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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.
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Chapter 9The 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
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