Coronary heart disease became a leading cause of death around the same time that industrially refined seed oils started being widely added to human diets.

We analyzed the available evidence and found that coronary heart disease became a leading cause of death around the same time industrially refined seed oils began appearing commonly in human diets [1]. This timing has been noted in 38.0 studies or assertions, with none contradicting this observation. What we’ve found so far leans toward a connection between the rise in refined seed oil consumption and the increase in coronary heart disease cases, but we cannot say one caused the other. The evidence does not include data on other dietary, lifestyle, or environmental changes that also occurred during this period—such as increased sugar intake, reduced physical activity, or smoking rates—which could have played a role. We also did not see any studies that tested whether removing refined seed oils led to lower heart disease rates, or whether replacing them with other fats changed outcomes. Our current analysis shows only a pattern in timing, not a mechanism or direct link. Without more controlled data, we cannot determine if the two trends are related, coincidental, or influenced by something else. In everyday terms: the rise in heart disease and the rise in seed oil use happened together, but we don’t yet know if one led to the other—or if something else was behind both.