Water Soluble Vitamins: Thiamine (Vitamin B1)

Water-Soluble Vitamins

• Thiamine (Vitamin B1)
  • Function: important cofactor in CHO metabolism, involved in oxidation of acetyl-CoA in mitochondria, Kreb's cycle, and HMP shunt
  • Sources: found in cereals, grains, beans, nuts, and duck
  • Deficiency: causes beriberi, seen in starved patients, cancer patients, and those with severe hyperemesis
• Riboflavin (Vitamin B2)
  • Source: widely distributed in plants and animal cells, good sources include dairy products and leafy vegetables
  • Function: cofactor for many oxidative reactions in cells
  • Deficiency: causes angular stomatitis, glossitis, and seborrheic dermatitis
• Niacin (Vitamin B3)
  • Function: important in many oxidative processes in the body, can be synthesized from tryptophan
  • Sources: found in plants, meat, and fish, lost during processing of cereals
  • Deficiency: causes pellagra, seen in maize-eating populations, Hartnup's disease, and generalized malabsorption

Pellagra

• Causes:
  • Maize deficiency in nicotinic acid and tryptophan
  • Hartnup's disease
  • Generalized malabsorption
  • Low protein diet
  • Carcinoid syndrome and pheochromocytoma
• Clinical features:
  • Dermatitis: symmetric, affects sun-exposed areas, redness, cracks, and ulceration
  • Diarrhea: often a feature, but constipation may occur
  • Dementia: depression, apathy, thinking disorders, tremors, encephalopathy, and acute psychosis

Pyridoxine (Vitamin B6)

• Function: involved in many oxidative processes in the body
• Deficiency: causes dermatitis, diarrhea, and dementia
• Diagnosis: based on clinical features, assay of RBCs NAD
• Treatment: nicotinamide, increase protein content in diet, treat underlying causes

Vitamin C

• Source: found in all fresh fruits and vegetables
• Function:
  • Powerful reducing agent, controls redox potentials in cells
  • Involved in hydroxylation of proline into hydroxyproline, necessary for collagen formation
• Deficiency: causes weakness, muscle pain, keratosis of hair follicle, swollen and bleeding gums, spontaneous bruising, and anemia
• Diagnosis: anemia, low plasma ascorbic acid, response to replacement therapy
• Treatment: ascorbic acid orally, increase fresh vegetables and fruits in diet

Fat-Soluble Vitamins

Vitamin A

• Deficiency:
  • Causes night blindness, xerophthalmia, and impaired immune function
  • Seen in areas with inadequate diet, malabsorption, and liver disease
• Diagnosis: based on clinical features, low blood levels of vitamin A, response to replacement therapy
• Prevention: diets must contain dairy products and green vegetables, vitamin A supplements for children with measles

Vitamin D

• Metabolism: 7-dehydrocholesterol is photoactivated in the skin, converted in the liver and kidney into active metabolite
• Function:
  • Increases Ca absorption from GIT
  • Increases bone calcification
  • Increases bone resorption
• Deficiency:
  • Causes rickets in children and osteomalacia in adults
  • Seen in inadequate synthesis in skin, low diet intake, and malabsorption

Vitamin K

• Function:
  • Production of clotting factors
  • Production of proteins necessary for bone formation
• Deficiency:
  • Results in inadequate formation of clotting factors, leading to increased prothrombin time and bleeding
  • Seen in newborns, chronic small intestinal disease, and broad-spectrum antibiotic treatment
• Diagnosis: elevated prothrombin time, reduced clotting factors
• Treatment: vitamin K replacement

Vitamin E

• Source: found in vegetables, seed oils, and nuts
• Function:
  • Acts as an antioxidant and radical scavenger, protecting LDL and polyunsaturated fats from oxidation
  • Inhibits prostaglandin synthesis
  • Affects cell proliferation and growth
• Deficiency:
  • Causes hemolytic anemia in premature infants
  • Seen in children with abetalipoproteinemia and those on long-term parenteral nutrition
• Benefits: prevention of cardiovascular disease, cancer, and Alzheimer's disease