Salt intake is an interesting topic. Similar to what we think about fat in diets, what we know about salt is evolving, but the public health guidelines are often lagging behind. In the US, the dietary guidelines still only have an upper limit (2.3 g sodium, corresponding to 5 g salt). This is suggested for
everyone, regardless of blood pressure. No lower limit is given. The guidelines are based on the effect of salt on hypertension, and the negative health effects of hypertension. If you study entire populations, high salt intake is linked to high blood pressure, and poor health outcomes.
There are two problems with the current guidelines:
- they ignore individual variation to how we react to salt (see figure below)
- they do not provide a recommended or minimum intake, but not getting enough salt is also bad for your health
The individual sensitivity to salt is something we are really just starting to understand. Here is a figure from a recent clinical study that shows very large individual variation:

(Picture from the GenSalt study,
www.ncbi.nlm.nih.gov/pmc/articles/PMC8192427/).
So there is the small (blue) group (about 20% in this study) where blood pressure increases a lot when eating more salt. But for about half of the people (yellow), the reaction is
a lot smaller. For a third group (red), the effect of salt is actually reversed: more salt
reduces blood pressure. In a population study, all these people get grouped together, and the larger effect of the "high sensitivity" group dominates. But for about half of all people, the guideline makes little sense, and for some people (the "sodium resistance" group), it may even be wrong.
The lack of a recommended or minimum intake is another problem. Our body needs sodium to function (and more so when we sweat due to physical activity, as MarkSSC pointed out). Simple guidelines like "salt is bad - eat less of it / avoid it" will have some people cut down their consumption drastically. They are based and overly simplistic assumptions, like a linear relation between salt intake and blood pressure. Multiple studies have shown a J (or V)- shaped relation, though: too little salt will also raise blood pressure, and have negative health effects.
The relation between salt intake and inflammation is even fuzzier than that. When I dug into that, the only studies that people were referring to where cell cultures and animal studies, which showed that inflammation markers are higher if you bath the cells in salt, or feed animals a high-salt diet. I'll need to see if I can find more studies, though.