Minerals in the Human Body

Minerals in the Human Body

• Minerals are essential nutrients, crucial for various bodily functions. Numerous minerals (Ca, Mg, Co, K, Si, Cr, Zn, Mo, Na, Mn, Se, Cu, P, I, Fe, S) are required in varying amounts.

Average Amounts of Minerals in Adults

• Charts show average amounts of various minerals in the adult human body.
  • This data ranges from grams for major minerals like calcium (1200g) to milligrams for trace minerals like manganese (12-20mg).

Calcium

• Calcium is the most abundant mineral in the body.
• Approximately 99% of body calcium is stored in bones and teeth.
• The remaining 1% is distributed in intracellular and extracellular fluids, and found in its ionic form in body fluids.

Calcium Sources

• The best calcium sources include dairy products (milk, yogurt, cheese) and certain sea foods (salmon, sardines with bones).
• Vegetables like broccoli and cauliflower are also good sources.
• Fortified foods and calcium supplements provide additional sources.

Calcium Absorption

• Calcium is primarily present in ionic form, and also in protein and insoluble salts (like calcium carbonate and calcium citrate)
• Some calcium is released from these salts at acidic pH (similar to that of the stomach) before absorption.
• Stomach acid assists in calcium release to improve absorption.
• Solubilization does not automatically lead to better absorption. Free calcium can bind, reducing bioavailability.
• Absorption occurs mostly in the small intestine, via two primary mechanisms:
  • Active transport (transcellular): occurs in the duodenum and jejunum, needs energy (ATP) and involves calcium-binding proteins (CBP), stimulated by calcitriol (active vitamin D).
  • Passive transport (paracellular): occurs in the jejunum and ileum, does not require energy; more effective with higher calcium intake.

Factors Affecting Calcium Absorption

• Growth, pregnancy, and lactation: Significantly increase calcium requirements and improve absorption. Growing children absorb up to 75% of dietary calcium while adults have an average of around 30% absorption.
• Calcitriol (vitamin D3): Aids in synthesis of calcium-binding transport protein, essential for transporting calcium into cells; thus improving calcium absorption. Decreased renal calcitriol occurs with age, reducing absorption.
• Vitamin D synthesis: UV light from the sun assists in production of vitamin D in the skin. Dietary vitamin D from sources like fatty fish, meat, supplements, is processed further through liver and kidney to become physiologically active calcitriol.
• Dietary factors:
  • Lactose intake enhances calcium absorption (increases solubility).
  • Protein intake aids calcium absorption.
  • Phytate (contained in some fibers) inhibits calcium absorption. Calcium and phytate ratio greater than 0.2:1 decreases availability
  • High fiber intake may also bind calcium, reducing absorption.
  • Oxalate chelates calcium, lowering solubility and increasing fecal calcium excretion.
• Excess magnesium: Magnesium and calcium compete for intestinal absorption, affecting absorption.
• Unabsorbed dietary fatty acids: (steatorrhea) interfere with calcium absorption, forming insoluble calcium soaps.
• Phosphorus: High levels of phosphorus reduce calcium absorption.
• Sodium and caffeine: High levels of sodium and caffeine increase urinary calcium excretion, potentially impairing calcium balance.
• Iron: Increased calcium intake decreases non-heme iron absorption.
• Lead: Reduced calcium intake increases lead absorption.
• Estrogen: Estrogen deficiency, such as at menopause, may lead to reduced vitamin D-mediated calcium absorption.

Calcium Transport

• Approximately 50% of blood calcium is free (ionized). This is the physiologically active form.
• Approximately 10% of blood calcium is bound to anions like sulfate, phosphate, or citrate; which is diffusible.
• Approximately 40% of blood calcium is bound to protein (mainly albumin), rendering it non-diffusible.

Total Calcium Distribution

• 99% of calcium exists in bones (hydroxyapatite structure).
• 1% of calcium is distributed throughout the body.

Calcium Homeostasis

• Parathyroid hormone (PTH), calcitonin, and vitamin D work together in a feedback loop to maintain calcium homeostasis. The three key organs in this process are intestine, bone, and kidneys

Regulation of Blood Calcium Levels

• Calcitriol (vitamin D): Increases absorption of calcium in intestinal mucosa.
• Vitamin D: Also acts independently on bone to increase osteoblast activity and numbers
• Parathyroid Hormone (PTH): released when calcium levels fall, which increases calcium levels by increasing calcium reabsorption in the kidneys, stimulating bone resorption (release of calcium into the bloodstream), increasing calcium absorption in the intestines.
• Calcitonin: Released when calcium rises too high in the blood. Lowers calcium levels by slowing bone resorption and promoting calcium excretion.

Functions of Calcium

• Bone mineralization and maintenance
• Muscle contraction
• Secretion of hormones (insulin, PTH, calcitonin)
• Activation of enzymes (like kinases needing calmodulin)
• Blood coagulation

Calcium Imbalances

• Hypercalcemia: Blood calcium is above 11 mg/dL, caused by hyperparathyroidism, hypervitaminosis D or hypothyroidism.
• Hypocalcemia: Blood calcium is below 8.8 mg/dL, caused by hypoparathyroidism, surgical removal of parathyroid glands, hyperthyroidism, renal failure, vitamin D deficiency, or low protein diet, If below 7.5mg/dL, tetany may result.

Calcification

• Calcium buildup in tissue, blood vessels, or organs. This hardening can disrupt normal bodily functions. Calcification can occur nearly anywhere in the body given the transport of calcium to the relevant portions through the blood stream.

Causes of Calcification

• Infections
• Calcium metabolism disorders causing hypercalcemia
• Genetic or autoimmune disorders affecting the skeletal or connective tissues
• Persistent inflammation

Calcium Deficiency

• Inadequate calcium intake
• Poor calcium absorption
• Excessive calcium losses

Calcium Deficiency Diseases

• Rickets (children)
• Osteoporosis (adults)

Calcium Relationship with Other Diseases

• Hypertension: Inverse relationship between calcium intake and blood pressure. (Lower calcium intake increases hypertension)
• Colon cancer: Calcium may decrease colon cancer risk by binding and increasing excretion of bile acids.
• Obesity: Low calcium intake associated with obesity and high body weights. High calcium intake modulates fat metabolism with decreased fat synthesis and more fat breakdown

Explore the essential minerals necessary for human health, including their average amounts in adults and specific functions. This quiz highlights the significance of calcium and its sources, as well as the roles of various trace minerals. Test your knowledge on nutrition and minerals!