Vitamins

Fat-Soluble Vitamins

• Vitamin A (Retinol)
  • Function: Vision, epithelial cell differentiation, immune function.
  • Deficiency: Night blindness, xerophthalmia (dry eyes, Bitot spots, keratomalacia), dry scaly skin, immunosuppression.
    • High-Yield: Teratogenic (isotretinoin).
• Vitamin D (Calciferol)
  • Function: Calcium and phosphate absorption, bone mineralization.
  • Deficiency: Rickets (children - bowed legs), osteomalacia (adults - bone pain, weakness), hypocalcemia.
• Vitamin E (Tocopherol)
  • Function: Antioxidant (protects RBCs and membranes).
  • Deficiency: Hemolytic anemia, neuromuscular dysfunction (ataxia, peripheral neuropathy).
• Vitamin K (Phylloquinone, Menaquinone)
  • Function: Coagulation (activates factors II, VII, IX, X, Protein C & S).
  • Deficiency: Bleeding, increased PT/aPTT (normal bleeding time), hemorrhagic disease of newborn.

Water-Soluble Vitamins

• Vitamin B1 (Thiamine)
  • Function: Carbohydrate metabolism (cofactor for dehydrogenase enzymes).
  • Deficiency:
    • Beriberi: Dry (peripheral neuropathy), Wet (high-output heart failure).
    • Wernicke-Korsakoff Syndrome (alcoholics): Confusion, Ophthalmoplegia, Ataxia (Wernicke); Amnesia, Confabulation (Korsakoff).
• Vitamin B2 (Riboflavin)
  • Function: Redox reactions (FAD, FMN).
  • Deficiency: The "2 C's": Cheilosis (cracks at mouth corners), Corneal vascularization; also magenta tongue, seborrheic dermatitis.
• Vitamin B3 (Niacin)
  • Function: Redox reactions (NAD${}^{+},NAD{P}^{+}$).
  • Deficiency: Pellagra ("3 D's"): Dermatitis (photosensitive, Casal necklace), Diarrhea, Dementia; (can add Death).
• Vitamin B5 (Pantothenic Acid)
  • Function: Component of Coenzyme A.
  • Deficiency: Rare; dermatitis, enteritis, alopecia, "burning feet syndrome." (Generally low-yield for deficiency).
• Vitamin B6 (Pyridoxine)
  • Function: Amino acid metabolism, neurotransmitter & heme synthesis.
  • Deficiency: Sideroblastic anemia, peripheral neuropathy, seizures, cheilosis, glossitis.
    • High-Yield: Isoniazid can cause deficiency.
• Vitamin B7 (Biotin)
  • Function: Carboxylation reactions.
  • Deficiency: Rare; dermatitis, alopecia, enteritis.
    • High-Yield: Avidin (raw egg whites) induces deficiency.
• Vitamin B9 (Folate)
  • Function: DNA/RNA synthesis (1-carbon transfers).
  • Deficiency: Megaloblastic anemia (hypersegmented neutrophils), NO neurological symptoms. Glossitis.
    • High-Yield: Neural tube defects in pregnancy.
• Vitamin B12 (Cobalamin)
  • Function: DNA synthesis, methionine synthesis.
  • Deficiency: Megaloblastic anemia + neurological symptoms (subacute combined degeneration - paresthesias, ataxia).
    • High-Yield: Pernicious anemia, vegan diet, elevated methylmalonic acid.
• Vitamin C (Ascorbic Acid)
  • Function: Collagen synthesis (hydroxylation), antioxidant, iron absorption.
  • Deficiency: Scurvy: Bleeding gums, petechiae, poor wound healing, corkscrew hairs.