Lecture 6: The VItamins Flashcards
vitamins
-organic compounds
-do not yield energy
-micronutrients
-vital to life
-indespensible to body function
Precursor to vitamins
provitamins
-transform chemically to one or more active vitamin forms
measure of a vitamin in a food, generally includes:
vitamin and the vitamin activity potential from its precursors
Bioavailability
the rate and extent to which a nutrient is absorbed and used
subclinical deficiency
a deficiency in the early stages, before the outward signs have appered
Fat soluble vitamins
A,D, E, K
Characteristics of fat soluble vitamins
-absorbed into lymph
-required bile for absorption
-travel in blood associated with protein carriers
-stored in tissues (liver & fatty tissue)
-may be toxic in excess
-found in fats&oils of food
-body can survive weeks without
water soluble vitamins
B & C
water soluble vitamins characteristics
-absorbed directly into blood
-travel freely in bloodstream
-most not stored
-excess excreted in urine
-low risk toxicity
fat soluble vitamin deficiency
-fat malabsorption
-mineral oil laxatives can cause vitamin loss
-low fat diets interfere with absorption
Vitamin A 3 active forms in body
-retinol
-retinal
-retinoic acid
plant derrived precursor of Vitamin A
beta-carotene
roles of vitamin A
-vision
-gene expression
-maintain body skin & lining
-immunity
-Growth
-normal cell development
-important for reproduction
how does vitamin A interact with eyesight
-light bleaches the vitamin A-containg pigment rhodospin
>this breaks off vitamin, initiating impulse to the optic center in the brain
>vitamin reunites with the pigment & there is vitamin A destruction
>vitamin A must regenerate the supply
if vitamin A supply runs low….
night blindness
>a lag occurs before the eye can see again after a flash of bright light
Eyesight & vitamin A deficiency corresponding illness
-Keratin accumulation (keratinization) of the cornea can occur with vitamin A deficiency
>can lead to xerosis (drying) & xerophalamia (thickening)
>if detected early, can be reversed with vitamin A supplement
vitamin A & the skin and body linings
-vitamin A needed by all epithelial tissues
-promotes cell differentiation
Vitamin A control of gene expression
retinoic acid activates or deactivates certain genes thereby affecting protein production
Vitamin A & immunity
-regulation of genes that produce immune system proteins
-deficiency can lead to malnutrition and infection
Vitamin A & Growth
-assists in growth of bone & teeth
-needed in dismantling of old bone structure
outcomes of Vitamin A deficiency
-cell differentiation & maturation are impaired
-failure of mucus-producing cells to produce mucus
-subsequent increase in keratin-producing cells
-tissues more vulnerable to infection
what worsens vitamin A deficiency
diarrhea and reduced food intake
benefits of supplemental vitamin A
-cuts childhood death rates
-benefit those suffering complications from diseases such as malaria, lung diseases and HIV
Vitamin A toxicity
-supplemets or fortified foods
early symptoms of vitamin A toxicity
-loss of appetite
-blurred vision
-headache
-skin itching
long term symptoms vitamin A deficiency
weaken bones, bone and joint pain, abdominal pain, stunt growth & liver damage
Vitamin A toxicity in pregnant women
-fetal malformation (teratogenic)
-chronic use of supplements exceeding recommendation
-single large dose
why do adolescents take large doses of vitamin A
-accutane is derrived from vitamin A but vitamin A supplements do not help with acne
can beta-carotene cause vitamin A toxicity
no
what is the most abundant of the carotene precursors
beta-carotene
retinol activity equivalents
vitamin A activity for vitamin A precursors
12mcgs of beta-carotene =1microgram RAE
does eating carrots really promote good vision
they do not improve vision if vitamin A is already adequate but vegetables rich in beta-carotene have a role in healthy eyesight
lack of foods rich in beta-carotene increases risk of
macular degeneration
adequate beta-carotene is associated with
reduced cancer risk
**not seen with supplements
beta-carotene supplements assocaited with increased risk of _____ in smokers?
