In this brilliant chart by David McCandless from 2010, you can see a gorgeous visualization of how many supplements are actually helpful — based on scientific studies — and how many are basically nothing more than snake oil.
McCandless, writing on Information is Beautiful, explains:
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.
source: Information Is Beautiful