Published 11th March 2025
Butter vs. seed oils: New evidence
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If an alien was planning on visiting planet Earth, they might spend a bit of time on social media finding out what makes us tick.
For instance, they might try to learn about our dietary habits to ensure they don’t make a fool of themselves when trying to blend in.
But if social media was their only source of information, this hypothetical alien would be very confused.
Depending on the algorithm, they might be convinced that humans thrive when they eat butter with every meal but develop heart disease and obesity if they ever touch seed oils.
In previous articles, we’ve written about butter and its health risks and outlined the scientific evidence showing that seed oils, when eaten in normal amounts, are linked to health benefits. So, we won’t go over them in detail again here.
Instead, we’ll summarize a fascinating new, large-scale study published in JAMA Internal Medicine that directly compares butter with plant oils.
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Why do we need another study on this?
Although many studies have looked at the health effects of specific types of fats, like saturated fats and unsaturated fats, people don’t eat fats, they eat foods.
So, in this study, the scientists looked specifically at the items consumed — butter and plant oils.
An important question to ask in nutrition science is “instead of what?” If someone decides to cut out a particular food item, they need to replace it with something else.
If that something else is just as bad or worse than the thing they’re cutting out, they won’t see any benefits.
So, in this study, the researchers also investigated how swapping butter for plant oils would impact health.
Finally, most of the long-term studies on oils and health have focused on olive oil, so this time, the researchers also included safflower, soybean, corn, and canola oils.
What did they do?
The researchers accessed data from three large studies: the Nurses’ Health Study, the Nurses’ Health Study II, and the Health Professionals Follow-up Study.
This included data from 221,054 adults who were followed for around 33 years. Every 4 years, participants completed food diaries.
The researchers also had access to information about which participants died and why.
Butter vs plant oils: The results
When the researchers looked at the overall mortality risk, they found that:
Those who ate the most butter had a 15% higher risk of dying during the study’s follow-up than those who consumed the least butter.
Those who ate the most plant oils had a 16% lower risk of dying during the study’s follow-up than those who consumed the least plant oils.
As part of their analysis, the scientists looked at the impact of different oils individually. They found a significant relationship between canola, soybean, and olive oils and the risk of dying during the study.
Specifically, they found that for each extra 5-gram serving per day:
Canola oil was associated with a 15% reduced mortality risk.
Soybean oil was associated with a 6% reduced mortality risk.
Olive oil was associated with an 8% reduced mortality risk.
Important notes:
The researchers didn’t account for different forms of olive oil, such as extra virgin olive oil, which is generally associated with more benefits than standard olive oil.
The scientists found benefits with each 5-g increase in plant oil per day. They calculated this using the amounts consumed by participants as part of their normal diet. However, increasing your intake of these oils would only be beneficial up to a point — if you drank 20 liters of oil (or anything) each day, it wouldn’t benefit your health.
When looking at death from specific conditions, the researchers found that every 10-g per day increase in plant oil intake was linked to an:
11% lower risk of cancer mortality
6% lower risk of cardiovascular disease mortality
Conversely, a higher intake of butter was linked to a 12% increase in cancer mortality.
Overall, the researchers calculated that substituting 10 grams of butter per day with an equivalent amount of plant-based oils was associated with an estimated:
17% reduction in total mortality
17% reduction in cancer mortality
6% reduction in cardiovascular mortality (this wasn’t statistically significant, though)
What should you do?
If you are the hypothetical alien we mentioned in the introduction, this study is a sign that you need to better curate your social media feed.
If you constantly encounter people praising the health benefits of butter while slamming seed oils, it’s time to unfollow.
Nutrition and its impact on health are complex, which is why scientists are still examining butter and plant oils.
However, according to the evidence we have, you should enjoy butter just once in a while, and cooking with seed oils is actually going to help support your health, so do that every day.
Now, enjoy your stay on our planet.
