Vitamins
Definition and Classification
* Non-caloric organic nutrients
* Needed in very small amounts
* Facilitators – help body processes proceed; digestion, absorption, metabolism, growth etc.
* Some appear in food as precursors or provitamins
Definition and Classification
* 2 classes, Table 7.1
o Fat soluble:
o Water soluble:
* Fat soluble vitamins
o Found in the fats and oils of food.
o Absorbed into the lymph and carried in blood with protein transporters = chylomicrons.
o *Stored in liver and body fat and can become toxic if large amounts are consumed.
* Water soluble vitamins
o Found in vegetables, fruit and grains, meat.
o Absorbed directly into the blood stream
o Not stored in the body and toxicity is rare. Alcohol can increase elimination, smoking, etc. cause decreased absorption.
Fat Soluble Vitamins
* Vitamin A (precursor – beta carotene)
o 3 forms: retinol (stored in liver), retinal, retinoic acid
o Roles in body:
+ Regulation of gene expression
+ Part of the visual pigment rhodopsin, maintains clarity of cornea (yes eating carrots is good for your eyesight)
+ Required for cell growth and division - epithelial cells, bones and teeth
+ Promotes development of immune cells, especially “Natural Killer Cells”
+ Antioxidant
* Vitamin A
o Deficiencies cause:
+ Night blindness, xerophthalmia (keratin deposits in cornea), macular degeneration.
+ Skin and mucous membrane dryness and infection, keratin deposits.
+ Anemia
+ Developmental defects – bones, teeth, immune system, vision
o Toxicities (RetinA/Accutaine, single large doses of supplements, eating excessive amounts of liver) cause:
+ Fragile RBCs, hemorrhage
+ Bone pain, fractures
+ Abdominal pain and diarrhea
+ Blurred vision
+ Dry skin, hair loss
+ Liver enlargement
o DRI: 700(women)-900(men) micrograms/day, UL 3000 micrograms
o Sources, see snapshot 7.1
* Vitamin D – precursor is cholesterol, converted by UV from sunlight exposure, therefore is a “non-essential” vitamin.
o Roles:
+ Increases calcium absorption in bone, intestines, kidney. Promotes bone growth and maintenance.
+ Stimulates maturation of cells – heart, brain, immune system, etc.
o Deficiencies: rickets (children), osteomalacia (adults). What are some of the causes of deficiencies?
o Toxicities (5X DRI)
+ Loss of calcium from bone and deposition in soft tissues.
+ Loss of appetite, nausea and vomiting, psychological depression.
Bowed legs – Characteristic of rickets
Beaded ribs – Characteristic of rickets
* Vitamin D
o DRI – 5 micrograms/day for ages 19-50, 10 for ages 51-70, 15 for ages >70.
o Sources, see snapshot 7.2
Fat Soluble Vitamins
* Vitamin E – tocopherol, *alpha-, beta -, gamma-, and delta-
o Roles:
+ Antioxidant (protects polyunsaturated fats)
+ Prevention of damage to lungs, RBCs, WBCs (immunity), heart
+ Necessary for normal nerve development
* Vitamin E
o Deficiencies (decreased absorption of fats- liver disease, low fat diets)
+ Premature babies – fragile RBCs (hemolysis)
+ Loss of muscle coordination, vision, immune functions
o Toxicities (more than 1000 milligrams/day)
+ Increases the effects of anticoagulants (Coumadin, Warfarin)
o DRI 15 milligrams/day (alpha-tocopherol)
o Sources, see snapshot 7.3
* Vitamin K – produced by bacteria in large intestine
o Roles
+ Promotes synthesis of blood clotting proteins (**Interferes with Coumadin)
+ Bone formation
o Deficiencies are rare but seen in infants, after prolonged antibiotic therapy, and in patients with decreased bile production.
o Toxicities (>1000 mg/day): rupture of RBCs and jaundice
o DRI: 90(women) – 120(men) micrograms/day
o Sources, see snapshot 7.4
Water Soluble Vitamins
* 8 B vitamins – Tender Romance Never Fails with 6 to 12 Beautiful Pearls (Thiamin, Riboflavin, Niacin, Folate, B6, B12, Biotin, and Pantothenic acid)
o Aid in metabolism of and energy release from carbohydrates, lipids, amino acids.
o Mode of action – coenzymes or parts of coenzymes that are necessary for the proper activity of enzymes, Without the coenzyme, compounds A and B don’t respond to the enzyme.
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