Overview of Micronutrients

• Micronutrients are essential dietary components required by the body in small quantities for the maintenance of health, growth, and normal physiological processes.
• They do not yield energy directly but act as regulators of metabolic processes, cofactors for enzymes, and structural components,.
• They are broadly classified into Vitamins (organic compounds) and Minerals (inorganic elements).

Vitamins: Functions and Dietary Sources

Vitamins are classified into fat-soluble and water-soluble groups.

Fat-Soluble Vitamins

1. Vitamin A (Retinol)

• Functions:
  • Vision: Essential for the formation of rhodopsin (visual pigment) required for dim light vision (scotopic vision),.
  • Epithelial Integrity: Maintains the integrity of epithelial tissues (skin, respiratory, and gastrointestinal tracts) by regulating keratin synthesis and mucus production,.
  • Immune Function: Enhances immunity and resistance to infections,.
  • Growth and Differentiation: Regulates gene expression involved in cell growth and differentiation.
• Dietary Sources:
  • Animal Sources (Preformed Retinol): Liver, fish liver oils (cod, shark), egg yolk, whole milk, butter, and cheese,,.
  • Plant Sources (Provitamin A/Carotenoids): Green leafy vegetables (spinach, amaranth), yellow and orange vegetables and fruits (carrots, pumpkin, mango, papaya), and red palm oil,,.

2. Vitamin D (Calciferol)

• Functions:
  • Calcium and Phosphorus Homeostasis: Promotes intestinal absorption of calcium and phosphorus,.
  • Bone Mineralization: Essential for the mineralization of the organic bone matrix (osteoid) and growth plate cartilage,.
  • Renal Reabsorption: Facilitates calcium reabsorption in the kidneys.
• Dietary Sources:
  • Endogenous: Synthesized in the skin from 7-dehydrocholesterol upon exposure to UV-B sunlight,.
  • Dietary: Fatty fish (salmon, sardines), fish liver oils, egg yolk, mushrooms, and fortified milk or cereals,,.

3. Vitamin E (Tocopherol)

• Functions:
  • Antioxidant: Acts as a chain-breaking antioxidant in cell membranes, protecting polyunsaturated fatty acids (PUFA) from lipid peroxidation by free radicals,.
  • Neurological Function: Maintains the structural integrity of neurons and axons.
  • RBC Stability: Protects red blood cell membranes from hemolysis,.
• Dietary Sources:
  • Vegetable oils (corn, sunflower, safflower, soy), nuts (almonds), seeds, whole grains, and green leafy vegetables,,.

4. Vitamin K

• Functions:
  • Coagulation: Essential cofactor for the gamma-carboxylation of clotting factors II (prothrombin), VII, IX, and X in the liver,.
  • Anticoagulant Proteins: Activates Proteins C and S.
  • Bone Health: Activates osteocalcin, a calcium-binding protein in bone.
• Dietary Sources:
  • Green leafy vegetables (spinach, cabbage, collards), liver, soy, and vegetable oils,,.
  • Significant amounts are synthesized by intestinal bacteria (menaquinones),.

Water-Soluble Vitamins (B-Complex and C)

1. Thiamine (Vitamin B1)

• Functions: Coenzyme (Thiamine Pyrophosphate) in carbohydrate metabolism (pyruvate dehydrogenase) and branched-chain amino acid metabolism; essential for nerve conduction,,.
• Sources: Whole grains (unpolished rice), wheat germ, legumes, nuts, pork, liver, and eggs,,.

2. Riboflavin (Vitamin B2)

• Functions: Component of coenzymes FAD and FMN involved in oxidation-reduction reactions and cellular respiration,,.
• Sources: Milk and dairy products, eggs, liver, meat, and green leafy vegetables,,.

3. Niacin (Vitamin B3)

• Functions: Component of NAD and NADP, coenzymes crucial for redox reactions, glycolysis, and fatty acid synthesis,,.
• Sources: Meat, poultry, fish, legumes, peanuts, and cereals. Can be synthesized from the amino acid tryptophan,,.

4. Pyridoxine (Vitamin B6)

• Functions: Coenzyme (PLP) for amino acid metabolism (transamination), neurotransmitter synthesis, and heme synthesis,,.
• Sources: Meat, liver, fish, whole grains, legumes, bananas, and nuts,,.

5. Folic Acid (Vitamin B9)

• Functions: Essential for DNA synthesis, cell division (erythropoiesis), and neural tube development in the fetus,,.
• Sources: Green leafy vegetables, legumes, citrus fruits, liver, and fortified cereals,,.

