Vitamins: Classifications and role Flashcards
What are vitamins?
A group of organic nutrients which are:
1) Needed in minute quantities (microgram and milligram amounts)
2) Are generally not synthesized by the body
3) Are necssary for metabolism, growth, reproduction, maintenance of tissue and aid in immune phenomena
4) Are destroyed by excessive heat, light and storage
What is a provitamin?
An inactive precursor to a vitamin
What are the functions of vitamins?
Co-enzymes in the metabolism of carbohydrates, fat and proteins (vitamin-B)
Anti-oxidants (beta carotene, Vitamin E & C)
Act as steroid hormones (Vitamin D, retinoic acid)
What may cause deficiency of micronutrients?
Inadequate intake (or general malnutrition)
Poor absorption from the intestinal tract (old age)
Inefficient utilization
Increased loss
Increased demand (pregnancy or the adolescent growth spurt)
May manifest during illness
May occur as a result of surgical procedures on GIT
Multiple deficiencies are much more common than single deficiencies and lead to specific clinical syndromes
What are the characteristics of fat soluble vitamins?
Hydrophobic compounds
Absorbed efficiently only when there is normal fat absorption
Absorbed in the small intestine
How are fat soluble vitamins absorbed?
Requires micelles formed with bile salts, which facilitate the solubilization of dietary lipids and other hydrophobic molecules
How are fat soluble vitamins transported in blood?
Blood in lipoproteins or bound to specific proteins
What happens to excess fat soluble vitamins?
Excess fat soluble vitamins are stored so toxicity can result from their excessive intake
What factors may lead to deficiency of fat soluble vitamins?
Dietary deficiency
Fat malabsorption (vitamins A, D, E and K)
Mineral oil (laxatives): Indigestible and may carry fat soluble vitamins out of the digestive system
What conditions may cause deficiency of vitamins A, D, E and K
Steatorrhea, disorders of biliary system, diseases of liver or gallbladder, inflammatory bowel disease (Crohn’s disease, celiac disease) and cystic fibrosis
What are the functions of fat soluble vitamins?
Vitamin A: Vision and cell differentiation
Vitamin D: Calcium and phosphate metabolism
Vitamin E: Antioxidants
Vitamin K: Blood clotting
What do deficiencies of fat-soluble vitamins cause?
Vitamin A deficiency: Night blindness & xerophthalmia
Vitamin D deficiency: Rickets & osteomalacia
Vitamin E deficiency: Neurologic disorders & hemolytic anemia of newborn
Vitamin K deficiency: Hemorrhage of the newborn
What is orlistat?
Drug which inhibits absorption of fat-soluble vitamins A, D, E, and K
What is the clinical use of orlistat?
Weight loss
What are some potential adverse effects of orlistat?
Abdominal pain, flatulence, bowel uregency/frequent bowel movements, steatorrhea, decreased absorption of fat-soluble vitamins
What is the mechanism of orlistat?
Inhibits fastric and pancreatic lipase which decreases teh breakdown and aborption of dietary fats
What are the characteristics of the B group of vitamins?
Water soluble
Free absorption & transportation
Excesses excreted
No significant stores
Most function as coenzymes
What are the categories into which the B group of vitamins can be subdivided?
Energy releasing: Thiamin, Riboflavin, Niacin, Pantothenic acid & Biotin
Hematopoietic: Folic Acid and B12
Vitamin with both & other functions: Pyridoxine
Why does deficiency of B vitamins produce a number of overlapping symptoms?
Participate in many biochemical reactions
Have common food sources
Where may deficiency symptoms arise?
In rapidly growing tissues
What happens to excess water soluble vitamins?
Excesses of water-soluble vitamins are excreted and so unlikely to reach toxic levels.
What are the names of the water soluble vitamins?
Effects of B complex deficiencies
Dermatitis glossitis and diarrhea
Do all B-complex vitamins get washed out from the body easily?
B12 remains in the liver for 3-4 years
B9 remains in the liver for 3-4 months
