Partially Hydrogenated Oils (Trans Fat)
Last reviewed October 18, 2026 · Evidence strength: Strong · How we grade evidence
In plain words: Partially hydrogenated oil is the source of artificial trans fat, which clearly raises heart disease risk. It's essentially banned in US food now, but it can still appear in older or imported products. If you see "partially hydrogenated" on a label, put it back. "Fully hydrogenated" oil is different: it has essentially no trans fat.
Also listed on labels as: Partially hydrogenated soybean oil, Partially hydrogenated vegetable oil, Partially hydrogenated cottonseed oil, PHO, Artificial trans fat
What is it, and why is it in food?
Partial hydrogenation turns liquid oil into a solid fat for shortening, margarine, frosting and fried snacks. The process creates trans fats as a side effect. It was used for decades in crackers, cookies, microwave popcorn, frosting and frying.
What does the science say?
| The popular claim | "Hydrogenated and partially hydrogenated oils are absolutely the worst fats" and labels can say 0 g trans fat if a serving has less than 0.5 g. (Gary Brecka; Dr. Steven Gundry and Dr. Mindy Pelz make similar points.) |
| Our verdict on that claim | Supported |
| Evidence strength | Strong: meta-analyses of large population studies, lipid trials and a US ban. |
| Kinds of studies | Meta-analysis, randomized lipid trials, reviews, FDA action |
- Heart and death: A 2015 BMJ meta-analysis found total trans fat was linked with 34% higher death from any cause, 28% higher death from heart disease and 21% more heart disease. Industrial trans fat specifically was linked with 42% more heart disease.1
- How: Trans fat raises LDL, lowers HDL and promotes inflammation.2
- The 0.5 g rule: US labels can say "0 g trans fat" if a serving has less than 0.5 g, so the ingredient list is the better check.
What do regulators say?
- FDA ruled partially hydrogenated oils are no longer GRAS: no new uses after June 18, 2018, with final compliance by January 1, 2021.3
- EU limits trans fat to 2 g per 100 g of fat (since 2021).
Who should be careful?
- Everyone. This is the best-established harmful food ingredient.
How common is it in US foods?
In our check of USDA's Branded Foods database, 8,400 of 438,129 US packaged foods with an ingredient list name a partially hydrogenated oil (about 1.9%, or roughly 1 in 52).4 It shows up most often in: cakes, cupcakes, snack cakes (798); cookies & biscuits (777); popcorn, peanuts, seeds & related snacks (689); candy (661); ice cream & frozen yogurt (470). Most of these records are dated 2021 (6,457), when the ban took full effect, so most products have likely been reformulated. A product listing it today is old, imported or out of compliance. (The scanner's matcher counted 2,930 because it missed spellings like "partially hydrogenated soybean oil".) These are label records companies sent to USDA, mostly in 2021 to 2023, so some products have changed since. Counts come from a text match of ingredient lists and are approximate.
Swaps and tips for families
- Check the ingredient list, not just the trans fat line.
- Choose products made with liquid oils or butter.
- Be extra careful with imported snacks and old pantry stock.
Beyond the plate: related non-food exposures
None.
Frequently asked questions
Is partially hydrogenated oil banned?
Yes, in the US. Companies couldn't add it after June 18, 2018, with final compliance by January 1, 2021.
Is fully hydrogenated oil a trans fat?
No. Fully hydrogenated oil has essentially no trans fat. Only partially hydrogenated oil is the trans-fat source.
Can a food say 0 g trans fat and still have it?
Yes. US labels can round to 0 g if a serving has under 0.5 g. Check the ingredients for "partially hydrogenated."
Related guides
Sources
Every source below was checked against PubMed, the publisher or the official page by our research team in October 2026.
- Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies. BMJ (Clinical research ed.), 2015. PubMed 26268692 · doi:10.1136/bmj.h3978
- Trans fatty acids and cardiovascular disease. The New England journal of medicine, 2006. PubMed 16611951 · doi:10.1056/NEJMra054035
- FDA: Trans Fat. Link
- FoodData Central, Branded Foods dataset (release 2026-04-30). U.S. Department of Agriculture, Agricultural Research Service, 2026. Link
This guide is for general education. It is not medical advice and does not replace advice from your doctor, pediatrician, allergist or registered dietitian. If you think you or your child reacted to a food, talk to a health professional. Research changes; we review these pages when new evidence or rules come out. Last reviewed October 18, 2026. Spotted an error? Email [email protected].