Magnesium
Guidelines
Unit of measurement
mg/l
World Health Organisation Standards (1993)
No guideline
Standards for private water supplies in England (2016)
Not mentioned
Standards for private water supplies in Scotland (2006)
Not mentioned
Standards for private water supplies in Wales (2017)
Not mentioned
European Union Drinking Water Directive (1998)
No guideline

Magnesium

Magnesium is the ninth most abundant element in the universe and makes up 13% of the Earth's mass. It makes up a large fraction of the planet's mantle and after sodium and chlorine, it is the third most copious element dissolved in seawater.

As a mineral, it is an important contributor to the proper growth and maintenance of bones in the human body. It is also essential for the correct functioning of nerves, muscles and the stomach as well as other body parts. Much of the magnesium we ingest comes from food sources, and particularly, those that are high in fibre such as whole grains, vegetables, seeds and nuts.

Magnesium and Calcium are largely responsible for hard water as a result of water percolating through limestone, chalk and gypsum stones. Whilst hard water is said to have moderate health benefits, especially as a dietary supplement for calcium and magnesium, it can cause a multitude of problems for appliances that use water as it is responsible for limescale build-up. It can also cause soaps and detergents to be less effective and produce a lack of foam, leading to increased cleaning and laundry costs.

The NHS recommends that men aged 19-64 should intake 300mg of magnesium a day and that women aged 19-64 should intake 270mg. Taking higher doses of magnesium (more than 400mg) in the short term can cause diarrhoea but there is currently not enough evidence to show what the effects of long-term high doses are.

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