It’s time to audit the oils in your pantry! The so-called “heart healthy” processed oils could be causing you more harm than good.

If talk of cooking oils, smoke points and rancidity causes your eyes to glaze over, you’re not alone. There’s a whole lot of confusion and misinformation around cooking oils – which is alarming considering most of us use them every day. However, there’s an easy way to sort your good oils from bad.

Good nutrition usually comes down to the same basic principle: eat real food. Despite the name, most processed vegetable oils are far from anything resembling a vegetable. To clarify, we’re talking about processed industrial oils such as sunflower, canola, corn, grapeseed, soybean, rice bran and peanut oil. Any oil labelled “vegetable oil” or “blended vegetable oil” is most likely canola or a mix of the above, anyway.

So what’s so wrong with these oils? For one, they require a large amount of chemical processing. At the very least, they’re usually treated with a petrol-based solvent called hexane, bleached, de-gummed and deodorized to disguise the foul smell. Doesn’t sound very “real” to us.

However, the chemical processing is really just the start of the issue, says THR1VE nutritionist Shannon Young. “These oils are higher in polyunsaturated fatty acids (PUFAs) making them more prone to rancidity,” she says. They become rancid when they oxidise through exposure to air, heat and light – then become unstable.

Consuming these rancid oils can promote inflammation and ultimately oxidative stress in the body. “Oxidative stress can cause everything from wrinkles and premature aging, but also damage our blood vessels and cell membranes and wreak havoc on our insides causing fatigue, memory loss, muscle pain and a high susceptibility to disease and illness,” Young explains.

It’s important to point out that oxidation is a natural process in our body. “It occurs during the natural metabolism process, when our immune system defends off bacteria or is detoxifying from pollutants,” Young says. However, when there is too much oxidation without a balance of antioxidant action, it can become harmful.

Vegetable oils also tend to have a high concentration of one particularly troubling polyunsaturated fatty acid called linoleic acid. “It is a fragile fatty acid that becomes inflammatory when exposed to heat and creates oxidative stress within the body,” Young explains. Yet, these oils are most commonly used at high heat in deep fryers and in frying pans. It’s a dangerous combination.

So what should we use?