See this extremely interesting information: World Action on Salt and Health (WASH)
Look at this amazing quotation from the website:
"It was calculated that a modest reduction in salt intake from 10g to 5g would have the same effect on hip bone density as an increase in calcium intake of 1000mg, a difficult amount to achieve without resorting to supplements."
"Diuretics, through a reduction in extra cellular volume, reduce calcium excretion leading to a positive calcium balance, increase bone density and reduce bone fractures."
Don't forget to make sure you have enough vitamin D too, because you need vitamin D to metabolise the calcium.
You may be interested to read my Mensa article on Obesity and the Salt Connection