Purified water causing magnesium deficiency?

Magnesium is an important mineral found in our body, whose impact is high. Deficiency of this mineral can cause severe damage to the body and disrupt several biological functions including the nervous system. Therefore, health agencies and experts advise to include magnesium rich foods in diet so that the body is not deprived of this essential mineral.
But, what if you have been depriving your body of this important nutrient for a long time? A study by the Taub Center, conducted by researchers from the Taub Center Research and Policy Initiative for Environment and Health in Israel has found that desalinated water lacks magnesium and this deficiency increases the prevalence of type 2 diabetes and ischemic stroke.
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“Before the desalination era, natural water provided 10%–20% of magnesium intake in Israel, but in desalinated water — now comprising the water supplied to about 70% of Israel’s households — there is no magnesium at all,” the researchers have said and have said that the extra burden of magnesium deficiency can be addressed by “adding magnesium back into desalinated water.”

What happens during desalination of water?

Desalination is the process of removing salt and other impurities from seawater or brackish water to produce fresh, potable water. The most common methods of desalination are reverse osmosis and thermal distillation.

In reverse osmosis (RO), seawater is forced through a semipermeable membrane that blocks salt and other dissolved solids but allows water molecules to pass through. High pressure is applied to overcome the natural osmotic pressure, separating freshwater from the salty brine. RO is energy-efficient compared to other methods but requires extensive maintenance of the membranes and high operational costs. Thermal distillation mimics the natural water cycle by heating the water to produce steam, which is then condensed into freshwater, leaving behind the salt and other impurities.

During desalination, minerals are removed from water alongside salts to make it suitable for drinking or industrial use. This process primarily occurs through methods like reverse osmosis or thermal distillation. In reverse osmosis, a semi-permeable membrane filters out not only salt but also minerals such as calcium, magnesium, and other dissolved solids.
A study published in 2022, in Nature journal, found that HbA1c, fasting insulin, and HOMA-IR of the group that consumed the high magnesium dose (50 mg/L) are significantly lower than those of the placebo group after three months of ingestion, indicating a significant benefit of the oral magnesium supplement added to the desalinated water in improved insulin sensitivity and long-term glycemic control.

How much magnesium should be ideally present in drinking water?

As per a 2006 study, two liters of water rich in magnesium (40 mg/l) would provide about 25% of an adult’s total requirement, and magnesium may be more bioavailable in drinking water than food.
As per another study, daily consumption of at least 1 litre of natural mineral water with a magnesium concentration of 84 mg/l reduced blood pressure significantly at 4 weeks.