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A new controlled trial challenges the blanket assumption that all processed hard fats are harmful to heart health. Researchers tested two common industrial fats—interestified fats rich in palmitic acid or stearic acid—used in margarines, pastries and spreads, and found no measurable harm to key cardiovascular risk markers when consumed at typical dietary levels.
A controlled study found that interesterified fats have no measurable negative impact on key heart health markers when eaten at normal dietary levels. Credit: Stock
What the study tested and why it matters
The research, led by teams at King’s College London and Maastricht University and published in the American Journal of Clinical Nutrition, examined whether interesterified (IE) fats used as industrial replacements for trans fats and some animal fats change short-term markers of cardiometabolic health. Interestification is a processing method that rearranges fatty acids on glycerol molecules to make solid or semi-solid fats without creating trans fats.
Understanding the health effects of these fats matters because food manufacturers increasingly use interesterified fats in margarines, bakery products and confectionery as they reformulate products to reduce trans fats or alter saturated fat profiles. Public concern around processed foods has made clarity on these ingredients a priority for regulators, clinicians and consumers.
How the trial was run
The trial enrolled 47 healthy adults in a double-blind, randomized crossover design. Participants followed two different six-week diets, separated by a washout period. Each diet provided about 10% of daily energy from test fats delivered in everyday foods such as muffins and spreads. Neither participants nor investigators knew which fat was consumed during each diet period.
Investigators measured a broad suite of cardiometabolic endpoints: total cholesterol and HDL, triglycerides, the total-to-HDL cholesterol ratio (a commonly used cardiovascular risk indicator), insulin sensitivity, markers of inflammation, liver fat and vascular function. These are standard clinical and research measures used to detect meaningful changes in short-term heart-disease risk.
Key findings: no short-term harm detected
The trial found no significant differences between the palmitic acid–rich and the stearic acid–rich interesterified fats across the measured outcomes. Blood lipid profiles, including total cholesterol, HDL and triglycerides, remained statistically similar. The researchers also reported no adverse effects on inflammation, insulin resistance, liver fat accumulation or measures of vascular function over the six-week periods.
Lead investigators interpreted the results as reassuring for the consumer-level use of these industrially processed fats at typical intake amounts. Professor Wendy Hall of King’s College London noted that the findings indicate these interesterified fats are unlikely to harm cardiovascular health when consumed at feasible levels in everyday diets. Professor Sarah Berry added that interesterification can help produce hard fats without generating harmful trans fats and may support efforts to lower saturated fat content in some products.
Limits and next steps
The trial duration—six weeks per diet—is adequate to detect changes in cholesterol and many cardiometabolic biomarkers, but it does not address long-term outcomes such as clinical heart disease over years or decades. The study was conducted in healthy adults, so further work is required in older individuals and those with metabolic disease. Longer and larger trials, plus epidemiological analyses, will help determine whether subtler or cumulative effects appear with chronic consumption.
For now, the study offers evidence that not all processed fats carry the same risk profile and that interesterified palmitic and stearic acid–rich fats used at realistic levels do not raise short-term cardiovascular risk markers. That nuance matters for public health guidance, food reformulation, and consumer choice.
Source: scitechdaily
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