Transcript Chapter 9: Vitamins: Vital Keys to Health

Chapters
9/10
Vitamins
Understanding Vitamins
• A few myths…
– If a little is good, then a lot is better.
– Vitamins are energy boosters.
– Vitamins work exclusively of one another.
• Vitamins in foods
– Natural sources: all food groups
– Enriched and fortified foods
Vitamins: An Overview
• All types of foods contain vitamins. Provitamins are vitamin
precursors that the body can convert to the active vitamin
form. Growing conditions, storage, processing, and cooking all
affect the amounts of vitamins in foods.
• For at the last 3,000 years, there has been an empirical
understanding that some diseases (which we now call vitamin
deficiency diseases) could be cured by eating certain foods.
Vitamins and Energy
• The body does not metabolize vitamins to
yield ATP.
• They are not a source of energy.
• Many of the B-vitamins (water-soluble)
facilitate the metabolic reactions that release
energy from carbohydrate, fat, and protein.
Fat-Soluble Vitamins
• Vitamins A, D, E, and K.
• These vitamins are like lipids and soluble in
fat.
• These vitamins are absorbed along with fat
into the lymphatic circulation.
• These vitamins often have precursors.
Fat-Soluble Vitamins
• Lipoproteins carry triglycerides and fat soluble
vitamins through the lymph and bloodstream.
• The liver stores most of the fat soluble
vitamins and packages them for delivery via
the bloodstream to other tissues.
• Fat soluble vitamins are less vulnerable to
cooking losses.
Water Soluble Vitamins
• The 8 B vitamins and vitamin C are soluble in
water.
• These vitamins are absorbed directly into the
bloodstream.
• Water soluble vitamins do NOT need
lipoprotein carriers.
Water Soluble Vitamins
• The kidneys filter out excesses of water
soluble vitamins and excrete them in the
urine.
• Most water soluble vitamins are not stored in
significant amounts.
• Water soluble vitamins are vulnerable to
cooking losses.
Storage and Toxicity (Fat Soluble)
• Fat soluble vitamins accumulate in the liver
and adipose tissues.
• Once the vitamin stores have been
established, we can go for days, weeks, or
even months without these vitamins.
• Excessive intake can exceed the body’s storage
capacity and have toxic effects.
Storage and Toxicity (Water Soluble)
• Water soluble vitamins are not stored in
appreciable amounts.
• Therefore, they should be part of your daily
diet.
Storage and Toxicity (Water Soluble)
• Consuming excesses of water soluble vitamins
usually is harmless. The body secretes the
excess.
• Megadoses of the following water soluble
vitamins can be toxic: vitamin B6, folate,
niacin, and vitamin C.
Exceptions to the Storage Rule
• Water soluble vitamin B12 is stored more
readily than the other water soluble vitamins.
• Fat soluble vitamin K is excreted more readily
than the other fat soluble vitamins.
Vitamin Toxicity
• Vitamin toxicity is rarely linked to high vitamin
intakes from food or to the use of
supplements that contain 100 to 150 percent
of the recommended amounts.
• People who take megadoses of one or more of
the vitamins run a high risk of toxicity.
Vitamin Absorption
Definitions
• Vitamins: Organic compounds necessary for
reproduction, growth, and maintenance of the
body.
• Provitamins: Inactive forms of vitamins that
the body can convert into active useable
forms.
• Vitamin precursers: Same as provitamins.
Fat Soluble Vitamins
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A
D
E
K
Vitamin A Functions
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Vision.
Cell differentiation.
Immune function.
Reproduction.
Bone health.
Vitamin A Food Sources
• Preformed Vitamin A
– Liver
– Milk
– Eggs
• Beta-carotene
– Yellow-orange fruits and vegetables
Forms of Vitamin A
• The body uses three active forms of vitamin A,
collectively known as the retinoids.
– Retinol – alcohol form of vitamin A.
– Retinal – aldehyde form of vitamin A.
– Retinoic acid – acid form of vitamin A.
Forms of Vitamin A
• Retinol is the key player.
