Polyunsaturated fatty acids
Fatty acids with several double bonds, including the essential omega-3 and omega-6 families, which are indispensable but fragile and sensitive to oxidation.
Polyunsaturated fatty acids (PUFAs) have several double bonds in their chain. They include the two essential families: omega-3 (ALA, EPA, DHA) and omega-6 (linoleic acid, arachidonic acid). The body cannot make either one from scratch.
The original angle (fragility, the flip side of the coin): the multiple double bonds that make PUFAs biologically valuable also make them chemically fragile: each double bond is a point of attack for oxidation.
Crucial practical consequences:
- Do not cook at high temperature with oils rich in PUFAs (sunflower, flax, walnut, grapeseed): they oxidise and form harmful compounds (aldehydes). Flax in particular should be used raw and cold, stored in a cool place away from light
- Rancidity: foods rich in PUFAs (nuts, seeds, oils) go rancid quickly. A walnut oil that “stings” is oxidised
- For cooking, prefer stable fats: olive oil (monounsaturated), a little butter or saturated fats
The omega-6/omega-3 imbalance: the modern diet supplies too much omega-6 (sunflower/maize/soya oils are omnipresent in processed foods) and not enough omega-3. Rebalancing means more omega-3 (oily fish, flax, walnuts, rapeseed) and fewer industrial oils rich in omega-6.
Roles: cell membranes (fluidity), signalling (PUFAs are precursors of molecules that regulate inflammation, clotting and immunity), and the brain (DHA is structural). Essential but to be handled with care (raw, fresh, protected from heat and light).