Only vegans need be concerned about too little sodium, since all animal products contain sodium. Everyone else should reduce their sodium intake as much as possible. Each person reacts differently to excess sodium, but generally high sodium levels increase blood volume and constrict capillary size. Hypertension (high blood pressure) develops over decades and usually only rears its head late in life. The 30-year old marathoner drinking several coffees a day and consuming several grams of sodium per day is subtracting years from her or his life expectancy.
p.s. Table salt is sodium chloride. Foods contain sodium in many forms. Sodium is the culprit. For example, milk and bread are high in sodium.
I don’t think the proof is there. In fact, the opposite may be true for most people.
Cardiovascular risk: Low salt diets may be worse
http://www.sciencedaily.com/releases/2008/05/080515171020.htm
There are a small number of people who are truly salt sensitive and should consume less salt. For the vast majority, it does not help and may be harmful.