Dietary Magnesium and Asthma
Reprinted from Medical Sciences Bulletin , February 1995, published by
Pharmaceutical
Information Associates, Ltd.
See also: Magnesium
Magnesium is fourth on the list of the most abundant cations in the body
(following calcium,
sodium, and potassium), and it is second only to potassium as the most abundant
intracellular
cation. It is an essential cofactor in more than 300 different enzymatic
reactions, including
carbohydrate utilization, ATP metabolism, muscle contraction, transmembrane ion
transport
(calcium, sodium, chloride, potassium), and the synthesis of fat, protein, and
nucleic acids.
Magnesium also appears to play an important role in lung function. In a large
study of adults
selected randomly from the general population, Britton et al. found that high
dietary magnesium
intake was independently associated with better lung function and less asthma
and wheezing.
The investigators calculated dietary magnesium intake (by food frequency
questionnaire) and
evaluated lung function and atopy in 2633 volunteers aged 18 to 70 years. Lung
function was
measured as one-second forced-expiratory volume (FEV1) and by airway reactivity
to inhaled
methacholine. Atopy was measured as skin-prick response to three environmental
allergens.
Subjects described their respiratory symptoms and gave social, medical,
occupational, and
smoking histories.
Mean magnesium intake was 380 mg/day, although intake varied widely and was
significantly
lower in females than males. Intake also decreased significantly with increasing
age. After
adjusting for age, sex, height, and the effects of atopy and smoking, the
investigators found that a
100 mg/day higher magnesium intake was associated with a significantly higher
FEV1 and a
reduction in lung hyperreactivity. Magnesium has several antiasthmatic actions:
as a calcium
antagonist it relaxes airway smooth muscle (in vitro) and dilates bronchioles
(in vivo). It also
inhibits cholinergic transmission, increases nitric oxide release, and reduces
airway inflammation
(by stabilizing mast cells and T- lymphocytes). The investigators concluded,
"Low magnesium
intake may therefore be involved in the etiology of asthma and chronic
obstructive airways
disease."
Dietary magnesium is obtained from cereals, nuts, green vegetables, and dairy
products. However,
according to Britton et al., a substantial amount is lost in cooking or in
refining foods. Diets
high in
refined or processed foods are thus likely to be low in magnesium. Magnesium
deficiency is
surprisingly common. In one study, hypomagnesemia was found in 65% of an
intensive care
population and 11% of an outpatient population. Magnesium is used
pharmacologically in acute
myocardial infarction, angina, cardiac arrhythmias, alcohol withdrawal, and
pre-eclampsia. It has
been used to treat acute asthma, and now it appears that magnesium may also help
prevent
asthma. (Britton J et al. Lancet. 1994; 344: 357-361. McLean RM. Am J Med. 1994;
96: 63-76.)
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