Chapter 9 The Fat-Soluble Vitamins

Copyright 2010, John Wiley & Sons, Inc. Fat-Soluble Vitamins Vitamins A, D, E and K are fat-soluble vitamins. Fat-soluble vitamins require bile and dietary fat for absorption. Once absorbed, they are transported with fats through the lymphatic system in chylomicrons before entering the blood. Fat-soluble vitamins can be stored in body fat, meaning that intakes can vary without a risk of deficiency (as long as there are average intakes over time). Because they can be stored in body fat, fat-soluble vitamins are not easily excreted. This increases the risk of toxicity with high intakes.

Copyright 2010, John Wiley & Sons, Inc. Vitamin A Vitamin A is found preformed, from animal products or supplements, or in precursor form, from plant foods, in the diet. Vitamin A plays a key role in night vision, cell differentiation and growth regulation. Preformed vitamin A compounds are known as retinoids. Plants contain precursors to vitamin A known as carotenoids. A derivative of retinoic acid is used topically to treat certain skin conditions.

Copyright 2010, John Wiley & Sons, Inc. Vitamin A in the Diet

Copyright 2010, John Wiley & Sons, Inc. Vitamin A and the Visual Cycle

Copyright 2010, John Wiley & Sons, Inc. Vitamin A and Gene Expression

Copyright 2010, John Wiley & Sons, Inc. Vitamin A Deficiency and Toxicity Vitamin A deficiency is a threat to the health, sight and lives of millions of children around the world. Vitamin A deficiency can be caused by insufficient intake of vitamin A, fat, protein or zinc. Preformed vitamin A can be toxic if taken in high amounts. Medications made from vitamin A, such as Retin A or Accutane, can cause serious side effects.

Copyright 2010, John Wiley & Sons, Inc. Vitamin D Vitamin D is known as the “sunshine vitamin” because it can be produced in the skin by exposure to UV light. Only a few foods are natural sources of Vitamin D, including liver, fatty fish, fish oils and egg yolks. Vitamin D can be toxic at high levels, so there are strict limitations on the categories of foods that can be vitamin D-fortified. Vitamin D is important for bone health, normal functioning of the parathyroid gland and regulation of the immune system.

Copyright 2010, John Wiley & Sons, Inc. Vitamin D in the Diet

Copyright 2010, John Wiley & Sons, Inc. Vitamin D from UV Light or the Diet

Copyright 2010, John Wiley & Sons, Inc. Vitamin D Deficiency and Toxicity When vitamin D is deficient, dietary calcium cannot be absorbed efficiently and there can be improper bone mineralization and abnormalities in bone structure. In children, vitamin D deficiency can result in rickets; in adults, osteomalacia. Oversupplementation of vitamin D can result in high blood and urine calcium concentrations, depositing of calcium in blood vessels and kidneys, cardiovascular damage and possibly death.

Copyright 2010, John Wiley & Sons, Inc. Vitamin E Vitamin E is also called tocopherol. Vitamin E has antioxidant properties. Alpha-tocopherol is the form of vitamin E absorbed by the human body. Vitamin E absorption depends on normal fat absorption. Once absorbed, vitamin E is incorporated into chylomicrons. Vitamin E deficiency in newborns might result in hemolytic anemia.

Copyright 2010, John Wiley & Sons, Inc. Vitamin E in the Diet

Copyright 2010, John Wiley & Sons, Inc. Vitamin E is an Antioxidant

Copyright 2010, John Wiley & Sons, Inc. Vitamin K Vitamin K was named for koagulation, the Danish word for coagulation. Vitamin K is found in several forms, including phylloquinone and menaquinones. Abnormal blood coagulation is the major symptom of vitamin K deficiency. Vitamin K deficiency is very rare in the US.

Copyright 2010, John Wiley & Sons, Inc. Vitamin K in the Diet

Copyright 2010, John Wiley & Sons, Inc. A Summary of the Fat-Soluble Vitamins

Copyright 2010, John Wiley & Sons, Inc. A Summary of the Fat-Soluble Vitamins

Copyright 2010, John Wiley & Sons, Inc. Benefits and Risks of Fat-Soluble Vitamin Supplements

Copyright 2010, John Wiley & Sons, Inc. Chapter 9 Copyright 2010 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information herein..