Homemade Soup & Salt/Sodium

You can use plain water, but stock will give you more flavor. There are a lot of lower sodium varieties of broths and stocks out there in cans or cartons - look for them next time you're shopping. You can also add a lot of flavor without salt with herbs and salt-free spice varieties.

Make your own stock. Just google plenty of simple Vege stock recipes (I now make mine up as I go along) I make a large batch and freeze it in Pint containers

Store Bought Stock - If you are going to buy store bought stock, I recommend Rachel Rays Chicken Low-Sodium Stock. It's got less than half of the amount of sodium of every single of thing on the shelve (including the health food section). If I am in a pinch and can't make homemade, I make that.

Homemade - Homemade stocks are the way to go. When I make a soup from scratch, I started off cooking a giant pot of water on low with beef stewers and let them cook all day. What some people don't realize is that is the key to a great soup (I deal with Italians and Croatians all the time who are VERY big into their soup.). It's an all day adventure, but you can portion it off and toss it in the freezer for soups down the road.

Vegeta - Yes, it has sodium. However, when you are just putting in a couple teaspoons of it into a giant pot of soup (at the end, which is key) it goes far!

I make all the soups in my house homemade. Let me know if you would like any recipes!

The only way to determine how much in your entire recipe would be to enter it into the "recipes" section of your food section. My low sodium veg soup base has 240 mg of sodium per 5g and the math is complicated (I hate math) but if you enter the recipe and the information properly as a recipe then MFP will give you a breakdown of sodium content etc. I have started using more of the low sodium premade stocks in the carton it is easier to see exactly how much per serving or carton but the cube itself contains that much sodium and is then put into a pot with more ingredients and distributed throughout so it's probably not as bad as you think. The package usually tells you how much water to put with the cube.

Unless you've recently increased the amount of sodium you're consuming , it's not likely that it's preventing you from losing weight. Steady state of sodium in your body = steady state of water retention (insofar as it's affected by your sodium intake).

If you do want to use stock with less sodium (and, honestly, way more taste, since salt is used to disguise the fact that the commercial stocks don't have much taste to begin with), homemade stock or broth is the way to go, as others have said. And veggie stock (which is what your OP said you were using -- I don't know if that's an always thing for you, or just for this recipe) can be made essentially for free. Just toss veggie scraps in a sealed bag or closed container in your freezer until you are ready to make a batch. I would guess I generally use about a half-cup to a cup of solids to each quart of water, but different kinds of veggies have more or less flavor, so it's hard to give a hard an fast ruleAlso, I don't find that it's an "all-day" affair, especially with veggie broth. After an hour or so, you've pretty much go all of the flavor out of the veggies, I think. Turn off the heat, let it cool (in a bath of ice water, if you're in a hurry or a stickler for food safety), strain (I just use a colander, but you can line it with cheesecloth if you want a really clear broth), portion into containers that hold about the amount you expect to use in a recipe, and freeze (or refrigerate if you will be using in the next couple of days. If something comes up to change your plans and you don't use broth after it's been in the refrigerator three days, just put in on the stove and bring it back to a boil for several minutes and store it in a clean container, although quite honestly I've probably let it go a week sometimes and I'm not dead yet.)

Pretty much everything I use is stuff that would have gone to waste otherwise: stalks of celery from an aging bunch, mushroom stems and trimmings, extra onion when I don't need a whole one and don't feel like chopping the rest to freeze for a future recipe (you don't need to chop the stuff you're going to use for stock/broth), herb stems (mostly parsley) or aging whole herbs that I'm not going to use before they go bad. I've even used more unusual things like asparagus ends and the trimmed parts of fennel, but you probably should plan on using things like that for broth that is going in recipes that will contain asparagus or fennel, etc. You can use the skins of yellow onions (probably others too, but I haven't tried them) and tomatoes to get a darker veggie broth where that's appropriate. In addition to the stuff saved in the freezer, I'll generally toss in some peppercorns and maybe bay leaves or fresh garlic, especially if I'm making it for a specific recipe that I know will want those flavors.

For non-veggie broths, freeze chicken and other poultry carcasses, ham bones, roast beef, veal, and pork bones (generally you only want to use bones from one kind of animal in any given batch) to throw in the stock pot, along with the veggies. You can buy soup bones especially for this purpose if you don't ever cook chickens, bone-in roasts, etc. If you buy raw bones, you may want to roast them before using them to make stock.