• Your body can easily convert retinol to retinal.
• Retinal can reform retinol or irreversibly form
retinoic acid.
• Carotenoids (provitamin A) are precursors of
vitamin A.
Causes of Vitamin A Deficiency
• Newborns (esp. premature) are at risk. Their
liver stores are low.
• Impoverished people may suffer marginal
vitamin A deficiency due to poor diets.
• Liver damage due to alcoholism and liver
disease can prevent the liver from storing
much vitamin A.
• Some medicines alter lipid absorption.
Causes of Vitamin A Deficiency
• Fat absorptions conditions: chronic diarrhea,
celiac disease, Crohn’s disease, cystic fibrosis,
pancreatic insufficiency.
• Restrictive diets such as in anorexia nervosa.
• Zinc deficiency will causes symptoms of
vitamin A deficiency because it is required for
A to function properly.
Vitamin A Deficiency
• Vitamin A deficiency is rare in the United
States and Western Europe.
• Leading causes of childhood blindness
worldwide. (Est. 500,000 per year)
Symptoms of Vitamin A Deficiency
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Night blindness.
Xerophthalmia – dryness of the eyeball
Hyperkeratosis – skin thickening
Infection
Retards growth and development
Leads to bone deformities
Death
Causes of Vitamin A Toxicity
• The Tolerable Upper Intake Level (UL) for
vitamin A is 3,000 micrograms RAE as retinol.
• Occurs with supplementation, but is rare from
diet.
• A sustained diet of liver or fish oils could cause
it.
Symptoms of Vitamin A Toxicity
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Fatigue
Vomiting
Abdominal pain
Bone and joint pain
Loss of appetite
Symptoms of Vitamin A Toxicity
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Skin disorders
Headache
Blurred or double vision
Liver damage which leads to jaundice
Can be fatal
Excess Vitamin A and Birth Defects
• Preformed vitamin A, taken in excess, is a
known teratogen.
• Birth defects associated with excess vitamin A:
– Cleft palate
– Heart abnormalities
– Brain malfunction.
Excess Vitamin A and Birth Defects
• Excess vitamin A is most hazardous when
taken two weeks prior to conception and the
first two months of pregnancy.
• Can also cause spontaneous abortions.
• Prenatal supplements should not have retinol.
• Beta-carotene is safe.
Carotenoids
• Carotenoids are naturally occuring compounds
that give the deep yellow, orange, and red
colors to fruits and vegetables.
• They are also abundant in dark green
vegetables, but the carotenoid colors are
hidden by chlorophyll.
Carotenoids
• Some carotenoids can be converted to vitamin
A and are called provitamin A carotenoids.
Some cannot be converted.
Carotenoids
Carotenoid Functions
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Many function as vitamin A precursors.
Antioxidants
Boost the immune system.
Filter harmful blue light in the macula.
Carotenoid Functions
• Decrease risk of certain types of cancer.
– Lycopene (prostate cancer)
– Lutein, zeaxanthin, alpha-carotene, and lycopene
(lung cancer)
– Alpha-carotene, beta-carotene, lutein, and
zeaxanthin (breast cancer)
Carotenoid Toxicity
• Large intakes of carotenoid rich foods have
not been associated with toxicity.
• Carotenodermia – a harmless yellow-orange
cast to the skin due to high levels of
carotenoids in the bloodstream resulting from
consumption of extremely large amounts of
carotenoid rich foods, such as carrot juice.
Carotenodermia
Carotenoid Food Sources
• Food sources
– Yellow-orange vegetables
– Orange fruits
– Dark-green leafy vegetables
Cooking Carotenoids
• In foods, fibrous proteins tightly bind
carotenoids, so your body absorbs only 20 to
40 percent of what you consume.
• A few minutes of cooking breaks some of the
chemical bonds in food.
• This helps release carotenoids making them
easier to absorb.
Mucous Membrane Integrity
• Mucous membranes
contain a higher
percentage of goblet
cells.
