Prof Sarah Berry said ‘For years, people have worried that they might raise cholesterol or harm heart health’
11:15, 24 Nov 2025Updated 11:31, 24 Nov 2025
Professor Sarah Berry, chief scientist at healthy eating App Zoe has published new research into margarine(Image: Zoe)
A scientist has given an alert to anyone who has ‘ever eaten a pastry, margarine, or plant-based spread.’ Concerns have been rising about the potential impact of some processed oils.
Professor Sarah Berry, chief scientist at healthy eating App Zoe and academic at Kings College, London said a new study published this week has major news for food fans.
In recent years, processed oils have become the target of countless social media posts, with people claiming that they are “toxic”, “poisonous” and, ultimately, are damaging our health.
However these claims have largely been dismissed by scientists and the new research backs this up, Prof Berry said.
She said in a post on Instagram: “If you’ve ever eaten a pastry, margarine, or plant-based spread, you’ve probably eaten interesterified (IE) fats—a type of “hard fat” made from vegetable oils. Food companies use them because the process makes fats stable, spreadable, and functional for bakery products.
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“These IE fats can be rich in different building blocks, mainly palmitic acid (often from palm oil) or stearic acid (from other vegetable oils). For years, people have worried that the palmitic-acid versions might raise cholesterol or harm heart health compared to stearic acid.
“That’s why this new randomized controlled trial, conducted by ZOE’s Chief Scientist @drsarahberry, @wendyhall1284, King’s College London, Maastricht University, and international partners is so exciting.
“Participants ate muffins and spreads containing either the palmitic acid-rich or stearic acid-rich IE fat for six weeks, at a high intake level that’s realistic for a daily diet (10% of total energy). The results showed no meaningful difference between the two fats on major heart health measures. This includes cholesterol levels (like the total:HDL cholesterol ratio), inflammation, and blood sugar control.
“The takeaway: you don’t need to stress about which of these two IE fats shows up on an ingredient list. At real-life levels, neither one appears to have negative effects on your heart health.”
She said their new study out this week in the American Journal of Clinical Nutrition showed that industrially processed fats with different saturated fatty acids show no difference in heart health effects. She explained: “Now with the current demonisation of everything processed, this research highlights that not all food processing is bad for us. Our trial investigated the health effects of intrasterified fats. These are modified hard fats widely used by the food industry in foods such as bakery. Products margarines and spreads that are rich in either palmytic or seric saturated fatty acids.
“Now these fats are now used by the food industry to replace trans fats or hard animal fats, which we know are harmful for our heart health.” The trial saw 47 healthy adults consume diets containing muffins and spreads made with either palmmitic acid rich or seric acid rich in. providing 10% of their daily energy intake for 6 weeks.
Dr Berry said: “Now we measured lots of cardio metabolic risk factors including blood fats, markers of inflammation, insulin sensitivity, liver fat, vascular function, both in the fasting state and also following high fat test meal challenges. And we found that there were no significant differences in blood cholesterol or triglycerides.
“There were no adverse effects or markers of inflammation. Insulin resistance, liver fat or vascular function. And so these results suggest that industrially processed fats currently used in everyday foods, whether they’re rich in palmytic or stearic acid, are unlikely to have any harmful effects on cardiovascular health. And I think this is really important given the widespread use of these fats in processed foods such as margarines, pastries, and confectionery.“
To read the full research click here.