Dietary Fats and Chronic Diseases: A Critical Analytical Review

BackgroundThe official nutritional policy that took shape in the mid-twentieth century rests on three fundamentalpropositions: that saturated fat causes cardiovascular disease, that maintaining LDL cholesterol as low aspossible is beneficial to health, and that vegetable oils are superior to animal fats. This paradigm has beensustained, in part, by research funding subject to conflicts of interest, in part by selective presentation of data, and in part by large-scale clinical trial data that remained incompletely published for decades. ObjectiveThis analytical review aims to critically evaluate each of these propositions within the framework ofhistorical and contemporary evidence, to systematically elucidate the mechanistic risk profile of industrialseed oils, and to present an evidence-based comparative analysis across dietary fat classes. MethodsA non-systematic literature search was conducted across PubMed/MEDLINE, the Cochrane Library, andGoogle Scholar, covering the period from 1950 to 2025. Randomized controlled trials, systematic reviewsand meta-analyses, prospective cohort studies, mechanistic investigations, and unpublished or belatedlypublished clinical data were included. Key FindingsThe Minnesota Coronary Experiment (n=9,423) and Sydney Diet Heart Study (n=458) showed that replacingsaturated fat with omega-6 linoleic acid (LA)-rich oils lowered cholesterol but increased all-cause mortality;these findings remained underpublished for decades. Four meta-analyses and the PURE study (n=135,335)identified no significant association between saturated fat and cardiovascular mortality. Oxidized LAmetabolites (OXLAMs) are mechanistically linked to atherogenesis, NASH, and neurodegenerativepathology. Although the PREDIMED trial remained statistically significant upon republication,methodological limitations restrict its generalizability to the broader population. ConclusionThe available evidence strongly indicates that industrial seed oils exhibit a substantially more extensive andmechanistically better-documented chronic disease risk profile than either saturated fat or olive oil. Thestandard lipid panel, which treats LDL cholesterol independently of particle quality, does not adequatelyreflect cardiovascular risk. Nutritional policy requires a comprehensive reassessment in light of thisevidence.