Vitamins
Dr Hadeel Ali Ghazzawi
Fundamental to Nutrition Science
Nutrition Department 2016
The Nature of Vitamins
• Vitamins are organic (carbon) compounds needed for
normal function, growth and maintenance.
• Vitamins are co-factors, they don’t do anything by
themselves.
• They are individual units rather than long chains of
smaller units.
• Essential for normal functioning, growth and
maintenance.
• They are differ than fat, carbs and protein.
• The need is in a small amount.
• Not a source of energy.
• They play a crucial roles in regulating the chemical
reactions that allow us to extract energy from those
nutrients.
• Vitamin toxicity is rarely linked to high vitamin intakes
from food or to the use of supplements that contain
100 to 150% of the recommended amounts.
• People who takes mega doses of one or more vitamins
run a high risk of toxicity.
Fat soluble Vs water soluble
• The difference in the solubility affects the way the
body
– Absorbs
– Transport
– And stores vitamins,
• Intestinal cells absorb fat-soluble vitamins along with
dietary fat.
• The amount absorbed typically varies from 40-90% of
the amount consumed.
• Efficiency of absorption generally falls as the dietary
intake rises above the body needs.
• Lipoprotein carry absorbed fat-soluble vitamins
through the lymph and bloodstream.
• As chylomicrons move through the blood, cells take
out most of the TG and leave chylomicron remnants
that contain the fat-soluble vitamins.
• The liver picks up these remnants and either stores
the vitamins fro future use of repackages them, for
delivery by way of the blood-stream to other tissues.
FAT SOLUBLE VITAMINS
• A – orange, carotenoids, vision, antioxidant
• D – we make it with sunlight, deficiency causes rickets, in milk,
regulates Ca:P ratios
• E – tocopherols, antioxidants, role in preventing stroke, cancer,
heart disease- used as antioxidant
• K – contributes to blood clotting factor
Storage and toxicity
• Accumulate in the liver and adipose tissue.
• They can be drawn from there upon need.
• Once stored, body can go for days, weeks or even
months without consuming more or suffering from ill
effects.
• Over consumption can exceed the body’s storage
capacity and lead to toxic effects.
Provitamins/ Vitamin precursors
• Inactive forms of vitamins that the body can convert
into active usable forms.
• Certain vitamins in foods are in inactive forms that
the body cannot use directly.
• Once a provitamins is ingested the body converts it to
the active vitamins form.
• Ex. Beta-carotene. Once absorbed, the body can
convert it to the active form of vitamin A.
Vitamins in Foods
• Vitamins are found in every food group.
• The amount of vitamins in food depend on several
factors.
• In general:
– Growing condition of the food source,
– Storage,
– Processing,
– And cooking.
VITAMIN A: THE RETINOL
Forms of vitamin A
• The body uses 3 active forms of vitamin A.
– Retinol : the alcohol form.
– Retinal: the aldehyde form.
– Retinoic acid: the acid form.
• All 3 forms are essential functions but the Retinol is
the key player in the vitamin A family.
• Our body can easily convert retinol to retinal.
• In turn, retinal can re-form retinol OR it can
Irreversibly form retinoic acid.
Retinol
Retinal
Retinoic acid
Functions of Vitamin A
1. Vision:
– Rhodopsin is the combination of protein opsin and vitamin A
(retinal).
2. Cell differentiation:
– Retinoic acid interact with receptor sites on a cells’ DNA- the
genetic material that spurs production of particular proteins.
– Vitamin A (retinoic acid) is required to turn on cells
differentiation of many cells.
3. Reproduction:
– Exact mechanism still unclear.
– Vitamin A affect both male and female reproductive
processes.
– Both retinol and retinal support reproduction while retinoic
dose not.
– In men: vitamin A supports the production of sperms.
– In women: it helps maintain fertility by supporting the
production of reproductive tract secretion.
4. Bone health:
– retinol, retinal and retinoic acid all are needed for both bone
growth and bone remodeling.
– Unclear mechanism; but lack of vitamin A makes bone
weaker and thicker than normal.
– Disrupts bone remodeling and develop immature bone cells.
– Too much vitamin A can interfere with the ability of vitamin
D to promote calcium absorption and can increase risk of
bone loss and hip fracture.
