Analysis of 13,335 Australians revealed distinct lipid fingerprints for major food groups: dairy consumption elevated sphingomyelins and odd-chain fatty acids (14:0, 15:0, 17:0), red meat increased arachidonic acid-containing phospholipids, and fish intake boosted omega-3 DHA while reducing inflammatory 22:4 fatty acids. Higher-quality diets measured by three validated indices showed 11-13% reductions in all-cause mortality risk, with similar cardiovascular protection from nuts and Mediterranean-style eating patterns. This research fills a critical gap by identifying the molecular lipid pathways that mediate diet's health effects. Unlike previous studies that relied on self-reported dietary assessments, this lipidomic approach provides objective biochemical evidence of how foods alter metabolism. The findings suggest that dietary guidelines work partly through optimizing specific lipid species rather than just macronutrient ratios. However, the observational design cannot prove causation, and the Australian population may limit global applicability. The work represents a significant advance toward precision nutrition, potentially enabling personalized dietary recommendations based on individual lipid metabolic profiles rather than one-size-fits-all approaches.