Transcript Student Module_5-1_Fat_Soluble_Vitamins

Fat
Soluble
Vitamins
Module 5.1
Vitamins
 An organic* substance-coenzyme and/or regulator of metabolic
processes
 Do not supply calories (energy)
 Vitamins are classified by their biological and chemical activity,
not their structure-made of single units not long chains
 Vitamins must be absorbed by the body in order to perform
their functions.
 Approximately 40–90% of vitamins are absorbed in the small
intestine.
 Some vitamins are absorbed in inactive provitamin or vitamin
precursor forms that must be converted into active forms by the
body
 Two classes: water soluble; fat soluble
 Water soluble not stored in body
 8 B vitamins, Vitamin C
 Fat soluble stored in the liver and fat tissue
 Vitamin A, D, E, K
* organic – contains carbon
Comparison of Vitamins in the Body
• Fat-soluble vitamins require fat in the diet to be absorbed.
 Micelles transport to intestinal wall for absorption
 Escorted by chylomicrons via lymph into blood to the liver
 Stored in the liver and body fat
 absorbed into lymph, many require protein carriers, not
readily excreted,
 intake deficiency signs and symptoms occur more slowly
 toxicity is possible even when intake is normalized.
• Water-soluble vitamins may require transport molecules or
specific molecules in the GI tract.
• absorbed into blood stream directly
• circulate, travel, and stored in water
• Compartments excrete in urine, without intake
• deficiency signs and symptoms occur more quickly
• toxicity is possible though shorter lived when intake is
normalized.
Diagnosing Nutritional Deficiency or Toxicity
1.
Dietary records: Demonstrate low/high intake. Medical records
can confirm a metabolic or physiological problem that creates an
altered need.
– Toxicity often found with history of excessive intake of
supplements
2. Clinical deficiency or toxicity symptoms: Observable
deficiency in actual patients; compatible with low/high dietary
intake or altered need. Deficiency attributed to lack of proper
nourishment seen in poverty situations, young children and
frequent pregnancies.
– Toxicity-intake of single supplements such as Vitamin C, E
3. Biochemical tests: Such as blood levels, tissue levels & urine
levels demonstrate low/high body levels of the nutrient.
4. Nutrient supplementation: Serves as biological evidence by
correcting the deficiency signs & symptoms. For toxicity, removal
of the excess.
Fat-Soluble Vitamins
Vitamin A
 Two types
– Retinoids –preformed or active form
– Carotenoids –precursor
 Functions: vision, maintenance of healthy epithelial
tissue (skin and cells lining cavities), sperm production,
fetal development, immune response, hearing, taste,
and growth
Vitamin A Chemistry
Two types
Retinoids –preformed or active form
Carotenoids –precursor
1. Retinoids - preformed or active form
– Retinol – active form of vitamin A
– Retinal – vision- combines with opsin to form pigment for
retinal
– Retinoic acid- cellular growth and maintenance; skin:
wrinkles (Retin-A), acne
Retinol ↔ Retinal → Retinoic Acid
Retinyl Esters
(animal foods)
Retinol
(reproduction)
Beta-Carotene
(plant foods)
Retinal
(vision)
Retinoic Acid
(Growth Regulator)
Retinol activity equivalents (RAE)
Amount of vitamin A in foods is expressed in retinol
activity equivalents (RAE)- a measure of the amount of
retinol the body will derive from food.
RAE Equivalents: Based on active form retinol
1 RAE = 1 µg retinol
1 RAE = 2 µg supplemental beta-carotene
1 RAE = 12 µg dietary beta-carotene
Vitamin A Fat-Soluble Vitamins
2. Carotenoids – Vitamin A precursor
• Intestinal cells convert carotenoids into vitamin A.
• Found in plant products
• Beta-carotene: an orange pigment found in plants that is
converted into vitamin A inside the body. Beta-carotene
is also an antioxidant
• Sources: apricots, cantaloupe, carrots
http://www.superlutein.net/export/sites/superlutein/en/gl/images/faq/image-01.jpg
Vitamin A Functions
1. Vision
2. Skin
3. Internal & external surface
linings
(epithelial cells)
4.
