MINERALS

MINERALS

1. Definition of Minerals

  • Minerals are defined as inorganic elements occurring in nature.

  • They are termed inorganic because they do not originate from animal or plant life but are derived from the earth’s crust.

  • Although minerals constitute a small portion of body tissues, they are essential for growth and normal functioning of the body.

  • The body synthesizes most of its needs from energy foods and amino acids in proteins, but cannot produce vitamins and minerals.

  • Functions of minerals include:

    • Acting as co-factors in enzyme-catalyzed reactions

    • Regulating acid-base balance

    • Facilitating nerve conduction

    • Contributing to muscle irritability

    • Serving as structural elements in the body

2. Classification of Minerals

  • Nutritionally, minerals are classified into two groups:

    • Major Minerals (Macrominerals)

    • Required in amounts greater than 100 mg per day.

    • Examples include Calcium, Sodium, Chloride, Potassium, Phosphorus, Magnesium, and Sulphur.

    • Trace Minerals (Microminerals)

    • Required in amounts less than 100 mg per day.

    • Examples include Iron, Zinc, Selenium, Iodine, Fluoride, Copper, Manganese, Molybdenum, and Chromium.

3. Major Minerals

3.1 Calcium

  • Most abundant mineral in the body.

  • Total body Calcium (Ca²⁺) is approximately 1-1.5 kg, with 99% found in bone and 1% in Extracellular Fluid (ECF).

  • Majority of body calcium is present as Calcium phosphate (CaPO₄) crystals, which contribute to the structural integrity of bones and teeth.

  • Calcium exists as both:

    • Unbound ionic form (Ca²⁺), which is essential for:

    • Muscle contraction

    • Blood coagulation

    • Enzyme action

    • Nerve impulse transmission

    • Ion transport

  • Factors influencing calcium absorption:

    • Increased by Vitamin D, Parathyroid Hormone (PTH), an acidic environment, and amino acids (lysine and arginine).

    • Decreased by phytate, oxalates, malabsorption syndromes, and phosphate.

  • Sources of Calcium:

    • Milk

    • Egg

    • Fish

    • Green leafy vegetables

    • Bones

    • Cereals

3.2 Functions of Calcium

  • Bone and teeth formation, including dentin and enamel.

  • Essential for blood clotting as required for prothrombin activation.

  • Regulates capillary wall permeability and ion transport across membranes.

  • Aids in contraction of the heart and skeletal muscles.

  • Acts as a cofactor for enzymes such as pancreatic lipase.

3.3 Deficiency of Calcium

  • Similar clinical presentation as Vitamin D deficiency.

  • Hypocalcemia: Serum Ca²⁺ level below 8.8 mg/dl; Hypercalcemia: Above 11 mg/dl.

  • In children, deficiency leads to rickets due to inadequate calcification of growing bones.

  • In adults, causes osteomalacia and may contribute to osteoporosis.

  • Decreased extracellular calcium increases nerve irritability, causing tetany and convulsions.

3.4 Toxicity of Calcium

  • Symptoms arise from hypervitaminosis D or hypercalcemia caused by hyperparathyroidism.

  • Excess calcium can depress cardiac activity, potentially leading to respiratory or cardiac failure.

3.5 Phosphorus (P)

  • Total body phosphate approximately 1 kg; 80% in bone and teeth, 10% in muscles.

  • Phosphate is essential in all cells and primarily intracellular.

  • Normal blood phosphate level is 40 mg/dl.

  • Sources of Phosphorus:

    • Phosphate food additives

    • Green leafy vegetables

    • Fruits, especially bananas.

3.6 Functions of Phosphorus

  • Synthesis of high-energy phosphate compounds (e.g., ATP, CTP, GTP).

  • DNA and RNA synthesis, with phosphodiester linkages forming the backbone.

  • Activates enzymes via phosphorylation (e.g., glycogen phosphorylation).

  • Maintains blood pH via phosphate buffer system (Na₂HPO₄/NaH₂PO₄).

  • Bone and teeth formation.

  • Assists in synthesizing phospholipids and phosphoproteins.

  • Involved in forming nucleoside co-enzymes (e.g., NAD and NADP).

3.7 Deficiency of Phosphorus

  • Hypophosphatemia: Low serum phosphorus; Hyperphosphatemia: High serum phosphorus.

  • Inverse relationship with calcium: Excess Ca²⁺ induces excretion of phosphate.

  • Deficiency can cause bone diseases like rickets and osteomalacia.

  • May lead to muscle weakness, bone pain, and increased infection susceptibility.

3.8 Toxicity of Phosphorus

  • Rare but possible; low toxicity.

  • Hyperphosphatemia associated with low parathyroid hormone (hypoparathyroidism).

  • Toxic symptoms include low serum Ca²⁺: P ratio.

3.9 Magnesium (Mg)

  • Distributed widely within tissues; total body magnesium around 25 g, 60% complexed with Ca²⁺ in bone.

  • Normal serum level 1.8-2.2 mg/dl.

  • Functions of Magnesium:

    • Works alongside calcium and phosphorus in energy-producing enzyme reactions.

    • Protects arterial linings and contributes to bone formation.

    • Co-factor for enzymes, particularly kinases.

    • May prevent calcium oxalate kidney stones with Vitamin B6.

    • Lowers neuromuscular irritability during transmissions.

    • Enhances insulin-dependent glucose uptake and improves glucose tolerance.

3.10 Sources of Magnesium

  • Cereals, beans, leafy vegetables, and fish; daily requirement about 400 mg for men and 300 mg for women. Increased demand during lactation.

3.11 Deficiency of Magnesium

  • Hypomagnesemia: Low serum Mg²⁺ below 1.7 mg/dl.