• Without retinoic acid,
fewer stem cells
become goblet cells
and these surfaces
become hard and
scaly.
Vitamin A and Vision
• Deficiency of vitamin A results in progressive vision
loss from temporary night blindness, then reversible
blindness, and finally permanent blindness.
• In addition, the lack of mucous secretions and
reduced immune function make the person with
vitamin A deficiency vulnerable to infections. Vitamin
A toxicity can result from the use of supplements,
even with dosages just a few times higher than the
RDA.
Vitamin A: Not Just For Eyes
• A recent study conducted in Nepal showed that
women who took vitamin A supplements during
pregnancy had a much lower risk of maternal
mortality than those who took a placebo.
• The researchers concluded that regular and
adequate intake of vitamin A or beta-carotene can
reduce the risk of pregnancy-related death in areas
where vitamin A deficiency is common.
Vitamin D
• Synthesis
– Made in the skin from cholesterol
– Activated in liver and kidney
Vitamin D Functions
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Regulate blood calcium levels.
Regulates cell differentiation and growth.
Protective against colorectal cancer.
Essential for bone health.
Vitamin D Adequate Intake (AI)
• The AI levels for infants and children from
birth to 18 years is 5 micrograms per day.
• Vitamin D synthesis decreases with age, so the
vitamin D recommendations increase.
– 19 to 50 years – 5 micrograms
– 51 to 70 years – 10 micrograms
– 71 and up – 15 micrograms
– 1 microgram = 40 international units (IU)
Vitamin D Sources
• Given sufficient sunlight, your body can
synthesize all of the vitamin D it needs.
• Vitamin D is found in oily fish (e.g. herring,
salmon, and sardines) as well as cod liver oil
and other fish oils.
• Few foods naturally contain vitamin D, so milk
and other foods such as cereal are fortified
with it.
Causes of Vitamin D Deficiency
• Inadequate sun exposure.
• Sunscreens with an sun protective factor (SPF)
of 8 or more block vitamin D synthesis.
• Living in a northern region.
– Sunlight is too weak to synthesize vitamin D
during the winter months.
Symptoms of Vitamin D Deficiency
• Without vitamin D, the intestines absorb only
10 – 15% of dietary calcium.
• Rickets in children.
• Osteomalacia (“soft bones”) in adults.
• Osteoporosis – increased bone turnover, with
an increased risk of fractures.
Causes of Vitamin D Toxicity
• Sun exposure does NOT cause vitamin D
toxicity.
• High supplement doses can be toxic.
Symptoms of Vitamin D Toxicity
• Hypercalcemia – a high concentration of
calcium in the blood.
– Inhibits the kidney’s ability to concentrate urine.
– Can cause excess calcium in the bloodstream to
leave deposits in the soft tissues of the body,
including the kidneys, blood vessels, heart, and
lungs.
• Promotes bone loss as increased blood levels
of vitamin D pull calcium from the bones.
Vitamin D
• Deficiency
– Rickets in children
– Osteomalacia and
osteoporosis in
adults
• Toxicity
– Hypercalcemia
Osteoporosis
• A lack of vitamin D can lead to osteoporosis.
• Vitamin D supplements in elderly women slows
bone turnover, increases bone density, and
decreases non-vertebral fractures.
Vitamin D and Colon Cancer
• A recent study examined whether
people who have high vitamin D
intakes have a lower risk of colon
cancer than people with low
vitamin D intakes.
• Researchers collected data from
subjects from 13 VA medical
centers aged 50–75. These
participants were followed, and
data collected for three years.
• The hypothesis was confirmed,
with results indicating that
consuming vitamin D plus calcium
may be a low-risk preventive
strategy for colon cancer.
• This study also showed that
smoking and moderate to heavy
alcohol use increased the risk of
colon cancer.
Vitamin E Functions
• Antioxidant properties.
• Stops peroxidation – a form of free radical
damage that promotes atherosclerosis.
• May lower the risk of some chronic diseases
such as heart disease.
• May slow the progression of Alzheimer’s
disease.
