Early research in 1939 suggested a specific lipid fraction (SF 20-40) was associated with plaque and heart attack deaths, but this was not pursued due to methodological limitations and potentially biased research leadership.

“they correlated all they had were centrifuges back in the 30s to figure out what stuff was made out of so they took biopsies from people who had plaque and had died from a heart attack and they centrifuged it and they made up like these the centrifuge spins things really fast and so that less dense stuff goes to the top and the more dense stuff goes to the bottom and they layered it out and there was this one fraction that was like SF 20 to 40 or something like that because it was very not dense”