Minerals are inorganic nutrients that are vital for numerous physiological functions. They are categorized based on the quantity required by the body: macrominerals (needed in larger amounts) and microminerals (trace minerals) (needed in smaller amounts).
General Functions of Minerals
- Some participate with enzymes in metabolic processes (cofactors).
- Some have structural functions (Ca, P in bone; S in keratin).
- Acid-base and water balance (Na, K, Cl).
- Nerve & muscle function (Ca, Na, K).
- Unique functions (e.g., heme, B12, thyroid hormones).
Classification of Minerals
- Macrominerals: Required in amounts greater than 100 mg per day.
- Calcium (Ca)
- Phosphorus (P)
- Magnesium (Mg)
- Sodium (Na)
- Potassium (K)
- Chloride (Cl)
- Microminerals (Trace Minerals): Required in amounts less than 100 mg daily.
- Iron (Fe)
- Zinc (Zn)
- Copper (Cu)
- Manganese (Mn)
- Selenium (Se)
- Iodine (I)
Macrominerals
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Calcium (Ca)
- Functions:
- Bone Health: Approximately 99% of the body’s calcium is stored in bones and teeth, providing structure and strength.
- Muscle Function: Facilitates muscle contraction by interacting with proteins in muscle cells.
- Nerve Transmission: Calcium ions are involved in neurotransmitter release and signal transmission between nerves.
- Blood Clotting: Participates in the cascade of reactions that lead to blood coagulation.
- Food Sources:
- Dairy products (milk, cheese, yogurt), leafy greens (collard greens, kale), fish with bones (sardines, salmon), nuts (almonds), seeds (chia, sesame), and fortified foods (orange juice, tofu).
- Absorption:
- Dietary calcium is absorbed from the small intestine and the unabsorbed calcium is excreted in stool.
- Factors affecting calcium absorption:
- Vitamin D: 25-dihydroxy cholecalciferol helps the absorption of calcium and phosphorus from the intestine.
- Parathyroid hormone: Parathyroid hormone helps the absorption of calcium and phosphate from the intestine, probably by converting vitamin D into its active form (1,25- dihydroxy cholecalciferol).
- Solubility of Calcium: Calcium absorption is reduced by factors that decrease its solubility in the intestine. These include:
- High pH as it occurs in
- Excess oxalate, phosphate and phytate, which occur in some vegetables and
- Excess unabsorbed fatty acids occur in pancreatitis, obstructive jaundice, sprue and celiac disease.
- Deficiency Symptoms:
- Osteoporosis: Reduced bone density, increasing fracture risk.
- Rickets: In children, characterized by softening and deformity of bones.
- Hypocalcemia: Symptoms include muscle cramps, numbness, and convulsions.
- Recommended Daily Intake:
- Adults: 1,000 mg; Women over 50 & Men over 70: 1,200 mg.
- Bioavailability:
- Age, vitamin D levels, and phytates (in grains) and oxalates (in spinach) can influence calcium absorption.
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Phosphorus (P)
- Functions:
- Bone and Teeth Formation: Works with calcium to form hydroxyapatite, the mineral complex that strengthens bones.
- Energy Production: Part of ATP (adenosine triphosphate) is essential for cellular energy transfer.
- DNA and RNA Synthesis: Integral for forming nucleotides, the building blocks of DNA and RNA.
- It helps in the regulation of the acid/base balance in the
- It plays a central role in the formation & utilization of high-energy phosphate compounds (ATP, GTP).
- It is required to form phospholipids, phosphoproteins & nucleic acids(DNA &RNA).
- It is an essential component of several nucleotide coenzymes- NAD, NADP, PLP, ADP, and AMP.
- Food Sources:
- Meat (chicken, turkey, beef), fish (salmon), dairy products, nuts, seeds, legumes (lentils, chickpeas), and whole grains.
- Deficiency Symptoms:
- Weakness, bone pain, loss of appetite, impaired growth and development in children, and bone disorders.
- Recommended Daily Intake:
- Adults: 700 mg.