Dietary recommendation of Vit A
• Dietary retinoids and carotenoids do not provide the
same amount of vitamin A.
• Therefore scientists developed a standardized
measurements based on retinol called retinol activity
equivalents (RAEs).
• One retinol activity equivalent is the amount of a
given form of vitamin A equal to the activity of 1
micrograms (μg) of retinol
• 1 μg = 1/100,000 of a gram.
Sources of vitamin A
• Most dietary intake comes from animal food sources.
• Liver and fish liver oils are the top sources.
• Milk fat and food fortified.
• Retinoids (storage form of vitamin A) found only in
animal.
– 10% found as retinol
– 90% as retinyl ester.
• ¼ to ⅓ of our dietary comes from fruits and
vegetables.
• The best sources of provitamin A carotenoids are dark
green and yellow-orange vegetables:
– Carrots, spinach, broccoli, orange, peaches, mangos and
apricot.
• Body absorbs provitamin less efficiently than it can
absorb retinol or retinyl esters.
Vitamin A Deficiency
• Retards growth and development and leads to bone
deformities.
• Eyes: night blindness.
• Skin: hyperkeratosis (excessive accumulation of the
protein keratin).
• Immune function: person is more likely to get
infections. Children are at more risk of diarrhea,
respiratory tract infections and measles.
Vitamin A toxicity
• Wide range of symptoms:
– Fatigue.
– Vomiting
– Abdominal pain
– Bone and joint pain
– Hip fracture
– Kiss if appetite
– Skin disorders
– Headache
– Blurred or double vision
– Liver damage
– Jaundice.
Excess
Deficiency
•
•
•
•
•
• Night blindness
• Xerophthalmia
Death
Liver damage
Bone fracture
Skin disorders
Birth defects
– (eye fails to produce tears)
• Hyperkeratosis
• Infection
• Death
VITAMIN D
New ideas about Vit D
• Called the sunshine vitamin.
• Its unique!!!
– If the body got sufficient sunlight body can synthesize all
it needs.
• It is synthesized and functions like a hormone.
• Not always necessary in the diet !!!!!
• When the ultraviolet rays of the sun strike the skin,
they alter a precursor derived fro, cholesterol
converting it into vitamin D.
Functions
• Essential for bone health.
• Can help reduce cancer risk by preventing cells from
dividing.
• Primary role In regulating blood calcium levels.
• Regulating cell differentiation and growth.
• Has anti-inflammatory properties.
• Involved in the regulation of insulin formations and
secretion blood sugar maintenance.
• In children, promotes bone development and growth.
• In adults, important for bone maintenance.
• In older, supplements help prevent osteoporosis.
Under investigation
• Its role in the prevention of CVD, type 2 diabetes and
cancer.
Forms and formation
• Ten compounds from D1 through D10 exhibit
antirachitic properties.
• Antirachitic: curing or preventing rickets.
• The most important forms are
– D2 (ergocalciferol) found only in plant foods
– D3 (cholecalciferol) found in animal foods (eggs and fish
oil), but most synthesize in the skin.
Rickets: “children’s disease of
the English”
th
in 17 century
Rickets can be caused by lack of
sunlight, but also from
insufficient calcium. Vitamin D
linked to calcium absorption.
Dietary recommendation
• According to the limited exposure of sun exposure,
the panel recommends that
• all infants consume at least 400 IU of daily vitamin D.
• People between 1 -70 years 600 IU.
• Vitamin D skin synthesizing decreases with age thus
after age 70 yrs old  800 IU.
Sources of vitamin D
• Exposure from sunlight, diet and supplements.
• Sunlight:
– Arms and legs from 5-30 min between the hours of 10 a.m.
to 3 p.m. twice per week is adequate.
– Depends on:
• Time of day midday
• Season summertime
• Location closer to the equator
• Sunscreen use SPF > 8 block UV light
• And type of skin dark skin< light skin
Dietary sources
• Few naturally:
– Oil fish,
– Egg yolk,
– Butter,
– Liver
• The major fortified.
– Fortified milk.
– Fortified breakfast cereal,
– Orange juice.
– Margarine.
Deficiency
• Rickets, osteomalacia and osteoporosis.
• Long term deficiency takes a profound toll o the
skeleton.
• When vitamin D is in short supply, the intestine absorb
only about 10-15% of dietary calcium. So bones don’t
get enough of this bone-building mineral.
