Arachidonic Acid

Every cell in your body contains arachidonic acid locked inside its outer membrane. It sits there quietly until your cells receive a signal, at which point enzymes release it and it becomes raw material for some of the most powerful chemical messengers in human biology. Measuring your arachidonic acid level, typically as a percentage of total fatty acids in your red blood cell membranes or plasma phospholipids, tells you how much of this signaling fuel your cells are carrying and how primed your system is to generate inflammatory and clotting responses.

This is not a test most clinicians order routinely. But if you are trying to understand your inflammatory biology, your cardiovascular risk, or how your diet is shaping your cell membranes at a molecular level, it is one of the most direct windows available to you.

What Arachidonic Acid Is and What It Does

Arachidonic acid is a 20-carbon fat with four double bonds, making it one of the most chemically active fatty acids in your body. It belongs to the omega-6 family. You get it two ways: directly from animal foods like meat, eggs, and fish, or your body builds it from linoleic acid, the omega-6 fat abundant in vegetable oils and nuts. Once inside your cells, it is woven into the fatty layer that forms every cell membrane, where it contributes to how fluid and flexible that membrane is.

The membrane is not just a passive container. It is a dynamic platform for signaling. When a cell is activated, whether by injury, infection, or mechanical stress, an enzyme called phospholipase A2 clips arachidonic acid free from the membrane. That released fatty acid then enters one of three enzymatic assembly lines.

The first is the cyclooxygenase pathway, which produces the chemical messengers known as prostaglandins, prostacyclin, and thromboxanes. These regulate inflammation, fever, and blood clotting. The second is the lipoxygenase pathway, which generates leukotrienes and lipoxins. Leukotrienes drive airway constriction and immune cell recruitment. Lipoxins help resolve inflammation once it has served its purpose. The third is the cytochrome P450 pathway, which produces signaling molecules involved in vascular tone and kidney function.

All of these downstream products are called eicosanoids, a family of short-range chemical messengers that do not travel in the bloodstream the way hormones do. They act locally, at the site of release, with powerful effects. The same molecule that helps your platelets clump together to seal a wound can, in excess or in the wrong context, contribute to an arterial clot or a sustained inflammatory response.

Cardiovascular and Inflammatory Risk

Understanding what your arachidonic acid level predicts requires separating two bodies of evidence that point in different directions. Genetic studies and blood biomarker studies do not always agree, and knowing why helps you interpret your own result more clearly.

Mendelian randomization studies use genetic variants as a tool to estimate what happens when a biological factor is chronically elevated from birth, independent of lifestyle. A Mendelian randomization study by Zhang et. al. used genetic variants to estimate the cardiovascular consequences of higher plasma phospholipid arachidonic acid across a large population.

What this means for you: the genetic studies suggest that chronically elevated arachidonic acid, sustained over a lifetime, may raise cardiovascular risk through clotting pathways. The observational studies measuring actual blood levels suggest the opposite pattern. This divergence likely reflects the complexity of how diet, metabolism, and individual variation interact. Your measured level reflects your current biology, not a lifetime genetic exposure, so it is most useful interpreted alongside other cardiovascular markers.

The clotting mechanism is well established. Inside platelets, arachidonic acid is converted to thromboxane A2, a potent signal that causes platelets to clump together and blood vessels to constrict. This is why aspirin works: it permanently disables the enzyme platelets use to make thromboxane A2, reducing clot formation. The vascular lining produces a counterbalancing signal called prostacyclin, which prevents clotting. The balance between these two signals shapes your moment-to-moment thrombotic risk.

In inflammatory disease, the picture is similarly context-dependent. A study by Ye et. al. found that in people with rheumatoid arthritis, arachidonic acid drives calcium signaling inside immune cells called T cells, amplifying joint inflammation through a protein called ORAI3. In asthma, leukotrienes derived from arachidonic acid cause airway constriction and recruit inflammatory cells to the lungs, which is why leukotriene inhibitor medications reduce asthma symptoms. These disease-specific effects appear more pronounced in people who already have these conditions than in healthy adults.

What Moves This Biomarker

Your arachidonic acid level reflects a balance between how much you consume, how much your body synthesizes, and how much the omega-3 fats in your diet compete for the same enzymatic pathways. Understanding these inputs gives you real leverage.

On the dietary side, direct intake from animal foods raises tissue and membrane arachidonic acid content. Animal research by Whelan et. al. demonstrated that dietary arachidonic acid increases tissue phospholipid arachidonic acid content by more than 50% and enhances production of eicosanoids including prostaglandin E2 and thromboxane B2 in immune cells and platelets. This suggests that dietary intake has meaningful downstream effects on signaling capacity, even when circulating inflammatory markers in healthy adults remain stable.

Controlled trials in healthy adults reviewed by Calder et. al. found that increasing dietary arachidonic acid intake up to 1000 to 1500 mg per day does not consistently raise systemic inflammatory markers. This finding applies specifically to healthy adults without pre-existing inflammatory conditions. The same review noted that the ratio of omega-6 to omega-3 fatty acids in your diet likely matters more than absolute arachidonic acid intake.

The omega-6 to omega-3 ratio matters because these two fat families compete for the same enzymes. When omega-3 fats are abundant, they reduce the proportion of arachidonic acid available for conversion into pro-inflammatory eicosanoids and may blunt the inflammatory effects of arachidonic acid more effectively than reducing arachidonic acid intake alone. A review by Innes and Calder found that high omega-6 intake may inhibit the anti-inflammatory effects of omega-3 fatty acids, reinforcing that the balance between these two families is a more actionable target than arachidonic acid in isolation.

Questions This Biomarker Can Answer

• Is my cell membrane fatty acid composition skewed toward pro-inflammatory signaling, based on how much arachidonic acid my membranes are currently carrying?
• Am I showing biochemical signs of essential fatty acid deficiency, based on my Mead acid to arachidonic acid ratio?
• Is my omega-6 to omega-3 balance at the membrane level consistent with reduced or elevated eicosanoid production capacity?
• Could my arachidonic acid status be contributing to symptoms of an inflammatory condition such as joint pain or airway reactivity?