Contemporary Nutrition: Issues and Insight 6th ed. Gordon M

Vitamins
Essential organic substances
 Produce deficiency symptoms when missing
from diet
 Yield no energy
 Basic functions

– Facilitate energy-yielding chemical reactions
– Function as co-enzymes
Fat-soluble vitamins (A, D, E, K)
 Water-soluble vitamins (B’s, C)

Fun Facts

Vitamins were named in order of discovery
(A, B, C, D, …)

Other substances found not to be essential
were dropped (e.g., vitamin P)

B-vitamins were thought to be one vitamin;
turned out to be many (e.g., B1, B2, B3,…)
Vital Dietary Components

Megadose (>3-10x needs as a starting
point)
– Proved useful in treating certain conditions
Plant and animal foods provide vitamins
 Most synthesized vitamins work equally
well in the body, some exceptions
 Scientists believe they have discovered all
the vitamins

Storage of Vitamins in the Body

Fat-soluble
– Not readily excreted (except vitamin K)

Water-soluble
– Generally lost from the body (except vitamins
B-6 and B-12)
– Excreted via urine

Vitamins should be consumed daily
– Occasional lapse is harmless
Vitamin Toxicity

Fat-soluble vitamins
– Can accumulate in the body
– Most common with Vitamin A

Water-soluble vitamins
– Some can cause toxicity
– Must 15 to 100x more than needed

Mostly likely due to supplementation
Preservation of Vitamins

Decreased vitamin content
– Improper storage
– Excessive cooking
– Exposure to light, heat, air, water, and alkalinity



Eat foods soon after harvest
Freeze foods not consumed within a few days
Blanching destroys enzymes (boil then ice)
– Slows down vitamin degradation
p. 293
Fat-Soluble Vitamins Overview
Dissolve in fats
 Not readily excreted

– Can cause toxicity
Absorbed along with fat
 Fat malabsorption

– May cause deficiency
– Cystic fibrosis, orlistat, mineral oil, extremely
high fiber diets

Transported with fat
– In lipoproteins
Vitamin A

Narrow optimal intake range

Preformed
– Retinoids
– Found in animal products

Proformed (body converts into Vitamin A)
– Carotenoids
– Found in plant products
– Beta-carotene most common (in orange veggies)
Functions of Vitamin A

Promote vision
– Night blindness

Promote growth
– Affects gene expression

Prevent drying of the skin and eyes
– Xerophthalmia
Promote immune function and resistance to
bacterial infection (esp. in epithelial cells)
 Cardiovascular disease prevention
 Cancer prevention
 Acne medication

Vitamin A Deficiency
p. 296
Recommended Amounts for
Vitamin A
g RAE for men
 700 g RAE for women
 Daily Value is 1000 g RAE or 5000 IU
 Upper Level is 3000 g (RAE of
preformed) or 10,000 IU
 Much stored in the liver
 No separate RDA for carotenoids
 900
Toxicity of Vitamin A

Large intake of vitamin A (preformed)
– Over a long period
– Use of Accutane and Retin-A

Signs and symptoms
– Bone/muscle pain, loss of appetite, skin disorders,
headache, dry skin, hair loss, increased liver size,
vomiting
– Fetal malformation and miscarriages
– Possible permanent damage

Effects of high carotenoid intake
– Can turn skin yellow-orange
– Not harmful
Vitamin D
Prohormone
 Derived from cholesterol-like molecule
 Synthesized from sun exposure

– Sunscreen SPF >8 decreases synthesis 95%
– Expose hands, face, arms 2-3 x/week for 5-10
minutes each time (light skinned people), 3050 minutes each time (dark skinned people)
Activated by enzymes in liver and kidneys
 Deficiency can cause disease

Activation of Vitamin D
Functions of Vitamin D

Regulates blood calcium
– Along with the parathyroid hormone
– Regulates calcium + phosphorus absorption
– Reduces kidney excretion of calcium
– Regulates calcium deposition in bones

Influences normal cell development
– Linked to reduction of breast, colon, and
prostate cancer
Role in Bone Formation
Causes calcium + phosphorus to deposit
in the bones
 Strengthens bones
 Rickets is the result of low vitamin D
– Breastfed infants with little sun
exposure
 Osteomalacia (soft bones)
– Rickets-like disease in adults
– Bones lose minerals and become
porous
http://www.thachers.org/ric

kets_photos.htm
Food Sources of Vitamin D
Fatty fish (salmon, herring, tuna)
 Fortified milk
 Some fortified cereal

Adequate Intake (AI) for
Vitamin D
g/day (200 IU/day) for adults
under age 51
5
g/day (400 - 600 IU/day) for
older adults
 10-15
 Supplement if a breastfed
– (See physician for details)
infant
Toxicity Warning
Vitamin D can be very toxic, especially in
infancy and childhood
 Upper Level is 50 µg/day
 Results in

