If I'm not mistaken, MREs have a higher caloric intake as well, and presumably in a survival situation you may not even be eating more than one meal a day. Plus these are designed for military use where a human body is under a great deal of stress and daily activity. So that soldier is burning a lot more calories than I am sitting on my can in front of my computer. They are also, presumably, drinking a lot of water and sweating. So the sodium intake is to put back what they are losing. They probably also need potassium and some other electrolytes.

6000mg of sodium might seem like a lot, but your average American diet probably takes well over the 2400mg anyway. A Super-size fries is about 400mg and a King-size BK fries is like 1100! A QuarterPounder with Chees is 1150. A McD's Chicken Selects 5pc has 1500mg and a deluxe breakfast has nearly 2000.

So don't go slamming MREs... they were designed for a specific purpose. Forward deployed troops without access to a mess hall are typically burning more calories and sweating out salt. The same might be true in a survival situation.

One thing I do know... if all I have to eat are MREs, I'm not going to care how much salt I'm eating as long as I have plenty of water. It might concern those with HBP, but meds should help with that as would eliminating as much of the salt as you can before eating and drinking plenty of water.

By the way, nuts and peanuts are really high quality sources of emergeny calories. Efficient, delivering good fat, protein and carbos (both complex and simple sugar) and in a good ratio (higher fats and about even protein and carbs. As long as you have a mix/blend, you should also get decent mix of vitamins and minerals.

Edit: By the way, I'm just saying that MREs have their place, and someone reading that they have a lot of salt may skip over them as an option without more information. :-) I really didn't mean this as any sort of directed flame or anything.