- Bioavailability:
- Phosphorus from animal sources is more bioavailable than from plant sources due to phytates in plants.
- Clinical significance
Hyperphosphataemia Causes:
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- Renal failure
- Hypoparathyroidism
- Pseudohypoparathyroidism
- Acromegaly
- Excessive phosphate intake/ administration
- Vit D intoxication
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Complication
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- It results in the inhibition of the 1-hydroxylation of 25-hydroxycholecalciferol in the kidneys;
- Hypocalcemia →Phosphate combines with calcium, resulting in metastatic calcium deposits in the tissues
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Management
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- Treat the underlying cause but, in practice
- Calcium or aluminium salts by mouth to bind phosphate in gut and reduce its absorption.
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Hypophosphataemia
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- Diabetic ketoacidosis
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(during the recovery phase there is increased uptake of phosphate into depleted tissues)
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- Renal loss
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Primary parahyperthyroidism Renal tubular disease Diuretics
Hypophosphatemic rickets
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- Decreased intake/absorption of Dietary
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Malabsorption Vomiting
Management
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- It is treated by the administration of phosphate, either enterally or parenterally, as appropriate
- Intravenous phosphate should not be given to a hypercalcaemic or oliguria patient.
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Magnesium (Mg)
- Functions:
- Cofactor for Enzymes: Involved in over 300 enzymatic reactions, including those related to ATP production.
- Muscle and Nerve Function: Regulates neuromuscular transmission and muscle contraction.
- Bone Structure: About 60% of the body’s magnesium is stored in bones.
- Food Sources:
- Nuts (almonds, cashews), seeds (pumpkin, sunflower), whole grains (brown rice, oats), legumes, leafy greens (spinach, Swiss chard), and dark chocolate.
- Deficiency Symptoms:
- Muscle cramps, fatigue, weakness, nausea, and increased heart disease risk.
- Recommended Daily Intake:
- Adult Men: 400–420 mg; Adult Women: 310–320 mg.
- Bioavailability:
- Magnesium absorption can be inhibited by high-fiber diets and excessive calcium intake. Alcohol and caffeine can also affect absorption.
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Sodium (Na)
- Functions:
- Fluid Balance: Regulates extracellular fluid volume and osmotic pressure.
- Nerve Impulses: Essential for generating and transmitting electrical impulses in nerves and muscles.
- Food Sources:
- Table salt (sodium chloride), processed foods (canned soups, snack foods), soy sauce, and salted meats.
- Deficiency Symptoms:
- Rare but can lead to hyponatremia, characterized by headache, confusion, seizures, and muscle cramps, especially in athletes.
- Recommended Daily Intake:
- Less than 2,300 mg; the ideal limit for most adults is around 1,500 mg.
- Excess Intake:
- High sodium intake can lead to hypertension (high blood pressure) and cardiovascular disease.
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Potassium (K)
- Functions:
- Fluid Balance: Helps maintain intracellular fluid balance and blood pressure regulation.
- Nerve and Muscle Function: Essential for normal functioning of muscles and nerves, including heart rhythm.
- Food Sources:
- Fruits (bananas, oranges), vegetables (potatoes, spinach, tomatoes), legumes, dairy products, and nuts.
- Deficiency Symptoms:
- Weakness, fatigue, muscle cramps, irregular heartbeat, and increased risk of hypertension.
- Recommended Daily Intake:
- Adults: 2,500–3,000 mg.
- Bioavailability:
- Potassium from fruits and vegetables is generally well absorbed; however, cooking can reduce potassium content in some foods.
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Chloride (Cl)
- Functions:
- Fluid Balance: Works with sodium to maintain the body’s osmotic balance and fluid distribution.
- Stomach Acid: Component of hydrochloric acid (HCl), essential for digestion.
- Food Sources:
- Table salt, seaweed, tomatoes, olives, and lettuce.
- Deficiency Symptoms:
- Rare but can result in disturbances in acid-base balance, muscle cramps, and digestive issues.
- Recommended Daily Intake:
- Adults: 2,300 mg.
