Our research · Cooking oils
How much trans fat and polyphenols are in cooking oils? Our pooled survey
In retail surveys, refined soybean and canola oils carry about 1.5 g of trans fat per 100 g and butter about 2 g, while most unrefined oils measure close to zero; extra virgin olive oil leads polyphenols at 20.7 mg per 100 g, about twice the next unrefined oil.
Published · Sources checked 29 Sep 2026 · By Assize Index
Summary
- Background.
- No single authority measures trans fat or polyphenols across every cooking oil, and composition databases leave many trans cells blank.
- What we found.
- Pooling published retail surveys from many countries, refined seed oils and butter carry the most trans fat, and extra virgin olive oil has the most polyphenols by a wide margin.
- What it means.
- Both are now columns on our oil tables. Trans fat takes points off inside each list; polyphenols add outside the 100-point fat core on Salad, Everyday, Heart Healthy and Ancestral & Primal.
Why we pooled surveys
No single authority measures trans fat or polyphenols across every cooking oil. USDA leaves trans blank for many oils, and its older rows skip C18:3 trans, the main trans isomer that refining makes in rapeseed, soybean and linseed oils. Polyphenol figures are scattered across small studies. So we pooled published retail surveys from many countries — 21 in use so far — into one sample-weighted mean per oil: each sample counts once, and a composite of several bottles counts as one.
What counts
- Oil as sold, per 100 g, bought at retail or sampled by an official program. No lab-made, spiked or used frying oil.
- Trans fat must include C18:3 trans: a named method that covers it (AOCS Ce 1f-96, Ce 1h-05, Ce 2b-11) or a reported C18:3 trans value.
- Polyphenols means total phenolics by the Folin–Ciocalteu test on a polar extract of the oil, with a gallic acid standard (mg GAE). The test also reacts with some other reducing compounds, so it is a broad measure, and labs can differ up to 100-fold on the same oil — which is why the method gate is strict.
- Newest first. Per oil we use surveys within 5 years of the newest one, widening to 10, 15 and 20 years only until the row reaches 10 samples.
- Something beats nothing, flagged. A row with no reading that passes the gate uses studies below the gate, then composition databases or producer figures, each flagged on hover. Paywalled surveys are dropped, because readers must be able to check the figure.
Full rules: Methods → Trans fat & polyphenols.
Trans fat: what we found
Refined seed oils carry the most trans among well-sampled plant oils: soybean 1.50 g and canola 1.44 g per 100 g. Butter carries 1.95 g of natural ruminant trans across 13 samples; WHO counts ruminant and industrial trans the same, and so do we, with a label on those rows. Extra virgin olive oil and unrefined coconut oil measured 0. 36 of 40 oils have a trans figure; the rest score at the 75th percentile of tested oils (0.91 g), because untested is not clean.
Polyphenols: what we found
Extra virgin olive oil leads at 20.7 mg per 100 g across 11 bottles — about twice unrefined sesame (9.54 mg) and unrefined coconut (8.56 mg). We score polyphenols on unrefined and unspecified oils only for now. Refining removes most of them, but refined oils have not had a full search, and scoring the few refined readings found by chance would favour those rows. Animal fats carry no plant polyphenols.
The pooled table
Trans fat in g per 100 g, polyphenols in mg GAE per 100 g (CAE = a caffeic acid standard, below the gate), n = samples in the mean. Hover any cell on our tables for the surveys behind it.
Downloads: pooled table (CSV) · every candidate reading, kept or not, with the reason (CSV).
Limits
- Most rows have fewer than 10 samples. Polyphenols still score — outside the 100-point fat core — but coverage is thin outside olive oil, and High heat gives them no bonus.
- Folin totals cannot say which phenolics an oil has. EFSA’s olive oil heart claim covers hydroxytyrosol measured by HPLC, which this test cannot separate.
- Benzo[a]pyrene, glycidyl esters and 3-MCPD are still being audited and are not scored.
Table impact
Two new columns. Two columns on every oil table: Trans fat and Polyphenols. Trans fat costs 10 × a list’s saturated-fat points per gram. Polyphenols add outside the 100-point fat core — up to +15 on Salad & Cold, +9 on Everyday Sauté, +7 on Heart Healthy and Ancestral & Primal; High heat gives them no bonus. Extra virgin olive oil sits at #2 on Salad & Cold and #4 on Everyday Sauté (high-oleic algae and sunflower lead the fat core). On Ancestral & Primal, unrefined coconut oil stays #1 over palm kernel oil. See the recipes.
