Transcript Copyright 2010 John Wiley & Sons, Inc.

Chapter 9
The Fat-Soluble
Vitamins
Fat-Soluble Vitamins
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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.
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Absorption
of Vitamins
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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
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Since vitamin A and
carotenoids are bound to
proteins in foods, ______
is necessary to release
them for absorption.
Pepsin
Bile
Amylase
Lactase
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Vitamin A
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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.
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Vitamin A
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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).
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The carotenoid with the
most vitamin A activity is
_____.
a)
Beta-carotene
b)
Zeaxanthin
c)
Lutein
d)
Lycopene
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Vitamin A in the Diet
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Beta-carotene is least
plentiful in which food?
yellow squash
spinach
yellow apples
carrots
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hypercarotenemia
Large 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.jpg
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Vitamin A and the Visual Cycle
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Keratomalacia from vit A deficiency
http://webeye.ophth.uiowa.edu/eyeforum/atlas/photos/8healed-keratomalacia-with-buphthalmos.jpg
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Vitamin A is stable
except when exposed to:
a)
heat
b)
light
c)
lack of oxygen
d)
fat
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Which form of vitamin A is
involved in vision?
carotenoids
preformed vitamin A
retinal
retinoic acid
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Vitamin A and Gene Expression
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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)
c)
d)
retinal
retinoic acid
retinol
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Vitamin A Deficiency and Toxicity
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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.
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Vitamin D
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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.
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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
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Vitamin D
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Vitamin D is important for
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bone health
normal functioning of the parathyroid gland
regulation of the immune system.
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Vitamin D Deficiency and Toxicity
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When vitamin D is deficient, dietary calcium cannot be
absorbed efficiently and there can be improper bone
mineralization and abnormalities in bone structure.
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In children, vitamin D deficiency can result in rickets; in
adults, osteomalacia.
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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.
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Vitamin D
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Rickets is a
syndrome
characterized by
bone deformities in
children, and caused
by vitamin D
deficiency.
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Osteomalacia
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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.
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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.
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Vitamin D in the Diet
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Vit D
What macronutrient is the base for Vit
D?
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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
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Vitamin E
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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.
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Converting Vit E units (pg 403)
To estimate alpha tocopherol in foods
If values are given as mg alpha-Tes
1.
1.
Mg x0.8= mg alpha tocopherol
If values given in IUs
2.
1.
2.
3.
First determine if the source is synthetic or natural
IU natural alpha tocopherol x 0.67=mg alpha
tocopherol
IU synthetic x0.47= mg alpha tocopherol
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Vit E
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Roles of vitamin E?
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Antioxidant
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maintains the integrity of cell membranes
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Preserves lipids such as LDL and PUFAs
Red Blood Cell: Vitamin E deficiency in newborns might
result in hemolytic anemia.
Lung cells
Nervous system cells
protects against some environmental pollutants.
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Heavy metals (lead, mercury), toxins (carbon
tetrachloride, benzene), pollutants (ozone).
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In the liver, vitamin E is
incorporated into _____ and from
there distributed to other
lipoproteins and delivered to
cells.
Chylomicrons
VLDL
LDL
HDL
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Vitamin E in the Diet
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Which is NOT considered a good
source of vitamin E?
a)
peanuts
b)
soybean oil
c)
fortified breakfast cereals
d)
orange and yellow
vegetables
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Vitamin E is an Antioxidant
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Vitamin K
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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.
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Vitamin K in the Diet
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A Summary of the Fat-Soluble Vitamins
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Vitamin A toxicity occurs most frequently
when large amounts of _________ is (are)
ingested.
a)
b)
c)
carrot juice
egg yolks
polar bear liver
d)
vitamin A supplements
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A Summary of the Fat-Soluble Vitamins
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The recommended intake
of vitamin E is expressed
in:
a)
b)
c)
REs
µg
alpha-tocopherol
equivalents
d)
mg alphatocopherol
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Benefits and Risks of Fat-Soluble
Vitamin Supplements
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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
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A deficiency of vitamin A
can result in
a)
beriberi
b)
goiter
c)
scurvy
d)
xerophthalmia
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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
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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
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Vitamin E's primary function in
the body is:
a)
b)
to act as an
antioxidant
to increase absorption
of calcium in the small
intestine
c)
to regulate acid-base
balance
d)
to regulate phosphorus
levels
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Chapter 9
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