Minerals in the Body (Note 6 Nov 2024) PDF

3. Minerals of the body  Minerals represent about up to 5 % of body weight: 1. 50 % of this weigh is calcium. 2. 25 % of this weight is phosphorus. 3. the remaining 25 % is made up of: Magnesium, sodium, potassium, chloride, sulfur, iron, zinc, iodide, sel...

3. Minerals of the body  Minerals represent about up to 5 % of body weight: 1. 50 % of this weigh is calcium. 2. 25 % of this weight is phosphorus. 3. the remaining 25 % is made up of: Magnesium, sodium, potassium, chloride, sulfur, iron, zinc, iodide, selenium, manganese, fluoride, molybdenum, copper, chromium and cobalt.  In general, minerals exist in the body in two forms: a. Charged ions which are either anions (chloride, sulfur and phosphorus) or cations (sodium, potassium and calcium). b. Components of organic compounds such as phosphor-proteins, 48 phosphor-lipids, metallo-proteins (hemoglobin) and metallo-enzymes.  3. Minerals Calcium  Calcium is the most abundant mineral in the body, where 99 % of calcium exists in bones and teeth and 1 % is in blood, extracellular fluids and intracellularly in all tissues.  Bone is the dynamic tissue that returns calcium and phosphorus to the extracellular fluids and blood on demand. Also, bone takes up calcium and phosphorus from the blood after the dietary intake.  In late life, bone retention of dietary consumed calcium is limited, unless consumed along with sufficient amounts of vitamin D or bone- conserving drug. 49  3. Minerals Calcium  Functions of calcium: 1. adequate consumption of calcium is required for the optimal gain of bone mass and density in the period of sexual maturation and adolescent years. a. This is important for young women as to provide additional protection against osteoporosis in years after menopause. b. Postmenopausal women also require sufficient amounts of calcium to maintain bone health. 2. Additional calcium is required during pregnancy and lactation. 3. Calcium is also involved in the transport functions of cell membranes, release of neurotransmitters, the function of hormones as well as release and activation of extra- and intracellular enzymes. 50  3. Minerals Calcium 4. The proper balance of calcium, sodium, potassium and magnesium ions, maintains heart muscle function and nerve irritability (the ability to act in response to a stimulus). 5. Calcium initiates the formation of blood clot and it serves as a cofactor for the several enzymatic reactions involved in blood coagulation, such as the conversion of prothrombin to thrombin. 51  3. Minerals Calcium  Deficiency of calcium: Osteomalacia, osteoporosis, tetany, paresthesia, foot cramp, muscle aching, spasm of facial musculature, dementia, depression and psychosis.  Toxicity of calcium: 1. A very high intake of calcium combined with high intake of vitamin D, associated with hyper-calcemia, which leads to calcification in soft tissues specially kidneys (may be life threatening). 2. High calcium intake may also leads to increased bone fractures in elderly (could be due to high bone remodeling rates, a process where old bone is removed and new bone is added, which in turns could exhausts the osteoblasts). 3. High calcium intake reduces absorption of other divalent cations such as zinc, iron and manganese. 4. Constipation is common in older women who take calcium supplements. 52  3. Minerals Phosphorus  About 85 % of phosphorus is present in the bones and teeth as calcium phosphate crystals (hydroxyapetite(Ca5(PO4)3OH), where apatite is a group of phosphate minerals, a major inorganic molecule in teeth and bones).  The remaining 15 % exists in cells and in extracellular fluids.  Functions of phosphorus: 1. Phosphate serves as a structural component of various essential compounds such as: DNA and RNA, ATP and phospholipids. 2. Activation and deactivation of cytosolic enzymes by kinases or phosphatases (i.e. phosphorylation and de-phosphorylation). 3. The phosphate buffer system is important in the intracellular fluid and in the kidney tubules. 53  3. Minerals Phosphorus  Deficiency of phosphorus: Because phosphorus is widely available in food, phosphate deficiency is rare, however it could develop in individuals who are taking phosphate binder drugs. Patients with chronic renal failure cannot get rid of phosphate, thus their serum level of phosphate is high. Phosphate binders such as calcium carbonate are a group of medications which are taken to reduce the absorption of the dietary consumed phosphate from the GI tract to the blood, as to reduce the elevated levels of phosphate in the serum of these patients. 54  3. Minerals Phosphorus  Toxicity of phosphorus: Chronic consumption of a low-calcium, high-phosphorus diet, result is increased secretion of parathyroid hormone (PTH) in the blood (as to re-balance both minerals in the blood). This increase in PTH concentration leads to increased bone turnover or remodeling, which in turn results in a reduction in bone mass and density. If this condition is chronic, it could lead to fragility fractures. 55  3. Minerals Iron  The adult human body contains iron in two major pools: 1. Functional iron; homoglobin, myoglobin and enzymes. 