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

Chapter 8
Vitamins
What are 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
 Water-soluble vitamins

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 vs natural
 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 (e.g. Vitamin A)
– Can accumulate in the body

Water-soluble vitamins
– Some can cause toxicity

Mostly likely due to supplementation
Preservation of Vitamins

Decreased vitamin content
– Improper storage
– Excessive cooking >40*C
– Exposure to light, heat, air, water, and alkalinity
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

Eat foods soon after harvest (EAT FRESH)
Freeze foods not consumed within a few days
Blanching destroys enzymes (bacteria)
– Slows down vitamin degradation
Preservation Tips
Fat-Soluble Vitamins Overview
Dissolve in organic solvents
 Not readily excreted

– Can cause toxicity
Olestra
Absorbed along with fat
 Fat malabsorption (Xenical/Olestra)

– May cause deficiency
– Cystic fibrosis (Vit. deficiency)

Transported with fat
– In lipoproteins
Xenical
Confirming your knowledge
What are the fat Soluble vitamins,
why (i.e. non polar)?
1
3
2
4
Vitamin A

Narrow optimal intake range

Preformed
– Retinoids
– Found in animal products (fish/organ meats)

Proformed (proVitamin A)
– Carotenoids
– Found in plant products
– Can be converted to Vit A
by the body
B carotene
Functions of Vitamin A

Promote vision
– Night blindness
Promote growth
 Prevent drying of the skin and eyes

– Xerophthalmia (figure 8-1) & macular degeneration
Promote immune function and resistance to
bacterial infection
 Cardiovascular disease prevention (b/c antioxidant)
 Cancer prevention (antioxidants and other)
 Acne medication (Retin-A, Accutane)

Challenge Question

What is the name following compound
(which has been shown to reduce prostate
cancer risk) and what are good sources?
Gann et al., 1999, Cancer Research, 59, 1225
Food Sources of Vitamin A: see: 8-2
Recommended Amounts for
Vitamin A
g RAE for men
 700 g RAE for women
 Daily Value is 1000 g (RAE) ~ 5000 IU
 Upper Level is 3000 g, 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 ≥ 10,000 IU or 3000 RAE

Signs and symptoms
– Bone/muscle pain, loss of appetite, skin disorders,
headache, dry skin, hair loss, increased liver size,
vomiting
– Fetal malformation (binds to DNA  cell develop.)
– Possible permanent damage (infants)
– < 3000 IUs/day if pregnant
Vitamin D
Prohormone
 Derived from cholesterol
 Synthesized from sun exposure

– Sunscreen SPF >8 decreases synthesis 95%
– Expose hands, face, arms 2-3 x/week for 5-10
minutes each time (more for darker skin)
Insufficient sun exposure makes this a vitamin
 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
Challenge Question
According to the USDA and ODS – Vitamin
D is now considered a deficiency in N.
American diets
– what are the two major reasons?
 1.
 2.

Food Sources of Vitamin D
Fatty fish (salmon, herring)
 Fortified milk (N. fat, Low fat or Whole)
 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 (kidneys) & blood vessels
– Growth retardation
Vitamin E



Fat-soluble antioxidant
α β δ gamma tocopherol
forms
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)


Adivse mixture of natural tocopherols (vs synthetic sources)
(400 IUs)
 Toxic effects
– Inhibit vitamin K metabolism and anticoagulants
– Possible hemorrhage
– Muscle weakness, headaches, nausea
Vitamin E

SHOW Vit E video
Vitamin K (“Koagulation”)
Synthesized by bacteria in the colon (10%)
and absorbed (diet)
Frequent anti-biotics  deficiency. . .


Role in coagulation process (fig 8-10)

Role in calcium-binding potential
Food Sources of Vitamin K
Liver
 Green leafy vegetables
 Broccoli
 Peas
 Green beans
 Resistant to cooking losses
 Limited vitamin K stored in the body (<24hr)

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
 High Levels  CVD, prevent reduced clotting
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Overview of Water-Soluble
Vitamins
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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
U.S. Enrichment Act (grains milledloose vitamins . .)
– Must be added back (enriched) to products (cereals)

Why experts recommend whole grains/brown rice vs
Refined grain products
Confirming your Knowledge
Overview of Water-Soluble Vitamins

What are the water soluble vitamins and why (i.e. polar) ?
(4)
(3)
(2)
(1)
(5)
(6)
(9)
(7)
(8)
Overview of Water-Soluble Vitamins
Participate in energy metabolism
Thiamin
Sensitive to alkalinity (base) and heat
 Coenzyme form used in energy metabolism
 Deficiency: Beriberi (severe muscle weakness
 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, fig. 8-14
Riboflavin
Coenzyme forms participate in energyyielding metabolic pathways
 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
 Deficiency

– Pellagra: rough/painful skin (epidemic US < 1930s)
– Dementia, diarrhea, dermatitis,
 RDA
– 14 mg/day for women
– 16 mg/day for men
 Toxicity
– Upper Level is 35 mg/day
Food Sources of Niacin
Enriched grains (breakfast cereals)
 Beef
 Chicken/turkey
 Fish
 Heat stable; little cooking loss
 60 mg tryptophan (Amino acid) can be
converted into 1 mg niacin

Pantothenic Acid
 Part
of Coenzyme-A
– Essential for metabolism of
carbohydrate, fat, and protein
 Deficiency
rare
– Usually in combination with other
deficiencies
Food Sources of Pantothenic
Acid
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Meat
Milk
Mushrooms
Liver
Peanuts
Adequate Intake = 5 mg/day
Average intake meets AI
Biotin
Free and bound form
 Co-enzyme

– Metabolism of 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 (10%)
 Avidin egg protein 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 via
transamination
– Synthesize neurotransmitters
– Synthesize hemoglobin and WBC
Food Sources of Vitamin B-6, fig. 8-22
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?

