Vitamins and Deficiencies - Comprehensive Study Notes

Water-Soluble vs. Fat-Soluble Vitamins

  • Water-soluble vitamins: C (ascorbic acid) and B-complex vitamins (B1, B2, B3, B5, B6, B7/biotin, B9/folic acid, B12).
  • Fat-soluble vitamins: A (retinol, β-carotene), D (cholecalciferol), E (tocopherols), K (phylloquinones, menaquinones).
  • Categorization reflected in SMU notes: Water soluble (C) and B-complex; Fat soluble (A, D, K, E); with specific emphasis on energy-releasing (B1, B2, B3, biotin, pantothenic acid) and hematopoietic group (folic acid B9, B12); others include B6/B6 derivatives.

Folic Acid (Vitamin B9)

  • NECESSARY FOR AA and purine synthesis: DNA & RNA, ATP, etc.
  • PRIMARY EFFECT: macrocytic anemia (megaloblastic anemia) due to increased demand or poor absorption.
  • RISK FACTORS/CAUSES:
    • Alcoholism
    • Malabsorption issues
  • Neural tube defects and related conditions:
    • Spina bifida: affects the spine; usually obvious at birth.
    • Anencephaly: failure of rostral end of neural tube to close between day 23 and 26.
  • Cytoplasm develops faster than nucleus in cells with folate deficiency (impaired DNA synthesis).

Foods High in Folic Acid (B9)

  • Dark green leafy vegetables: turnip greens, spinach, romaine lettuce, asparagus, Brussels sprouts, broccoli.
  • Beans; Peanuts; Sunflower seeds.
  • Fresh fruits and fruit juices; Whole grains; Liver; Aquatic foods.

Vitamin B12 (Cobalamin)

  • Water-soluble and stored; key diagnostic sign: ↑ methylmalonic acid in blood.
  • Roles: crucial in DNA synthesis and myelin formation; interacts with folate cycle.

Pernicious Anemia (Megaloblastic Anemia) – B12 Deficiency Treatment

  • Treatment: high-dose vitamin B12 injections or cyanocobalamin injections.
  • Pathophysiology: Autoimmune destruction targeting parietal cells → intrinsic factor (IF) deficiency; storage of B12 in the liver delays onset of deficiency; synthetic B12 can be given because the vitamin is stored and can be supplied exogenously.

Foods High in B12

  • Animal liver and kidneys; Clams; Sardines; Beef; Fortified cereals; Tuna; Fortified nutritional yeast.

Vitamin B3 (Niacin) – Niacin Forms and Pellagra

  • Nicotinic acid and nicotinamide form NAD/NADP; essential coenzymes in redox reactions.
  • Deficiency: Pellagra – diarrhea, dermatitis, dementia, and death; can begin with stomach symptoms.
  • Tryptophan can partially compensate to generate niacin.
  • At-risk populations: malnourished groups.

Foods Rich in Niacin

  • Red meat; Poultry; Fish; Brown rice; Fortified cereals & bread; Nuts & seeds; Legumes; Bananas.

Vitamin B1 (Thiamine) – Thiamine Pyrophosphate (TPP)

  • Active coenzyme: Thiamine pyrophosphate (TPP).
  • Beriberi disease: risk factors include white rice diet, alcoholism, dialysis, diuretics.
    • Wet beriberi (cardiovascular): fast heart rate, shortness of breath, leg edema.
    • Dry beriberi (nervous system): numb hands/feet, confusion.
    • Acute beriberi: in babies—loss of appetite, vomiting, lactic acidosis, enlarged heart.
  • Wernicke-Korsakoff syndrome: chronic alcoholism; neurological deficits; impaired absorption; dietary insufficiency can contribute.

Foods Rich in Thiamine

  • Fortified breakfast cereals; Pork; Fish; Beans, lentils; Green peas; Enriched cereals, breads, noodles, rice; Sunflower seeds; Yogurt.

Vitamin B6 (Pyridoxine) – PLP

  • Active form: Pyridoxal phosphate (PLP).
  • Involved in over 150 reactions; key coenzyme for:
    • Transamination, deamination, decarboxylation, condensation.
  • Associated toxicity: sensory neuropathy.
  • Deficiency symptoms: seborrheic dermatitis, microcytic anemia, epileptiform convulsions.

Foods High in Vitamin B6

  • Beef liver; Tuna; Salmon; Fortified cereals; Chickpeas; Poultry; Dark leafy greens, bananas, papayas, oranges, cantaloupe.

Vitamin C (Ascorbic Acid)

  • Important for collagen formation (connective tissue).
  • Deficiency: Scurvy – bleeding gums, loose teeth, bleeding under skin.
  • Also important for wound healing.
  • Microcytic anemia can result due to impaired iron absorption.
  • Vitamin C enhances iron absorption by reducing ferric (Fe3+) to ferrous iron (Fe2+) and chelating iron to improve absorption.

