The Salt Claims on the Front of the Box
Low sodium, no salt added and lightly salted are three regulated phrases with three different meanings, and none of them is the meaning most people read into it. What each one is required to mean, and what changes in the pan.
Why I stopped reading the front of the box
The dish that sent me into this was a lentil soup. I cooked the smoked paprika lentil soup twice in one week with everything the same except the stock: one carton marked low sodium, one marked no salt added, same shelf, same size. The two pots were not small variations on each other. One was seasoned the moment the lentils went soft; the other wanted a good pinch and then another one. Turning the cartons around, the panels said 140 milligrams a cup and 15 milligrams a cup. Two phrases on two fronts, and neither told me the thing that changed the pot.
That is the reason for this page. The phrases are not marketing invention. Each has a definition written into federal food-labeling rule, each is enforceable, and no manufacturer prints one at will. What they do not do is mean what a person standing in an aisle takes them to mean. They mean something narrower, and the narrow version is where the cooking difference hides.
Low sodium is a number, and the number is 140
The sodium phrases live in Title 21 of the Code of Federal Regulations, section 101.61. It is short, it is free to read, and the definitions are arithmetic rather than opinion:
- Sodium free — less than 5 milligrams per reference amount.
- Very low sodium — 35 milligrams or less.
- Low sodium — 140 milligrams or less.
- Reduced sodium — at least 25 percent less than an appropriate reference food.
Two words in that list carry more weight than all the others: reference amount. The regulation does not measure against the portion anybody actually eats. It measures against a reference amount customarily consumed, which is a figure set in the rules for each category of food and is the same for every brand in that category. That makes brands comparable, which is the point of it. It is a poor way to shop, because the reference amount and the serving in front of you are frequently not the same.
A carton of stock is the clean example. Low sodium is judged against a cup. A pot of soup for four takes six cups. The carton is honestly labeled and the pan still receives well over 800 milligrams before a single other ingredient goes in. The definition was not written against the thing I was doing with it.
No salt added is a statement about the factory
This one describes a step that did not happen. No salt was put in during processing. It says nothing at all about the sodium the ingredients brought with them, and some ingredients bring a great deal: celery, tomato, cheese, anything cultured, anything brined earlier in its life. A no-salt-added product can sit well above a low-sodium one and both labels are correct.
The rule anticipates exactly this confusion. Where a no-salt-added food is not itself sodium free, the label has to carry a line on the information panel saying so in plain language. It is on the back, in small type, among everything else on the back. That the regulation requires the sentence is a good indication of how often the front of the box is read as meaning something stronger.
In a kitchen it is still the most useful of the three phrases, and not because of the number. It is useful because it hands the seasoning decision back to the cook. A stock with nothing added can be reduced hard without turning into a salt lick, and a reduction is where most of the flavour in a pan sauce comes from. A low-sodium stock reduced by half is no longer a low-sodium anything.
Lightly salted is half of a number nobody shows you
Lightly salted means 50 percent less sodium than is normally added to that reference food. Half of usual. The label never states what usual was, which is the whole trouble with it: the claim is a ratio with the denominator left off the package.
Half of a lightly seasoned food is a very low number. Half of a heavily salted snack is a moderately salted snack, sold with a phrase that reads like restraint. Both uses are legitimate and they land in different places. The rule also requires that if the food is not low sodium, the panel has to say so. Again on the back.
At the stove it matters because lightly salted nuts, butter and crackers get folded into other dishes as though they were neutral. They are a seasoning decision somebody else made, at a level nobody stated, landing on top of whatever you add.
Where the salt in a week of eating actually comes from
This is the measurement that changed how I cook, and it has nothing to do with labels. Harnack and colleagues, in Circulation, 2017, DOI 10.1161/CIRCULATIONAHA.116.024446, recruited 450 adults across three places — Birmingham, Palo Alto, and Minneapolis and St. Paul — and traced sodium back to where it entered the food rather than simply totalling it up.
The split came out like this. Sodium added to food outside the home, which means commercial processing and restaurant kitchens, accounted for 70.9 percent of the total. Sodium naturally present in the food itself accounted for 14.2 percent. Salt added while cooking at home came to 5.6 percent. Salt added at the table came to 4.9 percent.
