The AA/EPA Ratio is a biochemical index formed by dividing the blood concentration of arachidonic acid (AA) by eicosapentaenoic acid (EPA). Both AA and EPA are long‑chain polyunsaturated fatty acids (PUFAs) incorporated into cell membranes and released to form signaling molecules called eicosanoids. AA is an omega‑6 PUFA and EPA is an omega‑3 PUFA; their relative proportions influence the types of signaling lipids produced. Historically, researchers and clinicians have used AA/EPA and related PUFA ratios to characterize dietary fatty‑acid patterns, metabolic processing, and inflammatory signaling potential. At the biochemical level AA and EPA compete for the same enzymes (lipoxygenases and cyclooxygenases), so their ratio modifies the balance of downstream lipid mediators that affect vascular tone, platelet activity, and immune cell signaling.

Elevated AA/EPA values generally indicate a higher proportion of arachidonic acid relative to EPA. This pattern often reflects greater omega‑6 input or lower omega‑3 availability and is associated with a relative shift toward AA‑derived eicosanoid signaling. Possible contributors include diet, recent fatty‑acid intake, metabolic conversion, and genetic variants that influence PUFA metabolism. Low AA/EPA values generally indicate higher EPA relative to AA, reflecting greater omega‑3 availability or lower AA. That pattern is associated with a shift toward EPA‑derived signaling pathways. Interpretation requires the full Nutrient Zoomer context: absolute AA and EPA concentrations, other fatty‑acid markers (e.g., omega index), and nutrient‑processing genetics help clarify whether the ratio reflects intake, metabolism, or storage differences.

The Nutrient Zoomer includes AA/EPA to evaluate systemic fatty‑acid balance and signaling potential. As a functional ratio, it integrates dietary and metabolic information about omega‑6 versus omega‑3 status and—when combined with fatty‑acid, nutrient, and genetic data—helps providers tailor nutrition strategies to an individual’s biochemical pattern.