Fat-Soluble Vitamins (A, D, E, K)

Key points

• • Vitamins A, D, E and K dissolve in fat, are absorbed with dietary fat, and are stored in the body (mainly the liver and fat tissue, though the amount stored differs by vitamin), so they can build up to harmful levels if taken in excess.
• • Vitamin A is needed for vision in dim light and for healthy surface tissues, and a lack causes night blindness and dry eyes.
• • Vitamin D helps absorb calcium and harden bone, and a lack causes rickets in children and soft bones (osteomalacia) in adults.
• • Vitamin E is an antioxidant that protects cell membranes from damage by free radicals.
• • Vitamin K is needed to make several clotting factors, so a lack leads to easy bleeding, and newborn babies are especially prone to it.
• • Because they are stored rather than passed in the urine, fat-soluble vitamins are more likely than water-soluble ones to cause toxicity in excess, most clearly vitamins A and D.