What is the Deal with Sodium?

The other day I had a really great question from a friend, she asked me "why is salt so bad for you?" I informed her that over the long term, high salt intake can promote our bodies to hold onto a greater amount of fluid. If our bodies are carrying more fluid, this can increase blood pressure, and then this high blood pressure over time can damage blood vessels and lead to heart disease. However, I had a feeling this explanation didn't quench her need for a more detailed explanation, so here we go!
We normally need 1500-2300mg of sodium/day. Foods such as deli meats, canned soups, sauces, cheese, pickles, pizza, and fried foods can have up to or more than 1000mg of sodium per serving~the equivalent of more than half of our sodium needs for the entire day!
The kidneys in our body function to filter our blood, remove toxins, and remove excess fluid. By the process of osmosis and a balance between sodium and potassium, extra water is drawn out of our blood and removed as urine. If we have a long-term diet high in sodium, this can increase the sodium levels in our blood. In response, to keep our sodium in balance our bodies attempt to dilute this high salt, hold on to fluid, and make it more difficult for the kidneys to draw water out of the bloodstream. This extra fluid in the bloodstream can increase blood pressure and can cause extra strain on the vessels of the kidneys. Over time, high blood pressure can permanently damage the kidneys and lead to kidney failure. In later stages of kidney failure, toxins and fluids build up and cannot be removed by the body; this build up can poison the body and external removal through dialysis may be needed.
High blood pressure also strains arteries. In response to the pressure, artery walls can become thicker and  harder which can make the space inside the artery even smaller (picture a garden hose that gets thicker and more rigid over time). High pressured blood flowing through a tight restricted space, can further increase blood pressure. Over time the pressure can cause arteries to burst or become clogged, limiting blood flow and oxygen to the heart, brain, and other parts of the body. This limited blood flow can result in heart attack, dementia, and/or stroke, where parts of our heart and brain die due to the lack of oxygen from blood.
I normally don't go into such physiological detail, and in no way am trying use physiology as a scare tactic, but the easiest thing you can do to protect your kidneys, arteries, heart and brain is to become more aware of your daily salt intake and consider alternative, lower sodium options.

For low sodium food ideas take a peek at the detailed Edmonton Southside PCN Low Sodium Brochure

Information Sources:
http://www.mayoclinic.com/health/sodium/NU00284
http://www.bloodpressureuk.org/microsites/salt/Home/Whysaltisbad/Saltseffects
http://www.cdc.gov/salt/