Cutting down salt intake will help to ameliorate fluid retention. When humans go from a low to a high salt intake, there is retention of sodium and thereby water and this expands the extra cellular volume. This increase in extra cellular volume is a trigger for various compensatory mechanisms to allow an increase in urinary sodium excretion but at the expense of continued retention of sodium and water. Approximately 1.5 litres of extra cellular fluid is retained and this continues as long as a higher salt intake is consumed. Patients already with heart failure, nephrotic syndrome and cirrhosis of the liver, will particularly benefit in a cut in salt intake. Many women with idiopathic and cyclical oedema also find, by reducing their salt intake, considerable improvement in their symptoms.
Fluid retention can occur on long journeys, particularly aircraft journeys, when sitting for long periods of time without exercise. This can cause fluid to build up in the legs and ankles. Reducing salt in the diet can help to alleviate this.