Which statement best describes the role of iodine in nutrition?

• A. It supports thyroid hormone production.
• B. It promotes calcium absorption.
• C. It provides energy to cells.
• D. It supports immune function.

Answer: (A)

Iodine is essential for thyroid hormone production. The thyroid gland uses iodine to make the hormones T3 and T4, which regulate the body's metabolic rate, growth, and development, especially brain development in fetuses and young children. When iodine intake is adequate, thyroid hormone production supports normal energy use and growth. If iodine is deficient, thyroid hormone production drops, leading to goiter and potential developmental issues. Good dietary sources include iodized salt, seafood, dairy products, and some grains. Other statements miss the central role of iodine—calcium absorption is mainly influenced by vitamin D, energy for cells comes from calories in the diet rather than iodine, and immune function is affected by many nutrients but iodine's primary function is in thyroid hormone production.