New study says vegetable oils aren't bad for your heart, but not everyone's convinced

Some processed vegetable and seed oils — the kind found in everyday foods like margarine and baked goods — may not be as bad for your heart as once thought, a new study suggests.

After a carefully controlled six-week trial involving 47 healthy adults, researchers from King's College London and Maastricht University in the Netherlands said they found no significant differences in health markers when participants ate muffins and spreads made with either palm-rich or fully hydrogenated seed-oil "interesterified" (IE) fats.

After checking the participants' cholesterol, blood sugar, liver fat and inflammation, scientists found that cholesterol and other heart-health markers stayed about the same for both types of fats.

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The short-term results, published in the American Journal of Clinical Nutrition, suggest the two processed oils have similar effects on healthy people. 

Plant oils can be modified to create IE fats that behave like butter or lard, giving spreads a rich texture without using now-banned trans fats that raise heart disease risk. These fats usually appear on labels as "vegetable oil" or "palm oil."

Participants in a study who ate different processed oils showed no significant changes in cholesterol or other heart-health markers. (iStock)

"The findings suggest that the types of IE fats commonly used by the food industry can be included as part of a healthy, balanced diet," Wendy Hall, a professor of nutritional sciences at King's College London and the study's lead author, told Fox News Digital.

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"This research highlights that not all industrial processing techniques are inherently harmful, which is often implied in prevailing discussions about ultra-processed foods," she said. 

"Food processing can sometimes be used to improve safety or nutrition," she added, "such as replacing trans fats, or natural fats high in saturated fatty acids, with safer alternatives like IE fats for specific food types that require hard fats."

"It's too early to call these fats 'heart healthy.'"

The key is to look at the nutritional profile rather than just the processing technique, she said.

The study, however, was short term and involved only healthy people.

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"Six weeks is long enough to detect short-term changes in cholesterol," Hall said. "But longer-term studies are needed to assess heart disease risk."

Experts say longer studies are needed to see how these fats affect heart disease risk in the long run.

The study suggests that some plant oils can fit within a balanced diet. (iStock)

Dr. Steven Goldberg, chief medical officer at HealthTrackRx in Texas, noted that this is one of the first well-controlled human studies comparing two common IE fats.

"This trial provides evidence that these replacement fats, when used in realistic amounts, are metabolically neutral … aligning with prior findings that stearic acid is relatively cholesterol-neutral," he told Fox News Digital. 

"Unlike trans fats, which alter LDL/HDL ratios adversely, IE fats contain the same fatty acids found in natural fats — palmitic, stearic, oleic — but in different structural positions," Goldberg added. "This structure influences digestion and metabolism but does not appear to have the same deleterious cardiovascular profile."

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Nonetheless, "safe" should be interpreted cautiously, he advised. 

"This study's six-week window is insufficient to determine long-term effects, especially in higher-risk populations," he added. 

"As with all saturated fats, moderation within an overall diet rich in unsaturated oils, fruits, vegetables and whole grains remains prudent. This study suggests that processing is not inherently harmful — what matters is the biochemical outcome."

Experts say longer-term studies are needed to determine how processed oils affect heart disease risk. (iStock)

Dr. Sam Setareh, director of cardiology and cardiovascular performance at the Beverly Hills Cardiovascular and Longevity Institute, said the findings are encouraging — especially since IE fats are widely used as replacements for trans fats and have not been rigorously studied in humans. But he agreed the findings should still be viewed with caution.

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"It's too early to call these fats 'heart healthy,'" Setareh told Fox News Digital. 

It does, however, challenge the long-held assumption that all processed fats are inherently harmful to cardiovascular health, he said. 

Past research has found mixed results on IE fats.

"The findings suggest that not all processed fats are metabolically equivalent, and replacing trans fats with certain IE fats may be a reasonable transition, particularly when used in moderation in the context of an overall healthy diet."

Past research has found mixed results on IE fats. Animal and infant studies published in Nutrition Research Reviews suggest that the way these fats are structured can affect how the body digests them and processes cholesterol, while adult studies have shown inconsistent results that appear to depend on the type of fat and how much people consume.

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The study was funded in part by the Malaysian Palm Oil Board, but the authors said it was carried out independently and reviewed through the standard peer-review process.