For years, people have been told to stay away from processed fats in food. These fats are often blamed for raising cholesterol and increasing the risk of heart disease.
But a new study from King’s College London and Maastricht University shows that some types of processed fats may not be as harmful as once thought—at least in the short term.
The study looked at two types of hard fats often found in baked goods, margarines, and spreads. These fats are known as interesterified (IE) fats. One type is high in palmitic acid, which comes from palm oil.
The other is rich in stearic acid, found in other plant fats. These fats are often used to replace trans fats and animal fats in food. Trans fats are widely known to increase the risk of heart disease, so food makers have looked for safer alternatives.
To see if these processed fats affect heart health, scientists ran a tightly controlled experiment. They asked 47 healthy adults to follow two different diets for six weeks each. During both diet phases, participants ate muffins and spreads made with either palmitic acid or stearic acid fats.
These fats made up about 10% of their total daily calories. The study used a double-blind design, which means neither the participants nor the researchers knew which fat type was being used during each phase.
After each diet, the researchers measured key health markers. They checked blood cholesterol levels, insulin sensitivity, liver fat, inflammation, and how well blood vessels functioned.
The results were surprising: there were no major differences between the two fats. Cholesterol levels, including the ratio of total to “good” HDL cholesterol, stayed the same. There were also no signs that either fat type caused inflammation, liver problems, or insulin resistance.
Professor Sarah Berry from King’s College London, one of the senior researchers, said the findings challenge the idea that all processed foods are bad.
She explained that interesterified fats are created through a process that helps make solid fats without the need for harmful trans fats. These fats also allow food manufacturers to use less saturated fat overall, which could make processed foods a bit healthier.
Lead author Professor Wendy Hall added that their results offer some peace of mind. She said that when these processed fats are eaten in realistic amounts—like what most people might consume in a regular diet—they don’t seem to increase the short-term risk for heart disease.
This is good news, since these fats are already widely used in foods like margarine, pastries, and candy.
However, the researchers do caution that their study lasted only six weeks. While that is enough time to notice changes in cholesterol and similar markers, longer studies are needed to find out what could happen over months or years. They also noted that their work was supported by the Malaysian Palm Oil Board, which is important to keep in mind.
Still, this study offers a fresh perspective on food processing. It shows that not all processed ingredients are automatically bad, and some might even be safe when used wisely. As more research comes out, scientists hope to better understand which types of fats are truly risky and which are not.
If you care about heart health, please read studies about top 10 foods for a healthy heart, and how to eat right for heart rhythm disorders.
For more health information, please see recent studies about how to eat your way to cleaner arteries, and salt and heart health: does less really mean more?
The study is published in The American Journal of Clinical Nutrition.
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