Chapter7Vitamins
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Transcript Chapter7Vitamins
Chapter 7
Vitamins
Key Concepts
Noncaloric
Essential nutrients necessary for
many metabolic tasks and the
prevention of certain diseases
Organic substances
Needed by body for normal
metabolism, growth & maintenance
Key Concepts
Vitamins do not provide energy
Vitamins work as “coenzymes” to
activate other enzymes in the body
Discovery: Early
Observations
Discovered while searching for cures
for classic diseases
Dr. James Lind, 1753
Sailors
dying on long voyages without fresh
food
Scurvy = deficiency vitamin C, causes severe
bleeding
Lemons and limes provided, no one became
ill
Era of Vitamin Discovery
Most vitamins discovered in early
1900’s
At first scientists assigned letters to
each vitamin
A, C, D, E, K
This practice was abandoned in favor
of more specific names
Riboflavin, niacin, thiamine, etc.
Definition of Vitamin
vital, organic substance
only necessary in extremely small
amounts.
cannot be manufactured by the
body in sufficient quantities to
sustain life
Vitamins = micronutrients
Carb/fat/protein = macronutrients
Function of Vitamins
1. Metabolism: coenzyme needed for
metabolism
2. Tissue & Bone building
3. Prevention of deficiency diseases
Scurvy,
beri beri, pellagra
Vitamins:
Classes
Fat soluble (vit. A,D,E,K)
Best absorbed when eaten with fat
May be stored for long periods in liver and
adipose tissue
ie: Vit A best absorbed w/ whole milk
Water soluble (vit. B,C, folate)
Easily absorbed by intestinal cells and
transported by the portal (liver) circulation
Not stored, so must be eaten on regular basis
Fat-Soluble Vitamins:
Vitamin A
Functions
Vision (healthy retina, prevent macular degeneration)
Immunity (production of immune cells, fight infection)
Growth (of muscle and soft tissue)
Deficiency: Night Blindness
Toxicity symptoms: IU= 3000mcg/day, liver
damage, joint pain, headaches
Food sources: Liver, egg yolk, milk fat, butter
Stability – cooking veggies can inactivate vit A
*best absorption w/ fat
Vitamin D
Functions
Absorption of calcium and phosphorus
Bone mineralization
Requirements: none if exposed to sun
Deficiency: Rickets (malformation of long
bones in kids) and osteoporosis
Deficiency rare – milk is fortified w/ Vit. D
Toxicity: unusual, kidney damage
Food sources: Milk, margarine
Vitamin D
OTC vitamin D (ie: Caltrate w/ D)
From a plant source
Humans lack enzyme needed to
adequately absorb vit. D
We only absorb about 1%
Rx vit. D much more effective – Drisdol
given orally, weekly or monthly
recommended for US residents living north of
Virginia, less daily sunshine
**Kidneys must activate Vit. D first
Child with Rickets
Vitamin E
Functions
Antioxidant (prevents oxidation of molecules
& prevents free radicals from changing healthy
cells, accepts oxygen)
Deficiency: Hemolytic anemia (breakdown
of RBC), premature infants
Toxicity: none
Food sources: vegetable oils, nuts,
avocado, fortified cereals
Vitamin K
Functions
Blood clotting
Bone development
Requirements: intestinal bacteria produces vit. K
Deficiency: Uncommon, newborns, long
term antibiotic use
Toxicity: none
Food sources – green, leafy vegetables
Spinach, broccoli, turnip greens)
Water-Soluble Vitamins:
Vitamin C (Ascorbic Acid)
Functions
Build connective tissue (collagen)
Antioxidant function (protect from free rad.)
Helps w/ absorption of iron
NOT truly proven to treat colds & URI’s
Requirements: More w/ preg, lactation, smokers
Deficiency: Scurvy
Toxicity: tissue, gum bleeding, soft teeth, poor
wound healing
Food sources – strawberries, melon, oranges,
tomato, broccoli, potato, peppers, cabbage
Thiamin (Vitamin B1)
Functions
**needed for utilization of
energy, helps metabolize carbohydrates
GI system (normal appetite, digestion and
elimination)
CNS (alertness, normal reflexes)
CV (normal function)
Requirements: increased in pregnancy
Deficiency: Alcoholism, Beriberi (CNS)
Food sources: beef, pork, enriched grains,
legumes
Riboflavin (Vitamin B2)
Functions
Energy production
Tissue building
Requirements: increased w/ preg. &
lactation
Deficiency: usually occurs with protein
malnutrition
Toxicity: none
Food sources: Milk !
Niacin (Vitamin B3)
Functions
Energy production (extracts energy from
CHO, fat, prot.)
Helps to improve lipid levels
Requirements: higher w/ preg., lact.
Deficiency: Pellagra (4 D’s)
Toxicity: from supplements = reddened skin
w/ itching and burning
Food sources: meat, poultry, fish, whole
grains
Niacin Defeciency
4 D’s
Dermatitis
Diarrhea
Dementia
Death
Pellegra
Folate
Functions
Regulation of blood homocysteine levels – high levels
can cause CV disease !
Reduces likelihood of neural tube defects in
unborn
Requirements:
Deficiency diseases: Neural tube defects
400 mcg/day. Pregnant women,
women of child bearing age should take in dietary form +
supplements = 600mcg/day
(spina bifida, anencephaly)
Toxicity: minimal, some nerve damage
Food sources–green leafy veg, beans, OJ
Vitamin B12 (Cobalamin)
Functions
Regulation of blood homocysteine levels
Hemoglobin production
Nervous system functioning
Requirements: higher w/ preg, lact.
Deficiency: Pernicious anemia
(irreversible nerve damage)
Toxicity: none
Food sources: lean meats, clams, oysters,
crab
Vitamin Supplementation
Ongoing debate……yes or no ??
Biochemical individuality: the body’s
chemical composition varies for each
person, this also changes based upon:
Life cycle needs
Pregnancy
and lactation (folic acid +++)
Infancy (vit K at birth)
Children and adolescents (rapid growth)
Aging (decreased food intake)
Vitamin Supplementation,
cont’d
Lifestyle
Oral
contraceptive use (may lack B & C)
Restricted diets (vegetarians – may lack B12)
Exercise programs (may need more riboflavin)
Smoking (need more vit. C)
Alcohol (thiamin, folate)
Caffeine (4-6 c/day coffee = diuretic effect – may
lack B’s)
Disease (increased nutrient needs)
Vitamin Supplementation,
cont’d
Megadoses
Toxicity: megadose of fat soluble
vitamins (vit. A) - liver/brain damage
**fat sol. – stored in body
Vit. B6 - folate (over 5 gm/day) - severe
nerve damage
Vit. C (ascorbic acid) (over 2 gm/day) kidney stones