On our tables
References
- AIMS Agric Food 2021 — crude peanut oils, Burkina Faso. Folin–Ciocalteu on a methanol–water extract, gallic acid standard; 16 oils. doi.org/10.3934/agrfood.2021055
- Davoodi Zanjani et al., J Hum Environ Health Promot 2020 — cold-pressed sesame oils, Zanjan market. Method performance not stated; used only where a row has no reading that passes the method gate. www.academia.edu/47865732/Evaluation_of_the_Composition_and_Oxidative_Stability_of_Cold_pressed_Sesame_Oils_in_the_Market_of_Zanjan_Province
- De Santis et al., Food Sci Nutr 2025 — Italian retail extra virgin olive oils, 2022/23 harvest. Folin–Ciocalteu, gallic acid standard; 11 oils. doi.org/10.1002/fsn3.70471
- Dipasa refined avocado oil facts sheet (updated 2023). Typical value, not a lot analysis; used only where a row has no research reading. dipasa.com/documents/1-Oil---Avocado-RBWD.pdf
- DTU Food, Næringsstofindhold i fedtstoffer (Denmark, 2021) — products bought August 2018. AOCS Ce 1f-96 (Eurofins); pooled sample. backend.orbit.dtu.dk/ws/portalfiles/portal/264101367/Rapport_fedtstoffer_final.pdf
- Grajzer et al., Foods 2020 — Polish cold-pressed oils. Caffeic acid standard, not gallic acid; median reported. doi.org/10.3390/foods9111630
- Hishamuddin et al., J Oil Palm Res 2022 — Malaysian retail oils, bought 2017–19. AOCS Ce 1f-96; 75 retail samples. doi.org/10.21894/jopr.2021.0029
- Iida et al., Bunseki Kagaku 2024 — Japanese retail vegetable oils, bought 2020. AOCS Ce 2b-11 and Ce 1h-05; 24 brands. doi.org/10.2116/bunsekikagaku.73.45
- J Food Sci Eng 2014 — Chilean avocado oils. Folin–Ciocalteu on a methanol–water extract, gallic acid standard. www.davidpublisher.com/Public/uploads/Contribute/55519aca1d40c.pdf
- Japan Food Safety Commission trans fat survey (Japan Food Research Laboratories, report 2007). AOCS Ce 1f-96 based GC; FY2006 samples. www.fsc.go.jp/fsciis/attachedFile/download?fileId=01-001&retrievalId=cho20070330002
- Kabir et al., Bangladesh J Sci Ind Res 2025 — commercial oils. Sampling year not stated; used only where a row has no reading that passes the method gate. www.banglajol.info/index.php/BJSIR/article/view/79017/52728
- Naturex, FDA GRAS Notice 1077 — Oat Oil PL40 (filed 2022). Producer data, 3 lots 2020–21; used only where a row has no research reading. www.fda.gov/media/170570/download
- Prasanth Kumar & Gopala Krishna, Grasas Aceites 2015 — Indian coconut oils. Folin–Ciocalteu on a methanolic extract, gallic acid standard; each brand 5 batches mixed. doi.org/10.3989/gya.0228141
- Sanders, J Agric Food Chem 2001 — peanut butters and roasted-peanut paste (USDA-ARS). Roasted peanut lipid, not the oil as sold; abstract only. pubmed.ncbi.nlm.nih.gov/11368602/
- Siger et al., J Food Lipids 2008 — Polish cold-pressed oils, 2005–06. Caffeic acid standard, not gallic acid. doi.org/10.1111/j.1745-4522.2007.00107.x
- Sumara et al., PLOS One 2023 — Polish cold-pressed oils. Folin–Ciocalteu on a methanol–water extract, gallic acid standard. doi.org/10.1371/journal.pone.0284599
- Tang, J Oil Palm Res 2002 — Malaysian refinery and retail oils. Sampling year not stated; used only where a row has no reading that passes the method gate. jopr.mpob.gov.my/files/2013/09/joprv14june2002-tang1.pdf
- UK Composition of Foods Integrated Dataset (CoFID) 2021. Method not documented; used only where a row has no research reading. www.gov.uk/government/publications/composition-of-foods-integrated-dataset-cofid
- USDA FoodData Central — Foundation Foods, samples acquired 2020. fdc.nal.usda.gov/food-details/1750348/nutrients
- USDA FoodData Central — SR Legacy (2018 edition, analysis year unknown). No C18:3 trans component; used only where a row has no research reading. fdc.nal.usda.gov/food-details/167702/nutrients
- Vingering et al., OCL 2010 — French supermarket oils sampled by Afssa for Ciqual, January 2007. Supermarket oils are composites of 5 brands (each counted as 1 sample). doi.org/10.1051/ocl.2010.0309
Declaration of interests
Assize Index takes no payment or commission from any product or brand named here.
Cite this
Assize Index. How much trans fat and polyphenols are in cooking oils? Our pooled survey. Behind the Table, 29 Sep 2026. assizeindex.com/behind-the-table/cooking-oil-trans-fat-polyphenols-survey Reuse terms
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