“Trans fat” is one of the few phrases on a nutrition label that almost everyone knows to avoid. A new review argues that the naturally occurring trans fats in milk, butter, yogurt and cheese don’t deserve the same reputation as the industrial kind, though who paid for the work is worth knowing too.
Two Kinds of Trans Fat
Most of the trans fat that worried doctors came from partially hydrogenated oils, once common in fried and processed foods. The FDA determined in 2015 that these oils were no longer “generally recognized as safe,” and manufacturers had to stop adding them to most foods by Jan. 1, 2021, at the latest. Ruminant animals like cows, sheep and goats also make small amounts of trans fat naturally, so it still shows up in dairy and meat.
What the Review Found
Researchers including Ian Givens of the University of Reading pooled 22 studies, published in Nutrition Research:
- 10 controlled diet trials, in which people ate between 1.3 and 13.2 grams a day of dairy trans fat. Blood cholesterol and other lipid markers looked no different with trans-fat-enriched dairy than with regular dairy.
- 12 long-term cohort studies from Europe, Canada and the U.S., some running more than 20 years. People with higher blood levels of dairy trans fats were not more likely to have heart disease, stroke, cardiovascular death or type 2 diabetes.
Givens said people tend to assume the worst when they hear “trans fats,” and that dairy eaten as part of a balanced diet shouldn’t be a heart worry on this account.
The Catch
- The work was funded by the U.S. National Dairy Council, and the university notes that several authors work for or are funded by dairy industry organizations. One co-author directs nutrition research at the Dairy Research Institute.
- The trials measured blood lipids, a stand-in for heart risk, not heart attacks themselves.
- The cohort studies show associations. They can’t prove that dairy trans fats are harmless.
- The review looked only at trans fats. It says nothing about the saturated fat, salt or calories in butter and cheese.
The Bottom Line
If you’ve been avoiding a yogurt or a slice of cheese purely because the label lists a gram of trans fat, this review suggests that number isn’t the industrial fat it was meant to flag. It doesn’t make butter a health food. The bigger picture of your diet, like the whole grains you eat and how much processed food is in the mix, still matters more.
This article is for general information, not medical advice.
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