Twenty-two studies, pooled in one review, turned up no link between the trans fats found naturally in milk, butter and cheese and heart disease or type 2 diabetes. The group behind the review, led from the University of Reading, split the evidence into 10 controlled dietary trials and 12 long-term prospective cohort studies drawn from Europe, Canada and the United States.
Professor Ian Givens of Reading, one of five authors, said people hear the words “trans fats” and assume the worst, and that dairy eaten as part of a balanced diet is not a cardiac worry. The paper appeared in Nutrition Research in 2026, and the university announced it on May 26, so the October coverage is a recap of work already several months old.
Ten trials and twelve cohorts in the 22-study pool
According to the University of Reading’s release, the 10 dietary trials compared dairy with naturally enriched trans fat against ordinary dairy, at intakes of 1.3 to 13.2 grams a day. Blood lipid markers used to gauge heart disease risk showed no meaningful differences between the groups. Those trials measured biomarkers, not heart attacks or diagnoses, which is a narrower claim than a blanket statement that dairy trans fat never harms the heart.
The disease outcomes come from the 12 prospective cohorts, some of which followed participants for more than two decades while measuring dairy trans fat levels in blood. Higher levels were not associated with heart disease, stroke or cardiovascular death, and not with type 2 diabetes either, as laid out in the recap of the paper. Cohort studies track associations over time and cannot prove cause on their own, a limit the summary does not dwell on.
The paper itself spans pages 33 to 48 of volume 150, and the release describes the combination of a meta-analysis of trials with a systematic review of cohorts as the first of its kind on this question. The release reports no participant totals per study, nor trial sizes, beyond saying the cohorts covered thousands of people across three regions, so the strength of any single result cannot be judged from the summaries alone.
Industrial and ruminant trans fat on the label
The review’s central distinction is between two sources of the same chemical family. Industrial trans fat comes from partially hydrogenated oils, which the Food and Drug Administration ruled no longer generally recognized as safe in 2015, with the final compliance date for removing them from most foods set at January 1, 2021. The FDA adds that those actions did not affect trans fat occurring naturally in ruminant products such as milk, butter, cheese and meat.
The FDA’s page states plainly that eating trans fat raises LDL, the so-called bad cholesterol, which increases heart disease risk; the American Heart Association adds that trans fats lower HDL and are linked to a higher risk of type 2 diabetes. That is the mechanism the Reading trials tested with dairy as the source, using blood lipid markers as the yardstick. The Reading authors argue the natural kind behaves differently in the body, and say the work could help consumers and regulators tell the two apart and clear up confusion over labeling policies. The release gives no detail on which policies it means.
Funding and the agencies that disagree
The research was funded by the National Dairy Council in the United States, and several of the authors work for, or receive funding from, dairy industry or interbranch organizations, according to the university release. The paper’s byline reads Constance Gayet-Boyer, Fanny Tenenhaus-Aziza, Moises Torres-Gonzalez, Givens and Cindy Schweitzer in that order, and the release does not say which of them hold the industry ties. Funding by a trade body does not by itself invalidate a pooled analysis, but it is the context a reader needs when weighing a result that favors the funder’s product, and the cohort data on which the disease claims rest are observational.
Public health bodies have not adopted the distinction. The World Health Organization’s fact sheet, which locates industrial trans fat in margarine, shortening, fried foods and baked goods, states that both industrially produced and naturally occurring trans fat are equally harmful, recommends keeping trans fat below 1 percent of total energy intake, about 2.2 grams a day on a 2,000-calorie diet, and attributes more than 278,000 deaths a year worldwide to industrial trans fat. The American Heart Association’s guidance likewise treats the small amounts in dairy and meat as harmful and tells people to steer clear of trans fats.
The highest intake in the trials, 13.2 grams a day, sits well above the WHO’s 2.2-gram benchmark. How the 22-study result squares with the WHO and AHA positions is a question the Reading authors have yet to answer in public.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
More from Morning Overview
- Lake Powell sank to a record 3,517 feet, nearing the level that stops Glen Canyon Dam’s turbines
- Seven of Earth’s nine planetary boundaries are breached, and all seven are worsening
- The NSA says three phone features should be off whenever you aren’t using them
- Hurricane Hunter radar shows four warning signs that a tropical cyclone is about to strengthen, a University of Miami study found
