Glossary
Omega-3 index.
Direct answer
The omega-3 index states what proportion the long-chain fatty acids EPA and DHA make up of all fatty acids in the membrane of red blood cells, expressed as a percentage. Because red blood cells are long lived, the value reflects supply over weeks rather than the most recent meal.
The omega-3 index is neither the plasma content nor the intake calculated from a ration. Plasma values swing over short periods, and an intake figure says nothing about incorporation into membranes. The method and its interpretation were moreover developed in humans, under laboratory conditions that can differ from one study to the next.
In horses, plant-derived alpha-linolenic acid comes from grass and linseed, whereas EPA and DHA occur mainly in marine sources, and conversion inside the body is limited in herbivores. Target ranges taken from human medicine therefore cannot be carried over to the horse, even though the same measurement is used.
The evidence letter
Once a month: new syntheses, checked studies, and what has changed in the state of the evidence.