Final answer:
When taken in megadoses, Vitamin C can inhibit iron absorption, which is in contrast to its usual role of enhancing iron absorption at normal intake levels.
Step-by-step explanation:
The micronutrient that inhibits iron absorption when taken in megadoses is Vitamin C. However, it is essential to note that under normal circumstances, Vitamin C actually enhances iron absorption. Only exceptionally high doses, far exceeding daily nutritional recommendations, can lead to an inhibition of iron absorption. Micronutrients like Vitamin C are necessary for health in small amounts and have various roles, such as supporting immune function and enhancing the absorption of iron from plant-based foods.