A study from Norway have shown that drinking water with a relatively high level of magnesium may reduce the risk of hip fractures. On the other hand, the researchers found no independent preventive effect from the water's calcium content. Although the study was made in Norway, several issues are also relevant in other European countries.
Norway has a high incidence of hip fractures, and it is worst in the cities. The population's intake of calcium is considered to be sufficient, because the Norwegians have a high intake of dairy products. The Norwegian health authorities generally regard the magnesium intake of the population to be adequate, but recognize that it may be too low for certain groups, such as the elderly.
The main source of magnesium is the diet, but the drinking water's natural content of calcium and magnesium salts pose a low but persistent source of these two important minerals, not least because the minerals are dissolved in water and therefore has a generally high absorption in the body.
Magnesium deficiency damage the bones
Magnesium is known to directly stimulate bone formation and increase bone strength in addition to having an effect on the production of thyroid hormone and calcium metabolism. Lack of magnesium can be associated with a reduced content of vitamin D in the blood and, therefore, a reduced absorption of calcium from the intestine. In addition, magnesium deficiency shown to promote some inflammation-promoting signaling molecules called cytokines that increase the breakdown of minerals in the bones and release them into the blood. This is achieved by stimulating a special type of cells called osteoclasts that attaches to the bone tissue and secrete acid and enzymes whereby the bone tissue is broken down.
In Norway most people drink tap water. The consumption of bottled water is relatively low, as the average consumption was 18 liters a year per capita in the period 1994-2003. The problem with tap water is that the cold climate and the bedrock causes only a very low amount of calcium, magnesium and other minerals to be released into the groundwater. Therefore, the Norwegian drinking water is generally soft and acidic although there are large differences in the quality of the tap water.
Fewer hip fractures in the country
In the period 1986-1991, water from the 556 Norwegian waterworks supplying 64 % of the population with drinking water were tested for the content of trace minerals. This was compared with geographic data of hip fractures from the country's hospitals in the period 1994-2000. They showed that during this period there were 5472 men and 13604 women aged 50-85 years who had had a hip fracture. They found the highest number of hip fractures in the cities compared to rural areas. It is not clear why.
The study showed that low levels of magnesium in drinking water resulted in a high number of hip fractures. This correlation was by the way most pronounced for men. The researchers end up concluding that magnesium in drinking water may have a protective role against hip fractures but there's also a need for more studies.
Dahl C, et al . Nationwide data on municipal drinking water and hip fracture: Could calcium and magnesium be protective? A NOREPOS study. Bone 2013;57(1):84–91
It is worth noting that the study showed a higher benefit of magnesium for men than for women. Could it be that men generally eat less magnesium rich vegetables than women?