Magnesium is the fourth most abundant cation (a positively charged
ion) in the body, with 60% in the bone and 40% distributed equally between
muscle and non-muscular soft tissue. Only 1% of magnesium is extracellular.
Magnesium has an important role in at least 300 fundamental enzymatic
reactions, including the transfer of phosphate groups, the acylation of
coenzyme A in the initiation of fatty acid oxidation, and the hydrolysis
of phosphate and pyrophosphate. In addition, it functions in the
activation of
amino acids and synthesis and degradation of DNA and has a key role in
neurotransmission and immune function.
Magnesium acts as a
calcium antagonist and interacts with nutrients, such as
potassium,
vitamin B6, and
boron.
IMPORTANCE: Plays an important role in regulating
the neuromuscular activity of the heart; maintains normal heart rhythm;
necessary for proper
calcium &
Vitamin C metabolism; converts blood sugar into energy.
Deficiencies: Because the kidneys are extremely
efficient in maintaining homeostasis of magnesium, a primary deficiency in
healthy individuals is uncommon. Symptomatic deficiency is often observed
in the presence of a predisposing disease state, such as severe
malabsorption, chronic alcoholism, renal dysfunction, hyperparathyroidism,
or the use of certain medications. Clinical manifestations of deficiency
are related to its role as a cofactor in enzymatic reactions and in
regulating neurotransmitters. Hypertension, arrhythmias, neuromuscular
manifestations, and personality changes occur during deficiency.
Clinical uses: Accepted clinical uses of
magnesium include the treatment of tachycardia and electrolyte
depletion. It is also used for the management of premature labor, and for
the prophylaxis and treatment of seizures in toxemia of pregnancy and
hypomagnesemia associated with such conditions as alcoholism, Crohn's
disease and hyperthyroidism. Magnesium is an active ingredient in antacids
and laxatives.
Diet recommendations: The 1997 Dietary Reference
Intakes (DRIs) and the Tolerable Upper Limits (ULs) for magnesium from the
Food and Nutrition Board, National Academy of Sciences have been
published. The DRIs, according to age and sex, are as follows: Infants 0-6
months, 30 mg and 7-12 months, 75 mg; ages 1-3 years, 80 mg; 4-8 years,
130 mg; 9-13 years, 240 mg; males 14-18 years, 410 mg; males 19-30 years,
400 mg; males >30 years, 420 mg; females 14-18 years, 360 mg; females
19-30 years, 310 mg; and females >30 years, 320 mg. Since no adverse
effects from naturally occurring magnesium in foods have been observed,
the UL applies only to supplements and magnesium for pharmacological
purposes. The ULs are as follows: 1-3 years, 65 mg; 4-8 years, 110 mg; and
9 years and above, 350 mg.
Food sources: Good dietary sources of
magnesium include legumes, whole grain cereals, nuts, dark green
vegetables, and cocoa. Hard water and mineral water may be important
sources of magnesium.
Recent research:
Magnesium deficiency has been shown to be involved throughout the
development of atherosclerosis, including oxidation of cholesterol and
lipoproteins and calcification. As a calcium,
magnesium supplementation has been shown to exert a cardioprotective
effect. Necrotizing enterocolitis, a common cause of death in preterm
infants, may be related to magnesium deficiency. Because of its role in
neurotransmission, magnesium is being investigated in migraine headaches
and attention deficit hypersensitivity disorder. |