Expansion
Saturated, monounsaturated and polyunsaturated, with omega-3 and omega-6 essential
Expansion
- Saturated: no double bonds. Solid at room temperature; raise LDL
- Monounsaturated: one double bond, such as oleic acid in olive oil
- Polyunsaturated: two or more
- Omega-6: linoleic acid, essential. Precursor of arachidonic acid and therefore of the eicosanoids
- Omega-3: alpha-linolenic acid, essential; also EPA and DHA from fish. Give rise to less inflammatory eicosanoids
- Trans fats: industrially hydrogenated. Raise LDL and lower HDL, and are the most atherogenic class
The essential fatty acids are essential because human desaturases cannot act beyond carbon 9 counting from the carboxyl end, so the omega-3 and omega-6 double bonds cannot be introduced de novo.
Deficiency of essential fatty acids causes a scaly dermatitis, poor wound healing and growth failure, seen historically in fat-free parenteral nutrition.
DHA is a major structural component of the retina and brain, which is why it is added to infant formula and why maternal intake matters in pregnancy.