Toxicity
• Exposure to sun doesn't cause vitamin D toxicity.
• Excess consumption than 10,000 IU/day leads to
hypercalcemia (high concentration of calcium in
blood). Affect:
– Bone loss
– Kidney stones
– Excessive urination and thirst.
– Affect CNS  depression+ nausea, vomiting and loss of
appetite.
VITAMIN E
• In 1922, an unknown substances was discovered in
plant oil that is important for rat reproduction.
• Scientists named it by tocopherol from greek work
tokos (childbirth), phero (to bring forth).
• 40 years later, researchers showed evidence that this
substances is important and labeled it by Vitamin E.
• It is not a single compound.
• It is 2 sets of 4 compounds of tocopherol:
– Alpha, beta, gamma, and delta.
• Only alpha-tocopherol meet vitamin E requirement in
the body and the most common form in the food.
• Absorption needs dietary fat.
• It travels by chylomicrons and other lipoproteins for
distribution throguhout the body.
• GI tract absorbs 20-80% of dietary alpha-tocopherol.
• The % declines as the amount of intake increases.
• Unabsorbed vitamin E is excreted in fecal matter.
• Unlike vitamins A and D, Vitamin E doesn’t accumulate
in the liver.
• Adipose tissue contains about 90% of the body
vitamin E.
• The remaining 10% is found in virtually every cell
membrane in every tissue.
Functions
• Vitamin E is an antioxidant.
• Its activity is also enhanced by other nutrients
involved in antioxidant pathways, such as Vit C and
selenium.
What dose antioxidant mean?
• During normal metabolic processes, oxygen react with
other compound to generate free radicals.
• Free radical are highly unstable, toxic molecules that
contain one unpaired electron.
• These unpaired electron make free radicals highly
reactive.
• A free radical attacks a nearby compound and steals
an electron from it.
• Although that stabilizes the original free radical ”
thief”, it turns the “robbed” molecule into a free
radical.
• Under normal state, the body generates free radicals
to help eliminate unwanted molecules.
• If various enzymes and antioxidants fail to control free
radical activity, these highly reactive compounds
attack cell membranes and cell constituents, including
DNA.
• Here where many disease occur such as cancer and
atherosclerosis.
• Vitamin E acts as a potent antioxidant and interrupts
the cascade of free radical formation.
• Vitamin E donates an electron to the electron-seeking
free radical which prevent the free radical from finding
an electron somewhere else and cause damage.
• This makes vitamin E itself a free radical but not a very
reactive one.
• The body excretes some of this altered vitamin E and
recycles the rest by adding an electron from another
antioxidants such as vitamin C.
• This vitamin C radical can regain its antioxidant form
by swiping an electron from glutathione.
• The PUFAs in cell membranes are especially vulnerable
to assault by free radicals.
• Vitamin E resides in cell membranes and defenses
against damage by free radicals.
• Longer intake of 15 mg/day (22 IU) decreases:
– Chronic diseases.
– Reduce the risk of blood clots in women.
– Heart diseases.
– Eyes disorders,
– Alzheimer’s diseases,
– Cancer.
Dietary recommendation
• The intake mist be related to body size and PUFA
intake.
• When PUFA intake is minimal, small amounts of
vitamin E prevent symptoms of deficiency.
• As PUFA increases, the concentration of PUFA in
tissues also rises and more Vit E is needed to prevent
oxidation.
• As vitamin E content of oils tends to parallel the PUFA
concentration, balancing the 2 is usually not a
problem.
• When people limit fat intake they also may limit
vitamin E intake.
• 15mg/day alpha-tocopherol for adults.
• 19mg/day for lactating women.
Sources of Vitamin E
• In both plant and animal sources.
• The highest found in wheat germ oil.
• Seeds oil and nuts.
Stability
• Cooking, processing and storage can reduce the
vitamin E content of foods substantially.
• During the milling of wheat to make white flour,
vitamin E-rich wheat germ is removed.
• Refining and purifying vegetable oils takes a
substantial toll on their vitamin E.
• Oxygen, light and heat attack vitamin E.
Deficiency
• Rare in rich countries according to the plenty of
vegetable oil use.
• Most occur in people with fat-malabsorption
syndrome such cystic fibrosis.
