Not All Trans Fats Are Created Equal — New Study Clears Dairy of Heart Disease Risk

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The Study That Challenges a Long-Standing Fear

Trans fats have one of the worst reputations in nutrition. The name alone tends to trigger alarm. But a new peer-reviewed study published in the journal Nutrition Research has found that the trans fats naturally present in dairy products — milk, butter, cheese, and yogurt — do not raise the risk of heart disease or Type 2 diabetes.

Researchers at the University of Reading analyzed evidence from 22 studies involving thousands of participants across Europe, Canada, and the United States. Their conclusion: natural dairy trans fats behave very differently in the body than the industrial kind.

The findings are drawing attention precisely because dairy has long occupied an uncomfortable position in nutrition science — full of saturated fats and naturally occurring trans fats, yet repeatedly linked to neutral or even positive health outcomes.

Two Types of Trans Fats — One Very Different Story

To understand the study's significance, it helps to know where trans fats actually come from.

Industrial trans fats are manufactured through a chemical process called partial hydrogenation, in which liquid vegetable oil is treated with hydrogen gas and metal catalysts. This process creates high concentrations of a compound called elaidic acid, which has been strongly linked to cardiovascular disease and metabolic syndrome (a cluster of conditions including high blood sugar, excess body fat, and abnormal cholesterol levels). The U.S. Food and Drug Administration banned the use of partially hydrogenated oils in January 2020 because of these risks.

Natural trans fats are a different matter entirely. They are produced by bacteria in the digestive systems of grazing animals such as cows, goats, and sheep. The result is two distinct compounds — vaccenic acid and conjugated linoleic acid (CLA) — that have been linked in research to potential anti-obesity and anti-cancer effects.

"People hear the words 'trans fats' and assume the worst," said Professor Ian Givens of the University of Reading, co-lead author of the study. "But the trans fats in your morning milk, yogurt, butter, or cheese are not the same as the ones from industrial partially hydrogenated fats."

What the Research Actually Found

The study drew on two distinct bodies of evidence.

The first involved ten clinical trials in which participants consumed dairy products with naturally elevated trans fat content, with daily intake ranging from 1.3 to 13.2 grams. Researchers tracked blood markers linked to cardiovascular risk — including total cholesterol, LDL (so-called "bad" cholesterol), triglycerides (a type of blood fat), and apolipoprotein B-100 (a protein used to assess cardiovascular risk). Higher dairy trans fat intake showed no significant effect on any of these markers.

The second body of evidence came from twelve long-term studies tracking thousands of individuals over more than two decades. Researchers measured actual levels of dairy-derived trans fats in participants' blood samples. Again, the data showed no meaningful link between higher levels of dairy trans fats and increased rates of heart disease, stroke, cardiovascular death, or Type 2 diabetes.

The research team at the University of Reading described the review as the first of its kind — and noted it may have significant implications for how dairy products are labeled in stores.

A Broader Picture of Dairy and Health

These findings fit into a growing body of research that has been quietly reshaping how scientists view dairy fat.

Studies published in peer-reviewed journals including the American Journal of Clinical Nutrition have explored potential mechanisms through which dairy components — including specific fatty acids like vaccenic acid and CLA — may support cardiovascular and metabolic health. Research published in Nutrition Research Reviews has examined how CLA from dairy sources has been associated with a range of health benefits in both human and animal studies.

This stands in contrast to the decades-long push toward low-fat dairy products driven by concern over saturated fat. That guidance is now being questioned as researchers emphasize the importance of looking at the "total food matrix" — meaning not just a single nutrient in isolation, but the full spectrum of compounds in a food and how they interact in the body.

"It's not enough to just look at total saturated fats," said Hope Barkoukis, chair of the Department of Nutrition at Case Western University. She noted that different types of fats affect the body in different ways, and that nutritional science in this area is still developing.

What This Means for Consumers

For everyday shoppers, the practical takeaway is straightforward: not every food labeled as containing trans fats carries the same risk.

If a product contains "partially hydrogenated oil" or "partially hydrogenated vegetable oil" in its ingredient list, nutritionists say it should be avoided — those are the artificial trans fats with well-documented links to heart disease. Products still imported from countries without such bans may still contain them.

Dairy products, on the other hand, appear to be in a different category. Professor Givens, whose research has focused on dairy and human nutrition for years, said he is unaware of any current food labeling policy that accurately distinguishes between natural and industrial trans fats — a gap he hopes the new study will help address.

For now, the message from the researchers is one of reassurance: dairy consumed as part of a balanced diet is, as Professor Givens put it, "not something to worry about for your heart."

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Sources

1. University of Reading – "Natural trans fats in dairy do not raise heart disease risk" (official press release, 2026): https://www.reading.ac.uk/news/2026/Research-News/Natural-trans-fats-in-dairy-do-not-raise-heart-disease-risk

2. Medical News Today – "Dairy-derived trans fats may not pose same risks as industrial forms": https://www.medicalnewstoday.com/articles/natural-trans-fats-dairy-not-linked-increased-heart-disease-diabetes-risk

3. Study Finds – "Trans Fat From Cheese, Butter May Not Raise Heart Disease Risk": https://studyfinds.com/trans-fat-dairy-no-heart-risk/

4. Nutrition Research (original study, DOI): https://doi.org/10.1016/j.nutres.2026.03.009

5. Cambridge Core / Nutrition Research Reviews – "Human health effects of conjugated linoleic acid from milk and supplements": https://www.cambridge.org/core/journals/nutrition-research-reviews/article/human-health-effects-of-conjugated-linoleic-acid-from-milk-and-supplements/19BCF17E6A77507D9BFCF967C009B12E

6. Canadian Journal of Public Health – "Human health benefits of vaccenic acid": https://cdnsciencepub.com/doi/abs/10.1139/H09-079

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