  • Common causes: vomiting, diarrhea, liver cirrhosis, diuretics, alcoholism.

  • Symptoms include tremors and cardiac arrhythmias.

3.12 Toxicity of Magnesium

  • Hypermagnesemia is rare, typically due to excessive intake.

  • Symptoms include neuromuscular depression, lethargy, hypotension, and respiratory depression.

3.13 Sodium (Na⁺)

  • Principal cation in extracellular fluids.

  • Functions of Sodium:

    • Regulates plasma volume and acid-base balance.

    • Maintains osmotic pressure and ion permeability.

    • Essential for muscle and nerve function; involved in Na⁺/K⁺-ATPase activities.

3.14 Sources of Sodium

  • Table salt, added food salt, and most natural foods.

3.15 Deficiency of Sodium

  • Hyponatremia: Low serum sodium associated with conditions like Addison’s disease, vomiting, diarrhea, etc.

  • Symptoms include dehydration, hypotension, confusion, and tremors.

3.16 Toxicity of Sodium

  • Hypernatremia: Increased serum sodium, associated with conditions like Cushing’s disease and after sweating.

  • Excess sodium intake linked to hypertension and cardiovascular disease.

3.17 Potassium (K⁺)

  • Major intracellular cation, crucial for maintaining osmotic pressure.

  • Normal plasma level 3.5-5.5 mmol/L; primarily excreted through urine.

  • Functions of Potassium:

    • Vital for heart depolarization and contraction.

    • Regulates osmotic pressure and cell membrane functions.

  • Sources of Potassium:

    • Bananas, oranges, apples, pineapples, almonds, beans, yams, potatoes.

3.18 Deficiency of Potassium

  • Hypokalemia: Plasma levels below 3 mmol/L, often linked to sodium deficiency and dehydration.

  • Symptoms: muscle weakness, fatigue, muscle cramps, and hypotension.

3.19 Toxicity of Potassium

  • Hyperkalemia: Serum potassium over 5.5 mmol/L, seen in conditions such as Addison’s disease.

  • Symptoms can include heart expansion or cardiac arrest.

3.20 Chlorine (Cl⁻)

  • Principal anion in extracellular fluid, important for regulating osmotic pressure.

  • Chief anion of gastric juice, aiding in digestion.

3.21 Sources of Chlorine

  • Table salt and drinking water.

3.22 Deficiency of Chlorine

  • Results from salt-free diet or loss through vomiting or renal disease.

4. Trace Minerals

4.1 Iron

  • Integral to hemoglobin (Hb), myoglobin (Mb), cytochrome components, and enzymes like catalase.

  • Sources of Iron:

    • Organ meats, fish, poultry, eggs, beans, dark green vegetables.

4.2 Functions of Iron

  • Oxygen transport in Hb and Mb.

  • Involvement in oxidative phosphorylation and neurotransmitter synthesis.

4.3 Deficiency of Iron

  • Leads to iron deficiency anemia.

  • Higher requirements for menstruating women and during blood loss.

4.4 Toxicity of Iron

  • Iron overload from hereditary hemochromatosis or transfusional overload.

  • Symptoms include gastrointestinal injury, cellular metabolism impairment, and potential cell death.

4.5 Iodine (I₂)

  • Absorbed efficiently; stored in the thyroid for thyroid hormone synthesis (T3 and T4).

  • Sources of Iodine:

    • Sea foods, salt, water, fish, crabs.

4.6 Functions of Iodine

  • Essential for normal thyroid function and growth regulation.

4.7 Deficiency of Iodine

  • Causes hypothyroidism, goiter, and developmental brain impairments.

4.8 Toxicity of Iodine

  • Acute poisoning can damage the gastrointestinal tract.

4.9 Zinc (Zn²⁺)

  • Present in grains, beans, nuts, dairy, meats, and shellfish.

  • Functions of Zinc:

    • Plays roles in cell protection, immune function, protein synthesis, and digestive actions.

4.10 Deficiency of Zinc

  • Increased losses in burns or renal diseases.

  • Symptoms: growth retardation, skin lesions, impaired immunity.

4.11 Copper (Cu)

  • Component of enzymes and proteins involved in antioxidant activity.

  • Sources of Copper:

    • Organ meats, shellfish, legumes, nuts.

4.12 Functions of Copper

  • Copper is essential for enzyme activity and the formation of connective tissues and bones.

4.13 Deficiency of Copper

  • Leads to anemia, bone fragility, heart failure, and growth issues.

4.14 Toxicity of Copper

  • Excess can impair liver function and cause jaundice.

4.15 Selenium

  • Component of selenoproteins; acts as an antioxidant.

  • Sources of Selenium:

    • Organ meats, fish, shellfish, cereals.

4.16 Deficiency of Selenium

  • May result in heart disease (Keshan disease) and other systemic symptoms.

5. Antioxidant Minerals

  • Antioxidant minerals (e.g., Copper, Zinc, Selenium) are essential for combating oxidative stress and damage from free radicals.

  • Antioxidants stabilize reactive free radicals, preventing cellular damage and supporting immune function.

  • Free Radicals: Atoms or molecules with unpaired electrons that seek to stabilize by borrowing from other atoms, causing chain reactions.

  • Relevant diseases linked to oxidative stress include cancer, neurodegenerative diseases, and aging.

6. Mineral Requirements

  • Daily mineral requirements vary; adequate intake ensures health and prevention of deficiency diseases.

  • Table 41.2 outlines the major dietary sources and functions of minerals.

7. Conclusion

  • Minerals are crucial for numerous biological functions, and both deficiency and excess can have severe health implications.