A diet that is low in sodium is a good idea for most people regardless of age. The body requires very little sodium, and so it's something most people would benefit from reducing.
Typically, as my doctor told me, a low sodium diet is around 2000mg of sodium a day. Normal intake should be around 2400mg of sodium. Everybody eats way more sodium than they should.
A low glycemic diet helps control the amount of carbohydrates and their effect on blood sugar levels. This is important because blooed sugar can be dangerous.