The fat-soluble vitamins include A, D, E and K and are found in fats and oils of foods. Fats are a concentrated source of energy that take longer for your body to digest and can help you feel full. Fat-soluble vitamins do not need to be replaced daily because they are stored in the liver and fatty tissues until the body is ready to use them.
Absorption
Fats take the longest for the body to digest because they must be broken down into smaller digestible molecules so that the body can absorb them. Fats travel through the lymphatic system by way of your blood, then on to the liver and other fat storage areas of your body. The liver secretes an acid called bile to emulsify and absorb fat-soluble vitamins. In food preparation, fat-soluble vitamins are removed, then added or used to enrich low-fat foods during processing. A very low-fat diet can cause deficiencies, while consuming too much of any one fat-soluble vitamin can be toxic.
Vitamins A and D
Vitamin A acts as an antioxidant to support your immune system, but also helps maintain healthy vision and skin. Forms of vitamin A are found in animal and plant sources of food, including eggs, meat, carrots, mangoes, pumpkin, spinach, broccoli and winter squash. A deficiency can cause dry skin, slow bone growth and vision-related problems, including blindness. Toxicity symptoms include blurred vision, skin rashes and dry, brittle hair.
Vitamin D helps your body absorb calcium and build strong bones and teeth. Vitamin D is unlike the other fat-soluble vitamins in that your body can make it from cholesterol and in the skin from exposure to sunlight. A severe vitamin D deficiency can cause bone abnormalities. Toxicity is dangerous, but does not result from sunlight. Symptoms include gastrointestinal distress, kidney stones and joint pain. Vitamin D is found in animal sources of food, including fortified milk, egg yolks and fatty fish.
Vitamins E and K
Vitamin E functions primarily as an antioxidant, but might have other roles in the body. Food sources include whole grains, vegetable oils, and nuts and seeds. Vitamin E deficiency and toxicity are rare, but symptoms such as neurological problems and fatigue, respectively, might occur. Vitamin K is necessary for proper blood clotting, and it helps regulate calcium levels. It is found in dark green leafy vegetables and can be made from the bacteria inside your gastrointestinal tract. Deficiency is rare, but bleeding and bone weakness can occur if you don't have enough vitamin K in the diet. Toxicity occurs mainly from taking supplements and can cause jaundice and brain damage.
Warning
Consuming a variety of nutrient-dense foods can decrease risks associated with vitamin deficiencies. The Dietary Guidelines for Americans suggests that supplements be recommended if you are unable to obtain specific nutrients, such as vitamin D, through the diet, says the Food and Drug Administration, which regulates vitamin supplements. Speak to your doctor or dietitian about your diet before you take any vitamin products.
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