2. Storage iron; ferritin (blood protein that stores and transfer iron in controlled fashion), transferrin (a glycoprotein that transfers iron in the blood) and hemosiderin (an iron storage complex exists in cells).  Functions of iron: The function of iron is related to its ability to participate in oxidation-reduction reactions (Fe2+  Fe3+): 1. Iron has a role in blood and respiratory transport of oxygen and carbon dioxide. 2. Iron is an active component of the cytochromes involved in cellular respiration and ATP production. 3. Iron is involved in immunity and cognitive (mental processes) performance. 56  3. Minerals Iron  Deficiency of iron: Anemia, is the most of all nutritional deficiency diseases. The final stage of iron deficiency is hypochromic (red blood cells are paler than normal), microcytic (smaller red blood cells) anemia.  Toxicity of iron: 1. The major cause of iron overload is hereditary hemochromatosis, where iron overload is linked to a distinct gene that exceed the iron absorption from diet. 2. Frequent blood transfusion (in individuals suffer from sickle cell disease or thalassemia) and long-term ingestions of large amounts of iron could lead to accumulation of iron in the liver. 57  3. Minerals Iron 3. Saturation of tissues with iron leads to the formation of insoluble hemosiderin. Hemosiderosis, is a condition of large accumulation of iron in the tissue, and if associated with tissue damage, it is called Hemochromatosis. 4. Due to the redox potential of iron , it may contributed to diseases of cardiovascular system (due to enrichment of the oxidative environment) and to cancer (due to generation of excessive amounts of free radicals that attach cellular molecules). 58  3. Minerals Magnesium  About 60 % of magnesium is found in bones, 26 % is in the muscle, whereas the remaining is in the soft tissues and body fluids.  Magnesium homeostasis is regulated by the intestinal absorption and renal excretion, where no hormone is involve in such serum homeostasis as in calcium and phosphate.  Functions of magnesium: 1. The major function of magnesium is the stabilization of ATP structure and ATP-dependent enzyme reactions. 2. It serves as a cofactor for more than 300 enzymes involved in the metabolism and the synthetic processes. 3. Magnesium is important in the formation of c-AMP, the “second messenger” 59 that is formed in the response to hormones and other hormone-like molecules.  3. Minerals Magnesium 4. magnesium plays a role in neuromuscular transmission in combination with calcium, in which calcium stimulates muscle contraction and magnesium relaxes the muscle.  Deficiency of magnesium: Although it is rare, however sever magnesium deficiency symptoms include tremors, muscle spasms, personality changes, anorexia, nausea, vomiting.  Toxicity of magnesium: 1. Excess consumption of magnesium is unlikely to result in toxicity, and it can inhibit bone calcification. 2. Magnesium toxicity was only reported in smelter workers (a place to refine gold and metals) who inhaled toxic levels of magnesium. 60  3. Minerals Sulfur  Sulfur exists in the body as a constituent of two amino acids, and different organic molecules.  Functions of Sulfur: 1. The tertiary structure of proteins is due to the disulfide bridge (-S-S-) between two cysteine residues, which is required for the activities of enzymes and hormones. 2. Iron-sulfur clusters present in electron transfer proteins are required for oxidative phosphorylation (a life sustaining process). 3. Cysteine constitutes one of the amino acids of the triple amino acid- containing protein, glutathione (Glu-Cys-Gly), which acts in the reduction of hydrogen peroxides (i.e. sulfur can act as an antioxidant). 61  3. Minerals Sulfur 4. Sulfur is a component of both of heparin in the liver (anticoagulant), and chondroitin sulfate in bone and cartilage. 5. Sulfur is an essential component of two vitamins.  Deficiency and toxicity of sulfur: Sulfur deficiency and toxicity are highly unlikely. 62  3. Minerals Iodine  75 % of iodine exist in the thyroid gland and the rest is distributed in lactating mammary gland, gastric mucosa and blood.  Function of iodine: 1. Iodine is stored in the thyroid gland, where it is used in the synthesis of triiodothyronine (T4) and thyroxine (T3) (thyroid hormones). 2. The uptake of iodide ions by the thyroid cells could be inhibited by Goitrogens (substances that present naturally in food, some chemicals, drugs and minerals).  Deficiency of iodine: 1. Very low iodine intakes is associated with the development of goiter (an enlargement of the thyroid gland, and a shortened height). Fortunately, goitrogens containing foods such as cabbage, turnip, peanuts, sweet potatoes, kelp and soybeans are inactivated by cooking. 63  3. Minerals Iodine 2. Sever iodine deficiency during the period of pregnancy and after child birth results in infants cretinism, a syndrome characterized by mental retardation. Toxicity of iodine: In general, high iodine intake has a wide safety margins. 64  3. Minerals  Potassium: A predominant intracellular cation.  Sodium: A predominant extracellular cation.  Chlorine: A predominant extracellular anion. All above minerals are required for ion balance and nerve function. (phosphate is the predominant intracellular anion) 65