Vitamin E
• Functions
– Antioxidant
• Protects cell membranes from free radicals
Vitamin E Food Sources
• Wheat germ oil contains the highest
concentration of useable vitamin E.
• Vegetable and seed oils, such as safflower,
cottonseed, and sunflower seed oils are also
rich sources.
• Nuts and seeds.
• Strawberries and some leafy green vegetables.
Loss of Vitamin E from Food Sources
• Cooking, processing, and storage of food
reduce vitamin E content.
• Milling of wheat to make white flour removes
most of the vitamin E rich wheat-germ.
Chloride oxide for bleaching removes any
remaining.
Loss of Vitamin E from Food Sources
• Oxidation destroys vitamin E. Heat and light
accelerate oxidation.
• Roasting destroys 80% of the vitamin E in
almonds.
Causes of Vitamin E Deficiency
• Fat mal-absorption syndromes (such as cystic
fibrosis).
Symptoms of Vitamin E Deficiency
• Premature hemolysis – Red blood cells
breakdown due to oxidation.
• Hemolytic anemia occurs in premature infants
who are born before the mother tyramsfers
vitamin E to the baby during the last few
weeks of pregnancy.
Symptoms of Vitamin E Deficiency
• Neurological problems that affect the spinal
cord and peripheral nerves occurs with
prolonged vitamin E deficiency.
Causes of Vitamin E Toxicity
• Over-supplementation.
Symptoms of Vitamin E Toxicity
• It counters vitamin K’s blood clotting
mechanism.
• People on anticoagulant medications such as
warfarin (Coumadin) or aspirin should be
cautious with vitamin E supplementation.
Vitamin E
• Food sources
– Nuts and seeds
– Wheat germ
– Oils, margarine,
salad dressing
• Deficiency
– Hemolysis
• Toxicity is rare.
Photo © Photodisc
Free Radical Damage
• Vitamin E helps
prevent free radical
damage to
polyunsaturated fatty
acids in cell
membranes.
Vitamin K Functions
• Necessary for blood clotting.
• Assists in bone formation.
Vitamin K Sources
• Food sources. (absorbed in the SI).
– Green leafy vegetables (especially spinach, turnip
greens, broccoli, and Brussels sprouts.
– Vegetable oils (soybean, cottonsead, canola, and
olive)
– Egg yolks, butter, and some cheeses have small
amounts. Liver.
• Bacteria in our Large Intestine (colon).
(Absorbed in the LI).
Causes of Vitamin K Deficiency
• Inadequate dietary intake.
• Fat-malabsorption syndromes.
• Prolonged use of antibiotics destroy the
intestinal bacteria that produce vitamin K in
the colon.
Symptoms of Vitamin K Deficiency
• Bleeding.
Causes of Vitamin K Toxicity
• The body excretes vitamin K much more
rapidly than the other fat-soluble vitamins.
• Toxicity from food is rare and no upper limit
has been established.
• Excessive supplementation could cause
toxicity.
Symptoms of Vitamin K Toxicity
• A vitamin K overdose can cause hemolytic
anemia.
Vitamin K
• Functions
– Blood clotting
– Formation of bone
• Food sources
– Green vegetables,
liver, egg yolks
Vitamin K and Bone Health
• Osteocalcin is an
abundant bone protein
that is required for bone
mineralization and
maturation.
• Vitamin K helps in the
carboxylation of
osteocalcin, greatly
enhancing its calciumbinding properties.
Water Soluble Vitamins
• Eight B vitamins
– Thiamin (B1), roboflavin (B2), niacin (B3),
pantothenic acid, biotin, folate, B6, and B12
• Vitamin C
Water Soluble Vitamins
• The kidneys readily remove and excrete excess
water-soluble vitamins, with the exception of
B12.
• Water-soluble vitamins are particularly
susceptible to destruction by heat or alkalinity,
which can break the chemical bonds between
atoms.
• Prolonged heat such as baking destroys
chemical bonds.
