For many years, people have been told to avoid trans fats because they increase the risk of heart disease. This advice has helped improve public health, and many countries have removed industrial trans fats from processed foods.
However, not all trans fats are the same. A new study suggests that the naturally occurring trans fats found in milk, butter, cheese, and yogurt do not appear to harm heart health or increase the risk of type 2 diabetes.
Trans fats are a type of unsaturated fat. There are two main kinds. The first type is created during an industrial process called partial hydrogenation, which has been used to make some packaged foods last longer.
These industrial trans fats have been linked to higher levels of harmful cholesterol, lower levels of protective cholesterol, and a greater risk of heart attack and stroke. Because of strong scientific evidence, many countries have restricted or banned them.
The second type occurs naturally in dairy products and the meat of animals such as cows, sheep, and goats. These natural trans fats are produced by bacteria living in the animals’ stomachs. Although they share the same name as industrial trans fats, scientists have questioned whether they affect the body in the same way.
To answer this question, researchers analyzed evidence from 22 scientific studies involving thousands of people in Europe, Canada, and the United States. The research was published in Nutrition Research.
The team examined two different kinds of evidence. First, they reviewed 10 carefully controlled dietary studies in which participants ate dairy products containing higher natural trans fat levels and compared them with regular dairy foods.
Scientists measured blood fats such as cholesterol, which are commonly used to estimate heart disease risk. Across all studies, natural dairy trans fats did not produce meaningful differences in these blood markers.
The researchers also reviewed 12 large population studies that followed people for many years, in some cases for more than 20 years. These studies measured natural dairy trans fats in participants’ blood and compared them with later health outcomes.
People with higher levels of dairy trans fats were no more likely to develop heart disease, suffer a stroke, die from cardiovascular disease, or develop type 2 diabetes.
Professor Ian Givens from the University of Reading said these findings should reassure people that the natural trans fats in dairy foods are very different from industrial trans fats. The researchers also believe the results may help reduce confusion about food labels, since many consumers assume all trans fats are equally harmful.
The findings do not suggest that people should eat unlimited amounts of butter or cheese. Dairy foods can still contain saturated fat and calories, so they are best enjoyed as part of a balanced diet that includes fruits, vegetables, whole grains, beans, nuts, and healthy protein sources.
Study review and analysis: This research is a strong evidence review because it combined results from controlled feeding trials and long-term observational studies. Together, these provide a broad picture of health effects.
However, the study cannot prove that natural dairy trans fats actively protect health; it only suggests they do not increase the risk of heart disease or type 2 diabetes. Overall, the findings strengthen current evidence that naturally occurring dairy trans fats behave differently from industrial trans fats.
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Source: University of Reading.