5.
6.
7.
8.
9.
Growth
Reproduction
Embryonic development
Gene expression
Immune function
Provitamin A forms have
antioxidant properties
Vitamin A and the Visual Cycle
Rhodopsin
is a visual
pigment
found in the
retinal cells
known as
rods
Copyright 2010, John Wiley & Sons, Inc.
Fat-Soluble Vitamins - Vitamin A
Up to a year’s supply can be stored; 90% in the liver.
 Transported through the blood by retinal binding protein.
 Vitamin A toxicity can lead to consequences.
 Hypercarotnemia – orange hue to skin – result of excessive
intake – often seen in vegetarians
• Vitamin A deficiency result of insufficient intake of vitamin A,
fat, protein or zinc
 Deficiency occurs after reserves depleted.
 Consequences include night blindness and reduced
resistance to infection, skin conditions, poor bone growth
 Xerophthalmia - dry eyes- condition where the eye fails
to produce tears. Cornea thickens- interferes with light
entering the eye-results in irreversible blindness
 Medications made from vitamin A, such as Retin A or
Accutane, can cause serious side effects – birth defects,
increase in LDL cholesterol
Vitamin A
Deficiency vs Toxicity
•
•
•
•
•
•
•
Deficiency
Adequacy
Toxicity
(<66% of DRI)
Approx. <500 µg RE/day
DRI: 700-900 µg RE/day
(>UL)
>3,000 µg RE/day
Hypovitaminosis A
Bone & tooth:
Impaired growth
Central Nervous
System:
Night blindness,
complete blindness
(Xerophthalmia)
GI System: Diarrhea
Immunity: Depressed
immunity, more
infections
Skin: Hyperkeratosis
(thickened skin)
RDI: 5,000 IU
Normal vision, gene
expression,
reproduction, embryonic
development, epithelial
cell maintenance,
growth, and immune
function
25 mg betacarotene (provitamin A is safe
to take daily if you
are not a smoker
or drinker).
• Bone & tooth:
Decreased bone
mineral density
• Central Nervous
System: Headache,
vertigo
• GI System: Nausea
and vomiting, liver
abnormalities
• Neuro-Muscular:
Incoordination
• Skin: orange color with
excess beta-carotene
• Other: Retinoid
embryopathy
Adult deficient, adequate, toxic values
Vitamin A: Food Sources
Retinol: (animal)
• Fortified milk, cheese, butter, margarine
• Eggs
• Liver
Beta-Carotene: (Plant)
• dark green leafy vegetables
• broccoli, deep orange fruits, & vegetables
Vitamin A in Foods
Adult DRI: 700-900 µg
RE/day
Fat-Soluble Vitamins Vitamin D
• Both a vitamin and a hormone
• Functions in bone production and maintenance
– Increases bone mineralization
• Assists in the absorption of dietary calcium
 Increases intestinal absorption of calcium (Absorption
from food in intestines)
 Re-absorption of calcium in kidneys
• Regulates and balances calcium and phosphorus
availability in blood
» Increase phosphorus excretion
• Reduces cell division (Antiproliferative) – of cancer cell
formation and promotes cellular differentiation of new cells
(Prodifferentiation)
• The body synthesizes with sunlight (5-15 mins)
• Deficiency diseases
 In children, rickets
 In adults, osteomalacia
Vitamin D Synthesis
1.Vitamin D3 (cholecalciferol)
synthesized by the cholesterol in
skin’s exposure to sun.
2.Cholecalciferol converted to
calcidiol in liver
3.Calcidiol converted to calcitriol
in kidneys to active form of
Vitamin D.
Vitamin D Chemistry
Synthesis & Functions
http://thumbs.dreamstime.com/z/rickets-osteomalacia-28181309.jpg
Vitamin D
Deficiency vs Toxicity
Deficiency
Adequacy
Toxicity
(<66% of DRI)
Approx. <3 µg/day
DRI: 15 µg/day
(>UL)
>50 µg/day
RDI: 400 IU = 6.5 µg
• Rickets (children)
Normal calcium
• Osteomalacia (adults)
and phosphorus
• Bone & tooth: poor growth,
balance and
bowed legs, soft bones, pigeon
chest, knocked knees, and
cell metabolism
malformed teeth in children.
