The following correction was printed in the Guardian's Corrections and clarifications column, Wednesday August 8 2007

The article below mistakenly stated that almost any cooking of olive oil beyond the gentlest of sweating would transform it into trans fats. Most trans fats in food are the result of an industrial hydrogenation process. Frying in oils such as sunflower or olive oil has an insignificant effect in producing trans fats.

Sales of extra-virgin olive oil hit a record £71m last year, which means it now accounts for more than 30% - the largest share - of the UK oil market. These figures have led some people to conclude that we're adopting "a healthier, Mediterranean diet".

There are as many things wrong with that statement as with the over-use of the oil in the first place. Yes, as a mono-unsaturated fat, it is healthier than animal fats, but that's not what we're normally substituting it for: usually, we use it in preference to other oils - predominantly sunflower oil - which is poly-unsaturated and, as such, healthier than both olive oil and butter. In practice, any monounsaturate heated to smoking point turns into a trans fat, which is worse for you than all other fats put together. And since olive oil has a much lower smoking point than, say, groundnut oil, almost any cooking activity beyond the gentlest of sweating will bring about this bad-fat transformation. In any case, except in dishes such as ratatouille, which showcase the oil as much as other ingredients, I would never use olive oil for cooking, but rather for dressings.

Even here, though, it's terribly over-used - you find people mixing it with chilli and soy sauce and ginger, for a cheeky oriental theme, which is just lunacy, since in those cases, you want an oil that brings nothing to the table but oiliness. Even in Middle Eastern dressings, with cumin and tahini and whatnot, I might use a regular olive oil, if it were right next to my hand, but never extra virgin. This stuff is incredibly expensive.

Instead of being British about it, and just trying to hammer the price down with supermarket jiggery-pokery, we should try to be more Italian about olive oil, accept its very great expense as testament of its deliciousness, and only use it when we're really going to taste it.