Microminerals (Trace Minerals)
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Iron (Fe)
- Functions:
- Hemoglobin Formation: Essential for oxygen transport in red blood cells.
- Enzymatic Reactions: Involved in various enzyme systems for energy production and DNA synthesis.
- Food Sources:
- Heme iron sources: Red meat, poultry, fish.
- Non-heme iron sources: Lentils, beans, fortified cereals, spinach.
- Deficiency Symptoms:
- Iron-deficiency anaemia: Symptoms include fatigue, weakness, pale skin, and cognitive impairments.
- Recommended Daily Intake:
- Adult Men: 8 mg; Adult Women: 18 mg (higher during pregnancy).
- Bioavailability:
- Heme iron (from animal sources) is absorbed more efficiently than non-heme iron (from plant sources). Vitamin C enhances the absorption of non-heme iron.
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Zinc (Zn)
- Functions:
- Immune Function: Essential for the development and function of immune cells.
- Protein Synthesis and Wound Healing: Plays a critical role in cellular repair and growth.
- Food Sources:
- Meat (beef, pork), shellfish (oysters), legumes, seeds (pumpkin, sesame), nuts, and whole grains.
- Deficiency Symptoms:
- Impaired immune response, hair loss, diarrhoea, delayed wound healing, and taste abnormalities.
- Recommended Daily Intake:
- Adult Men: 11 mg; Adult Women: 8 mg.
- Bioavailability:
- The presence of phytates in plant foods can inhibit zinc absorption.
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Copper (Cu)
- Functions:
- Iron Metabolism: Necessary for the incorporation of iron into haemoglobin.
- Antioxidant Defense: Part of the enzyme superoxide dismutase, which protects cells from oxidative damage.
- Food Sources:
- Shellfish (oysters), seeds (sunflower), nuts (cashews), whole grains, and organ meats (liver).
- Deficiency Symptoms:
- Anaemia, bone abnormalities, cardiovascular problems, and increased infection susceptibility.
- Recommended Daily Intake:
- Adults: 900 mcg.
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Manganese (Mn)
- Functions:
- Bone Formation: Involved in the formation of bone and connective tissues.
- Antioxidant Function: Plays a role in the defence against oxidative stress.
- Food Sources:
- Whole grains, nuts, leafy vegetables, teas, and legumes.
- Deficiency Symptoms:
- Rare but can result in bone malformation, poor wound healing, and reproductive issues.
- Recommended Daily Intake:
- Adult Men: 2.3 mg; Adult Women: 1.8 mg.
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Selenium (Se)
- Functions:
- Antioxidant Protection: Works as a part of selenoproteins, which help prevent cellular damage from free radicals.
- Thyroid Hormone Metabolism: Important for the proper function of thyroid hormones.
- Food Sources:
- Brazil nuts, seafood (tuna, shrimp), meats, whole grains, and dairy products.
- Deficiency Symptoms:
- Fatigue weakens immune function and increases the risk of certain diseases (e.g., Keshan disease, which affects the heart).
- Recommended Daily Intake:
- Adults: 55 mcg.
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Iodine (I)
- Functions:
- Thyroid Hormones: Essential for synthesising thyroxine (T4) and triiodothyronine (T3), which regulate metabolism, growth, and development.
- Food Sources:
- Iodized salt, seafood (fish, seaweed), dairy products, and pieces of bread.
- Deficiency Symptoms:
- Goiter (enlarged thyroid gland), hypothyroidism (fatigue, weight gain), and developmental delays in children.
- Recommended Daily Intake:
- Adults: 150 mcg.
General Functions of Minerals
- Structural Components: Minerals provide structural support in bones, teeth, and soft tissues.
- Electrolyte Balance: Help maintain fluids, electrolytes, and acid-base balance homeostasis.
- Cofactors for Enzymes: Act as essential components for various enzymes, influencing metabolic pathways.
- Hormonal Regulation: Some minerals are integral for hormone production, affecting growth, metabolism, and other functions.
- Immune System Support: Many minerals (like zinc and selenium) are crucial for proper immune function.