I'd suspect that there is also caloric and absorption components. If you don't have calories your hunger wont be satiated because of energy needs. Vitamins do

I'd suspect that there is also caloric and absorption components. If you don't have calories your hunger wont be satiated because of energy needs. Vitamins don't absorb as well as nutrients found in foods (they have a low gut surface area and may not contain the easiest molecules for your body/gut to breakdown into nutrients). In my personal experience a complete protein powder (like PlantFusion products) has a strong effect on general satiety as well as health unlike vitamins.