Elena had always believed that supplements were harmless little helpers. When a friend told her that magnesium could improve sleep, reduce muscle discomfort, and fight tiredness, she decided to try it. At the store, she found a liquid magnesium supplement and read the front of the bottle. The instructions seemed simple: take two tablespoons daily. Elena nearly bought it immediately.

Before paying, however, she remembered something she had recently learned about supplements: the amount listed on the front might not tell the whole story. She turned the bottle around and studied the small print. Different magnesium compounds contain different amounts of elemental magnesium, and the number of spoonfuls alone could not tell her how much magnesium she would actually consume.

Then Elena noticed another warning about excessive magnesium intake. She paused, suddenly less certain. As she reached for her phone to investigate, she noticed something that made her stomach tighten…