Water Soluble Vitamins
• Baking soda is used to reduce cooking time
and intensify the vegetable’s color. It is
alkaline and degrades vitamins. Vitamin C,
thiamin, and riboflavin are especially
vulnerable to heat and alkalinity.
Water Soluble Vitamins
• Water soluble vitamins are hydrophillic and
leach into water during cooking.
• Steaming and stir-frying use less water and
are therefore better cooking methods.
B Vitamins
• B vitamins act primarily as coenzymes, or as
parts of coenzymes.
• All B vitamins function in energy producing
metabolic pathways.
• Some also function in other metabolic
pathways not related to energy.
B Vitamins as coenzymes
Refined Grains and Nutrients
• During the milling process, much of the B
content is removed along with the germ, bran,
and husk.
Refined Grains and Nutrients
• The FDA requires enrichment with the B
vitamins thiamin, riboflavin, niacin, and folic
acid. The process of refining also removes
vitamin B6, magnesium, and zinc which are
NOT replaced.
• Consume whole-grains instead.
Thiamin (B1) Functions
• Thiamin is the vitamin portion of the
coenzyme thiamin pyrophosphate (TPP).
• TPP participates in decarboxylation during
glucose metabolism. (Coenzyme in energy
metabolism)
• TPP helps in synthesizing and regulating
neurotransmitters.
Thiamin Food Sources
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Pork
Legumes
Some nuts and seeds
Whole grains
Causes of Thiamin Deficiency
• Heavy alcohol consumption contributes
calories without nutrients and interferes with
Thiamin absorption.
• Highly processed foods that are not enriched.
Symptoms of Thiamin Deficiency
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Beriberi
Wernicke-Korsakoff Syndrome
Muscle weakness
Loss of appetite
Nerve degeneration
Beriberi
• This deficiency disease occurs in people whose
main source of energy is polished rice, which
is common in Southeast Asia.
• Beriberi is from the Singhalese language
(spoken in Sri Lanka) that means “I can’t, I
can’t”.
• Initial symptoms include weakness, irritability,
headache, fatigue, and depression (appear
withing 10 days without Thiamin).
Beriberi
• 2nd stage “dry” beriberi (without edema):
nerve degeneration, muscle wasting, poor arm
and leg coordination, deep pain in the calf
muscles.
• 3rd stage “wet” beriberi: enlarged heart, heart
failure, severe edema.
Beriberi
Wernicke-Korsakoff Syndrome
• Alcohol induced malnutrition is the most
common cause.
• Symptoms include mental confusion,
staggering, and constant rapid eye
movements or paralysis of the eye muscles.
Thiamin Toxicity
• There are no known reports of Thiamin
toxicity.
• The kidneys rapidly excrete excess Thiamin via
the urine.
Riboflavin (B2 or vitamin G)
Functions
• Part of two coenzymes: flavin
mononucleotide (FMN), and flavin adenine
dinucleotide (FAD).
• Participate in oxydation-reduction reactions.
• Participate in the citrus acid cycle.
• Supports antioxidants.
Riboflavin Food Sources
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Milk, yogurt, cottage cheese.
Organ meats such as liver and kidney.
Mushrooms.
Added to enriched grain products.
Causes of Riboflavin Deficiency
(ariboflavinosis)
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Rare.
Alcoholism.
Barbiturate drug use (e.g phenobarbital).
Cancer, heart disease, and diabetes may also
cause or worsen a riboflavin deficiency.
Symptoms of Riboflavin Deficiency
• Glossitis – tongue gets shiny, smooth, and
inflamed.
Symptoms of Riboflavin Deficiency
• Angular Stomatitis – the skin at the corners of
the mouth becomes cracked.
• Cheilosis – the lips become inflamed and split.
Symptoms of Riboflavin Deficiency
• Seborrheic dermatitis – the oil producing
glands of the skin become clogged.
Symptoms of Riboflavin Deficiency
• If the deficiency becomes severe, anemia
develops.
Causes of Riboflavin Toxicity
• There are no known reports of riboflavin
toxicity.