– Over-absorption of calcium (hypercalcemia),
increase calcium excretion
– Calcium deposits in organs and blood vessels
– Weakness, vomiting, diarrhea, confusion
– Growth retardation
Vitamin E
 Fat-soluble
antioxidant
 Resides
mostly
on cell
membranes
Other Functions of Vitamin E
Protects double bonds in unsaturated fats
 Improves vitamin A absorption
 Deficiency

– Breakdown of cell membranes
– Hemolysis
– Nerve degeneration

RDA for adults is 15 mg/day
– Many adults are not meeting this goal
Food Sources of Vitamin E
Toxicity of Vitamin E
Upper Level is 1,000 mg/day
(supplementary alpha-tocopherol)
 Upper Level is 1500 IU (natural
sources) or 1100 IU (synthetic forms)
 Toxic effects

– Inhibit vitamin K metabolism and
anticoagulants
– Possible hemorrhage
– Muscle weakness, headaches, nausea
Vitamin K (“Koagulation”)

One form is synthesized by bacteria in
the colon and absorbed

Role in coagulation process

Role in calcium-binding potential
http://www.londonlupuscentre.
co.uk/hughes-syndrome/
Food Sources of Vitamin K
Liver
 Green leafy vegetables
 Broccoli
 Peas
 Green beans
 Resistant to cooking losses
 Limited vitamin K stored in the body

Adequate Intake for Vitamin K
90 µg/day for women
 120 µg/day for men
 Excess vitamins A and E

– Interferes with vitamin K
– May cause hemorrhage and fractures

Newborns
– Routinely injected with vitamin K
– Breast milk is a poor source

Toxicity unlikely; readily excreted
Overview of Water-Soluble
Vitamins
Dissolve in water
 Generally readily excreted from body
 Subject to cooking losses
 Function as coenzymes
 Participate in energy metabolism
 50-90% of B vitamins are absorbed
 Marginal deficiency more common
 Enrichment Act of 1998

B Vitamins
Thiamin
Sensitive to alkalinity and heat
 Coenzyme form used in energy metabolism,
especially breaking down carbs
 Deficiency: Beriberi (causes weakness,
tingling, poor coordination)
 RDA

– 1.1 mg/day for women
– 1.2 mg/day for men
– Most exceed RDA in diet

Surplus is rapidly lost in urine; non-toxic
Food Sources of Thiamin
Riboflavin
Coenzyme forms participate in energy
metabolism, antioxidant
 Deficiency

– Cheilosis, inflammation of mouth and tongue,
dermatitis, sensitivity to sun

RDA
– 1.1 mg/day for women
– 1.3 mg/day for men
– Average intake above RDA

Non-toxic
Food Sources of Riboflavin
Milk/milk products
 Enriched grains/cereals
 Eggs
 Liver
 Spinach
 Oysters
 Brewer’s yeast

Niacin
Coenzyme forms used in energy
metabolism (almost every metabolic
reaction uses niacin)
 Deficiency

– Pellagra (rough, painful skin)
– 3 D’s (dementia, diarrhea, dermatitis) + death
 RDA
– 14 mg/day for women
– 16 mg/day for men
 Toxicity
– Upper Level is 35 mg/day
Food Sources of Niacin
Enriched grains
 Beef
 Chicken/turkey
 Fish
 Heat stable; little cooking loss
 60 mg tryptophan can be converted
into 1 mg niacin

Pantothenic Acid
 Part
of Coenzyme-A
– Essential for metabolism of
carbohydrate, fat, and protein
 Deficiency rare
– Found in many different foods
– Usually in combination with other
deficiencies
Food Sources of Pantothenic
Acid







Meat
Milk
Mushrooms
Liver
Peanuts
Adequate Intake = 5 mg/day
Average intake meets AI
Biotin
Free and bound form
 Co-enzyme

– Helps synthesize carbohydrate and fat
– Helps breakdown certain amino acids

Deficiency–rare
– Scaly, inflamed skin
– Changes in tongue, lips
– Decreased appetite, nausea, vomiting
Food Sources of Biotin
Cauliflower, egg yolk, liver, peanuts,
cheese
 Intestinal synthesis of biotin contributes
very little
 Avidin inhibits absorption
– More than a dozen raw egg whites a
day to cause this effect

Biotin Needs
 Adequate
adults
 No
intake is 30 µg/day for
Upper Level for biotin
 Relatively
nontoxic
Vitamin B-6

Coenzyme forms
– Activate enzymes needed for metabolism of
carbohydrate, fat, and protein
– Synthesize nonessential amino acids by
breaking off Nitrogen group –NH2
– Synthesize neurotransmitters
– Synthesize hemoglobin and white blood cells
Food Sources of Vitamin B-6
RDA for Vitamin B-6
1.3 mg/day for adults
 1.7 mg/day for men over 50
 1.5 mg/day for women over 50
 Daily Value set at 2 mg
 Average intake is more than RDA
 Athletes may need more
 Alcohol increases vitamin B-6 destruction

Vitamin B-6 As a Medicine?

