information about different oils.

Last month a study in the European Journal of Clinical Nutrition suggested that a daily intake of 5g of butter was associated with lower levels of type 2 diabetes, a risk factor for heart disease.

But a larger recent investigation involving over 200,000 participants and published in the Jama Internal Medicine journal suggested that butter is the baddie, and a higher intake is linked to a 15 per cent increased risk of premature death. In that paper a consumption of plant oils such as olive, canola and soybean was associated with a 16 per cent lower risk of early death, particularly from cardiovascular disease and cancer.

Even olive oil is not without its critics. This week scientists at the University of Oklahoma College of Medicine announced in the journal Cell Reports that a high-fat diet containing relatively large amounts of oleic acid – a fatty acid found in olive, sunflower and many other plant-based oils – could spur the body into making more fat cells. Michael Rudolph, an author of the paper and assistant professor of biochemistry and physiology at Oklahoma, said the take-home message from his study is to aim for moderation and a variety of fats in the diet. “Relatively balanced levels of oleic acid seem to be beneficial, but higher and prolonged levels may be detrimental,” Rudolph says.

So which should you choose?

How much oil should I be consuming daily?

Healthy fats are an important part of a healthy diet, but the government recommends that total fat intake – including all plant oils – should not make up more than 35 per cent of our total daily calories. “Oils, even the healthy ones, are energy dense, meaning they provide a lot of calories in a small amount,” says Bahee Van de Bor, a dietitian and spokesman for the British Dietetic Association.

“Cooking with a small splash is good and that can help the absorption of fat-soluble vitamins from vegetables.”

Just two tablespoons of oil provides about 28g of fat and 238 calories which, if consumed in addition to your regular energy intake, won’t be kind to the waistline in the longer term.

Cooking with a small splash of olive oil on vegetables can help with absorption of fat-soluble vitamins.

“Maintaining a healthy weight is important for reducing the risk of heart disease and type 2 diabetes, and promoting healthy ageing,” Van de Bor says. “So keep an eye on overall fat intake.”

Why are so many saying seed oils aren’t good for health?

Seed oils are a subgroup of plant oils extracted from the seed rather than the fruit of a plant. They are rich in unsaturated fats – including both mono-unsaturated and polyunsaturated fats – which are beneficial for heart health when used in place of saturated fats. They also contain the omega-6 fat linoleic acid, an essential fatty acid.

“Some concerns raised about seed oils relate to the potential for high omega-6 intake, which may promote inflammation, especially if intake of anti-inflammatory omega-3 fatty acids in the diet is low,” Van de Bor says. “However, large reviews and well-conducted studies haven’t found any consistent evidence of harmful effects of seed oils.”

Sunflower oil is a seed oil.

In fact, using seed oils as part of a balanced diet is a healthy move. “Linoleic acid is actually very important for the skin and for controlling cholesterol,” Calder says. “Seed oils also contain tocopherols, which are antioxidants, and other phytochemicals such as phytosterols that can also help to lower blood fats.”

Of more concern is not the oils themselves, but how they’re used. Calder says the polyunsaturated fatty acids in seed oils are very prone to damage from high heat and seed oils shouldn’t be used for frying or reused for cooking.

Are nut oils a healthier option?

Nut oils, such as walnut, macadamia and almond, share some similarities with seed oils – both are sources of unsaturated fats, which support heart health. However, their fatty acid profiles differ. For example, almond and hazelnut oils are rich in mono-unsaturated fats, while flaxseed and sunflower oils are higher in polyunsaturated fats, including omega-3 and omega-6. Both mono-unsaturated and polyunsaturated fats are considered heart-healthy, and Van de Bor says there’s no need to favour one over the other. The British Heart Foundation recommends including a variety of unsaturated fats in a healthy diet. “Nut oils offer a favourable balance of polyunsaturated fats, including both omega-6 and the plant-based omega-3 fat alpha-linolenic acid (ALA),” Van de Bor says.

Almond oil is rich in mono-unsaturated fats.

Rhiannon Lambert, a registered nutritionist and the author of The Science of Nutrition, says unrefined peanut oil is good for adding to sauces or as a dressing, whereas the refined version can be cooked at high temperatures and used for frying.

How do I choose the best olive oil for my health?

All types of olive oil are relatively high in beneficial mono-unsaturated fatty acids – about 75 per cent by volume – which has been shown to help lower your “bad” low-density lipoprotein (LDL) cholesterol when substituted for saturated fats. But with extra virgin olive oil – the purest, most antioxidant-packed variety – you get some further health benefits, although you do of course pay more. Cold-pressed extra virgin olive oil is considered the gold standard because it is pressed from ripe olives and processed without high heat or chemicals, preserving many of the polyphenol compounds found in the plant.