cancer
what is beta-carotene
-dietary antioxidant
where is vitamin A found
food of animal origin
where is beta carotene found
plants
food sources of vitamin A
-liver and fish oil
-fortified milk & milk products
-eggs
what is beta-carotene found in
-dark green leafy foods
-rich yellow, and depp orange foods
Vitamin D
-not essential in some areas, essential in others
-body can make all it needs with help of sunlight
-many people border insufficiency
roles of vitamin D
-regulates blood calcuim & phosphorus levels to maintain bone integrity
-functions as a hormone
when more calcium is needed, what happens
vitamin D acts to raise blood calcium levels via:
-promotes absorption
-promotes retention by kidneys
-draws calcium from bone
hoe does vitamin D function as a hormone
plays role in brain, heart, stomach, pancreas, skin, reproductive organs, some cancer cells, stimulates cell maturation
what can a vitamin D deficiency promote?
high blood pressure, cancers, type 1 diabetes, heart disease, rheumatoid arthritis, IBD and multiple sclerosis
Rickets
-Vitamin D deficiency disease in children
-characterized by abnormal bone growth
-bowed legs, outward-bowed chest, knobs on ribs
reccomendation for brestfed healthy term infants by health canada
400IU vitamin D supplement each day
Risk for bone loss later in life due to potential lack of vitamin D in adolescents who:
- consume beverages with no vitamin D
-prefer indoor to outdoor activities
low levels of vitamin D in older adults can cause
painful joints and muscles
osteomalacia
-adult form of rickets
osteomalacia most often occurs in women with all three of the following:
-low calcium intake
-little sun exposure
-who go through repeated pregnancies & periods of lactation
too much vitamin D
-a danger to soft tissues
-most toxic of all vitamins in excess
toxicity symptoms of too much vitamin D
apppetite loss, nausea, vomitting, increased urination, and increased thirst, severe depression (effects on CNS)
continuous overdoses of vitamin D can cause
dangerously high blood calcium level, forcing calcium to deposit into soft tissue (heart, kidneys, lungs, blood vessels)
how can people make vitamin D from sunlight?
-UV exposure to a cholesterol compound in the skin transforms it into a vitamin D precursor which is absorbed into the blood
-the liver and kidneys convert precursor to active form of vitamin D
what type of vitamin D poses no risk to toxicity
skin synthesis
skin synthesis of vitamin D
-sun begins to break down excess vitamin D made in the skin
-when sun is overhead, this promotes skin synthesis
factors affecting sun exposure & vitamin D synthesis:
-skin colour, air pollution, city living, clothing, geography, indoor lifestyle, sunscreen, time of day
what SPF of sunscreen can reduce sun risks
sunscreens with SPF 8 or above
reccomendations from canadian cancer society
body makes vitamin D when skin is exposed to UV but sun exposure increases risk for cancer so best to get vitamin D from foods or supplement
health canada reccomendation for vitamin D for canadians over 50
400 IU supplement/day (canadas food guide 2017)
what happens to the vitamin D reccomendation with age
it increases (as people age sun exposure decreases)
sources of vitamin D
-sunlight
-small amnts from butter, cream, fortified margarine
-fortified milk
-egg yolks, liver, fatty fish and fish oil
-mushrooms
Vitamin E
consists of 4 tocopherol compounds with antioxidant activity
4 tocopherol compounds of vitamin E
- Alpha
- Beta
- Gamma
- Delta
antioxidant activity from vitamin E
- defending body against oxidative damage
-vitamin E is preferentially oxidized, protecting cells
oxidative damage results from :
free radicals
-formed during metabolism, disrupts structure of cellular lipids,DNA and proteins
-free radials may contribute to cancer, heart disease or other diseases
roles of vitamin E
-antioxidant effect: crucial in lungs (protects RBC & WBC)
-immunity
-nerve development
do vitamin E supplements provide health benefits
no unless deficient
vitamin E deficiency in infants