• The kidneys rapidly excrete excess riboflavin
via the urine.
Niacin Functions
• Niacin is a name for both nicotinic acid and
niacinamide.
• Conenzymes nicotinamide adenine
dinucleotide (NAD+) and nicotinamide
adenine dinucleotide phosphate (NAPD+).
• Coenzymes in energy metabolism.
Niacin Functions
• Participate in oxidation-reduction reactions.
• Supports fatty acid synthesis.
• Participates in at least 200 metabolic
pathways.
Niacin Food Sources
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Meat, poultry, fish.
Whole grains.
Enriched grain products.
Mushrooms, peanuts, liver, and seafood.
Stable when heated.
Causes of Niacin Deficiency
• A diet high in corn and little other variety. A
protein in corn tightly bounds niacin. Soaking
corn in a solution of lime releases niacin.
• Your body can make Niacin from the amino
acid tryptophan.
• Tryptophan is found in protein rich animal
foods.
Symptoms of Niacin Deficiency
• Pellagra
– Dementia
– Diarrhea
– Dermatitis
– Death (severe cases)
• Originally name aml de la rosa “red sickness”
• Redness around the neck
• Roughened skin
Pellagra
Causes of Niacin Toxicity
• Niacin in the form of nicotinic acid is known to
lower blood levels of LDL cholesterol while
raising HDL cholesterol when taken in doses of
1,300 to 3,000 milligrams.
• Adverse effects can be seen with doses as low
as 250 milligrams (15 to 17 times the RDA for
adults.
Symptoms of Niacin Toxicity
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Flushing of the face, arms, and chest
Itching
Headaches
Rash
Nausea
Symptoms of Niacin Toxicity
• Glucose intolerance
• Blurred vision
• Liver abnormalities can show up within a
week of supplementation.
Pantothenic Acid Functions
• A component of coenzyme A (CoA), which is in
turn a component of acetyl CoA.
• Acetyle CoA
– Starts the citric acid cycle.
– Building block for fatty acids.
– Precursor to ketone bodies
Pantothenic Food Sources
• Pantothenic acid id widespread in the food
supply.
• Chicken, beef, potatoes, oats, tomato, liver,
kidney, yeast, egg yolk, broccoli, whole grains.
• Damaged easily with freezing and canning.
Causes of Pantothenic Deficiency
• Virtually non-existent in the general
population.
• Diets that lack the nutrient.
Symptoms of Pantothenic
Deficiency
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Irritability
Restlessness
Fatigue
Apathy
Malaise
Sleep disturbances
Symptoms of Pantothenic
Deficiency
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Nausea
Numbness
Tingling
Muscle cramps
Staggering gait
hypoglycemia
Causes of Pantothenic Acid Toxicity
• Pantothenic acid does not appear to be toxic
at high doses.
Biotin Functions
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Amino acid metabolism
Fatty acid synthesis
Synthesizing DNA
Assists in energy production
Biotin Food Sources
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Cauliflower
Liver
Peanuts
Cheese
A biotin-lysine complex called biocytin is
found in some proteins.
Causes of Biotin Deficiency
• Biotin deficiency is rare.
• Raw eggs whites contain a protein called
avidin that binds to biotin and prevents
absoprtion.
• Some anticonvulsant drugs break down biotin.
• Some infants are born with a deficiency of the
enzyme biotinidase, which releases biotin
from biocytin.
Symptoms of Biotin Deficiency
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Initial hair loss.
Rash.
Convulsions and other neurological disorders.
Eventually, untreated deficiency causes
changes in blood pH that can lead to coma
and death.
Causes of Biotin Toxicity
• Biotin does not appear to be toxic at high
doses.
Vitamin B6 Functions
• Coenzyme in protein and amino acid
metabolism.
• Coenzyme in carbohydrate metabolism
• Supports the immune system by assisting in
while blood cell synthesis.
• Assists in red blood cell synthesis.
• Assists in the synthesis of neurotransmitters.
• Helps convert tryptophan to niacin.
