The olive oil test you can do with your throat

The cough is the point

Swallow a teaspoon of a genuinely good extra virgin olive oil and you get a peppery catch at the back of the throat that can make you cough once or twice. That sensation has a name and a cause: oleocanthal, a phenolic compound that irritates a receptor called TRPA1 in the throat, and only in the throat. It is the same receptor ibuprofen acts on, which is why the sting feels oddly familiar and why the compound was described as ibuprofen-like when it was characterised.

This matters because it is a test you can run without equipment. Polyphenol content is the single thing that separates an olive oil worth paying for from a bottle of expensive fat, and the cough tracks it. Supermarket oil that slips down like a mild vegetable oil is telling you something true about itself.

What the polyphenols are doing

Olive oil is roughly three-quarters monounsaturated fat, and that fraction is not the interesting part; you can get oleic acid from far cheaper sources. The interesting part is the minor fraction: oleocanthal, oleacein, hydroxytyrosol, tyrosol and their relatives, present at anywhere between under 50 and over 800 mg per kilogram depending on the oil.

The EU allows a health claim for olive oil polyphenols at 5 mg of hydroxytyrosol and derivatives per 20 g of oil, on the basis of protecting blood lipids from oxidative damage. Plenty of oils sold as extra virgin do not reach it. The claim is narrow and the evidence behind the broader enthusiasm is mostly observational, but the direction is consistent enough that if you are going to use a fat every day, this is a sensible one to make good.

How to buy it, and how to keep it

Ignore the front label, which is marketing, and look for four things. A harvest date, not a best-before: olive oil is a fruit juice and it declines from pressing, so you want the most recent harvest you can find and ideally to finish it within a year of that date. Dark glass or tin, because light degrades polyphenols quickly. A named region or estate rather than the legally meaningless blend of oils from more than one country. And a polyphenol figure if the producer publishes one, which the better ones increasingly do.

Then treat it properly at home: cool, dark cupboard, lid on, away from the hob. Heat, light and oxygen are what strip the compounds you paid for. And use it — a bottle kept for special occasions is a bottle slowly turning into ordinary oil.

• 01

  Look for a harvest date, not a best-before

  First thing
• 02

  Dark glass or tin, and a named origin

  Second
• 03

  Buy the one that makes you cough

  The free test