Download Fat-soluble vitamins

Vitamins
-Essential organic compounds required in small
amounts for normal metabolism and good
health
- not a source of energy
Water soluble - C and Bs
-must be replenished everyday
-Difficult to overdose
Fat soluble - A, D, E, K
-does not need to be replenished everyday
-can cause toxicity
Names and Roles
Vitamins
A
B1
B2
B3
B5
B6
B7
B9
B12
C
D
E
K
retinol
thiamine
riboflavin
niacin
Pantothenic acid
pyridoxine
pyridoxamine
pyridoxal
Biotin
Folic acid
cobalamin
ascorbic acid
cholecalciferol
tocopherols
phytylmenaquinone
multiprenylmenaquinone
phototransduction
carbohydrate metabolism
redox, respiration
redox
tca, fa and cholesterol
aa metabolism
glycogenolysis
gluconeogenesis, tca, fa, aa
1C metabolism
1C&H metabolism
hydroxylation
bone remodeling
antioxidant
coagulation
bone remodeling
Deficiencies and Sources
Vitamins
A - night blindness
B1 - beri-beri
B2 - pellagra
B3 - pellagra
B5 - none known
B6 - neurologic disease
preformed: liver, egg yolk, butter, milk
b-carotene: dark green and yellow veggies
seeds, nuts, wheatgerms, legumes, lean meat
B7 - widespread injury
B9 - anemia
B12 - pernicious anemia
C - scurvy
D - ricketts, osteomalacia
E - neurologic?, hemolytic anemia
K - bleeding disorders
meats, nuts, legumes
meats, nuts, legumes
yeast, grains, egg yolk, liver
yeast, liver, wheatgerm, nuts, beans, bananas
corn, soy, egg yolk, liver, kidney, tomatoes
yeast, liver, leafy veggies
liver, kidney, egg, cheese
citrus and soft fruits
milk, fortified food, fish oils, egg
yolks, liver
veggie oils, nuts
green leafy veggies, fruits, dairy products, veggie oils,
cereals, meats
Recommended Daily Allowances
(RDA)
Vitamin Absorption and Storage
• All absorption takes place in the small
intestine
• Fat-soluble vitamins
– Are absorbed in the duodenum
– Storage
•
•
•
•
Vitamin A is mainly stored in the liver
Vitamins K and E are partially stored in the liver
Vitamin D is mainly stored in the fat and muscle tissue
Can build up in body to point of toxicity
Vitamin Absorption and Storage
• Water-soluble vitamins
– Absorbed with water and enter directly into the
blood stream
– Most absorbed in the duodenum and jejunum
– Most are not stored in the body
– Excess intake excreted through the urine
– Important to consume adequate amounts daily
– Dietary excesses can be harmful
Digesting and Absorbing Water-Soluble
Vitamins
Figure 10.1
Water-Soluble
Vitamins
Small Intestine
Fat-Soluble
Vitamins
Small Intestine
Hydrophilic
Hydrophobic
Absorbed into the
Blood
Lymph
Stored in the body
Not Generally
Yes
Can build up and
become toxic
Not Generally
Yes
Need to consume
daily
Yes
No
Absorbed in the
Hydrophobic or
Hydrophilic
Bioavailability
• Varies based on
–
–
–
–
–
Amount in food
Preparation
Efficiency of digestion and absorption of food
Individual nutritional status
Natural or synthetic
• Fat-soluble vitamins are generally less
bioavailable than water-soluble vitamins
• Vitamins from animal foods are generally more
bioavailable than those in plant foods
Fat Soluble Vitamins
-
Many have precursors
Less vulnerable to cooking losses
Can cause toxicity
Transported like fat in chylomicrons, VLDL, LDL
vitamin A
•
•
•
•
•
aka: retinol
Converted to active form
Regulates response of rod and cone cells in the retina to light
Regulates gene expression of development of epithelial tissue
Used to treat severe acne, wrinkled skin
16
vitamin D
• A prohormone synthesized
from cholesterol
• Vitamin D3 = cholecalciferol
• Found in animal products
• Vitamin D2 = egocalciferol
• Found in plants and fortified
foods
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Vitamin D3 and D2
What affects your vitamin D level?
• Time spent outdoors
• Amount of skin exposed
• Skin color
• Clothing
• Body fat
• Latitude
• Season and time of day
Vitamin D Synthesis and Latitude
Childhood rickets
• Epidemic with industrialization in 19-20th
centuries
• With discovery of vitamin D and fortification,
rickets was almost entirely eliminated
• Until now…
London 1889
Idaho 1989
•
•
•
•
•
•
40-90% of US community dwelling elderly
50% of premenopausal women
50% of Hispanic and black adolescents
48% of French preteens
30-50 % of adults in Saudi Arabia and UAE
73 % of pregnant women taking prenatal
vitamins
…are DEFICIENT
How to get vitamin D...
