I'm not Sarah. However, you should open your eyes to ALL PREPARED FOOD, not just backpacking food.
If it is in a can, you can bet it is pretty salty.
If it is "flavored", you can bet it is pretty salty or high in Sodium.
For example, plain unflavored instant mashed potatoes have maybe 20 mg sodium. Buy some flavored instant mashed potatoes and the socium content soars to 400 to almost 800 mg per serving.
Unflavored instant rice has very low sodium, but if you get a Knorr flavored rice dish the sodium per serving jumps to 860 mg or 40% of RDA. The package contains 2.5 servings, and the typical backpacker will eat the whole thing or nearly 100% RDA.
Pasta unflavored is low sodium, but the Knorr flavored pasta in my hand has 820 mg sodium and that is nearly 40% RDA, and the backpacker who eats all 2.5 servings in a bag gets about 100% RDA right there.
If you get plain frozen vegetables with no flavoring, there is usually little sodium, but if you get that fake cheese sause or Asian seasoning, there is a giant jump to several hundred mg of sodium per serving.
Green beans in a can are horribly high in sodium. I don't have a can of that stuff for that reason, nor any cans of vegetables for similar reasons.
"On Food and Cooking" by Harold McGee discusses this at length. There are several reasons for putting sodium in prepared foods - mostly for the benefit of the manufacturer or to make it tasty or texturally or visually appealing for the consumer.