chapter 9 the fat-soluble vitamins. copyright 2010, john wiley & sons, inc. fat-soluble vitamins...

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.



Absorption of Vitamins


Fat soluble vitamins require _____ and _____ for absorption into the mucosal cell.

a) bile and lymph

b) lymph and dietary fat

c) lymph and chylomicrons

d) bile and dietary fat


Since vitamin A and carotenoids are bound to proteins in foods, ______ is necessary to release them for absorption.

Pepsin Bile Amylase Lactase


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 growth regulation.

Vitamin A

Preformed vitamin A compounds are known as retinoids.

In the diet, preformed Vit A is present as retinol bound to fatty acids. retinOl and retinAl are interconverted in the body.

Plants contain precursors to vitamin A known as carotenoids. Carotenoids can be converted into retinal in the intestinal mucosa and the liver. B carotene is not as well absorbed as preformed Vit A (about 12 mg dietary B carotene yeild 1 mg retinol).



The carotenoid with the most vitamin A activity is _____.

a) Beta-carotene b) Zeaxanthin c) Lutein d) Lycopene


Vitamin A in the Diet


Beta-carotene is least plentiful in which food?

yellow squash

spinach

yellow apples

carrots

hypercarotenemiaLarge intake of carotenoids. Not toxic as the conversion to retinoids is limited. Caused by excess carotenoids stored in adipose tissue.

http://www.dermnetnz.org/systemic/img/carot-s.jpgCopyright 2010, John Wiley &

Sons, Inc.


Vitamin A and the Visual Cycle


Keratomalacia from vit A deficiency

http://webeye.ophth.uiowa.edu/eyeforum/atlas/photos/8-healed-keratomalacia-with-buphthalmos.jpg


Vitamin A is stable except when exposed to:

a) heat

b) light

c) lack of oxygen

d) fat


Which form of vitamin A is involved in vision?

carotenoids

preformed vitamin A

retinal

retinoic acid


Vitamin A and Gene Expression


Cell differentiation, or the process by which a cell becomes more specialized, is most affected by which form of vitamin A?

a) preformed vitamin

A b) retinal c) retinoic acid d) retinol


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.


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's primary function in the body is to

a) prevent anemia

b) regulate calcium and phosphorus levels

c) regulate iron levels in the body

d) support night vision

Vitamin D

Vitamin D is important for bone health normal functioning of the parathyroid gland regulation of the immune system.



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.

Vitamin D Rickets is a

syndrome characterized by bone deformities in children, and caused by vitamin D deficiency.


Osteomalacia

A vitamin D deficiency disease in adults which is characterized by weak (principally affects bone remodeling


Low vitamin D levels have been found in 8% of women living in nursing homes, 6% of young women, and 1.6% of elderly people living in the community in Omaha, Nebraska For people of south Asian (Indian subcontinent) descent living in the UK, 56% of elderly and 41% of the young have been found to have significantly lower levels of vitamin D than Caucasian controls.May coexist with osteopersosis


African Americans are at increased risk of vitamin D deficiency for all of the following reasons except:

Darkly pigmented skin filters out more light.

They spend less time in the sun than people of other ethnic origins.

Milk consumption is low.

Lactose intolerance is common.


Vitamin D in the Diet

Vit D

What macronutrient is the base for Vit D?



Vitamin D from UV Light or the Diet

Cholecalciferol is a form of vitamin D, also called vitamin D3 or calciol. It is the unhydroxilated form of Vit D, formed right after 7-dehydrocholesterol is struck by light


Vitamin E Idenetified as the fat soluble component of grains

important for fertility. Vitamin E is also called tocopherol. (Greek tos: childbirth

and phero: to bring forth) Vitamin E has antioxidant properties. Alpha-tocopherol is the form of vitamin E absorbed by the

human body. The other forms cannot be distrubuted. The supplement form contains 8 different isomers, only ½ of which are active in the body.

Vitamin E absorption depends on normal fat absorption. Once absorbed, vitamin E is incorporated into

chylomicrons.

Converting Vit E units (pg 403)To estimate alpha tocopherol in foods

1. If values are given as mg alpha-Tes1. Mg x0.8= mg alpha tocopherol

2. If values given in IUs1. First determine if the source is synthetic or natural

2. IU natural alpha tocopherol x 0.67=mg alpha tocopherol

3. IU synthetic x0.47= mg alpha tocopherol


Vit E Roles of vitamin E?

Antioxidant Preserves lipids such as LDL and PUFAs

maintains the integrity of cell membranes Red Blood Cell: Vitamin E deficiency in newborns might

result in hemolytic anemia. Lung cells Nervous system cells

protects against some environmental pollutants. Heavy metals (lead, mercury), toxins (carbon

tetrachloride, benzene), pollutants (ozone).



In the liver, vitamin E is incorporated into _____ and from there distributed to other lipoproteins and delivered to cells.

Chylomicrons

VLDL LDL HDL


Vitamin E in the Diet


Which is NOT considered a good source of vitamin E?

a) peanuts

b) soybean oil

c) fortified breakfast cereals

d) orange and yellow vegetables


Vitamin E is an Antioxidant


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.


Vitamin K in the Diet


A Summary of the Fat-Soluble Vitamins


Vitamin A toxicity occurs most frequently when large amounts of _________ is (are) ingested.

a) carrot juice b) egg yolks

c) polar bear liver

d) vitamin A supplements


A Summary of the Fat-Soluble Vitamins


The recommended intake of vitamin E is expressed in:

a) REs

b) µg

c) alpha-tocopherol equivalents

d) mg alpha-

tocopherol


Benefits and Risks of Fat-Soluble Vitamin Supplements


Trends in the modern diet have reduced the consumption of fruits and vegetables. This has reduced our intake of all of the following except vitamin ____.

A D E K


A deficiency of vitamin A can result in

a) beriberi

b) goiter

c) scurvy

d) xerophthalmia


Which of the fat soluble vitamins can be synthesized by bacteria in the intestine?

a) vitamin A

b) vitamin D

c) vitamin E

d) vitamin K


Long term use of antibiotics may result in vitamin K deficiency because:

a) antibiotics may interfere with

absorption of the vitamin

b) antibiotics use vitamin K to function

properly

c) antibiotics may change the bacterial flora in the gut, decreasing vitamin K production

d) antibiotics may promote other vitamins which compete with vitamin K for absorptionc


Vitamin E's primary function in the body is:

a) to act as an

antioxidant

b) to increase absorption of calcium in the small intestine

c) to regulate acid-base

balance

d) to regulate phosphorus

levels


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.

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chapter 9 the fat-soluble vitamins. copyright 2010, john wiley & sons, inc. fat-soluble vitamins...

Documents

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diet slide

dietary fat slide

carotenoids preformed

apreformed vitamin

fatsoluble vitamins

absorption of vitamins

gene expression slide