Aside: I found the following visualisation fun and somewhat interesting (on supplements and the ailments they might be good for). It's changed a lot over the years and it links off to the underlying spreadsheet.
This is a nice graph (but does the X axis have a meaning?)
But the important thing there is that they're measuring their role as a supplement, however, most of them are needed (and present in a healthy diet), while some aren't
Potassium is a needed element of a diet, and as the article mentioned, there seems to be a lot of deficiency, but maybe a better understanding of deficiency/needed dose is needed.
Scroll down the page and you'll see a description.
"This image is a “balloon race”. The higher a bubble, the greater the evidence for its effectiveness. But the supplements are only effective for the conditions listed inside the bubble.
You might also see multiple bubbles for certain supps. These is because some supps affect a range of conditions, but the evidence quality varies from condition to condition. For example, there’s strong evidence that Green Tea is good for cholesterol levels. But evidence for its anti-cancer effects is conflicting. In these cases, we give a supp another bubble."
edit: Apologies, I misread your comment. The X-axis can be modified on the interactive version to sort by: alphabetically, popularity or scientific interest. The static version is alphabetical. Beyond that, it's just to help spread things out to be readable.
http://www.informationisbeautiful.net/visualizations/snake-o...