• Hemolysis (breakdown of red blood cells) because no
vitamin E to protect the cell membrane from
destruction.
Toxicity
• Not from food intake.
• Over does of supplements can increase bleeding
especially with people suffer from vitamin K
deficiency.
VITAMIN K
• Danish researcher (Henrik Dam) in 1929 discovered a
nutrient the play a critical role in blood clotting.
• He named it vitamin K for “Koagulantion”.
• Vitamin K stands between life and death.
• Without vitamin K to promote blood clotting, a single
cut would lead to death by blood loss.
Functions of vitamin K
• When skin get a cut, small or large, and start to bleed,
a series of reactions forms a clot that stops the flow of
blood.
• This cascade of reactions involves the production of a
series of protein and ultimately the protein fibrin.
• Four of the procaugualtion proteins in the cascade are
vitamin K dependent, and all require calcium for
activation.
• Vitamin K assists bone formation by facilitating a
process needed to allow the protein osteocalcin to
strengthen the skeleton.
• Low levels of vitamin K are associated with age-related
bone loss.
• Vitamin K strength bone and decreases fractures.
Dietary recommendations
• Varies with age.
• For males 120 μg/day
• For females 90 μg/day
• Absorption is poor with people suffer from fatmalabsorption syndrome.
• Under normal condition: absorption low as 40%.
• Supplements are important for bone health.
Sources
• We obtain vitamin K from 2 sources:
– Food mostly plant absorbed in SI.
– Bacteria living in our colon absorbed in the colon.
• Green leafy veg especially spinach, broccoli and
brussels.
• Animal products contain limited amounts
– Small amount in egg yolks, liver and butter.
Deficiency
• Body needs small amounts for blood clotting thus the
deficiency is rare in adults.
• Typical diet may supply less than optimal for bone
health.
• People with fat-malabsorption syndrome such celiac
disease, ulcerative colitis, cystic fibrosis and crohn’s
diseases; develop vitamin K deficiency.
• Prolonged use of antibodies can cause a deficiency
because the drugs can destroy the intestinal bacteria
that produce vitamin K.
• Mega doses of vitamin A and E counteract the actions
of vitamin K.
• Vitamin A appears to hamper intestinal absorption of
vitamin K.
• Excess vitamin E seems to decrease the vitamin K
dependent clotting factors thus promoting bleeding.
• New born babies run a risk of vitamin K deficiency
because at birth they lack of intestinal bacteria that
produce the nutrient, and they don’t receive much
vitamin K through diet.
• To prevent hemorrhaging , infants typically receive an
injection of vitamin K at birth.
• This dose usually meets their needs for several weeks
until the vitamin K-producing bacteria begin to
flourish.
Toxicity
• Vitamin K is stored primarily in the liver and also
found in the bone.
• Because the body excretes vitamin K much more
rapidly than the others fat-soluble vitamins, toxicity
from food is rare and thus no UL has been set for
vitamins K.
• Over dose can cause hemolytic anemia.
WATER SOLUBLE VITAMINS
Water Soluble Vitamins
• Although many people like to think of vitamins as energy
boosters.
• Vitamins do not supply calories for the body.
• They differ from fat, carbs and protein.
• Many B vitamins facilitate the metabolic reactions that release
energy.
• So vitamins help you get energy by allowing carbs, fat and
protein to become cellular fuel.
Water soluble vitamins
• Eight Bs and a C
• Although fat soluble vitamins tend to accumulate in
the body, the kidney’s generally remove and excrete
excess water-soluble vitamins.
• The exception is vitamin B12 which the liver stores in
large amounts.
• Therefore other vitamins should be supplied from diet
daily.
• Small variations in daily intake typically do not cause
problems.
• E.g. symptoms of vitamin C deficiency do not merge
until after 20-40 days of a diet deficient in it.
• Are dissolved in the watery compartments of foods.
• Once absorbed, these nutrients travel directly into the
bloodstream and then move independently in and
around the cells of the body.
• They don’t need lipoprotein carriers.
• Their storage and excretion differ from fat-soluble.
Expectations
• Most fat-soluble vitamins accumulate and can be
stored.
• Water-soluble are filtered by the kidney and excreted
in urine.
• B12 is stored.
• Vitamin K excreted.
