Magnesium is the quiet one. There's usually no clear day-to-day signal when you're running low, so it sits in the background with nothing obvious pointing to it.
It's a workhorse mineral, used in hundreds of processes from muscle and nerve function to steady energy. When intake stays low over time, that's been associated with muscle cramps, low mood, and disrupted sleep. And low intake isn't rare, with research on global dietary intake estimating around 31% of people fall short.
Adults usually need about 400 mg a day for men and 310 mg for women, mostly from food: nuts, seeds, dark leafy greens, legumes, and whole grains are all solid sources. One nuance: the 350 mg upper limit applies only to magnesium from supplements taken on top of your food, since concentrated doses can upset the gut. What you get from meals isn't capped the same way.