Bernard G. Stall's research while affiliated with Brookhaven National Laboratory and other places

... We believe that our long-term balance studies fit well with our notion of Na þ storage in skin and elsewhere and are also consistent with the idea that large amounts of Na þ can be stored without parallel water accumulation, as we found no relationship between body weight, extracellular water, and salt intake. We also suggest that our findings are consistent with far earlier studies, such as those of Dahl et al., 32 who used radioactive 22 Na þ to determine total exchangeable sodium. Dahl et al. restricted Na þ to 6 mmol per day (o250 mg) and found no correlation between changes in blood pressure and total exchangeable Na þ . ...

Reference:

Spooky sodium balance

... were conducted between the months of November and March when sweat losses would be small; furthermore, the volunteers were only moderately active and did not engage inintensive athletics. The small sweat output accords with published data showing that under normal circumstances people living in Northern latitudes lose less than 10 mmol of sodium per day [9][10][11][12][13]. In hot conditions unacclimatized subjects can have sweat sodium losses which are rugher, 59-70 mmoljday [14], but only c. P Sanchez-Castillo el al. ...

Reference:

A test of the validity of the lithium-marker technique for monitoring dietary sources of salt in man