30-75 mg/day therapy
– Reduce nausea during pregnancy

2-6g/day for ≥ 2 months
– Irreversible nerve damage

Upper Level set at 100 mg/day
Folate
 Coenzyme
– DNA synthesis
– Amino acid metabolism
– Neurotransmitter formation
 Sensitive
to:
– Heat, oxidation, ultraviolet light
Folate Deficiency

Megaloblast cells

Megaloblastic Anemia

Neural tube defects
http://accessmedicine.net/content.aspx?aID=2780654&s
earchStr=basophilic%20megaloblast
Food Sources of Folate
Liver
 Fortified breakfast cereals
 Grains, legumes
 Foliage vegetables
 Orange juice

RDA for Folate
 400
µg/day for adults
 600 µg/day for pregnant women
 Excess intake can mask vitamin B-12
deficiency
 Upper Level 1 mg (synthetic form)
– Folate in food has limited absorption
– Cooking destroys 50-90% of the folate
Vitamin B-12
Synthesized by bacteria and fungi
 Coenzyme

– Role in folate metabolism (converting folate to
active forms); can thus lead to megaloblasts
– Maintenance of the myelin sheaths around
neurons

Deficiency
– Pernicious (“causing death”) anemia
– Nerve degeneration and paralysis
B-12 Absorption
 Requires
a protein from salivary gland
 Requires stomach acid
 Requires the intrinsic factor
 Absorbed in the last part of the small
intestine
 About 50% of B-12 is absorbed
Therapy for Ineffective
Absorption
Many factors can disrupt this process
 Monthly injections of vitamin B-12
 Vitamin B-12 nasal gel
 Megadoses of vitamin B-12

– Allow for passive diffusion
Food Sources of Vitamin B-12








Synthesized by bacteria, fungi and algae
(Stored primarily in the liver of animals)
Animal products
Organ meat
Seafood
Eggs
Hot dogs
Milk
RDA for Vitamin B-12
 2.4
µg/day for adults
– Over age 50 meet needs with a
synthetic source
Average intake exceeds RDA
 B-12 stored in the liver
 Non-toxic

Vitamin C

Synthesized by most animals
– Not by humans
Decreased absorption with high intakes
 Excess excreted

– Diarrhea common with megadoses

Sensitive to
– Cooking/heat
– Iron, copper, oxygen
Functions of Vitamin C
 Synthesis
of collagen
 Iron absorption
 Immune functions
 Antioxidant?
Deficiency of Vitamin C

Scurvy
– Deficient for 20-40 days
– Fatigue, pinpoint hemorrhages
– Bleeding gums
– Weakness
– Fractures
– Wounds reopen, are slow to heal
– Associated with poverty
Food Sources of Vitamin C
Citrus fruits
 Potatoes
 Green pepper
 Cauliflower
 Broccoli
 Strawberries
 Romaine lettuce
 Spinach

RDA for Vitamin C
90 mg/day for adult males
 75 mg/day for adult females
 Daily Value is 60 mg
 +35 mg/day for smokers
 Average intake 70-100 mg/day
 Upper Level is 2 g/day

– At levels above 500 mg, most is excreted
Choline
 Essential
nutrient, though not a
vitamin
 All tissues contain choline
 Precursor for acetylcholine
(neurotransmitter)
 Precursor for phospholipids
 Some role in amino acid metabolism
Food Sources of Choline
Widely distributed in foods
 Milk
 Liver
 Eggs
 Peanuts
 Lecithin added to food
 Deficiency rare

Needs for Choline
Adequate Intake is 550 mg/day for males
 Adequate Intake is 425 mg/day for
females
 Average intake is ~700-1000 mg/day
 High doses

– Associated with fishy body odor, vomiting,
salivation, sweating, hypotension, GI effects

Upper Level is 3.5 grams/day
Vitamin-like Compounds
Carnitine
 Inositol
 Taurine
 Lipoic acid
 Synthesized in the body at the expense of
amino acids and other nutrients
 Body may not be able to make enough
during disease states or active growth

Functions in the Body
Dietary Supplements
Dietary Supplements
Vitamins
 Minerals
 Herbs
 Amino Acids
 A dietary substance to supplement the diet
 Supplement industry makes ~$25 billion
annually
 Not regulated closely without evidence of
danger
 Can’t claim to treat a “disease” w/o evidence
