EPA/AA ratio

The ratio of EPA to arachidonic acid – two fatty acids from which the body makes messengers with a predominantly dampening or predominantly amplifying effect on inflammatory reactions. How the ratio is to be read is set out in your findings report.

What the EPA/AA ratio shows

EPA and arachidonic acid compete for the same positions in membrane phospholipids – usually the middle position of the glycerol backbone – and for the same enzymes that convert them into messengers in response to a stimulus. The ratio therefore shows which raw material cells use to make their eicosanoids when they are activated: messengers from arachidonic acid tend to amplify vascular reactions, clotting and inflammation, while those from EPA act more weakly and partly contribute to ending an inflammation. Measured in the membranes of red blood cells, the ratio reflects the fatty acid composition of the last weeks to months. So it describes the store, not the inflammation currently taking place.

Low EPA/AA ratio – what happens in the body?

A low ratio means that there is a lot of arachidonic acid for every EPA molecule. When immune cells, platelets or vascular cells are activated, phospholipase A2 then mainly releases arachidonic acid: plenty of prostaglandin E2, thromboxane A2 and leukotriene B4 are formed, but few E-series resolvins. Inflammatory and clotting reactions are therefore stronger, and in studies they subsided more slowly. In observational studies a low ratio was associated with cardiovascular disease and raised inflammatory markers. It occurs with a low intake of long-chain omega-3 fatty acids and with plenty of arachidonic acid or linoleic acid in the diet.

High EPA/AA ratio – what happens in the body?

A high ratio shows that EPA has displaced a large part of the arachidonic acid from the membranes. On activation, more of the weaker-acting messengers from EPA are then formed, and platelets clump less readily because thromboxane A3 has hardly any clotting-promoting effect. Arachidonic acid does not disappear in the process, because it is still needed for membranes in the brain and for protective prostaglandins, for example in the stomach and kidneys. Very high ratios usually result from a high intake of long-chain omega-3 fatty acids; in this range, studies have observed a slightly prolonged bleeding time.