Which element is essential for proper carbohydrate metabolism in the human body?

Insulin is essential for proper carbohydrate metabolism in the human body because it is a hormone produced by the pancreas that helps regulate blood sugar levels. When carbohydrates are consumed, they are broken down into glucose, which enters the bloodstream. Insulin facilitates the uptake of glucose by cells for energy production or storage, enabling the body to maintain stable blood sugar levels. Without adequate insulin, glucose remains in the bloodstream, leading to hyperglycemia and related health issues, such as diabetes.

Other options, while they are important in various bodily functions, do not play a direct role in the metabolism of carbohydrates. Calcium is primarily associated with bone health, iron is crucial for oxygen transport in the blood, and sodium plays a vital role in fluid balance and nerve function, but none of these elements are directly involved in the metabolic process of carbohydrates like insulin is.