Foods High in Vitamin C

  • Citrus fruits (oranges, kiwi, lemon, grapefruit);
  • Bell peppers; Strawberries; Tomatoes; Cruciferous vegetables (broccoli, Brussels sprouts, cabbage, cauliflower);
  • White potatoes.

Riboflavin (Vitamin B2) – FMN and FAD

  • Flavin mononucleotide (FMN) and Flavin adenine dinucleotide (FAD).
  • Deficiency signs: hyperemia, normocytic anemia.

Foods High in Riboflavin

  • Dairy milk; Yogurt; Cheese; Eggs; Lean beef and pork; Organ meats (beef liver); Chicken breast; Salmon.

Vitamin D – Fat-Soluble

  • Sterol with hormone-like function.
  • Deficiency outcomes:
    • Nutritional rickets (kids; growth plate open) or osteomalacia (adults; growth plate closed): demineralization of bone, stunted growth, skeletal deformities.
    • Renal osteodystrophy: kidney failure leads to low calcium and high phosphate; managed by increasing calcium and decreasing phosphate.
    • Hypoparathyroidism: tingling in fingertips due to decreased parathyroid hormone.

Activation and Metabolism of Vitamin D

  • Activation pathway:
    • In skin: 7-dehydrocholesterol + sunlight → cholecalciferol (vitamin D3).
    • In liver: cholecalciferol → 25-hydroxycholecalciferol (25-hydroxy vitamin D).
    • In kidney: 25-hydroxycholecalciferol → 1,25-dihydroxycholecalciferol (1,25-dihydroxy vitamin D).
    • Active form: 1,25-dihydroxyvitamin D3.
  • Diagrammatic summary (text):
    • Skin: 7-dehydrocholesterol --sunlight--> cholecalciferol (D3)
    • Liver: cholecalciferol --25-hydroxylation--> 25-hydroxyvitamin D3
    • Kidney: 25-hydroxyvitamin D3 --1α-hydroxylation--> 1,25-dihydroxyvitamin D3 (active)
  • Maintains calcium balance in the body via the active form.

Foods Rich in Vitamin D

  • Cod liver oil; Salmon; Swordfish; Tuna; Orange juice fortified with vitamin D; Dairy and plant milks fortified with vitamin D; Sardines; Beef liver.

Vitamin A – Fat-Soluble

  • Structure: Fat-soluble retinoids; vision, growth, maintenance of epithelia; Retinoic acid for immune function; Retinol oxidation; Retinal (aldehyde version).
  • Provitamin A: β-carotene (plants) yields retinal; 2 molecules of retinol activity equivalents from β-carotene.
  • Important for vision; Vitamin A-related conditions:
    • Xerophthalmia: dryness of conjunctiva and cornea.
    • Night blindness: inability to adapt to darkness.
    • Hypervitaminosis: excessive vitamin A; various symptoms including vomiting, nausea, liver damage, birth defects, joint pain.
  • Retinol Activity Equivalents (RAE): 1 μg retinol = 1 RAE.
  • Daily RAE requirements:
    • Males: ~900 RAE/day; Females: ~700 RAE/day.
  • Other notes: Dry, scaly skin can occur with excess.

Foods High in Vitamin A

  • Preformed vitamin A foods: liver, fish, eggs, dairy.
  • Provitamin A foods: leafy green vegetables; orange/yellow vegetables; tomato; fruits.

Vitamin K – Fat-Soluble, Blood Clotting

  • Role: post-translational modification of blood-clotting proteins in the liver; carboxylation of glutamic acid residues.
  • Deficiency associations: hemorrhagic disease of the newborn; conditions such as cystic fibrosis, fat malabsorption, blocked bile ducts, and use of warfarin (Coumadin).

Foods High in Vitamin K

  • Leafy green vegetables; Broccoli; Spinach; Cabbage; Lettuce; Kale; Collard greens.

Vitamin E – Fat-Soluble, Antioxidant

  • Family: tocopherols and tocotrienols.
  • Alpha-tocopherol is the biologically active form.
  • Primary function: antioxidant – protects polyunsaturated fatty acids and LDLs from oxidation.

Foods High in Vitamin E

  • Wheat germ oil; Sunflower, safflower, and soybean oil; Sunflower seeds; Almonds; Peanuts/peanut butter; Beet greens, collard greens, spinach; Pumpkin; Red bell pepper.

Iron – Essential for Oxygen Transport

  • Iron oxidation states and Hb binding:
    • Ferric: Fe^{3+} — cannot bind oxygen (methaemoglobin).
    • Ferrous: Fe^{2+} — can bind oxygen in Hb.
  • Iron-deficiency anemia:
    • Inadequate intake; Increased requirement during pregnancy and breastfeeding; Impaired absorption (e.g., celiac disease); Bariatric surgery; Blood loss (menstrual bleeding, donations).
  • Hemochromatosis: iron overload; body stores too much iron.