A recent study challenges the growing concerns about the health effects of processed oils commonly found in margarine, pastries, and plant-based spreads. Professor Sarah Berry, chief scientist at the healthy eating app ZOE and an academic at King’s College London, has highlighted findings that may ease consumer worries about these ingredients.
Processed oils known as interesterified (IE) fats—used by food manufacturers to improve texture and stability—have been criticized in social media as harmful or “toxic.” These fats contain saturated fatty acids like palmitic acid (from palm oil) and stearic acid (from other vegetable oils). Many had feared that palmitic acid-rich fats might increase cholesterol and cardiovascular risk compared to stearic acid-rich fats.
However, the new randomized controlled trial, co-led by Prof. Berry alongside researchers from King’s College London, Maastricht University, and other international partners, reports no significant differences in heart health outcomes between the two fats. Over a six-week period, 47 healthy adults consumed muffins and spreads containing either palmitic acid or stearic acid-based IE fats, accounting for 10% of their daily energy intake.
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The study measured multiple cardiovascular risk markers—cholesterol levels (including total to HDL cholesterol ratio), inflammation, blood sugar control, insulin sensitivity, liver fat, and vascular function. None showed detrimental effects linked to either type of fat.
Prof. Berry commented, “At real-life consumption levels, neither palmitic acid-rich nor stearic acid-rich IE fats appear to negatively impact heart health. This is important given how commonly these fats are used in everyday processed foods as substitutes for trans fats and hard animal fats, which are known to be harmful.”
Published in the American Journal of Clinical Nutrition, this research underscores that not all processed fats are bad for us and calls for a more nuanced view on food processing—especially in the context of replacing harmful fats with safer alternatives.