6. Cobalamin (Vitamin B12)

• Functions: DNA synthesis, maturation of red blood cells, and maintenance of myelin sheaths in the nervous system,,.
• Sources: Exclusively animal foods: Liver, meat, fish, eggs, milk, and dairy products,,.

7. Vitamin C (Ascorbic Acid)

• Functions: Collagen synthesis (wound healing, bone formation), antioxidant activity, and enhancement of non-heme iron absorption,,.
• Sources: Amla (Indian gooseberry), citrus fruits (orange, lemon), guava, tomatoes, sprouted grains, and green leafy vegetables,,.

8. Pantothenic Acid (B5) and Biotin (B7)

• Functions: B5 is part of Coenzyme A (fatty acid metabolism); Biotin is a cofactor for carboxylase enzymes (gluconeogenesis, fatty acid synthesis),,.
• Sources: Widespread in foods; liver, egg yolk, grains, and legumes,,.

Mineral Micronutrients: Trace Elements

Trace elements are minerals required by the body in minute amounts (less than 100 mg/day or <0.01% of body weight) but are critical for specific biological functions,,.

1. Iron

• Functions:
  • Oxygen Transport: Essential component of hemoglobin in red blood cells and myoglobin in muscle,.
  • Enzyme Systems: Cofactor for cytochromes (electron transport chain), peroxidase, and catalase,.
  • Brain Function: Critical for neurotransmitter synthesis and myelin formation,.
• Dietary Sources:
  • Heme Iron (High Bioavailability): Liver, meat, poultry, fish,.
  • Non-Heme Iron: Green leafy vegetables, cereals, legumes, jaggery, dates, and dried fruits,.
• Effects of Deficiency:
  • Iron Deficiency Anemia (IDA): The most common manifestation, characterized by microcytic hypochromic anemia. Symptoms include pallor, fatigue, breathlessness, and tachycardia,.
  • Cognitive Impairment: Deficiency in infancy and childhood leads to irreversible impairment of cognitive function, attention span, and learning ability,.
  • Behavioral Changes: Irritability, apathy, and pica (geophagia, amylophagia, pagophagia).
  • Epithelial Changes: Koilonychia (spoon-shaped nails), glossitis, angular stomatitis, and esophageal webs (Plummer-Vinson syndrome).
  • Immunity: Increased susceptibility to infections due to impaired T-cell function and phagocytosis,.

2. Zinc

• Functions:
  • Enzymatic Role: Cofactor for over 200 enzymes (e.g., alkaline phosphatase, DNA/RNA polymerase, carbonic anhydrase),.
  • Growth and Repair: Essential for protein synthesis, cell division, nucleic acid metabolism, and wound healing,.
  • Immunity: Vital for the normal development and function of the immune system (T-lymphocytes),.
  • Sensory Function: Required for taste perception (gustin) and night vision (retinol-binding protein synthesis),.
• Dietary Sources:
  • Red meat, liver, shellfish (oysters), poultry, eggs, dairy, whole grains, nuts, and legumes,.
• Effects of Deficiency:
  • Growth Retardation: A hallmark of chronic deficiency, leading to stunting,.
  • Acrodermatitis Enteropathica: A severe deficiency state characterized by periorificial and acral dermatitis (crusting, vesiculobullous lesions), alopecia (hair loss), and diarrhea,.
  • Hypogonadism: Delayed sexual maturation and hypogonadism in adolescents,.
  • Immune Dysfunction: Increased susceptibility to infections, particularly diarrhea and pneumonia,.
  • Impaired Healing: Delayed wound healing and skin ulcers,.
  • Sensory Deficits: Hypogeusia (decreased taste) and night blindness,.

3. Iodine

• Functions:
  • Thyroid Hormones: Solely required for the synthesis of thyroxine (T4) and triiodothyronine (T3),.
  • Development: Regulates basal metabolic rate, physical growth, and crucial brain development in the fetus and young child,.
• Dietary Sources:
  • Seafood, fish, iodized salt, and plants grown in iodine-rich soil,.
• Effects of Deficiency (Iodine Deficiency Disorders - IDD):
  • Goiter: Enlargement of the thyroid gland due to TSH stimulation,.
  • Cretinism: Severe deficiency during fetal life causes permanent mental retardation, deaf-mutism, spastic diplegia, and short stature (neurological and myxedematous types),.
  • Hypothyroidism: Fatigue, weight gain, cold intolerance, dry skin, and mental slowing.
  • Reproductive Failure: Increased risk of stillbirths, abortions, and congenital anomalies,.