-born before transfer of vitamin E from the mother to the infant
-erythrocyte hemolysis
what is erythrocyte hemolysis
rupturing of red blood cells resulting in anemia
vitamin E deficiency in adults
-nerve damage
-associated with fat malabsorption diseases: damaged liver, gallbladder or pancreas
-low intake with extremely low fat diet for years
-people who rely soley on fat replacers
how is vitamin E destroyed
food processing and heating
vitamin E toxicity
-no toxicity seen wit natural food sources
-large doses may increase effects of anticoagnulant medications
-may be increased risk of death in those taking > 400IU from supplement
vitamin E food sources
-widespread
-vegetable oils
-avocados
-wheat germ
-meat, poultry, fish, eggs, milk products, nuts, seeds
-animal fat has almost no vitamin E
functions of vitamin K
-synthesis of blood clotting proteins
-synthesis of normal form of bone proteins that bind minerals to bone
how does vitamin K synthesize blood clotting proteins
-interferes with the function of certain anticoaguland medications (blood thinners)
sources of vitamin K
-intestinal bacteria (cannot meet needs)
-leafy green vegetables
-dark green vegetables richest
-canola and soybeans
-eggs and milk
-liver is only rich animal source
vitamin K and newborns
-newborns are given dose of vitamin K
-b/c sterile GI tract so vitamin K-producing bacteria will establish themselves
vitamin K deficiency
-unlikely in adults
-newborns & people taking antibiotics at risk
-people with fat malabsorption at risk
vitamin K toxicity
-no UL
-rare
-for infants & pregnant: toxicity can result from over-supplementation
-leads to jaundice and bilirubin
what leaches water soluble vitamins out of food
cooking and washing with water
general advice for meeting needs for water soluble vitamins
choose foods daily that are rich in water soluble vitamins to achieve RDA
are water soluble vitamins easily absorbed
yes
excess water soluble vitamins
-readily excreted in urine
toxicity of water soluble vitamins
-not from food
-can occur from large doses in vitamin supplements
-expend through urine
vitamins for athletes
athletes with appropriate diet generally don’t need vitamin supplements
nutrition experiment to find a cure for scurvy
-sailors divided into groups
-each group recieved supplemental ration
-those who recieved citrus quickly recovered
-found those with scurvy had vitamin C deficiency
supplemental ration given to those with scurvy and recovery examined
cider, vinegar, sulfuric acid, seawater, oranges or lemons
**oranges and lemons recovered fastest
to avoid scurvy, what was given to british sailors
lime juice
roles of vitamin C
-maintain connective tissues
-antioxidant
explain how vitamin C maintains connective tissues
-formation and maintenence of collagen
explain how vitamin C is an antoxidant
-protects substances found in foods and body
-protects iron from oxidation by promoting absorption
-protects blood constituents from oxidation and helps protect vitamin E and return it to active form
when are vitamin C supplements useful
-treat a deficiency disease
-not been proven to protect against heart disease, cancer or other diseases
vitamin C deficiency symptoms
-most scurvy symptoms due to collagen breakdown
-loose teeth
-bleeding gums
-pinpoint hemorrhages
-anemia
-tender to touch
-weak
-swollen ankles & wrists
-loss of appetite
-growth cessation
the risk of scurvy is low in north america. what are the excetpions for this
-elderly people with low intake of fruit/veg and poor appetite
-food insecure populations
-drug/alcohol addictions
-infants not given breast milk
how can scurvy be cured
100mg of vitamin C per day for 5 days (can be done with food)
research on vitamin C and colds
-supports immune function
-not shown to prevent colds
-one group found: some small benefit from vitamin C in high doses at onset of a cold will shorten duration of cold by 1/2 day ad reduce symptoms by 40%
research on 2 grams vitamin C per day for 2 weeks
-reduces blood histamins (this is responsible for sneezing, runny or stuffy nose, swollen sinuses)
-ath these doses, vitamin C may work as an antihistamine
