Cooking oil has become an unusually heated subject. Some of the argument is legitimate, some is not, and the metric everyone quotes (smoke point) is not the one that matters most.
Smoke point is the wrong headline number
Smoke point is the temperature at which an oil visibly smokes. It is easy to measure and easy to put in a table, which is why it dominates the discussion.
What actually matters is oxidative stability: how readily the fat forms harmful oxidation products when heated. These are related but not the same, and they can point in opposite directions.
The determining factor is how saturated the fat is. Saturated and monounsaturated fats have few or no double bonds and resist oxidation. Polyunsaturated fats have several, and each one is a point of vulnerability. A refined polyunsaturated oil can have a high smoke point and still oxidize readily: a high smoke point does not make it a good frying oil.
Extra virgin olive oil illustrates the point. Its smoke point is moderate, which has led to decades of advice not to cook with it, yet it performs very well under heat in practice because it is largely monounsaturated and carries polyphenols that act as built-in antioxidants.
The omega-6 question, fairly stated
Here is the part that gets argued about.
What is not in dispute: omega-6 intake has risen enormously over the last century as industrial seed oils became cheap and ubiquitous. Estimates of the omega-6 to omega-3 ratio in modern Western diets run from about 10:1 to 20:1, against something closer to 1:1 to 4:1 historically. Both omega-6 and omega-3 fats compete for the same enzymes, so the balance affects which downstream signaling molecules get made.
What is disputed: whether the ratio itself is the meaningful variable. Randomized trials replacing saturated fat with polyunsaturated fat have generally shown neutral or favorable effects on blood lipids, which does not fit the strongest version of the seed-oil argument. Many researchers hold that raising omega-3 intake matters more than cutting omega-6.
What is fair to say: the omega-6 in a walnut and the omega-6 in a bottle of oil that has been extracted with solvents, deodorized, and then used repeatedly at high heat in a commercial fryer are not equivalent exposures. Much of the health signal attributed to seed oils is difficult to separate from the fact that they arrive overwhelmingly in ultra-processed food. That confounding is real and it cuts both ways.
A defensible position: reduce industrial seed oils mainly by eating less fried and packaged food, raise omega-3 intake, and do not treat the occasional restaurant meal as a health emergency.
A short practical list
Everyday cooking, medium heat: extra virgin olive oil. It is the most thoroughly studied cooking fat there is, and the evidence behind it is unusually consistent.
High heat, roasting and searing: avocado oil, which is high in monounsaturated fat with a genuinely high smoke point. Ghee or butter for flavor at moderate heat.
Dressings and finishing, no heat: extra virgin olive oil, cold-pressed flax or walnut oil. Never heat flax: it is highly polyunsaturated and oxidizes rapidly.
Use sparingly: refined corn, soybean, cottonseed and generic “vegetable oil”, not because a single use is harmful, but because they are the oils you are already getting a great deal of without choosing them.
Storage matters more than people think
An oil that has gone rancid in the cupboard is worse than a less fashionable oil that is fresh. Buy quantities you will finish in a few months, keep bottles dark and closed, and away from the hob. If an oil smells like crayons or old nuts, it has oxidized: throw it out.
Related reading
- How to Choose a Fish Oil: The Numbers on the Back of the Bottle
- Omega-3s and Heart Health: An Honest Reading of the Evidence
- Grass-Fed vs Grain-Fed: What the Difference Actually Amounts To
Raising omega-3 intake is the easier half of the balance to change: OmegaEnergy provides 600 mg of EPA and DHA per softgel.
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