Storage and toxicity
• Body doesn’t store them in appreciable amounts, so
they should be a part of daily intake.
• Excess intake is harmless but large amount of vit B6,
folate, niacin, vit C can be problematic.
• Water-soluble vitamins are more fragile than fatsoluble vitamins.
• Cooking practice are particularly harmful.
• Heat and alkalinity (baking soda) destroy them.
• they are hydrophilic thus they will leach from
vegetables and fruits into water during cooking.
• Some cooking methods are less destructive than
others.
• To preserve vitamin content in foods, the best cooking
methods are:
– Steaming
– Stir-frying
– Microwaving using minimal amounts of water.
THE B VITAMINS
• Act primarily as coenzymes or part of coenzymes.
• Coenzymes: compounds that enable specific enzymes
to function.
• B vitamins also help in the working of metabolic
pathways in cells.
• Energy producing metabolic reactions.
• Thiamin B1
• Riboflavin B2
• Niacin B3
• Pantothenic acid
• Biotin
• Folate
• Vitamin B12
THIAMIN
Thiamin B1
• Beriberi diseases was discovered in 1885 when Dr
Takaki cured the sailors by supplementing their diets
with meat, milk and whole grains.
• Later Dr Ejikman a Dutch medical officer fed his birds
white rice only he induced beriberi then he cured
them by adding bran to their diet.
• Anti-beriberi factor (Thiamin) was discoverd.
Functions of Thiamin
• Important in energy-yielding reactions.
• Plays role in nerve function.
• Regulate the movement of chemicals involved in the
transmission of messages throughout the nerve
system.
Thiamin Dietary recommendation
• Adult male 1.2 mg/d
• Adult female 1.1 mg/d
• Pregnancy and lactation increase energy
requirements, 1.4 and 1.5 mg/d respectively.
•
Thiamin Sources
• Most foods contain only small amounts.
• Pork is the richest.
• Legumes, some nuts, seeds and some types of fish
and seafood are good sources.
Thiamin Deficiency
• In rich countries, deficiency is related to high alcohol
consumption:
– Alcohol contributes calories without contributing nutrients.
– Alcohol interferes with absorption thiamin and many other
vitamins.
• Poor and elderly are at risk of deficiency according to
their poor intake.
• Eating highly processes and un-enriched foods and
empty calorie food such as alcohol, sugars and fat can
lead to the deficiency.
Thiamin Toxicity
• Supplements up to 200 times of the daily
requirements.
• Kidney rapidly excrete excess thiamin in urine.
RIBOFLAVIN
Riboflavin
• At first, riboflavin and thiamin were considered the
same vitamin.
• Flavin in Latin means Yellow.
Functions of riboflavin
• The vitamin accepts and donates electrons with ease,
so it helps in many oxidation-reduction reactions.
• Coenzymes in reactions that remove ammonia during
the deamination of some amino acids.
• Help with the antioxidants of the glutathione
reductase.
– That promotes the breakdown of some types of fatty acids.
Riboflavin Dietary recommendations
• Intake reflect the higher energy needs.
• Therefore males needs more than females similar to
thiamin.
• So RDA is higher during pregnancy and lactating
periods.
Riboflavin Sources
• Most plants and animals foods.
• Milk, milk drinks and yogurt supply 15% of riboflavin
in our diet.
• Bread around 10%.
• Riboflavin is more stable than thiamin.
• It is resistance to acid, heat, and oxidation.
• Sensitive to light (can be broken).
• So milk should be stored in Impermeable package.
• Packaging milk in paper or plastic cartons rather than
clear glass better protects milk’s riboflavin content.
• Riboflavin absorption from food is good.
• 60 to 65% of the riboflavin in milk and spinach is
absorbed.
Riboflavin Deficiency
• Is rare.
• People with alcoholism tend to have poor diets.
• Usually exists along with other nutrient deficiencies.
• Riboflavin deficiency can make other deficiencies even
worse.
Riboflavin Toxicity
• Not been reported.
• Because the body readily excretes excess riboflavin.
• Even large doses appear to pose no risk of harm.
NIACIN
Niacin
•
st
In 1867, 1 discovered and called nicotinic acid by
oxidizing the nicotine from tobacco.
• Nicotinic acid is not the same as nicotine molecules.
• In 1940s the vitamin renamed niacin not to confuse
with nicotine.
