The Fat Phase of Food Systems: A Critical Review of the Effects of the Composition and Ratio of Animal and Vegetable Fats on Lipid Metabolism and Cardiometabolic Markers

Background: Animal fats and vegetable oils are often framed as uniformly harmful and uniformly beneficial, respectively. This dichotomy has been challenged by a recent commentary advocating a reassessment of lard in glucose homeostasis.

Purpose: To critically appraise current evidence on lard, other animal fats, and vegetable oils in relation to type 2 diabetes, lipid disorders, blood pressure, liver disease, cardiovascular events, and mortality.

Materials and Methods: A critical review with a structured PubMed/MEDLINE search and reference-list checking covered publications from 1 January 2021 to 4 July 2026. Randomized controlled trials, prospective cohorts, systematic reviews, and meta-analyses were prioritized. Animal studies were analysed separately as hypothesis-generating evidence.

Results: Direct human evidence on lard is limited to two 12-week controlled feeding trials in healthy adults comparing lard, soybean oil, and a 1:1 blend. The blend, but not pure lard, was associated with larger decreases in blood pressure or aminotransferase activity; no between-group differences were observed for glucose or blood lipids. These studies do not establish antidiabetic or cardioprotective effects of lard. Animal experiments are directionally inconsistent and depend on the model, dietary fat percentage, and comparator oil. For vegetable oils, the most consistent evidence concerns replacement of saturated fats with unsaturated fats rather than plant origin per se.

Conclusion: The relevant analytical unit is the isocaloric replacement model, the specific fatty-acid profile, culinary use, and the overall dietary pattern.

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