There is a Choice Magazine report advocating for stoplight rating of foods, to help consumers eat more healthily. Their rating system uses units of 100g/mL (see figure 1, below). That is tenths of a kilogram per milliliter. I don’t know what they are eating, but the densest known substance at the surface of the Earth is osmium metal, with a density of about 22 g/mL, or 0.22 100g/mL.
Their “green light” value for sodium is 0.3 100g/mL, which is about 50% denser than anything on Earth. For comparison, a pure halite crystal 1 centimeter on a side (salt conveniently grows in cubes) will contain 2.16 g/cc x 0.39 g(Na)/g(total) = 0.85 g sodium. In units of 100g/ml, pure salt thus has a value of 0.0085 100g/mL.
Never-the-less, they rate almost every cereal as having an orange or red light rating.
There can be only one explanation. While osmium may be the densest material at surface pressures, at higher pressures many things can be more dense. As an example, consider a white dwarf star. A white dwarf is the burned out core of a star which has run out of hydrogen fuel and collapsed into a super dense state. Although calculating a diameter (and thus density) is not easy, they are generally thought to be about a million g/cc, or a ton/cc. On the Choice Magazine scale, that would weigh in at ten thousand 100g/cc.
Of course, white dwarfs are mostly carbon and oxygen, not sodium. But lets assume that they have a solar O/Na ratio. Using the Asplund et al. (2006) values, the solar O/Na ratio is about 300. But since white dwarves have carbon, silicon, etc. in them as well, we should really look at the ratio of everything except H and He to sodium. This is about 600 (in other words, carbon plus nitrogen plus all the heavier metals are about as abundant as oxygen).
So a white dwarf sodium content, using choice magazine units, is about 16.7 100g/mL.
Figure 1. The traffic light rating table from the choice magazine report.
That is more than ten times the 1.5 100g/mL “red light” value they suggest.
So eating degenerate matter from the cores of burned out stars is not recommended by Choice. It contains too much sodium, and might give you high blood pressure.
M. Asplund , N. Grevesse, A. J. Sauval; The solar chemical composition; Nuclear Physics A 777 1–4 (2006)