The source provides an extensive overview of the scientific consensus regarding the health impact of replacing butter with plant-based oils, focusing primarily on mortality and longevity. It heavily cites a landmark 2025 study from Harvard that analyzed over 221,000 adults, concluding that higher butter intake correlates with increased total and cancer mortality, while substituting it with oils like soybean, canola, and olive oil results in a significant reduction in these risks. The episode explains the fundamental differences in fat structure—saturated fats in butter versus unsaturated fats in oils—and discusses the biological mechanisms by which plant oils improve heart health and curb inflammation. Furthermore, the source supports its argument by examining the dietary habits of Blue Zones, where olive oil consumption is high and longevity is notable, while also addressing and debunking the controversy surrounding highly processed seed oils.