Vitamin B6 Food Sources
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Meat, poultry, fish
White potatoes and other starchy vegetables
Non-citrus fruits
Bananas
Sunflower seeds
Causes of Vitamin B6 Deficiency
• Deficiencies are rare
• Alcohol decreases the absorption of B6
• Cirrhosis and hepatitis prevent the liver from
metabolizing B6 to its coenzyme form.
• Refined grains lose B6 and it is not replaced
during enrichment.
Symptoms of Vitamin B6 Deficiency
• Microcytic hypochromic anemia
• Seborrheic dermatitis
• Neurological symptoms
– Depression
– Confusion
– convulsions
Causes of Vitamin B6 Toxicity
• Megadoses of supplemental vitamin B6
– Often self-prescribed for PMS
– Often recommended for carpal tunnel syndrome
Symptoms of Vitamin B6 Toxicity
• Irreversible nerve damage
– Affects the ability to walk
– Causes numbness and tingling in the extremities
Protein & Carbohydrate
Metabolism
• One of the primary tasks of PLP
(pyridoxal phosphate) is to help
metabolize amino acids and other
nitrogen-containing compounds.
• PLP plays a key role in
transamination reactions, helping
transfer an amino group from an
amino acid to a keto acid and
produce a new amino acid.
• Transamination, catalyzed by PLP,
enables the body to make the 11
nonessential amino acids.
Without adequate supplies of
vitamin B6, all amino acids
become “essential,” meaning the
body cannot synthesize them and
must obtain them from the diet.
• Through its role in transamination
reactions, PLP participates in
gluconeogenesis —producing
glucose from amino acids. In
addition, PLP facilitates glycogen
breakdown.
Vitamin B6, Folate, and Heart
Disease
• Moderately high blood levels of
the amino acid homocysteine are
associated with fatal
cardiovascular events.
• Homocysteine blood levels are
influenced by dietary intake of B6,
folate, and vitamin B12. Low
intake of B6 or folate can result in
high homocysteine levels.
• Because the body accumulates
large vitamin B12 stores to draw
on when needed, variations in B12
intake seldom affect
homocysteine levels.
• The body lowers homocysteine
levels in one of two ways: (1) two
PLP-dependent enzymes help
convert homocysteine to
cysteine, or (2) folate and vitamin
B12-dependent enzymes help
convert homocysteine to
methionine.
• An increase in fruit and
vegetable intake also can affect
homocysteine levels.
Folate Functions
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Coenzyme that assists in DNA synthesis
Assists in amino acid metabolism
Assists in cell division
Needed for red blood cell synthesis and
maturation
Folate Food Sources
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Spinach and other dark-green leafy vegetables
Asparagus
Broccoli
Orange juice
Folate Food Sources
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Wheat germ
Liver
Sunflower seeds
Legumes
Folate Deficiency
• May be the most prevalent deficiency
• Up to 10% of the U.S. population may have
inadequate folate stores.
• Folate is extremely vulnerable to heat,
ultraviolet light, and exposure to oxygen.
• Cooking and other food processing techniques
destroy folate.
Causes of Folate Deficiency
• Inadequate folate consumption
– Malnutrition due to famine or poverty
– Cultural cooking methods
– Eating habits that avoid raw folate sources
– Alcoholism
– Excessive dieting, anorexia nervosa, and bulimia
• Inadequate folate absorption
– Abnormal mucosal cells in GI tract
Causes of Folate Deficiency
• Increased folate requirements
– Pregnancy and lactation
– Blood disorders, leukemia, lymphoma, psoriasis
• Impaired folate utilization
– Associated with vitamin B6 deficiency
Causes of Folate Deficiency
• Altered folate metabolism
– Alcohol
– Barbiturates
– Sulfa drugs and anticonvulsants impair folate
absorption
• Excessive folate excretion
– Prolonged diarrhea
Symptoms of Folate Deficiency
• Megaloblastic anemia
• Low birth weight babies and premature
deliveries
• Neural tube defects
– Spina bifida
– anencephaly
• Women of childbearing age need 400
micrograms / day of folic acid
Megaloblastic Anemia
• When red blood cell precursors in
the bone marrow cannot form
new DNA, they cannot divide
normally.