Virgin olive oil is similar but mechanically extracted from the plant. “Of the other types, olive oil or pure olive oil are typically a blend of refined olive oil with a small amount of virgin or extra virgin oil added back for flavour,” Lambert says. “And the term ‘light’ olive oil, which refers to its mild taste and lighter colour, not to reduced calories or fat, is more refined and processed, but still has health benefits.”

In theory, the higher concentrations of polyphenols in extra virgin olive oil may provide extra antioxidant and disease-fighting benefits, although there is no clear evidence that it has greater disease-fighting effects than other types.

Should I cook with extra virgin olive oil?

All fats have a smoke, or burn, point, the temperature at which they begin to degrade and produce unwanted chemical by-products that affect both the health profile and flavour of the oil. For decades it was thought that olive oil was best served cold, drizzled on salads, but Van de Bor says the idea that it shouldn’t be heated is a misconception. “In fact, extra virgin olive oil is stable enough for most everyday cooking methods like roasting, sauteing or pan-frying,” she says. “It contains natural antioxidants and polyphenols that help to protect it during heating, and its smoke point of around 190-210C is well above typical cooking temperatures used at home.”

More refined olive oils, including those labelled “light” or just “olive oil”, tend to have a higher smoke point because they contain fewer impurities. “Although they have less of the flavour and antioxidants of extra virgin olive oil, it makes them a bit better suited for higher-heat cooking like stir-frying,” Lambert says.

Are olive oil shots a good idea?

Taking daily shots of two tablespoons of olive oil is a wellness trend said to bring health benefits ranging from improved digestion to complexion. Beyonce, Gwyneth Paltrow and Jennifer Lopez are among those extolling its virtues on social media, with Goldie Hawn reportedly drinking olive oil before bed.

Is it worth doing an olive oil shot?

If you can bear to drink it, is it worth it? “Olive oil has health benefits, but taking shots of it rather than incorporating it into meals doesn’t offer added benefits,” Lambert says.

Is avocado oil even better than olive oil?

Avocado oil is considered an elixir for health, providing vitamin E, lutein for eye health and beneficial plant polyphenols and carotenoids, but it does come with a hefty price tag. A small 2017 study in the Journal of Functional Foods did show that swapping butter for avocado oil helped to lower blood fats and cholesterol levels, although it looked at people who were given the equivalent of a fry-up for breakfast and the removal of some saturated fat – the butter – in place of any plant oil might have provided the same benefits. Lambert says it’s a good choice for cooking at temperatures of 200C or higher. “But in health terms it’s probably no better for you than olive oil.”

What about coconut oil?

A few years ago coconut oil was on everyone’s shopping list due to its unique flavour and purported health benefits. It contains high levels of medium-chain triglycerides (MCTs) which because they are quickly absorbed by the body are thought to promote satiety and, in turn, prevent the storage of body and belly fat. However, MCTs are also a form of saturated fat, the type linked in many studies to increased LDL cholesterol, a risk factor for heart disease. In 2020, a review of 16 papers published in the American Heart Association’s journal Circulation concluded that regular “consumption of coconut oil results in significantly higher LDL cholesterol” than other plant oils. As a consequence, it began to fall out of favour.

Coconut oil has high levels of MCTs.

So, should we avoid it? “Current evidence suggests that coconut oil may have a neutral effect on blood cholesterol – not as harmful as butter, but not as beneficial as oils rich in unsaturated fats, such as olive or rapeseed oil,” Van de Bor says. “Using it occasionally when baking or sauteing foods is fine.”

Is butter a better choice after all?

The latest study suggesting we revert to 5g daily of butter to reduce the risk of type 2 diabetes and heart disease may have raised hope among butter-lovers, but Van de Bor says we should still eat it sparingly. “Broader and more robust evidence consistently supports choosing unsaturated plant-based oils over butter for long-term health,” she says. “Larger and more robust studies such as the JAMA Internal Medicine paper earlier this year underpin this by showing that replacing butter with unsaturated plant oils can reduce the risk of early death by around 17 per cent.

“Use it occasionally, but not in place of healthier plant oils,” she says.

Which oils do the experts use?

Calder says olive oil is his staple at home. “But rapeseed or canola is not bad at all as it has a mix of healthy plant fatty acids and is quite a balanced provider of omega-6 and omega-3 fatty acids,” he says.

We should still eat butter sparingly.

Van de Bor also has rapeseed oil and olive oil on standby for everyday use. “For salads, I sometimes reach for walnut oil, especially when making my own dressings,” she says. “And I do use coconut oil occasionally, particularly if I’m making homemade granola, as I simply enjoy the flavour.”

Lambert, who also favours olive oil, says variety is key. “Flaxseed or linseed oil is one of the richest sources of ALA, a plant-based omega-3, although it’s not recommended for cooking at high temperatures due to its low smoke point,” she says. “And sunflower oil, rich in omega-6 polyunsaturated fatty acids, can also be part of a healthy balanced diet when minimally processed versions are used.”

This article originally appeared on The Times.

Originally published as The truth about cooking oils: The experts’ guide