Niacin Functions
• Coenzymes, play key roles in oxidation-reduction
reactions.
• NAD+ accepts electrons and hydrogen is reduced to
form NADH.
• Many metabolic pathways that promote the synthesis
of new compounds, such as fatty acids rely on NADPH.
Niacin Dietary recommendations
• Niacin is unique among the B vitamin because body
can make it from the AA tryptophan as well as obtain
it from foods.
Niacin Sources
• Meat, poultry, fish , enriched and whole breads.
• Mushrooms, peanuts, liver, and sea food.
• Stable when heated.
• Food contain tryptophan are considered niacin
sources.
• 60 mg of tryptophan yield 1 mg niacin.
• To convert tryptophan to niacin in vivo, body needs
riboflavin, vitamin B6 and iron.
• So deficiency of one of those may lead to decrease the
conversion.
Niacin Deficiency
•
st
Pellagra wad 1 documented in 1735 by a Spanish
physician Gasper Casal.
• Pellagra (niacin-deficiency) was named mal de la rosa
“red sickness” for the redness that appears around the
necks of patients.
• Pelle “skin”, agra “rough” in Italian language.
Three Ds
• The Pellagra known as the three Ds:
– Dementia
– Diarrhea,
– Dermatitis.
th
– In sever cases 4 D Death.
• In early 1900s, corn was the stable in the
Southwestern United States, So Pellagra emerged in
epidemic disease.
• Because a protein in corm binds niacin tightly and
reduces niacin’s bioavailability.
• Soaking corn in lime solution releases that bound
niacin.
Niacin Toxicity
• Because mega-doses of niacin lower LDL cholesterol
and rise HDL, physician prescribe it.
• Niacin supplementation has been investigated for its
possible in treating other conditions such as
– Osteoarthritis. - Alzheimer
– Atherosclerosis - Diabetes
• For adults the UL for niacin is 35 mg/d from fortified
foods, supplements and medications.
• The principles side effects are:
– Flushing
– Related itching
– And tingling.
PANTOTHENIC ACID
Pantothenic acid
• In 1930s, a chemist named J. Williams discovered that
yeast requires a certain nutrient, which he called
pantothenic acid.
• He suggested that if yeast needed this nutrient, then
human might need it too.
• The name is derived from the Greek word pantothen
meaning “from every side”.
• This vitamin is widespread in the food supply.
Pantothenic acid Functions
• Is a component of coenzymes A, which in turn is a
component of acetyl CoA.
• Acetyl CoA is a median of number of metabolic
pathways.
• Both energy generating pathways and biosynthetic
pathways.
• It is formed from pyruvate starts the citric starts acid
cycle (the key building block of fatty acids).
• Fatty acids also are known as acyl groups and
pantothenic acid is a component of the acyl carrier
protein.
• During fatty acid synthesis, the acyle carrier protein
binds fatty acids and carriers them through a series of
reactions that increases their chain length.
Dietary recommendations
• 5 mg/ day
Pantothenic acid Sources
• Widespread in the food supply.
• Chicken, beef, potato, oats, tomato, liver, mushrooms,
yeast, broccoli and egg yolk.
• Pantothenic acid is damaged easily.
• Freezing and canning appear to decrease its amount in
vegetables, meant, fish and dairy products.
• Processing and refining grain reduce its content of
pantothenic acid vitamin by 75%.
Pantothenic acid Deficiency
• Nonexistent in the general population.
• The only observed cases are in people who were fed
diets that completely lacked the nutrients or given
substance that prevent metabolism of pantothenic
acid.
• Symptoms:
– Irritability, restlessness, fatigue
– Nausea, vomiting, muscle cramps, hypoglycemia.
Pantothenic acid Toxicity
• High doses have not caused adverse effects.
• Risk is extremely low and no UL been established.
BIOTIN
Biotin
• In 1924, 3 factors were identified as necessary for the
growth of microorganisms.
• They were called:
– Bios II
– Vitamin H
– And coenzyme R
• It soon became clear that all 3 factors were the same
water-soluble vitamin called Biotin.
• In food, biotin is found both free and bound to
protein.
• When protein are digested, a biotin-lysine complex
(called biocytin) is released.
Biotin Functions
• Like all other B vitmain, biotin acts as a coenzyme in
many reactions such as
– Amino acid metabolism, including the conversion of amino
acid to glucose (gluconeogenesis).