50-100 mg/day therapy
– Questionable treatment of PMS
– May treat pregnancy hypertension
Carpal tunnel syndrome
 Morning sickness

– (100 mg/day may help; see Ch. 13)

Toxicity potential
– > 200 mg/day can lead to irreversible nerve
damage

Upper Level set at 100 mg/day
Folate
 Coenzyme
– DNA synthesis
– Homocysteine metabolism
– Neurotransmitter formation
 Sensitive
to:
– Heat, oxidation, ultraviolet light
Folate Deficiency

Megaloblast cells
Megaloblastic Anemia
 10% N. Americans- genetic defect to process
folate (req. 2X RDA), need genetic testing. .

Neural tube defects
 Women need ample Folic acid:

– Neural tube closes w/i 28 days of pregnancy 
spinal bifuda
Megaloblast
cells
-Req. ample Folic acid
Child bearing Women need ample Folic acid:
Neural tube closes w/i 28 days of pregnancy
 spinal bifuda
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)

– Synthetic form 1.7 X more potent. . .
– Folate in food has limited absorption
(synthetic form)
(Natural form)
Vitamin B-12
Synthesized by bacteria and fungi
 Coenzyme

– Role in folate metabolism
– Maintenance of the myelin sheaths
– RBC formation

Deficiency (absorption problems)
– Pernicious anemia (weakness, sore tongue, back pain)
– Nerve degeneration and paralysis
B-12 Absorption -aging
Requires a protein from salivary gland
 Requires stomach acid (declines w/ age)
 Requires the intrinsic factor (declines w/ age)
 Absorbed in the last part of the small intestine
 About 50% of B-12 is absorbed
 Vegetarian/Vegan diets – low in Vit. B-12

– (need supplement or specified rich source)
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
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Synthesized by bacteria, fungi and algae
(Stored primarily in the liver of animals)
Animal products
Organ meat
Seafood
Eggs
yogurt
Milk
Corn flakes cereal (w/ soy milk)
RDA for Vitamin B-12

2.4 µg/day for adults
– Over age 50 recommended take synthetic form
– Not bound to foods (no require low stomach acid)

Average intake exceeds RDA

B-12 stored in the liver (> 3 years before deficiency)

Non-toxic
Vitamin C

Synthesized by most animals
– Not by humans

Decreased absorption with high intakes > 250mg

Excess excreted
– Diarrhea common

Sensitive to
– Cooking/heat (high temp) ~ use medium setting
– Iron, copper, oxygen
Functions of Vitamin C
 Synthesis
of collagen (connective tissue)
– Stretch marks
 Iron
absorption
 Immune functions
– Prevents duration of common cold?
– Interacts with w/ oxidized Vit. E ~ recycles?
– Anti-cancer agent and cataracts
 Antioxidant?
 Req.
for syn. Of hormones
Challenge Question
What has more Vitamin C/gram and is the best dietary
choice for combating the common cold and why?

1 medium orange

1 medium red pepper
Deficiency of Vitamin C

Scurvy
– Deficient for 20-40 days
– Fatigue, pinpoint hemorrhages
– Bleeding gums
– Weakness
– Fractures
– Associated with poverty
Food Sources of Vitamin C
Citrus fruits
 Potatoes
 Green pepper
 Cauliflower
 Broccoli
 Strawberries
 Romaine lettuce
 Spinach

RDA for Vitamin C
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90 mg/day for adult males
75 mg/day for adult females (enhances Fe absorptn.)
Daily Value is 60 mg
+35 mg/day for smokers
Average intake 70-100 mg/day
Upper Level is 2 g/day (inflammation diarrhea)
Better to take low doses (250 mg) more frequent
vs MegaDOSE 1 Gram (1000 mg) / day
Choline
 Essential
nutrient, though
not a vitamin
 All tissues contain choline
 Precursor for acetylcholine
(neurotransmitter)
 Precursor for phospholipids
Food Sources of Choline

Widely distributed in foods
– Fruits/vegetables
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
Choline
 Carnitine
 Inositol
 Taurine
 Lipoic acid


Synthesized in the body at the expense of
amino acids and other nutrients
Vitamins-SUMMARY
Functions in the Body
With a balanced diet – no need for supplements?
Dietary Supplements $21 Billion
Dietary Supplements –Classified as
Vitamins
 Minerals
Fe2+
 Herbs
 Amino Acids
 A dietary substance to supplement the diet
 Try a case study?

Vitamins, Supplements SUMMARY




If going to experiment . . .
Make sure < (upper limit) of toxic level
Min. 6 weeks for evaluation. . .
ANY SUPPLEMENT QUESTIONS? See below

Check any of the following 6 websites for validity
– 1. www.acsh.org
– 2. www.quackwatch.com
– 3. www.ncahf.org
– 4. http://dietary-supplements.info.nih.gov
– 5. www.eatright.org
– 6. www.usp.org/USPVerified/dietarySupplements/
**7. “web of science”- (use UCSC Lib login,
 http://oca.ucsc.edu/login (22200-0230485-15)