placebo effect on vitamin C
-group that received placebo vitamin C reported to have less colds
is too much vitamin C hazardous to health
-from food is safe
-can cause digestive upsets
-interfere with medications to prevent blood clotting
-dangerous for people with overload of iron
smoking and vitamin C
-smoking introduces oxidants that deplete vitamin C
-RDA set 35mg higher for smokers
food sources of vitamin C
-citrus fruit
-dark green vegetables
-cabbage
-strawberries
-cantaloupe
-lettuce
-tomato
-papaya
-mango
-potato
how did they find out potatoes were rich in vitamin C
scurvy became evidence in ireland during potato famine
vitamin C in fruit and vegetables
-prone to destruction by heat and oxygen
The B vitamins
-act as part of coenzymes
-role in metabolism
B vitamins role in metabolism
-metabolize carbs, lipids and amino acids
B vitamins that help release energy stored in the energy-yielding nutrients
-thiamin
-riboflavin
-niacin
-pantothenic acid
-biotin
what B vitamin helps make protein
B6
what B vitamins help cells multiply
folate & B12
B vitamin Deficiencies
-every cell is affected
-cell renewal depends on energy & protein which depends on the B vitamins
-digestive tract & blood damaged
-in children, full recovery may be impossible
thiamin deficiency during growth
can cause permanent brain damage
deficiency in one B vitamin
very rare as people eat foods that contain mixtures of nutrients
Thiamin (vitamin B1) role
-energy metabolism
-nerve processes and their responding tissues
thiamin deficiency: Beriberi
-first observed with polishing of rice in asia
-loss of sensation in hands & feet, muscular weakness, paralysis, abnormal heart action
Wet beriberi: edema
Dry beriberi: no edema
thiamin deficiency: Wernickle-Korsakoff
-alcohol abuse with severe thiamin deficiency
-alcohol displaces food, impairing thiamin absorption & promotes thiamin excretion
-symptoms: confusion, disorientation, loss of memeory, jerky eye movements, staggered gait, irritability
-treatmentL IV or oral thiamin
thiamin sources
-widespread
-pork, sunflower seeds, whole grain cereals, legumes
role of riboflavin
energy metabolism of all cells
riboflavin deficiency
-usually with other vitamin deficiencies
-ariboflavinosis
ariboflavinosis
-inflammation of membranes of mouth, skin, eyes, and GI tract; smooth, purple red tongue
-may go undetected because thiamin deficiences are more severe
who is at risk for ariboflavinosis
children who lack milk products & meat
ariboflavinosis treatment
diet that treats a riboflavin deficiency also resolves a thiamin deficiency
sources of riboflavin
-widespread
-milk & milk products
-leafy greens
-whole-grain bread
-enriched/fortified grains
-some meat and eggs
role of niacin
energy metabolism
niacin deficiency
-pellagra (4D’s): diarrhea, dermatitis, dementia & death
who is at risk for pellagra
-poorly nourished people living in poverty
-those with alcohol addiction
niacin sources
milk, eggs, meat, poultry, fish, whole grains, fortified and enriched grains, nuts and seeds
trytophan
-abundant in almost all proteins
-can be converted to niacin
-if eating adequate protein, not niacin deficient
niacin equivalents
1mg niacin is made from 60mg tryptophan
Niacin toxicity
-large doses cause niacin flush (pain & tingling)
-injure liver and cause blurred vision
large doses of niacin may be prescribed to
lower blood lipids
role of folate
-DNA synthesis
-part of coenzymes for new cell synthesis
folate deficiency
Anemia - megaloblastic or macrocytic
-immature RBC & WBC of Gi tract most vulnerable
-diminished immunity
-abnormal digestive function
-increase risk of CVD, colon and cervical cancer
Neural tube birth defects
-problems w spinal cord, mental delay, dininished brain size, death shortly after birth
-arise in first few weeks of pregnency
-due to lack of folate
what did bleached grain become fortified with in late 1990s
folic acid
-since then, intake has increased and neural tube defects have decreased
folate toxicity
-can mask vitamin B12 deficiency
-excess folate may be antagonistic to the actions of anticancer drugs
