ISSA Nutritionist Practice Exam

Which vitamin is classified as neither fat nor water soluble?

1. Vitamin D

2. Vitamin E

3. Vitamin K

4. Vitamin A

The correct answer is: Vitamin A

The vitamin that is classified as neither fat nor water-soluble is Vitamin D. It’s important to clarify that Vitamin D is unique among the vitamins because it can be synthesized in the body through exposure to sunlight, making it somewhat different from the classical definitions of fat-soluble and water-soluble vitamins. Fat-soluble vitamins, such as Vitamins A, D, E, and K, are stored in the body's fatty tissue and the liver. Water-soluble vitamins, which include the B-complex vitamins and vitamin C, are not stored in the body and need to be consumed more regularly. Vitamin D plays a crucial role in calcium absorption and bone health, and while it is classified as fat-soluble due to its absorption and storage characteristics, its classification does not fit squarely within traditional water or fat-soluble definitions in the context of how the body processes it. Understanding the difference between these classifications is essential in nutrition, as it influences how nutrients are absorbed, stored, and required in the diet.