What substance is necessary for the absorption of fat-soluble vitamins?

The substance necessary for the absorption of fat-soluble vitamins is fat. Fat-soluble vitamins, which include vitamins A, D, E, and K, require dietary fat for proper absorption in the intestines. When these vitamins are consumed with fats (e.g., oils, butter, fatty foods), they are incorporated into micelles, which are then absorbed by the intestinal cells. This process relies heavily on the presence of fats in the digestive system, making their presence essential for the efficient uptake of these vitamins into the body. Without adequate dietary fat, the absorption of these vitamins would be significantly hindered, potentially leading to deficiencies and associated health issues.