ALA is essential; EPA and DHA are membrane components relevant to brain, retina and inflammatory mediators.
Switzerland: ALA 0.5% of energy; EPA+DHA 250 mg/day for adults.
ALA: rapeseed oil, walnuts, flax and chia. EPA/DHA: oily fish and algae oil.
Clinical essential-fatty-acid deficiency is rare and can cause scaly skin, growth and wound-healing problems.
EPA/DHA lower triglycerides at effective doses; cardiovascular benefit from supplements depends strongly on indication, dose and baseline risk.
Skin changes are expected only in severe deficiency and are not specific.
No fish/algae source, fat malabsorption or long-term fat-free feeding.
Dietary pattern and indication are usually more important than a nonspecific single measurement.
Start with fish or algae sources. Use supplements for inadequate intake or a medical indication; supervise high doses clinically.
High doses can affect bleeding risk and atrial fibrillation in susceptible people.