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Magnesium - Benefits, Deficiency Symptoms And Food Sources

Magnesium is the second most abundant intracellular mineral in the body; 65% of it is in the bone, 34% in the intracellular space and only 1 % in the extra cellular fluid. Its role in the body is imperfectly understood. Recent findings, however, suggest that it also has important health-promoting benefits, from an ability to prevent heart disease to a role in treating such chronic conditions as fibromylagia and diabetes.

Serum magnesium estimation is not a routine laboratory procedure; hence, disturbed magnesium metabolism is often not recognized. Chemical estimation is difficult and requires an atomic spectrophotometer. Better understanding and correction of sodium, potassium and chloride imbalance have revealed disturbances due to magnesium deficiency or excess.

Absorption

There is no physiological mechanism for magnesium absorption. The jejunum and ileum absorb about 300/0-40% of ingested magnesium. During body deficiency, about 70% is absorbed.

Benefits and functions of Magnesium

Magnesium is needed for more than 300 biochemical reactions in the body. It helps maintain normal muscle and nerve function, keeps heart rhythm steady, supports a healthy immune system, and keeps bones strong. Magnesium also helps regulate blood sugar levels, promotes normal blood pressure, and is known to be involved in energy metabolism and protein synthesis. There is an increased interest in the role of magnesium in preventing and managing disorders such as hypertension, cardiovascular disease, and diabetes. Dietary magnesium is absorbed in the small intestines. Magnesium is excreted through the kidneys.

Recommended dosage of Magnesium

The minimum Recommended Dosage Allowance of Magnesium are :-

• Adults - 300 to 350 mg.
• Children - 200 mg.

Deficiency symptoms of Magnesium

The main intracellular elements are potassium, magnesium and phosphorus; deficiencies of all three usually arise together, thus confusing the clinical picture. Low serum magnesium should be suspected in hospitalized patients who have low serum potassium, phosphate, sodium or calcium. Magnesium deficiency occurs due to the conditions listed below.

1. Deficient intake, usually with prolonged starvation and during intravenous feeding without magnesium.
2. Alimentary loss of magnesium, as in vomiting, ileostomy dysfunction, and intestinal fistulae.
3. Urinary loss of magnesium, with prolonged diuretic therapy, especially in the presence of low dietary magnesium, soft water supply, and high alcohol intake.
4. Primary hyperparathyroidism. Reabsorption of magnesium from the bone with increased urinary excretion may result in negative magnesium balance. This can be restored to normal after parathyroidectomy. However, the deposition of magnesium in the bone during the post-operative period leads to clinical manifestations due to low serum magnesium.
5. Malabsorption after massive bowel resection, in the malabsorption syndrome and regional enteritis (Crohn's disease).
6. Diabetic acidosis is associated with raised serum levels of magnesium, but with insulin therapy the serum level decreases markedly (changes similar to potassium).
7. Low serum magnesium may also be noted in toxemia of pregnancy, with excessive lactation, and in protein-calorie malnutrition.
8. Cisplastin chemotherapy for cancer.

Early signs of magnesium deficiency include loss of appetite, nausea, vomiting, fatigue, and weakness. As magnesium deficiency worsens, numbness, tingling, muscle contractions and cramps, seizures, personality changes, abnormal heart rhythms, and coronary spasms can occur. Severe magnesium deficiency can result in low levels of calcium in the blood (hypocalcemia). Magnesium deficiency is also associated with low levels of potassium in the blood (hypokalemia).

Food sources of Magnesium

Whole grain cereals, nuts, dairy products, bananas, dulse, figs, garlic, grapefruit and chlorophyll-rich vegetables like cabbage and cauliflower, are good sources of magnesium.

EXCESS

Retention of magnesium occurs when there is scanty flow of urine due to kidney disease. With scanty urine, magnesium salts-such as magnesium sulphate for purgation-should be avoided. High serum magnesium suppresses the parathyroid hormone, which may produce low serum calcium levels.

The clinical manifestations of magnesium intoxication are drowsiness, when the serum level is 8 mEq per litre (4 mmol/l), and stupor and coma, when the serum level is about 14 mEq per litre (7 mmol/l). The electrocardiogram shows increased PR and QRS duration and increased height of T waves.