folate unit of measure
-synthetic folate absorbed more readily than naturally occuring
-dietary folate equivalents converts all forms of folate into units that are equvalent to folate in food
folate bioavailability
-ranges from 50%-100%
(50% foods,
100% supplements on empty stomach)
-folate from food is given full credit
-folate from foods and supplemetns are given extra credit (1.7 times more available)
DFE for 100mg folate from food and 100mg folate from supplements
100 + 170 = 270mg DFE
Sources of folate
-leafy green vegetables
-fresh, uncooked fruit & veg
-eggs
-orange juice & legumes
what destroys folate
cooking & oxidation
RDA for folate
healthy adults: 400mcg DFE/day
Pregnant: 600 mcg DFE/day
health canaca reccomends women who could become pregnant: 400 mcg/day of folic acid from supplements plus healthy diet
vitamin B12
-close relationship with folate:
-B12 activated by folate
role of vitamin B12
-maintain sheaths that surround & protect nerve fibres
Vitamin B12 deficiency
-damaged nerve sheaths
-creeping paralysis
-general malfunctioning of nerves & muscles
-failure of folate to make RBC (B12 deficiency same anemia as folate)
treating anemia with folate
-folate will clear up anemia but vitamin B12 deficiency will continue
-give vitamin B12 as well if there is symptoms of folate deficiency incase of B12 deficiency
who is at risk for vitamin B12 deficiency
-the elderly (have absorption problems bc decreased stomach acidity)
-atrophic gastritis (gene defect)
-vegans (take time)
vitamin B12 absorption
requires intrinsic factor
-compound made by stomach
-stomach acid liberates B12 from food: intrinsic factor binds to the vitamin
-complex then absorbed from SI to blood
Pernicious Anemia
a vitamin B12 deficiency disease cause by lack of intrinsic factor and characterized by large, immature RBC
treatment: B12 injection
Sources of vitamin B12
-animal sources only significant source
-bioavailability greatest in milk and fish
-fortified plant foods
Role of vitamin B6
-100+ rxns in tissues
-assists in conversion of one amino acid to another
-protein synthesis
-aids in conversion of tryptophan to niacin
-neurotransmitter synthesis: conversion of trytophan to serotonin
-hemoglobin synthesis
-assists in releasing stored glucose from glycogen, regulating blood glucose
-immune function
-steriod hormonal activity
-fetal brain & NS develop.
Vitamin B6 deficiency general symptoms
-weakness
-psychological depression
-confusion
-iritability
-insomnia
-anemia
-greasy dermatitis
-advanced: convulsions & weak IS
-may be related to increased risk of heart disease
VItamin B6 toxicity
-2+ g/day for 2+ months
-numb feet
-loss of sensation in hands
-unable to walk or work
-recoverey as soon as supplements stop
single B6 supplement
-can deliver 2g of the vitamin in equivalent of:
-3000 bananas
-3800 servings chicken
-1600 servings liver
need for vitamin B6
-due to roles in protein metabolism, need is proportional to protein intake
-unlike other water soluble vitamins, it is stored in muscle tissues
sources vitamin B6
-protein-rich foods
-legumes and peanut butter
-poataoes, leafy greens, fruit
B vitamins and heart disease
Homocysteine
-elevated homocystene may be indicator of CVD
-deficiencies of B12, B6 or folate cause homocysteine to build up
role of biotin
-energy metabolism
-cofactor for several enzymes in teh metabolism of carbs, fat, protein
biotin deficiency
-may occur with rare diseases
-consuption of dozens of raw egg whites per day
sources of biotin
widespread
Pantothenic acid role
-energy metabolism
-coenzyme that plays role in release of energy from the energy nutrients
-100+ steps concerned with lipid synthesis, neurotransmitters, steroid hormones and hemoglobin
panthothenic acid deficiency
may occur with some rare diseases
panthothenic acid sources
widespread
what percent of canadian population takes vitamin supplement
46%
who may likely need vitamin supplements
-nutrient deficient people
-habitual eaters
-vegans
-lactose/milk allergy
-certain stages of life
-injury/infection
-medications
