DIET
Intake of magnesium
Average; around 300 mg/day? But may be over-estimated.
Recent studies indicate that intake in several countries (Germany, UK, Newfoundland, Japan) may be as low as half this.
Sources: approximately equal contributions from
- vegetables
- fruits
- grains
- animal products
- dairy products
- (drinking water)
Dietary Supplement Fact Sheet: Magnesium
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Absorption of magnesium
The fraction of magnesium in the diet that is absorbed is greatest at lowest levels of intake. Thus it can vary from 25% (high magnesium diet) to 75% (low magnesium diet). The uptake process is saturable. Absorption occurs in all parts of the intestine. High zinc intake depresses magnesium absorption. High magnesium intake may lead to decreased calcium uptake.
Recommended intake
US (RDA)
- Infants (0-6 months) 30 mg/day
- Children (4-8) 130 mg/day
- Adults (18+) male ~400 mg/day
- Adults (18+) female ~300 mg/day
Nordic countries
- 350 (men)
Upper limit - 250 (EU), 350 (US) – but this refers to Mg as readily soluble salt (i.e. in medicinal preparations).
Hypermagnesiumemia and toxicity
At twice normal blood concentration, vascular smooth muscle relaxes (in vitro); blood pressure drops (in humans).
Magnesium sulphate is given parenterally (intravenously) to prevent preeclampsia and eclampsia (caused by severe hypertension).
Normal blood levels - ~0.9 mM. With increasing concentration, blood pressure falls; nausea, vomiting (1.5-4.5 mM); mental state changes; ECG changes (2-10 mM)… cardiac arrest.
However, 'There is no evidence of adverse effects from the consumption of naturally occurring magnesium in foods.'