Butter vs. Plant Oils: Impact on Longevity

Not such good news for butter lovers: seesawing research on how healthy or unhealthy butter might be received a firm push from a recent Harvard study published in JAMA Internal Medicine. Drawing on decades of data gathered through long-term observational studies, the researchers investigated whether butter and plant oils affect mortality.

Main Takeaway

"A higher intake of butter increases mortality risk, while a higher intake of plant-based oil will lower it," says Yu Zhang, lead author of the study. Importantly, choosing to substitute certain plant oils for butter might help people live longer.

Study Design

  • Participants: More than 221,000 adults from the Nurses' Health Study, Nurses' Health Study II, and Health Professionals Follow-Up Study.
  • Duration: Up to 33 years with dietary questionnaires every four years.
  • Groups: Divided into four based on reported butter or plant oil intake.
  • Adjustments: Accounted for age, physical activity, smoking status, family history of illnesses, and more.

Key Results

  • Butter: Those consuming the most butter had a 15% higher risk of death and an increased risk of cancer mortality compared with those consuming the least.
  • Plant Oils: High consumers of plant-based oils saw a 16% lower risk of death and reduced risk of dying from cancer or cardiovascular disease.
  • Beneficial Oils: Only soybean, canola, and olive oils were linked with survival benefits.
  • Substitution Model: Swapping approximately 10 grams (slightly less than a tablespoon) of butter daily for an equivalent amount of soybean, canola, or olive oil was associated with fewer total deaths and fewer cancer deaths.

Why Plant Oils Help

  • Rich in antioxidants, essential fatty acids, and unsaturated fats linked to healthier cholesterol and triglyceride levels.
  • Associated with lower insulin resistance and reduced chronic inflammation when replacing saturated fats like butter.
  • Aligns with American Heart Association recommendations and Dietary Guidelines for Americans for healthful eating that lower chronic disease risk.

Expert Insight

"Butter has almost no essential fatty acids and a modest amount of trans fat—the worst type of fat for cardiovascular disease," notes Dr. Walter C. Willett, professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health. "A little butter occasionally for its flavor would not be a problem. But for better health, use liquid plant oils whenever possible instead of butter for cooking and at the table."

He suggests sampling a variety of plant oils—different olive oils, mustard oil, sesame oil—to find preferred flavors, or blending butter with oils to satisfy taste buds.

Limitations

As an observational study, it cannot prove causation, and most participants were white health care professionals, so findings may not generalize to broader populations. However, the large sample size, long follow-up, and multiple adjustments strengthen the evidence.