How can too little fat in the diet lead to a vitamin deficency even if a person takes a vitamin supplement?

Too little fat in the diet cannot lead to a vitamin deficiency because fat is not a vitamin, it is one of the six nutrients, along with water, vitamins, minerals, carbohydrates, and proteins. ~a 7th grader I actually disagree with the answer from the 7th grader above...my answer is: Vitamins are essential nutrients your body needs in small amounts for various roles in the human body. Vitamins are divided into two groups: water-soluble (B-complex and C) and fat-soluble (A, D, E and K). Unlike water-soluble vitamins that need regular replacement in the body, fat-soluble vitamins are stored in the liver and fatty tissues, and are eliminated much more slowly than water-soluble vitamins. Fat soluble vitamins dissolve in fats; without sufficient fat in the diet to allow absorption, the body will pass these essential vitamins as waste rather than absorbing them for use. While diseases caused by a lack of fat-soluble vitamins are rare in the United States, symptoms of mild deficiency can develop without adequate amounts of vitamins in the diet. Additionally, some health problems may decrease the absorption of fat, and in turn, decrease the absorption of vitamins A, D, E and K. Joe Bigley Some vitamins (specifically A, D, E and K) are fat-soluble and require the fat in order to be synthesized. This fat has to be dietary fat, as opposed to adipose tissue already present in the individual.