Magnesium

Magnesium Atomic No. 12 Atomic mass: 24

Magnesium (Mg) Mg assures the strength and firmness of bones and makes teeth harder. As Mg participates in many biochemical reactions, it's no surprise that it is essential for healthy bones and teeth. Also Mg is essential for absorption and metabolism of calcium.

FUNCTIONS Mg is an essential cofactor in 80% of all cellular enzymes. It is necessary for the conversion of Vitamin D into its active form and a deficiency of Mg can lead to a syndrome known as vitamin D resistance. The enzyme that is required for forming new Ca crystals, alkaline phosphatase, also requires Mg for activation, and if levels are low, abnormal bone crystal formation can result. Even mild Mg deficiency is reported to be a leading risk factor for osteoporosis.

FUNCTIONS Mg has a role to play, together with the thyroid and parathyroid glands, in supporting bone health. It stimulates the thyroid’s production of calcitonin, and regulates parathyroid hormone.

FUNCTIONS Mg is a cofactor in more than 300 enzyme systems that regulate diverse biochemical reactions in the body, including ; Protein synthesis Muscle and nerve function Blood glucose/ control, and Blood pressure regulation.

FUNCTIONS Mg is required for; Energy production Oxidative phosphorylation, and Glycolysis Structural development of bone Is required for the synthesis of DNA, RNA, and Antioxidant glutathione

FUNCTIONS Mg also plays a role in the active transport of Ca and K ions across cell membranes, a process that is important : Nerve impulse conduction Muscle contraction and Normal heart rhythm

FUNCTIONS Mg is cofactor of hundreds of enzymes involved in lipid and nucleic acid synthesis. Mg stabilizes cell membranes. It also antagonizes calcium and functions as a signal transducer . It is therefore believed that alterations in Mg homeostasis has an impact on cell and tissue functions.

FUNCTIONS Like Ca much of the body’s reserves of Mg are held in the bone (60%), and the bones act as a storage reservoir, releasing Mg into the blood when needed. Adequate daily intake of Mg is important throughout life to keep the Mg that is stored in the bones from being lost. Low Mg intake, as well as low blood and bone Mg levels, has been widely associated with osteoporosis in women.

Sources Mg is an abundant mineral in the body. It is naturally present in many foods. Available as a dietary supplement, and Also present in some medicines (such as antacids and laxatives).

Generally we ignore the fact that Mg and Ca function together and deficiency of one affects the metabolism of the other. In fact, increasing Ca supplementation without increasing Mg can actually increase Mg loss. Similarly, the use of Ca supplements in the face of a Mg deficiency can lead to Ca deposition in the soft tissues, such as the joints. Where it can promote arthritis or In the kidney, contribute to kidney stones.

Magnesium and the Bone: Molecular Insights About 60% of total Mg is stored in the bone. One third of skeletal Mg resides on cortical bone either on the surface of hydroxyapatite or in the hydration shell around the crystal . It serves as a reservoir of exchangeable Mg ,required to maintain ECF conc. of the cation .

Bone surface Mg levels are related to serum Mg Bone surface Mg levels are related to serum Mg. Accordingly, surface bone Mg increases with Mg loading The larger fraction of bone Mg is probably deposited as an integral part of the apatite crystal and its release follows the re-sorption of bone.

Apart from a structural role in the crystals, Mg is essential to all living cells, including osteoblasts and osteoclasts. Mg is vital for numerous physiological Intracellular functions. Mg is fundamental for ATP, the main source of energy in the cells.

Magnesium Mg is one of three major minerals in human body 4th most abundant 20 – 35 grams is total body content Lowest in amount of the three major mineral

DISTRIBUTION Serum level is 1.5 – 2.5 mEqt/L 60 – 70% is complex with calcium and phosphorous in bones Remainder is present in the body fluids and concentrated Within cells. Mg : calcium( within cells) is about 3 : 1 Whole blood contains about twice as much Mg as in serum,as is concentrated in RBCs 2% of the body’s Mg is in ECF Serum level is 1.5 – 2.5 mEqt/L

DISTRIBUTION (Contd.) 80% is ionized and diffusible 20% bound to proteins Muscles contain more Mg than Ca++. (As is required as activator for many of phosphate group transfer enzymes)

REVIST OF Functions Essential element because is catalyst for numerous biologic reactions It helps maintain the electrical potential in: Nerves for the transmission of nerve impulses Muscle membrane for the muscle contraction 3. Involved in active transport across cell membrane 4. Inhibits ATP ase Activity

Functions (Contd.) Its salts are irritant to intestine, used as purgative while its hydroxide are used as antiacids. CNS depressant and lowers neuro - muscular irritability 7.In Kidney insufficiency, level in blood increases, Increased level have adverse effect on cardiac muscle

Dietary deficiency is rare Dietary Sources Widely distributed in foods Richest sources include Nuts Sea foods Whole grain Dried beans Peas Green leafy vegetables Dietary deficiency is rare

Recommended Dietary Allowances Infants 0 – 0.5 50 mg 0.5 – 1.0 70 mg Children 1 – 3 150 mg 4 – 6 200 mg 7 – 10 250 mg

Recommended Dietary Allowances (Contd.) Adults Male Female 11 – 14 350 300 15 – 18 400 300 19 – 22 350 300 23 – 50 350 300 51+ 350 300 Pregnancy and Lactation + 150 mg

Absorption and Metabolism 40 – 45% of dietary Mg++ absorbed from an average diet With High Mg++ diet the %age of absorption falls Low Mg++ diet the %age of absorption increase Absorption occurs mostly in small intestine

Absorption and Metabolism (Contd.) Ca++ and Mg++ competes for absorption sites in the intestinal mucosa,  intake of one  requirement for other Mg++ and K+ are conc. inside the cells. Any change in balance produces neuromuscular irritability

Absorption and Metabolism Many of the Factors affecting Ca++ affects Mg++ Excess fat phosphates oxalic acid and phytic acid

Control and excretion Body Mg++ level and pool is mainly controlled by kidney Filtered out of the blood by glomeruli Reabsorbed by renal tubules Unabsorbed is Excreted in feces

HYPOMAGNESEMIA Increased loss - Diabetic ketoacidosis Diuretic therapy Hyper aldosteronism Assoc. with hypercalcaemia Renal Mg wasting

Clinical Manifestation Deficiency or imbalance develops slowly due to persistent poor dietary intake or increased excretion. Mg++ slowly mobilized from bone. b. Low plasma level is associated with imbalance in ECF, leading to altered electrical potential of nerve and muscle cells. Deficiency: Leads to neuromuscular dysfunction.

Clinical Manifestation (Contd.) Mg++ deficiency causes muscular hyper excitability ,Tremors and convulsion. d. Behavioral disturbances are some time seen e. symptoms similar to Hypo calcaemic tetany are seen which can be differentiated by determining blood level of Ca++ & Mg++

Mg++ deficiency can occur with Cirrhosis liver Malnutrition Mal-absorption, Diarrhea, Laxatives Impaired intake Impaired absorption Chronic alcoholism

Hypermagnesemia. severe dehydration Aldosterone deficiency With decrease in urinary excretion, plasma level is raised ------ Hypermagnesemia. Chronic renal disease severe dehydration Aldosterone deficiency oral intake of MgSo4 for constipation (specially with impaired renal functions). .

Reference values serum / plasma: 1.5 – 2.5 meqt/L 0.65 – 1.05 mmoles/litre CSF: up to 3.0 meqt/L Muscles: up to 20 meqt/L RBCs: 5.4 – 7.8 mg /dl (5 meqt/L)