Porous bones in adults.
• Cardio-Vascular:
Needs are based
increased circulating levels
upon an inadequate
(PTH) and (AlkP) and decreased
exposure to
circulating levels of serum
sunlight.
phosphorus
Sunlight not
• GI System: Decreased calcium
implicated in
absorption
toxicity.
• Hypervitaminosis D
characterized by high
levels of 25(OH)D
from supplementation
• Cardio-Vascular:
High blood calcium
• Central Nervous
System: Weakness
• GI System: Nausea,
vomiting, anorexia
• Other: Kidney stones,
increased thirst,
urination, and urinary
calcium
Adult deficient, adequate, toxic values
Vitamin D in Foods
Food sources:
• Fortified products like milk, margarine, & some cereals
• Eggs & fatty fish
• Self-synthesis with unprotected peak sunlight exposure
Adult DRI: 15 µg/day
Fat-Soluble Vitamins Vitamin E-Tocopherol
• Vitamin E chemistry
• A family of alpha, beta, gamma, delta tocopherols &
tocotrienols.
• Alpha-tocopherol is believed to be the most active form.
• Known as a vitamin in search of a disease
• Needed for growth and fertility
– Vitamin E deficiency in newborns might result in
hemolytic anemia.
• Antioxidant
• Absorbed from small intestine and transported by chylomicrons
• Sources: vegetable oils, nuts, seeds, margarine, soybean
• Deficiencies of the nutrient are rare.
– risk of deficiency:
• Premature infants not receiving vitamin E from mothers.
• Fat malabsorption diseases.
• certain blood disorders.
Vitamin E Functions
And at the
molecular level
Vitamin E
Deficiency vs Toxicity
Deficiency
(<66% of DRI)
Approx. <10
mg/day
• Premature
infants:
hemolytic
anemia
• Adults: not well
characterized
Adequacy
DRI: 15 mg/day
RDI: 30 IU
Toxicity
(>UL)
>1,000 mg/day
Normal cell
• Relatively nontoxic
membrane integrity, • Toxicity with
reduced oxidative
supplements
stress, and molecular • Interferes with
functioning
vitamin K’s role in
blood clotting,
augmentation of
anti-blood clotting
medication and
increases hemolysis
Adult deficient, adequate, toxic values
Vitamin E in Foods
Food sources:
• Nuts
• Seeds
• Plant oils
• Wheat germ
• Fortified cereals
• Vegetables
Adult DRI: 15 mg/day
Fat-Soluble Vitamins
Vitamin K
Found in several forms, including phylloquinon and
menaquinone.
• Blood-clotting system of the body.
• Works with vitamin D to regulate calcium levels in the
blood. Calcium required in blood clotting mechanisms
• Deficiencies rare -obtained both in the diet and via the
intestinal bacteria. Antibiotics can decrease flora and
production of Vitamin K
– Newborn babies are the one group that is commonly
susceptible to a vitamin K deficiency.
• A baby’s digestive tract is free of bacteria until
birth.
Vitamin K Chemistry
• Phylloquinone (K1) from plant sources &
naphthaquinones (K2, multiple forms)
from animal sources & gut bacteria.
18-27
Vitamin K
Deficiency vs Toxicity
Deficiency
Adequacy
Toxicity
(<66% of DRI)
Approx. <60 µg/day
DRI: 90-120 µg /day
RDI: 90 µg
(>UL)
Not Determined
• CardioVascular:
• Increases
clotting time,
hemorrhaging
with cut or
injury
Normal blood Poorly described in adults
clotting & bone • GI System: High
levels from
metabolism
supplemented
menadione causes
jaundice and liver
damage in infants
• Cardio-Vascular:
Interference with antiblood clotting medication
Adult deficient, adequate, toxic values
Vitamin K in Foods
Food Sources:
• Green leafy & cruciferous vegetables
• Soybeans
• Some plant oils
Adult DRI: 90-120 µg/day