The research, published in Bone, examined whether there is a correlation between magnesium and calcium concentrations in drinking water and the incidence of hip fracture - finding that magnesium may protect against hip fracture for both men and women. However, the researchers found no independent protective effect of calcium.
Led by Cecilie Dahl from the Norwegian Institute of Public Health, the team noted that there are considerable variations in the quality of drinking water in Norway, which led them to study variations in magnesium and calcium levels in drinking water between different areas as these are assumed to have a role in the development of bone strength.
"The protective effect of magnesium was unsurprising but the correlation between calcium and magnesium in water and hip fracture was complex and somewhat unexpected," explained Dahl. "Therefore more research is needed to get a more reliable result of the relationship between drinking water and hip fractures and to get a better picture of the biological mechanism in the body."
Indeed, she suggested that the results can probably help to understand why there are so many hip fractures in Norway, suggesting that it is conceivable that enriching drinking water with magnesium may reduce the number of hip fractures.
"Perhaps water utility companies should use dolomite in addition, or as an alternative, to lime," commented Dahl. "Dolomite contains both magnesium and calcium, while lime contains only calcium carbonate."
The Norwegian team created a registry of all hip fractures in Norway, in addition to a map showing the coverage of the various water utility companies in Norway - this made it possible to determine which water utility company is most likely to supply each area in Norway.
Dahl and her colleagues used geographical information systems to do this, using data from a variety of sources that were linked together to create a compilation of fractures in areas with the highest and lowest areas of calcium and magnesium.
After following approximately 700,000 men and women over seven years, and registering close to 5,500 hip fractures among men and 13,600 hip fractures for women in this period the team analysed whether concentration of calcium and magnesium in drinking water was related to fracture incidence.
"An inverse association was found between concentration of magnesium and risk of hip fracture in both genders ... but no consistent association between calcium and hip fracture risk was observed," they revealed.
However, because intake of calcium and vitamin D in Norway is already high, Dahl and her colleagues noted that the lack of statistical effect from calcium in drinking water in the study could be due to an already sufficient intake from the diet, "making it unlikely that the low amount of calcium from water would make any difference."
Based on their results, the team concluded that improving the mineral status of drinking water through supplementation with magnesium may be 'a currently unexploited possibility of improving the mineral status', however they conceded that further research is clearly needed before introducing such a measure.
Volume 57, Issue 1, Pages 84–91, doi: 10.1016/j.bone.2013.06.017
"Nationwide data on municipal drinking water and hip fracture: Could calcium and magnesium be protective? A NOREPOS study"
Authors: Cecilie Dahl, Anne Johanne Søgaard, et al