Researchers wanted to know if two different types of hard fats commonly used in processed foods affect your heart health differently. They had 47 healthy adults eat foods made with one type of fat for six weeks, then switched to the other type. The study found that both types of fat had similar effects on cholesterol levels and other heart health markers. This suggests that from a heart health perspective, these two fats may be roughly equivalent, though scientists note that longer studies would be needed to confirm this.

The Quick Take

  • What they studied: Whether two common types of hard fats used in margarine and baked goods affect cholesterol and heart disease risk differently
  • Who participated: 47 healthy adults between ages 35-65 with normal weight (average age 52, about half were women)
  • Key finding: Both types of fat had nearly identical effects on cholesterol ratios and most other heart health markers. One small difference: the palmitic acid fat slightly reduced an inflammation marker compared to stearic acid fat.
  • What it means for you: If you eat processed foods containing these fats, switching between them probably won’t significantly change your heart health risk. However, this was a short-term study, so long-term effects remain unknown. Limiting overall intake of hard fats is still recommended.

The Research Details

This was a randomized controlled trial, which is one of the strongest types of nutrition studies. Researchers had participants eat specially prepared foods containing one type of fat for six weeks, then took a four-week break, and then ate foods with the other fat type for another six weeks. This crossover design means each person served as their own comparison, which helps control for individual differences.

The fats were incorporated into everyday foods like muffins and margarine spreads at levels matching what people typically eat (10% of daily calories). Researchers measured cholesterol levels, blood sugar control, inflammation markers, and even liver fat using advanced imaging in a subset of participants.

This study design is important because it tests fats in realistic food products at realistic amounts, rather than using pure oils in a lab. This makes the results more relevant to what actually happens when people eat these foods in their daily lives. The crossover design also reduces the influence of individual differences in how people respond to fats.

Strengths: Published in a highly respected nutrition journal, used rigorous measurement methods including advanced imaging for liver fat, and had good participant completion (47 of 51 finished). Limitations: The study only lasted six weeks per fat type, which is relatively short for detecting long-term health effects. The sample size was modest and included only healthy adults, so results may not apply to people with existing health conditions.

What the Results Show

The main finding was that both types of fat had essentially the same effect on the ratio of total cholesterol to HDL cholesterol (the ‘good’ cholesterol). The difference between the two fats was only 0.05 on this ratio, which falls well within the range researchers considered equivalent.

When researchers looked at individual cholesterol numbers, they found no meaningful differences between the two fats for LDL cholesterol (the ‘bad’ kind), HDL cholesterol, or triglycerides (another blood fat). Blood sugar control, measured through insulin sensitivity tests, was also similar for both fats.

Vascular function (how well blood vessels work) and most inflammation markers showed no differences between the two fats. The one exception was a marker called IL-10, which decreased slightly more with the palmitic acid fat compared to the stearic acid fat—though the practical significance of this small difference is unclear.

Researchers also measured liver fat in a subset of 20 participants using advanced imaging. Neither fat type significantly affected liver fat accumulation. Postprandial triglycerides (blood fats measured after eating) and various lipoprotein particles also showed no meaningful differences between the two fats.

Previous research on these individual fats has been mixed, with some studies suggesting palmitic acid might be less favorable for heart health than stearic acid. This study suggests that when these fats are incorporated into realistic food products and consumed at typical levels, any differences may be minimal. The findings align with recent evidence that the food matrix (what the fat is eaten with) and overall diet quality matter more than the specific type of fat.

The study lasted only six weeks per fat type, which is too short to detect effects on actual heart disease risk or long-term metabolic changes. All participants were healthy adults aged 35-65 with normal weight, so results may not apply to older adults, people with obesity, or those with existing heart disease or diabetes. The study couldn’t determine whether effects might differ with longer consumption periods or in different populations.

The Bottom Line

Based on this evidence (moderate confidence): If you consume processed foods containing these hard fats, switching between palmitic acid-rich and stearic acid-rich versions is unlikely to significantly impact your heart health markers in the short term. However, this doesn’t mean these fats are ideal—the overall recommendation remains to limit hard fat intake and choose foods with healthier fat sources like olive oil and nuts when possible.

This research is most relevant to people who regularly consume processed foods containing hard fats (margarine, baked goods, some spreads). It’s less relevant to people who already avoid processed foods or those with existing heart disease, diabetes, or other metabolic conditions—who should consult their healthcare provider about fat intake. The findings apply to healthy adults; effects in other populations remain unknown.

This study measured effects over six weeks, so any changes in cholesterol and inflammation markers would likely appear within that timeframe if they were going to occur. However, effects on actual heart disease risk would take years or decades to manifest and weren’t measured in this study.

Want to Apply This Research?

  • Track weekly cholesterol levels (if monitoring) and note which processed foods containing hard fats you consume, recording the type when possible. Monitor energy intake from these fats to stay within recommended limits (less than 10% of daily calories).
  • Use the app to identify and gradually reduce processed foods containing hard fats. Set a goal to replace one processed food item per week with a whole food alternative (like homemade baked goods with olive oil instead of store-bought muffins with hard fats).
  • Track overall fat intake quality rather than worrying about the specific type of hard fat. Monitor general heart health markers (cholesterol if available) every 3-6 months. Focus on increasing intake of unsaturated fats from sources like fish, nuts, seeds, and olive oil rather than distinguishing between types of hard fats.

This research suggests that two specific types of hard fats have similar short-term effects on cholesterol and heart health markers in healthy adults. However, this study lasted only six weeks and involved only healthy people, so long-term effects and effects in people with existing health conditions remain unknown. These findings do not constitute medical advice. If you have concerns about your heart health, cholesterol levels, or dietary fat intake—especially if you have existing heart disease, diabetes, or other metabolic conditions—consult with your healthcare provider or registered dietitian before making significant dietary changes. This research does not suggest that hard fats are ideal for health; limiting overall hard fat intake remains recommended.