Vitamin deficiencies

Introduction

Vitamins are organic compounds required in small amounts for metabolic processes, growth, immune function, and overall health. Vitamin deficiencies refer to a state in which the body has inadequate levels of one or more essential vitamins, leading to impaired physiological function and potential health problems.

Types of vitamins

• Fat-soluble vitamins
  • Vitamin A (Retinol)
  • Vitamin D (Calciferol)
  • Vitamin E (Tocopherol)
  • Vitamin K (Phytomenadione)
• Water-soluble vitamins
  • Vitamin B1 (Thiamine)
  • Vitamin B2 (Riboflavin)
  • Vitamin B3 (Niacin)
  • Vitamin B5 (Pantothenic acid)
  • Vitamin B6 (Pyridoxine)
  • Vitamin B7 (Biotin)
  • Vitamin B9 (Folate)
  • Vitamin B12 (Cobalamin)
  • Vitamin C (Ascorbic acid)

Vitamin A (Retinol)

• Function:
  • Essential for vision (retinal pigment)
  • Promotes cell differentiation
  • Supports immune function and reproduction
• Deficiency:
  • Causes: fat malabsorption, malnutrition
  • Signs: night blindness, xerophthalmia, Bitot spots, dry skin
• Toxicity:
  • Acute: nausea, vomiting, blurred vision, pseudotumour cerebri
  • Chronic: alopecia, dry skin, hepatotoxicity, arthralgia, teratogenicity

Vitamin B1 (Thiamine)

• Function: Coenzyme for carbohydrate metabolism and energy production.
• Deficiency:
  • Causes: alcohol misuse, malnutrition, hypermetabolic states
  • Clinical features:
    • Dry beriberi: peripheral neuropathy
    • Wet beriberi: high-output cardiac failure
    • Wernicke’s encephalopathy: confusion, ophthalmoplegia, ataxia
    • Korsakoff syndrome: confabulation, anterograde + retrograde amnesia

Vitamin B2 (Riboflavin)

• Function: Energy metabolism.
• Deficiency: cheilitis and corneal vascularisation (2 C’s).

Vitamin B3 (Niacin)

• Function: Redox reactions (NAD/NADP).
• Deficiency:
  • Mild: glossitis
  • Severe: pellagra (3 D’s – dermatitis, diarrhoea, dementia)
• Toxicity: flushing, hyperglycaemia, hyperuricaemia, hepatotoxicity.

Vitamin B5 (Pantothenic acid)

• Function: CoA component in fatty acid metabolism.
• Deficiency: rare; fatigue, irritability, burning feet syndrome.

Vitamin B6 (Pyridoxine)

• Function: Neurotransmitter synthesis, haem metabolism.
• Deficiency: irritability, depression, neuropathy, sideroblastic anaemia (isoniazid/alcohol misuse).
• Toxicity: sensory neuropathy with high doses.

Vitamin B7 (Biotin)

• Function: Coenzyme in carboxylation reactions.
• Deficiency: alopecia, dermatitis, glossitis (due to antibiotics or raw egg white consumption).

Vitamin B9 (Folate)

• Function: DNA synthesis, red cell production.
• Deficiency: macrocytic anaemia, neural tube defects.

Vitamin B12 (Cobalamin)

• Function: DNA synthesis, myelin formation.
• Deficiency: macrocytic anaemia, glossitis, neuropathy, subacute combined degeneration of spinal cord.

Vitamin C (Ascorbic acid)

• Function: Antioxidant, collagen synthesis, enhances iron absorption.
• Deficiency: scurvy – bleeding gums, poor wound healing, corkscrew hairs.
• Toxicity: GI upset, calcium oxalate stones, iron overload in haemochromatosis.

Vitamin D (Calciferol)

• Function: Calcium/phosphate absorption, bone mineralisation.
• Deficiency:
  • Children: rickets
  • Adults: osteomalacia
  • Hypocalcaemia with tetany (Chvostek’s and Trousseau’s signs)
• Toxicity: hypercalcaemia – “bones, stones, groans, psychiatric moans.”

Vitamin E (Tocopherol)

• Function: Antioxidant.
• Deficiency: rare; neuropathy, haemolytic anaemia, ataxia.

Vitamin K (Phytomenadione)

• Function: Gamma-carboxylation of clotting factors II, VII, IX, X.
• Deficiency: bleeding diathesis, prolonged PT (common in neonates, patients on warfarin, fat malabsorption).