The salt cellar and the stove together came to about a tenth. The cartons, jars, breads, sauces and restaurant plates came to seven tenths.
Read that next to the way salt usually gets discussed and something is off. Almost every conversation about cutting back is a conversation about the shaker, which is the smallest piece on the board. The largest piece arrives already decided, inside things that mostly do not taste salty: bread, cottage cheese, salami, stock, tortillas, anything from a jar.
What that does to a plate
The practical consequence is narrow and it is worth stating exactly. If the bases are bought already salted, the cook is seasoning on top of a level they did not set and cannot taste separately. If the bases are bought unsalted, the cook sets the whole level at the end of cooking, with a spoon in hand, and can stop when it tastes right.
That is the same argument this site makes about everything, which is that a preparation written down in full beats a preparation half decided by somebody upstream. It is also the argument behind the method notes in our walkthrough page, In the Test Kitchen: season late, taste, write the amount down, and cook it again the same way to find out whether the amount was right or the day was.
Four changes did nearly all of the work here, and none of them involves eating anything different:
- Stock and canned beans bought with no salt added, then seasoned in the pan.
- Bread and cheese treated as seasoning rather than as neutral ingredients, because by weight they often are.
- Condiments measured with a spoon once, so I know what a normal pour is worth.
- Salt added at the end of a reduction, since the pan concentrates whatever was in there.
What the feeding trials measured, and what they did not
The reference trial here is Sacks and colleagues in the New England Journal of Medicine, 2001, DOI 10.1056/NEJM200101043440101, generally called DASH-Sodium. Participants were fed at three sodium levels, on two eating patterns, with the food supplied to them rather than chosen by them, and blood pressure was measured at each level.
What that design can tell you is precise and limited: what happened to a group average when the sodium in a supplied diet was moved and most other things were held still. What it cannot tell you is what happens to one person shopping in a real store, cooking food they picked, in a week that also held a bad night and a restaurant meal. The trial never claimed to answer that. Pages citing it usually do.
The test here is the one the claims review pages on this site apply: has somebody measured the thing being asserted, in people, under conditions resembling the assertion? On the labeling rules, yes, in the regulation itself. On where sodium enters the diet, yes, and Harnack is the measurement. On what a front-of-box phrase does to a shopper in an aisle, no. Nobody has run that study.
Taste moves, and it moves slowly
One more finding, because it explains why the first week of cooking this way is unpleasant and the sixth is not. Bertino, Beauchamp and Engelman, American Journal of Clinical Nutrition, 1982, volume 36, pages 1134 to 1144, DOI 10.1093/ajcn/36.6.1134, followed people through a long stretch of reduced dietary sodium and tested what salt tasted like along the way. The perception shifted, and foods carrying the old amount came to read as too salty.
The kitchen translation is a matter of timing. Judging a change in seasoning after two days is judging the adjustment period. The verdict that means anything comes a month later, by which point the reference has moved — which is exactly why the notes are worth keeping.
What we still don’t know
- Nobody has measured what these three phrases do to an actual shopper in an actual aisle: which one gets chosen, how the portion changes afterwards, and whether the front of the box changes what goes on the plate at all.
- Reference amounts were set against eating patterns from an earlier period. How far the reference cup and the poured cup have drifted apart, category by category, we found measured nowhere.
- Harnack is 450 people in three metropolitan areas, the best-built sample of its kind we could find and still three metropolitan areas. Whether the split holds in a rural county is open.
- We did not test whether my two soups differed for the reason I think they did. One cook, one week is an anecdote and is written here as one.
- Nothing on this page says what any amount of sodium does to any particular person. That question is not a kitchen question, and this is a kitchen site.
If a study exists that closes any of those gaps, send it and this page gets rewritten. The address is at the foot of every page, and the review date under the headline moves when a correction lands. That process is described on the About page.
General information about food and kitchen equipment, which is what this site publishes. Not medical advice, and no replacement for asking somebody qualified who knows the rest of the picture. Nothing here is a reason to begin, stop or alter a prescription.