4. Copper

• Functions:
  • Iron Metabolism: Essential for ceruloplasmin (ferroxidase), which mobilizes iron from storage sites for hemoglobin synthesis,.
  • Connective Tissue: Cofactor for lysyl oxidase, required for cross-linking collagen and elastin.
  • Antioxidant: Component of superoxide dismutase (SOD).
  • Neurological: Involved in myelin formation and neurotransmitter synthesis.
• Dietary Sources:
  • Liver, shellfish (oysters), meat, nuts, legumes, whole grains, and cocoa,,.
• Effects of Deficiency:
  • Anemia: Refractory hypochromic microcytic anemia indistinguishable from iron deficiency but unresponsive to iron therapy alone,.
  • Neutropenia: Low neutrophil count increasing infection risk,.
  • Bone Abnormalities: Osteoporosis, pathological fractures, and scurvy-like radiological changes (metaphyseal irregularities),.
  • Depigmentation: Hypopigmentation of hair and skin (e.g., kinky hair in Menkes disease),.
  • Neurological: Hypotonia and psychomotor retardation (Menkes disease).

5. Selenium

• Functions:
  • Antioxidant: Essential component of glutathione peroxidase, which protects cells from oxidative damage,.
  • Thyroid Function: Involved in the conversion of T4 to T3 (deiodinase enzymes).
• Dietary Sources:
  • Seafood, organ meats, muscle meats, whole grains, and garlic (content depends on soil selenium),.
• Effects of Deficiency:
  • Keshan Disease: A fatal dilated cardiomyopathy seen in selenium-deficient areas (e.g., China),.
  • Kashin-Beck Disease: An osteoarthropathy leading to joint deformities.
  • Muscle Symptoms: Myopathy, muscle pain, and weakness,.
  • Hair and Nail Changes: Whitening of nail beds and hair loss.

6. Chromium

• Functions:
  • Glucose Metabolism: Potentiates the action of insulin (Glucose Tolerance Factor), facilitating glucose uptake by cells,.
• Dietary Sources:
  • Yeast, liver, whole grains, cheese, nuts, and spices (black pepper),.
• Effects of Deficiency:
  • Glucose Intolerance: Hyperglycemia, glycosuria, and insulin resistance mimicking diabetes mellitus,.
  • Neuropathy: Peripheral neuropathy and encephalopathy,.
  • Lipid Abnormalities: Potential contribution to elevated cholesterol and triglycerides.

7. Manganese

• Functions:
  • Enzyme Cofactor: Component of superoxide dismutase (Mn-SOD) in mitochondria, and enzymes involved in mucopolysaccharide synthesis and gluconeogenesis,.
• Dietary Sources:
  • Whole grains, cereals, nuts, leafy vegetables, and tea,.
• Effects of Deficiency:
  • Skeletal Defects: Growth retardation and bone demineralization.
  • Hair Changes: Reddening of hair.
  • Clotting: Increased prothrombin time.
  • Metabolic: Weight loss and hypocholesterolemia.

8. Fluorine (Fluoride)

• Functions:
  • Dental Health: Incorporated into tooth enamel (fluoroapatite), making it resistant to acid attack and preventing dental caries,.
  • Bone Health: Stimulates new bone formation.
• Dietary Sources:
  • Drinking water (main source), tea, seafood, and fluoridated toothpaste,.
• Effects of Deficiency:
  • Dental Caries: Increased susceptibility to tooth decay,.
  • Bone Health: Potential role in maintaining bone density (though excess is more clinically significant causing fluorosis).

9. Molybdenum

• Functions:
  • Enzyme Cofactor: Component of xanthine oxidase (uric acid formation) and sulfite oxidase,.
• Dietary Sources:
  • Legumes, whole grains, leafy vegetables, liver, and milk,.
• Effects of Deficiency:
  • Rare; observed in total parenteral nutrition (TPN).
  • Symptoms: Tachycardia, tachypnea, night blindness, central scotoma, irritability, and coma,.
  • Metabolic: Low uric acid levels and hypermethioninemia.

10. Cobalt

• Functions:
  • Integral component of Vitamin B12 (Cobalamin).
• Dietary Sources:
  • Meat, liver, milk, and fermented foods.
• Effects of Deficiency:
  • Manifests as Vitamin B12 deficiency: Megaloblastic anemia and neurological degeneration.

Other Trace Elements (Minor)

• Iodine: Deficiency causes goiter and cretinism.
• Nickel: Component of urease; deficiency may lead to dermatitis or liver issues.
• Silicon: Involved in collagen cross-linking; deficiency causes defective bone growth.
• Vanadium: Deficiency associated with nutritional edema and growth retardation.