• 100 IU/d raises level by about 1 ng/mL
• Sunlight
• Oily fish
3000 IU/10 minutes
300 IU/3 oz
– Salmon, sardines, mackerel, tuna
• Mushrooms 100 IU/3 oz
• Fortified drinks 100 IU/8 oz
– Milk, orange juice, yogurt, cereals
Endocrine, paracrine and intracrine
functions of Vitamin D
• Role in Cancer Prevention
– Low intake of vitamin D and calcium has been associated
with an increased risk of non-Hodgkin lymphomas, colon,
ovarian, breast, prostate, and other cancers.
– The anti-cancer activity of vitamin D is thought
to result from its role as a nuclear transcription
factor that regulates cell growth,
differentiation, apoptosis and a wide range of
cellular mechanisms central to the
development of cancer. These effects may be
mediated through vitamin D receptors
expressed in cancer cells.
– Vitamin D is not currently recommended for
reducing cancer risk
• Role in Cardiovascular Diseases
– Vitamin D deficiency activates the reninangiotensin-aldosterone system and can
predispose to hypertension and left ventricular
hypertrophy.
– Additionally, vitamin D deficiency causes an
increase in parathyroid hormone, which
increases insulin resistance secondary to down
regulation of insulin receptors and is associated
with diabetes, hypertension, inflammation, and
increased cardiovascular risk.
Updated Recommendations In Process
• Studies suggest that the daily vitamin D intakes
should be much higher than 400 IU/d.
• Daily intakes in the range of 800 to 1000 IU/d
should be strongly considered.
• Although there are concerns regarding vitamin D
toxicity, side effects at intakes exceeding the
current upper limit of 2000 IU/d have not been
reported to date.
• Assessment of vitamin D status with serum
measurements of 25(OH) vitamin D levels for a
broader range of patients should be encouraged.
Key clinical recommendation
• Daily vitamin D supplementation of 800 to 1,000 IU is
a reasonable dose for adults. Levels of 25-OH vitamin
D should be maintained > 32 ng per mL (80 nmol per
L) to maximize bone health.
• In patients with severe vitamin D deficiency, 50,000
IU of vitamin D should be given daily for one to three
weeks, followed by weekly doses of 50,000 IU.
Vitamin E
• There are four different tocopherol
compounds, but only the alpha-tocopherol
has vitamin E activity in human beings.
• Vitamin E as an Antioxidant
– Stops the chain reaction of free radicals
– Protection of polyunsaturated fatty acids and
vitamin A
– Protects the oxidation of LDLs
Vitamin E
• Easily destroyed by heat and
oxygen
• Deficiency symptoms
– Red blood cell breakage
– Nerve damage
• Toxicity symptoms
– Augments the effects of
anticlotting medication
Vitamin E Deficiency
– Primary deficiency due to inadequate intake is
rare
– Erythrocyte hemolysis
• Occurs in premature infants
• Hemolytic anemia can be treated with vitamin E.
Vitamin E Toxicity
– Rare and the least toxic of the fat-soluble vitamins
– Upper level for adults: 1000 mg/day
– May augment the effects of anticlotting
medication
Vitamin E
• Other name: alpha-tocopherol
• 2000 RDA
– Adults: 15 mg/day
• Upper level for adults:
1000 mg/day
• Chief function in the body
– Antioxidant (stabilization of cell
membranes, regulation of oxidation
reactions, protection of
polyunsaturated fatty acids and
vitamin A)
Antioxidant Nutrients In
Disease Prevention
Vitamin E
• Significant sources
– Polyunsaturated
plant oils
(margarine, salad
dressings,
shortenings)
– Leafy green
vegetables, wheat
germ, whole grains,
liver, egg yolks,
nuts, seeds
Vitamin K
• Also known as phylloquinone, menaquinone, menadione, and
naphthoquinone
• Vitamin K is unique in that half of human needs are met
through the action of intestinal bacteria.
• Vitamin K is essential in blood clotting.
• deficiency can cause uncontrolled bleeding.
• Deficiencies can occur in newborn infants and people taking
antibiotics.
Vitamin K
• Vitamin K Deficiency
– Symptoms include hemorrhaging
– Secondary deficiencies may occur with use of
antibiotics.
– Newborn infants receive a single dose of
vitamin K at birth because of a sterile intestinal
tract.
Vitamin K
• Other names
– Phylloquinone
– Menaquinone
– Menadione
– Naphthoquinone
• 2001 AI
– Men: 120 g/day
– Women: 90 g/day
vitamin K
– Blood clotting cofactor
– Prothrombin formation is blocked by warfarin
– Deficiency is rare
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Vitamin K
• Chief functions in the body
– Synthesis of blood-clotting
proteins and bone proteins that
regulate blood calcium
Vitamin K
• Significant
sources
– Bacterial
synthesis in the
digestive tract
– Liver
– Leafy green
vegetables,
cabbage-type
vegetables
– Milk
Vitamin K
• Deficiency symptoms
– Hemorrhaging
• Toxicity symptoms
– None known