Which mineral is a trace mineral (needed in less than 100 mg/day)?

• A. Calcium
• B. Sodium
• C. Iron
• D. Potassium

Answer: (C)

Think about how minerals are classified by daily need. Trace minerals are required in small amounts, typically less than 100 mg per day, while major minerals require more than 100 mg per day. Iron fits the trace mineral category because the daily need for adults is about 8–18 mg depending on sex and life stage, well below 100 mg. Iron is essential for making hemoglobin in red blood cells, which carries oxygen throughout the body, and it also supports energy metabolism. Calcium is a major mineral, with needs around 1000 mg per day for most adults, important for bone health and other functions. Sodium and potassium are electrolytes needed in relatively large amounts to regulate fluid balance and nerve signaling, with intakes in the grams per day range. So iron is the trace mineral among these options.