Fat has long been one of the most hotly debated topics in nutrition. One minute we’re being told to banish butter, the next we’re hearing that seed oils are the true villain. Now, thanks to a new study published in JAMA Internal Medicine, the conversation is shifting again — and the findings may challenge what’s in your pantry.
What the Research Looked At
Researchers analyzed decades of dietary data from over 220,000 adults in the long-running Nurse’s Health Study — one of the most comprehensive nutrition databases in the world. The goal was to assess how different types of fats, specifically butter and plant-based oils, were associated with long-term health outcomes like mortality, cancer, and heart disease.
The Oils in Focus
The plant-based oils in this study included a broad range: safflower, corn, canola, soybean, and olive oil. Participants self-reported their food intake over roughly 30 years through food frequency questionnaires filled out every four years. From there, researchers observed patterns in consumption and health outcomes.
Key Findings — and Why They Matter
Let’s break it down. Compared to those who consumed the least:
- High butter consumption was linked to a 15% increase in risk of death from any cause.
- Those who ate the most butter had a 12% higher risk of developing cancer.
- High intake of plant-based oils led to a 16% decrease in all-cause mortality.
- There was a 6% lower risk of heart disease-related death and an 11% lower risk of cancer in those who prioritized plant oils.
- Replacing just 10 grams of butter daily with plant-based oil correlated with a 17% reduction in cancer deaths and overall mortality.
These numbers reinforce the growing body of evidence that suggests unsaturated fats — the kind found in seed oils — may be more beneficial for long-term health than saturated fats like butter.
Why These Results Aren’t the Final Word
Nutrition science is complicated — and while these results are compelling, they aren’t perfect. Here’s what to keep in mind.
1. Self-Reporting Isn’t Always Reliable
Participants filled out their own food logs, which opens the door for human error. People may misremember what they ate, underestimate portions, or omit details — intentionally or not.
2. Lifestyle Habits Matter
Those who eat more butter might also smoke, be less active, or consume more processed foods. These other behaviors could be influencing their health as much as, or more than, the butter itself.
3. Diets Evolve Over Time
Even though the questionnaires were done every four years, people’s eating patterns can shift significantly between check-ins. That introduces variability that’s hard to control.
4. The Sample Wasn’t Fully Representative
Since the study was conducted on nurses, the results might not reflect the broader population. Nurses may have unique stressors, health habits, or access to healthcare that influence outcomes.
So What Should You Eat?
Despite these limitations, the trends in this and other studies consistently point in one direction: a balanced diet with a variety of fats is likely best for your long-term health.
Don’t Fear Fat — Just Be Smart About It
This doesn’t mean butter should be banished from your fridge. Saturated fat, in moderation, isn’t inherently dangerous. What matters is your overall dietary pattern. Including a healthy mix of fats — unsaturated from oils and nuts, plus some saturated from animal sources — gives your body the fuel it needs without overloading it with risk.
- Favor: Olive oil, avocado oil, canola, soybean, nuts, seeds
- Limit: Excess butter, lard, processed meats
- Avoid: Artificial trans fats (like partially hydrogenated oils)
The Bottom Line
There’s no one-size-fits-all approach to nutrition. But if you’re looking to improve longevity and reduce your risk of disease, the evidence continues to support shifting the spotlight toward plant-based oils — not just for their nutrients, but for the broader health impact they deliver over time.
Forget the food fads and loud online voices pitting fats against each other. Instead, lean into balance. It may not sound revolutionary, but in the long run, it’s the healthiest path forward.
