Foods highest in vitamin K2 in the Rotterdam study, such as meat, eggs, dairy, and butter, were not associated with other healthy behaviors, suggesting a reduced likelihood of healthy user bias confounding the results.

“the foods people were eating with the most vitamin K2 were Netherlands meat eggs dairy butter butter is very high in vitamin K2 because it's a fat soluble vitamin those Foods did not associate with other healthy behaviors so this is what's hard about observational studies is this healthy user bias”