A vitamin is either fat soluble or water soluble, depending on how it is absorbed and handled in your body. Fat soluble vitamins need dietary fat to be properly absorbed, whereas water soluble vitamins are absorbed with water. Vitamins A, D, E, and K are fat soluble; the B vitamins and vitamin C are water soluble.
The fat soluble vitamins are absorbed at the beginning of your small intestine. They are packaged with fatty acids and bile in micelles, small transport carriers that shuttle them close to the intestinal wall. Once there, the fat soluble vitamins travel through the cells in the intestinal wall and are packaged with fat and other lipids in chylomicrons. The vitamins then travel through your lymph system before they enter your bloodstream.
Fat soluble vitamins are stored in your body and used as needed when your dietary intake falls short. Your liver is the main storage depot for vitamin A and to a lesser extent vitamins K and E, whereas vitamin D is mainly stored in your fat and muscle tissues. Because they are stored in the body, large quantities of some of the fat soluble vitamins, particularly A and D, can build up to the point of toxicity, causing harmful symptoms and conditions.
Major functions: Vision, cell differentiation, reproduction, bone health, immune function.
Food Sources: Beef liver, fortified dairy products.
Toxicity symptoms: Compromised bone health, birth defects during pregnancy.
Deficiency Symptoms: Night blindness, xerophthalmia, stunting of bones.
Major functions: Calcium balance, bone health, cell differentiation, immune system.
Food Sources: Fatty fish (salmon, tuna, sardines), fortified foods (dairy products, orange juice, cereals).
Toxicity symptoms: Hypercalcemia.
Deficiency Symptoms: Rickets and osteomalacia.
Major functions: Antioxidant, health of cell membranes, heart health.
Food Sources: Vegetable and seed oils, nuts, seeds, fortified cereals, green leafy vegetables.
Toxicity symptoms: Interference with blood clotting and increased risk of hemorrhage.
Deficiency Symptoms: Nerve problems, muscle weakness, and uncontrolled movement of body parts.
Major functions: Blood clotting, bone health.
Food Sources: Green leafy vegetables, soybeans, canola and soybean oils, beef liver.
Toxicity symptoms: None known.
Deficiency Symptoms: Excessive bleeding