– Fatty acid synthesis
– Release energy from fatty acids
– DNA synthesis .
Biotin Dietary recommendation
• 30 micrograms/ day
Biotin Sources
• Most food composition tables do not list biotin
content because it has n’t been determined for many
foods.
• Good sources:
– Cauliflower
– Liver,
– Peanuts
– And cheese.
• Most fruits and meats are poor sources.
• Egg yolk are a good source of biotin, but a protein
called avidin in raw egg whites binds biotin and
prevents its absorption from raw egg.
Biotin Deficiency
• Eating raw egg can cause biotin deficiency.
• Heat destroys avidin, so its unlikely to cause a biotin
deficiency. (dozen daily of raw egg).
• Anticonvulsant drugs (antiepileptic drugs) break down
biotin.
• Deficiency can delay growth and development.
• Early diagnosis and high doses of biotin recover
Biotin Toxicity
• Has not been establish
VITAMIN B6
Vitamin B6
• Is a group of 6 compounds:
– Pyridoxal PL
– Pyridoxine PN
– Pyridoxamine PM
– And their phosphorylated forms
• PLP
• PNP
• And PMP
• Food contains the phosphorylated forms but digestion
strips off the phosphate groups.
Vitamin B6 Functions
• Vitamin B6 coenzyme PLP supports more than 100
different enzymes involved in reactions that include
the transfer of amino groups (NH2), carboxyl groups
(COO- or COOH), or water.
• These enzymes support
– protein metabolism,
– blood cell synthesis,
– carbohydrate metabolism
– and neurotransmitter synthesis.
Vitamin B6 Dietary recommendations
• Males and females aged between 19- 50 is
– 13 mg/d
• Men over 51 yrs old
– 1.7mg/day
• Women over 51 yrs old
– 1.5 mg/day
• Due to vitamin B6 role in amino acid metabolism,
people on very very-high protein diets may need
higher intakes.
Vitamin B6 Sources
• Banana, potato, sunflower seed
• Fortified cereal.
• Vitamin B6 is not stable and sensitive to temperature.
• Heat can destroy as much as 50% of food’s content.
• 75% of vitamin B6 is absorbed even when taken in
mega-doses.
Vitamin B6 Deficiency
• Rare,
• Leads to
– microcytic hypochromic anemia
– Seborrheic dermatitis,
– Neurological symptoms such as depression, confusion, and
convulsion .
• Alcoholic boosts the risk of B6 deficiency because
alcohol decrease the absorption.
Vitamin B6 Toxicity
• Mega doses of supplemental vitamin B6 can cause
– irreversible nerve damage that affect the ability to walk and
cause numbness in the extremities.
– Upset stomach, headache, sleepiness, and tingling.
– Nerve damage when prolong over doses.
FOLATE
Folate
• Because folate and B12 work together to perform a
number of biochemical functions, a deficiency of
either one products the same abnormalities in red
blood cells.
• Folate is named for its best natural sources: green
leafy vegetables (foliage).
Functions of folate
• As a coenzyme, folate is crucial
– to DNA synthesis and cell division,
– amino acid metabolism,
– And the maturation of red blood cells and other cells.
• This involvement in basic cell reproduction and growth
makes folate essential for healthy embryonic
development.
• Essential in early pregnancy to prevent the risk of birth
defects “neural tube defects”.
• That is why experts recommend folic acid
supplements before pregnancy to all women who
might become pregnant.
• Folate functions with vitamin B6 and B12, all of them
support red blood cell synthesis and help control
homocysteine levels.
Folate Dietary recommendations
• The bioavailability of folate varies depending on
stomach contents and the folate sources.
• The body absorbs nearly 100% of folic acid in
supplements and fortified foods.
• Only ½ to ⅔ of the folate naturally presents in food.
Sources of folate
• Dark-green leafy vegetables, asparagus, broccoli,
orange, and legumes.
• Folate is extremely vulnerable to heat, ultraviolet light,
and oxygen.
• Cooking and food processing can destroy 90% of a
food’s folate.
• Eat folate-rich fruits and vegetables raw or cook them
quickly in minimal amounts of water by steaming, stirfrying, or microwaving.
Folate Deficiency
• The most prevalent of all vitamin deficiency.
