Linoleic acid (omega-6)

The most common omega-6 fatty acid in the Western diet. The ratio of omega-6 to omega-3 is looked at in the fatty acid profile. How it is to be read is set out in your findings report.

What linoleic acid does in the body

Linoleic acid is an omega-6 fatty acid with 18 carbon atoms and two double bonds; the body cannot make it itself. It is the most abundant polyunsaturated fatty acid in cell membranes, lipoproteins and fat tissue. In the skin it is a component of special ceramides in the horny layer that form the water barrier. Via delta-6 desaturase, linoleic acid is converted into gamma-linolenic acid, then into dihomo-gamma-linolenic acid – the starting material for prostaglandin E1 – and finally into arachidonic acid. This conversion is tightly regulated: in studies, more linoleic acid raises arachidonic acid in the membranes only slightly. A large part of linoleic acid is used as fuel.

Low linoleic acid – what happens in the body?

A true linoleic acid deficiency is rare, because the fatty acid occurs in many foods and is stored in fat tissue. When it does occur, it shows first in the skin: without linoleic acid the ceramides for the water barrier are missing, the skin becomes dry and scaly, loses more water, and wounds heal more slowly; hair loss has also been described. At the same time, starting material for dihomo-gamma-linolenic acid and arachidonic acid is missing. Low values occur with disorders of fat absorption, for example in diseases of the pancreas, cystic fibrosis or chronic inflammatory bowel disease, and during prolonged fat-free artificial nutrition. A low share can also arise when a lot of omega-3 occupies the membrane positions.

High linoleic acid – what happens in the body?

A high value usually reflects a plentiful intake of vegetable oils over a longer period. Linoleic acid competes with ALA for delta-6 desaturase; when a great deal of it is present, less ALA is converted into EPA, and the ratio of omega-6 to omega-3 in the membranes shifts. More linoleic acid in LDL particles makes them more susceptible to oxidation; this produces oxidised linoleic acid products whose significance is debated in studies. At the same time, linoleic acid lowers LDL cholesterol when it replaces saturated fatty acids. The evidence on the significance of high linoleic acid values is therefore mixed; a high share does not automatically mean more arachidonic acid.