The fat-soluble vitamins include vitamins A, D, E and K. The B vitamins and vitamin C are water-soluble.
In our opinion, even small amounts of fat in food (not necessarily in a particular meal) are sufficient for the body to absorb the fat-soluble vitamins. Fruit and leafy greens also contain small amounts of fat, such as avocado or the seeds of grapes and apples, which is why we like to include them in our smoothies. In our opinion, this is quite sufficient for the absorption of fat-soluble vitamins. Especially if a piece of avocado wanders into the green smoothie. BUT: If it's still important to you to add some oil to your smoothie, feel free to do so. Svenja likes to say: "There is no smoothie police."