• In developed countries, associated with poor nutrition
such as
– older adults
– alcoholism
– Intestinal malabsorption
• Deficiency play role in the development of
– Anemia,
– Atherosclerosis,
– Neural tube defects
– Adverse pregnancy outcomes,
– And neuropsychiatric disorders.
• Body can store enough folate to last 2 to 4 months
without additional intake.
Deficiency causes
• Inadequate folate consumption.
• Inadequate folate absorption resulting from
abnormalities in the mucosal cells lining the GI tract.
• Increased the requirements.
• Excessive folate excretion.
Folate Toxicity
• Because folate works so closely with vitamin B12, it
can mask a vitamin B12 deficiency.
• In rare cases, when hypersensitive people take folic
acid supplements, they suffer from respiratory
distress.
• UL for adults is 1000 micrograms/day.
VITAMIN B12
Vitamin B12
• Unlike other B vitamins.
• Plants do not provide it, and body stores large
amounts.
• Known as cobalamin.
Vitamin B12 Functions
• Play a key role in folate metabolism.
• Reducing homocysteine blood levels thus lowers the
risk of heart disease.
• Helps maintain the myelin sheath, the protective
coating that surrounds nerve fibers.
• Helps prepare fatty acids to enter the citric acid cycle.
Vitamin B12 Absorption
• Unless the person is a vegan, it’s easy to get enough
vitamin B12 from diet.
• But absorbing vitamin B12 is complex and requires
several factors.
Factors that impair vit B12 absorption
– Lack of R-protein (a protein produced by salivary glands to
protect Vit B12 through stomach and SI).
– Absence or removal of the ileum or stomach.
– Overgrowth of bacteria In the stomach.
– Tapeworm.
– Reduction of gastric acid production due to long term use of
acid-inhibiting medications.
Vitamin B12 Dietary recommendations
• Age 19- 50 yrs old:
– 2.4 microgram/d
• Older people suffer from decreasing the bioavailability
.
Vitamin B12 Sources
• All naturally originates with bacteria.
• Bacteria produce it and animal obtain of from bacteria
on their food or from their intestinal bacteria.
• Animals concentrate and store vit B12 mainly in the
liver.
• Thus liver is the richest source.
• Milk, milk products and meat.
• Bioavailability is 50%
Vitamin B12 Deficiency
• Body can store enough B12 in the liver to last more
than 2 years.
• Symptoms might not appear for up to 12 years.
• Vegetarian who eat neither meat nor dairy products
are at risk of deficiency unless they take supplements.
Symptoms of deficiency
• Myelin sheath breaks down and swell which lead to
brain abnormality and spinal cord degeneration.
• Neurological symptoms include tingling and
numbness.
• Might be reversible depending on their duration.
Vitamin B12 Toxicity
• Has not been determined.
VITAMIN C
Vitamin C
• 1500 B.C.E. “Before the Common Era” scurvy disease occurred in a
seafaring men.
• They didn’t know why.
• In 1746, 30 yrs old ship’s surgeon in the British Navy
solved this mystery.
• He found that this disease recovered in patients who
received lemons or oranges.
Vitamin C - Scurvy
• Most animals manufacture their own vit C.
• Humans cannot.
• Humans require much less vit C than most other
animals.
Functions
• An antioxidants.
• Acts as a reducing agent.
• Participate in many reactions by donating electron or
hydrogen ions.
• It is not coenzymes.
• Play an important role in the collagen forming.
• Enhance the absorption of nonheme iron which come
mainly from plant foods.
• Helps in synthesizing carnitine (a compound that
carries fatty acids from the cytosol to the
mitochondria for energy production).
• Helps on synthesizing thyroxin, bile acids, and steroid
hormones.
Dietary recommendations
• 90 mg /day
• 120 mg/day for lactating.
• Because smoking increase the turnover of vit C,
smokers require 35 mg/d more than non-smokers.
Deficiency
• Scurvy.
• Loses the ability to synthesis collagen, connective
tissue starts breaking down and gums and joints begin
to bleed.
• Weakness.
• Previously healed wounds reopen.
Toxicity
• 2000 mg/d for long time can lead to nausea,
abdominal cramps, diarrhea, and nose bleeding.
• Contribute to oxalate-containing kidney stones.