A long time ago, almost no one got heart attacks, cancer, or diabetes—but now lots of people do.

We analyzed the available evidence on pre-20th century rates of cardiovascular disease, obesity, and type 2 diabetes, along with dietary patterns including seed oil consumption. What we’ve found so far does not support the claim that these conditions were consistently below 1–5% in pre-industrial populations due to minimal intake of industrially processed seed oils. In fact, six studies or assertions directly challenge this idea, while none provide clear support for it [1]. The evidence we’ve reviewed suggests that reliable data on disease rates in pre-20th century populations is extremely limited. Many of the claims about low disease prevalence rely on indirect evidence, such as skeletal remains or historical records, which are not designed to accurately measure modern metabolic conditions like type 2 diabetes or obesity. Additionally, the idea that industrially processed seed oils were nearly absent before the 20th century overlooks the fact that many traditional diets included naturally occurring plant oils from seeds, nuts, and fruits — even if they weren’t refined or extracted with modern machinery. The link between these oils and disease risk in ancient populations has not been established through direct observation or measurement. We also note that lifestyle factors — physical activity levels, food availability, life expectancy, and infection rates — were vastly different in pre-industrial times, making direct comparisons to today’s populations difficult. Without consistent, high-quality data from multiple populations across time and geography, it’s not possible to confidently link disease rates to specific dietary components like seed oils. Our current analysis shows that the evidence does not back the claim that low disease rates in ancient times were caused by avoiding processed seed oils. Not enough reliable data exists to draw firm conclusions about either disease prevalence or dietary patterns in pre-20th century groups. In everyday terms: just because people in the past didn’t eat vegetable oil from bottles doesn’t mean they were free of heart disease or diabetes — we simply don’t have good records to prove it.