• These precursor cells continue to
grow and become large, fragile
cells called megaloblasts.
• Megaloblasts displace red blood
cells, resulting in megaloblastic
anemia.
Spina Bifida
Causes of Folate Toxicity
• Over supplementation
Symptoms of Folate Toxicity
• Excessive folate intake can mask a B12
deficiency
• Hypersensitive people can suffer from hives or
respiratory distress (rare)
Can Folate Prevent Cancer?
• When women took multivitamins containing
folate for at least 15 years, they had a 75
percent reduction in colon cancer risk,
according to the Harvard Nurses’ Health
Study.
• Folate intakes of more than 600 milligrams per
day reduced breast cancer risk by 50 percent.
Vitamin B12 (Cobalamin) Functions
• Needed for normal folate metabolism
– Necessary for DNA and red blood cell synthesis
• Maintains the myelin sheath around nerves
Vitamin B12 Food Sources
• Animal foods
– Meats
– Fish
– Poultry
– Eggs
– Milk
• Fortified foods such as cereal
• Synthesized by bacteria in animal stomachs
Causes of Vitamin B12 Deficiency
• Inadequate intake
• Impaired absorption
– Pernicious anemia – autoimmune disorder in
which the body destroys the parietal cells in the
stomach
– A loss of parietal cells means a loss of intrinsic
factor, which is necessary for B12 absorption
Symptoms of Vitamin B12
Deficiency
• Deficiency anemia
• Nerve damage
– Myelin sheath swells and breaks down
– Brain abnormalities and spinal cord degeneration
– Neurological symptoms
• Tingling and numbness in extremities
• Abnormal gait
• Cognitive changes (loss of concentration, memory loss,
disorientation, dementia)
Causes of Vitamin B12 Toxicity
• Vitamin B12 does not appear to be toxic at
high doses.
Vitamin C Functions
•
•
•
•
Antioxidant – reducing agent
Assists in collagen synthesis
Enhances iron absorption
Helps synthesize carnitine (fatty acid shuttle),
norepinephrine, epinephrine, serotonin,
thyoxine (thyroid hormone), bile salts, steroid
hormones and purine bases (DNA synthesis)
• Enables lymphocytes to function properly
Vitamin C Food Sources
•
•
•
•
•
Citrus fruits
Tomatoes
Broccoli
Strawberries
Kiwi fruit
Vitamin C Food Sources
•
•
•
•
Cabbage
Spinach and leafy greens
Green peppers
Potatoes
Causes of Vitamin C Deficiency
• Vitamin C is highly vulnerable to heat and
oxidation; therefore, fresh fruits and
vegetables are the best source.
• Inadequate dietary intake
• Restrictive diets
• Alcoholism
Symptoms of Vitamin C Deficiency
• Scurvy
– Inability to synthesize collagen, connective tissues
breakdown
– Gums and joints begin to bleed
– Weakness develops
– Small hemorrhages around the hair follicles on
arms and legs
– Healed wounds reopen
– Bone pain, fractures, diarrhea, depression
Scurvy
Causes of Vitamin C Toxicity
• Supplementation with megadoses.
Symptoms of Vitamin C Toxicity
• Megadoses of vitamin C do not appear to be
acutely toxic; however, some people can
develop nausea, abdominal cramps, diarrhea,
and nosebleeds when taking more than 2,000
milligrams daily for a prolonged period.
Vitamin-like Compounds
• The body synthesizes many vitamin-like
compounds that assist in metabolism.
– Choline
– Carnitine
– Inositol
– Taurine
– Lipoic acid
Watermelon Works Overtime
• Compared to freshly picked fruit, watermelon stored
for 14 days at 70°F gained up to 40 percent more
lycopene and 50 percent to 139 percent extra betacarotene.
• Study findings showed watermelons continue to
produce these nutrients after they are picked and
that chilling slows this process.