The American label1 says "sodium", it does not say "salt". Surprising accuracy, but it really is just that one half of the salt molecule that counts and that is counted! It's really just the sodium. Only Na and not NaCl.
What It Is
The words “salt” and “sodium” are often used interchangeably, but they do not mean the same thing. Sodium is a mineral and one of the chemical elements found in salt. Salt (also known by its chemical name, sodium chloride) is a crystal-like compound that is abundant in nature and is used to flavor and preserve food.
FDA: factsheets: Sodium.pdf
"Salts" are also different from NaCl alone (e.g. KNO3 for meats) and very common sources from the industry include Sodium nitrate, Sodium citrate, Monosodium glutamate [MSG], Sodium benzoate, Baking powder, Baking soda.
To quickly estimate the salt equivalent of label-Na: 1g Na ~> 2.5g NaCl
This should result for the example, "a 20 fluid ounce bottle of Coke currently says that it has 75mg of 'Sodium' in it."
This means 75mg of sodium ions Na+ and this equals roughly 187,5mg of the dissolved table salt molecule NaCl.
Although a cola typically contains no salt at all according to the official Coca Cola website UK: Salt=0g, or 4mg/100g according to the USDA and usually very few sodium from other sources (example OpenCola, v2009: Sodium Citrate, Sodium Benzoate).
To quote from Reading Labels (worldactiononsalt):
- Foods high in salt have more than 1.5g salt / 100g (or 0.6g sodium / 100g)
- Foods low in salt have less than 0.3g salt /100g (or 0.1g sodium / 100g)
Calculating the salt content of food
Some food labels may only state the sodium content.
To convert sodium to salt, you need to multiply the amount by 2.5.
For example, 1g of sodium per 100g = 2.5 grams of salt per 100g
You then need to know the weight of the serving portion in grams e.g. 30g
Then divide the concentration of salt per 100g by 100 and multiply by the serving size.
e.g. Kellogg’s Rice Krispies contain 0.65g of sodium per 100g and 1 bowl (serving) is 30g;
0.65g sodium per 100g x 2.5 = 1.6g salt per 100g
1.6 ÷ 100 = 0.01 salt per 1g of Rice Krispies
0.1 x 30 = 0.3g salt per 30g serving
The maximum recommended intake for the day for a child aged 3 is 2g. Therefore, 1 bowl of the breakfast cereal contains around one-sixth (15%) of the recommended intake for the whole day.
Further information can be found at What Sodium Labels Mean: A Guide to Decoding Sodium Labels.
Many people think of salt and sodium as being the same thing, but they aren’t. Sodium is a mineral that occurs throughout nature in more than 80 forms. It is the sixth most abundant naturally occurring element on the planet, and it is essential to many of life’s functions. In the human body, in particular, sodium is crucial in maintaining the intricate balance of fluids in and around the body’s cells, and we can’t live without it.
Ninety percent of the sodium we eat comes in the form of salt. Salt is a naturally occurring compound that consists of 40 percent sodium and 60 percent chloride.
Source: American Heart Association: "Eat Less Salt", Clarkson Potter: New York, 2013.
1: Alas, the EU seems to go backward on this and proscribes now again on labels to use "salt" instead of "sodium". (Natrium-Kennzeichnung)