Longevity Briefs: Just How Deadly Is Butter?

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

The problem:

We need fat to live. Without fat, we’d have no long-term way to store excess energy from food, our nerves wouldn’t be able to carry fast electrical impulses, and our cells would dissolve in water. Yet we all know that consuming too much fat, especially the wrong kind of fat, can be harmful. Everyone has heard the recommendation to avoid saturated and trans fats in favour of unsaturated fats. Yet in practice, most fat-containing foods contain a combination of fats – even healthy plant-based foods contain some saturated fats, for example. For this reason, it’s sometimes more useful to compare classes of foods humans actually eat, rather than isolated food compounds. In this study, researchers compare butter to plant-based oils in a large study lasting over three decades to ask the age-old question: just how much worse is butter compared to its substitutes?

The discovery:

Researchers looked at data from three long-term studies in which healthcare professionals were followed up from 1990/1991 until 2023. There were a total of 221,054 participants. Every 4 years, researchers assessed their intake of butter and plant-based oils via questionnaires. After adjusting for confounding factors, they found that by the end of the study, those who were consuming the most butter were 15% more likely to have died from any cause than those consuming the least butter. Using butter for baking or frying was not associated with any statistically significant change in mortality, probably because the amounts used are typically small. Adding butter to foods like bread, on the other hand, increased mortality by 4% for every 5 grams/day.

The relationship for plant based oils was the opposite – those consuming the highest quantities were 16% less likely to have died from any cause compared to those consuming the least. Half of this was associated with olive oil consumption, as the mortality reduction dropped to 8% when olive oil was excluded. Canola oil and soybean oil, specifically, were also associated with significant mortality reductions, while corn and safflower oil were not.

When it came to specific causes of death, plant-based oils were associated with an 11% reduction in cancer mortality and a 6% reduction in cardiovascular mortality per 10g/day of consumption. Overall, the study estimated that substituting 10g/day of butter intake for an equivalent amount of plant-based oil would result in a 17% reduction in both all-cause mortality and cancer mortality.

The implications:

This research suggests that a relatively small dietary adjustment – substituting just 10g of butter for plant oil – could have a significant effect on mortality. This comes from a large study that followed participants over three decades, but it still has some weaknesses. Since this was not a controlled study (participants weren’t randomly assigned a diet containing butter or plant oils), we can’t be sure that all of the observed differences were due to these dietary components – people who consume more butter might be less healthy in other ways, and dietary questionnaires are prone to misreporting. Being healthcare professionals, the participants were not entirely representative of the general population.

Nevertheless, this research corroborates previous findings, including those concerning the benefits of olive oil. Saturated fats promote adipose (fat) tissue inflammation, which is a driving force behind many age-related diseases including cancer.