Fat soluble vitamins

• Forms of vitamin A


  • Preformed
  • Precursor forms
• Preformed vitamin A


  Derived from animal products, provide compounds (retinyl esters) easily hydrolysed to retinoids in the intestine, include retinol, retinal and retinoid acid
• Precursor forms of vitamin A


  Derived from yellow plants, provide carotenoids which serve as precursors of vitamin A
• Retinol functions


  • In the eye, combines with opsin to form the visual pigment rhodopsin, which participates in conversion of light energy into nerve impulses sent to the brain
  • Essential for reproductive processes in both males and females
• Retinoic acid function


  • Maintenance of epithelial cells - essential for normal growth and differentiation of epithelial tissues, and mucus secretion
• Deficiency of vitamin A results in


  • Impaired growth & bone development
  • Night blindness
  • Ear Infection
  • Acne
  • Weight loss
• Retinol can be converted to retinoic acid


  Retinoic acid can't be converted to retinol
• Retinol storage


  Stored as retinyl esters in liver and adipose tissue
• 1. dehydrocholesterol


  Sits under the skin and when UV rays hit it aids in the conversion to vitamin D3 (cholecalciferol)
• Vitamin D2 (ergocalciferol)


  Obtained through plants
• Active form of Vitamin D


  1,25-diOH-D3 (calcitriol)
• Calcitriol functions


  • Stimulates intestinal absorption of Ca2+ & PO43-
  • Stimulates the mobilisation of Ca2+ & PO43- from bone
  • Stimulates re-absorption of Ca2+ & PO43- from the urine in the kidneys
• You need parathyroid hormone and calcitriol


  To increase calcium levels
• Effects of Parathyroid Hormone (PTH) and Calcitriol


  • Bone: Increased Ca mobilisation
  • Kidney: Increased Ca reabsorption
  • Intestines: Increased Ca absorption
• Effects of Calcitonin


  • Bone: Decreased Ca mobilisation
  • Kidney: Decreased Ca reabsorption
  • Intestines: Decrease Ca absorption
• Vitamin D deficiency results in


  • Rickets in children
  • Osteomalacia in adults
• Vitamin D overdose results in hypercalcemia
• Vitamin E food sources


  • Vegetable oil
  • Liver
  • Eggs
• α-tocopherol is the predominant vitamin E in the blood
• Vitamin E function


  Natural antioxidant
• Sources of Vitamin K


  • Vitamin K1 (Phylloquinone) comes from plants
  • Vitamin K2 (Menaquinone) comes from animal tissues
  • Vitamin K3 is a synthetic water soluble drug
• Foods containing Vitamin K


  • Cabbage
  • Cauliflower
  • Spinach
  • Egg yolk
  • Liver
• Vitamin K


  • Required for biosynthesis of blood clotting factors, specifically II, VII, IX and X
  • Enables chelation of Ca2+