Salt affects the kidneys

Salt affects your kidneys which makes your body to contain more water. This excess water increases blood pressure and increases the burden on your kidneys, arteries, heart and brain
Your kidneys use osmosis to extract additional water from the blood. This process uses a delicate balance of sodium and potassium to pull water through the cell wall from the bloodstream to the collection channel that leads to the bladder. Salt consumption increases the amount of sodium in the blood and destroys the balance, reducing the ability of your kidneys to remove water.
The result is high blood pressure due to extra fluid and tension on the thin blood vessels leading to the kidneys. In course of time this additional stress can and does reduce their ability to filter out unwanted and toxic waste that begins to accumulate in the body.
Approximately 80% of the salt that we eat is in food products, such as bread, biscuits, cereals and take away meals. Our body receives only 20% of salt that we add while preparing food or eating. To exclude it is worth to throw out the salt shaker.
Links:
Blood pressure UK