ALA (alpha-linolenic acid)

Plant omega-3 (linseed oil, walnuts). The body converts only a small part of it into EPA and even less into DHA. No substitute for marine omega-3, but important for membrane function.

What ALA does in the body

Alpha-linolenic acid (ALA) is an omega-3 fatty acid with 18 carbon atoms and three double bonds. The body cannot make it itself because it lacks the enzyme that inserts a double bond at this point in the chain – which is why it is considered essential. A large part of the ALA taken in is broken down in the mitochondria for energy, and part of it is built into the phospholipids of cell membranes. Via delta-6 desaturase, elongases and delta-5 desaturase, ALA can be lengthened step by step into EPA; the further route to DHA additionally runs through the peroxisomes and is the most demanding step. The same enzymes also process the omega-6 fatty acid linoleic acid into arachidonic acid – so the two fatty acid families compete for the same conversion pathway.

Low ALA – what happens in the body?

Little ALA means that less starting material is available for the body's own production of EPA and DHA; their levels then depend more on the direct intake of these long-chain fatty acids. In this situation the desaturases mainly process linoleic acid, and omega-6 fatty acids take up more space in the membranes. A pronounced ALA deficiency is rare; it has been described mainly during prolonged artificial nutrition without omega-3 fatty acids, with abnormal sensations, weakness and visual disturbances that resolved again with ALA. Low values also occur with disorders of fat absorption in the gut, for example in diseases of the pancreas or the bile ducts.

High ALA – what happens in the body?

A high value usually reflects a plentiful intake in the weeks before the measurement. More ALA in the membranes partly displaces omega-6 fatty acids there, and at delta-6 desaturase ALA is preferentially converted over linoleic acid; this produces somewhat more EPA and somewhat less arachidonic acid. Conversion to DHA, by contrast, hardly increases, because the final steps are tightly regulated. Excess ALA is mostly burned and not permanently accumulated. According to current knowledge, a high ALA value has no pathological significance of its own; it is read together with EPA, DHA and the omega-6 fatty acids.

The interpretation is given in your report.