Is this claim true? My understanding is that if you eat a healthy diet there's no need to add oil to things like salads to increase vitamin absorption. Vegetables mostly have water soluble vitamins and fat soluble, well, they'll come with fat from animal products. Anything fat soluble that is in fruit or veg will be absorbed easily enough and if you eat healthy will be stored already, in whatever quantities. I can only find links to media interpretations of studies or places like "medical news daily" which I don't fully trust and they all seem to be talking about vitamin tablets.