The Fat Soluble Vitamins: A, D, E, and K

The fat soluble vitamins, A, D, E, and K, are stored in the liver and fatty tissues of the body until they are needed. They are found most often in the fat and oil of foods. The body can survive weeks without consuming foods that contain these vitamins as long as the diet as a whole provides average amounts that approximate DRI recommended intakes. Because these vitamins are stored by the body, toxicity is easier to reach if you take in too much.

Vitamin A (retinol): Vitamin A is a versatile vitamin that has a role in gene expression, maintenance of body linings and skin, immune defenses, bone and body growth and normal development of cells. The role of vitamin A in vision is probably the most familiar, helping to maintain a healthy cornea.

Vitamin A deficiency is a worldwide health problem because of poor nutrition and starvation. Researchers are close to developing a Vitamin A rich rice to serve to the world’s children who lack the vitamin. On the other side, Vitamin A toxicity, over 3000 micrograms/day, can pose health problems such as skin rashes, hair loss, birth defects, liver failure, and death.

DRI: Men 900 micrograms/day; Women 700 micrograms/day
Food Sources:
1c fortified milk 150 micrograms
½c carrots 671 micrograms
3 apricots 100 micrograms

Vitamin D (calciferol): Vitamin D is unique in that the body can get the amount it needs by synthesizing sunlight. This sounds simple, as being in the sun each day would mean you would not need to consume Vitamin D in food. However, research has shown many people are deficient in this vitamin. To counter this, many foods are being fortified with Vitamin D.

Vitamin D helps to regulate blood calcium and phosphorus levels to help maintain bone integrity. Vitamin D also plays a role in the functions of the brain, heart, stomach, pancreas, skin and reproductive organs.

Too little Vitamin D can cause rickets, an abnormality in the bones. Too much Vitamin D can cause too much calcium to be deposited in soft tissues and organs causing them to malfunction. More is not always better, especially in children and young adults.

DRI: Adults (19-50yr) 5 micrograms/day
Food Sources:
3oz salmon 4.3micrograms
1c fortified milk 2.5micrograms
3oz shrimp 3.0micrograms

Vitamin E (alpha-tocopherol): Vitamin E is an antioxidant and serves as a defender against damage to cell components and membranes. This action is very important in the lungs. White blood cells also depend on Vitamin E. Excess Vitamin E from supplements can increase the effects of anticoagulant medications.

DRI: 15mg/day
Food Sources:
Widespread in foods, especially those containing oils.
2tbs sunflower seeds 9mg
1tbs canola oil 2.4mg
1tbs mayo 3.0mg

Vitamin K (menadione): Vitamin K helps to clot the blood by synthesizing proteins. It is also needed for synthesis of some bone proteins. It is important to know that Vitamin K may interfere with blood thinning medications. Some bacteria in the intestines can synthesize Vitamin K for the body’s use.

DRI: Men 120 micrograms/day; Women 90 micrograms/day
Food Sources:
½ cauliflower 20micrograms
1c lettuce 60micrograms
1tbs canola oil 19micrograms

It seems that athletes may need more of Vitamins A and K, than their non-athlete counterparts. Typically, the higher needs are met by the increased number of calories required for in an athlete’s diet to power performance and maintain energy levels. There have not been conclusive studies showing that supplementation can actually increase performance.

Next week, we will focus on the minerals needed by the body.

Sources:
Bonci, L. Sports Nutrition for Coaches. 2009.
Sizer, F. and E. Whitney. Nutrition Concepts and Controversies, 10th ed. 2006.
Skolnik, H. and A. Chernus. Nutrient Timing for Peak Performance. 2010.