Unsaturated fatty acids
Fatty acids with at least one double bond, generally liquid at room temperature (oils), covering monounsaturated and polyunsaturated fats, which are considered beneficial.
Unsaturated fatty acids differ from saturated ones by the presence of double bonds in their carbon chain. These double bonds “bend” the molecule, preventing it from packing tightly, hence their liquid state (oils) at room temperature. They are divided into:
- Monounsaturated (one double bond): omega-9, oleic acid (olive oil, avocado)
- Polyunsaturated (several): omega-3 and omega-6 (fish, vegetable oils, nuts)
A fresh angle (structure explains everything): molecular geometry explains their properties:
- Physical state: double bonds prevent tight packing → liquid (versus solid saturated fats). The more double bonds, the more fluid and the lower the melting point (linseed oil stays liquid even in the fridge)
- Membrane fluidity: built into cell membranes, they make them more fluid and functional (saturated and trans fats stiffen them)
- Fragility: double bonds are points of oxidation → unsaturated fats go rancid and oxidise faster (especially polyunsaturated ones). Hence the need to protect them from heat, air and light
The cooking/health trade-off: a practical paradox, unsaturated fats are “healthier” but more fragile in cooking. Monounsaturated fats (olive oil) offer the best compromise: beneficial AND relatively stable (only one double bond). Fragile polyunsaturated fats (linseed, sunflower) are best kept for raw use.
Documented health benefits: replacing saturated and trans fats with unsaturated fats (especially monounsaturated and omega-3) improves the lipid profile and reduces cardiovascular risk. It is one of the pillars of the Mediterranean diet.
Sources: olive oil, avocado, nuts and seeds (mono); oily fish, walnuts, seeds, rapeseed/linseed oils (poly).