Chapter 8 - The Vitamins

Nutrition for Health and Health Care, 5th Edition
DeBruyne ■ Pinna © Cengage Learning 2014
The VitaminsChapter 8

The Vitamins–An Overview
• Potent, essential, nonkcaloric, and organic
nutrients needed from foods in trace
amounts to perform specific functions
– Promote growth, reproduction, and the
maintenance of health and life

The Vitamins–An Overview (cont’d.)
• How do vitamins differ from
carbohydrates, fats, and proteins?
– Structure
– Function
– Dietary intakes
• What is a vitamin’s bioavailability?
• Vitamin content in food (Appendix A)

• Factors affecting the bioavailability of a
vitamin
– Digestion efficiency and GI tract transit time
– Previous nutrient intake and nutrition status
– Other foods consumed at the same time
– Method of food preparation
– Nutrient source

• Precursors or provitamins
– Tables 8-4 and 8-5
• Organic nature
– Can be destroyed during processing
• Classes of vitamins
– Fat soluble: vitamins A, D, E, and K
– Water soluble: vitamins B and C

The Fat-Soluble Vitamins
• Overview
– Vitamins A, D, E, and K
– Usually occur together in fats and oils
– Absorbed in the same manner as lipids
– Stored in the liver and fatty tissues

The Fat-Soluble Vitamins
• Vitamin A and beta-carotene
– How is beta-carotene related to vitamin A?
– Vitamin A functions
• Gene regulation: retinoic acid
• Vision: cornea and retina health
• Protein synthesis and cell differentiation
• Immunity: “anti-infective” vitamin
• Reproduction, growth, and development

The Fat-Soluble Vitamins (cont’d.)
• Beta-carotene: antioxidant
– Food forms: may prevent cancer
• Vitamin A deficiency
– Major cause of preventable blindness
– All epithelial surfaces: cells harden and flatten
– Susceptibility to infection

• Vitamin A toxicity
– Teratogenic risk
– Weakens bones
• Sources
– Vitamin A: liver, fish oil, milk, cheese, etc.
– Beta-carotene: carrots, apricots, spinach, etc.

• Vitamin D
– Body can synthesize with help of sunlight
– Active vitamin form
• Requires conversions by the liver and kidneys
– Why is vitamin D actually a hormone?
– Roles
• Bone growth
• How does vitamin D raise blood concentrations of
bone minerals?

• Vitamin D deficiency
– U.S. population: almost 10 percent deficient
– Contributing factors
• Dark skin, breastfeeding without supplementation,
lack of sunlight, and not using fortified milk
– Diseases
• Rickets
• Osteomalacia
• Osteoporosis

• Vitamin D toxicity
– Excess blood calcium: calcification
• Maintain adequate vitamin D
– Sunlight
– Foods sources
• Eggs, liver, butter, some fatty fish, and fortified milk
• Why do DRI vitamin D dietary
recommendations increase with age?

• Vitamin E
– Tocopherol
– Antioxidant
• Protects the lungs
• Vitamin E deficiency
– Erythrocyte hemolysis: in premature infants

• Vitamin E deficiency
– Adult symptoms
• Loss of muscle coordination and reflexes
• Impaired movement, vision, and speech
• Vitamin E toxicity
– Interferes with blood clotting
• Vitamin E in foods
– Vegetable oils, wheat germ, whole grains, etc.

• Vitamin K
– Roles: blood clotting and bone protein
synthesis
– Intestinal tract bacteria: synthesize vitamin K
• Insufficient as a sole source
• Causes of vitamin K deficiency
– Fat malabsorption
– Antibiotics

• Vitamin K nutrition for newborn
– Single dose given a birth
• Vitamin K toxicity
– Tolerable Upper Intake Level: not established
• Vitamin K in foods
– Green leafy vegetables, cabbage, some
vegetable oils, etc.

The Water-Soluble Vitamins
• Overview
– B vitamins and vitamin C
– Easily absorbed into the bloodstream
– Easily excreted when blood concentrations
rise too high

The Water-Soluble Vitamins (cont’d.)
• The B vitamins
– Functions
• Help the body use energy-yielding nutrients
• Component in coenzymes
• Help cells multiply
• Assist enzymes in performing molecular
conversions

• B vitamin deficiencies
– Thiamin ► beriberi
– Niacin deficiency ► pellagra
• How do fortification and enrichment
protect people against deficiencies?

• Thiamin
– All cells: critical role in energy metabolism
– Necessary for normal nerve and muscle
functioning
– Who is most likely to develop a thiamin
deficiency?
– Food sources
• Pork, whole grain or enriched bread and cereals;
small amounts in nearly all nutritious foods

• Riboflavin
– Serves as a coenzyme: energy metabolism
– Deficiency
• Cracks at corners of mouth and sore throat
– Food sources
• Milk, enriched breads and cereals, green
vegetables, meats, etc.
– Notes
• Light sensitive, but heat stable

• Niacin
– Needed by every cell: energy metabolism
– Body can produce niacin from protein
• Niacin equivalents (NE)
– Tolerable Upper Intake Level: 35 mg NE
– Medicinal uses
• Lower blood cholesterol
• Treat atherosclerosis

• Niacin
– Food sources
• Meat, poultry, fish, legumes, enriched and whole
grains, etc.
• Pantothenic acid and biotin
– Important in energy metabolism
– Food sources
• Widespread in foods

• Vitamin B6
– Roles
• Protein and amino acid metabolism, amino acid
conversion to other lacking amino acids, synthesis
of hemoglobin and neurotransmitters, etc.
– Deficiency symptoms
• Weakness, depression, confusion, irritability, etc.
– Toxicity
• Recovery after discontinuing supplements

• Vitamin B6
– Recommendations
• Adults (19–50): 1.3 mg/day
– Food sources
• Protein-rich meat, fish, poultry, etc.
– Heat sensitive: lost in heated foods

• Folate
– Active in cell division
– Negative impact on folate status
• Alcohol
• Medications: aspirin, oral contraceptives, and
anticonvulsants
• Smoking

• Folate
– Prevents neural tube defects (NTD)
– Tolerable Upper Intake Level
• 1000 µg/day from fortified foods and supplements
– Best food sources
• Liver, legumes, beets, and leafy green vegetables
– “How to” Estimate Dietary Folate Equivalents

• Vitamin B12
– Needed for cell division
– What dangers are associated with folate
supplementation masking a vitamin B12
deficiency?
– Requires intrinsic factor for absorption
– Food sources
• Found exclusively in animal-derived foods

• Non-B vitamins
– Serve as coenzymes in metabolism
• Inositol, choline, and carnitine
– Others
• Para-aminobenzoic acid (PABA), bioflavonoids
(vitamin P or hesperidin), and ubiquinone

• Vitamin C
– Antiscurvy factor: ascorbic acid
– Multiple roles and modes of action
• Collagen formation
• Antioxidant
• Amino acid metabolism
• Possible antihistamine
• Cancer prevention and treatment

• Vitamin C deficiency
– Affect on blood vessels
• Bleeding gums and pinpoint hemorrhages
– What are symptoms of scurvy?
• Vitamin C toxicity
– Megadoses: toxic effects unconfirmed
• Vitamin C RDA
– Men: 90 mg Women: 75 mg

• Increased need for vitamin C
– Infections, burns, surgery, extremely high or
low temperatures, toxic doses of heavy
metals, smoking, etc.
• Safe limits
– 100 to 300 mg per day

• Vitamin C food sources
– Many fruits and vegetables
• How does vitamin C impact iron
absorption?

Chapter 8 - The Vitamins

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