What nutrient does insulin primarily assist in regulating besides carbohydrates?

Insulin plays a vital role in the metabolism of carbohydrates by facilitating glucose uptake into cells, but it is also instrumental in the regulation of proteins. After carbohydrates are consumed and insulin levels rise, the hormone not only helps to lower blood glucose levels but also promotes the uptake of amino acids into cells. These amino acids are the building blocks of proteins, and their absorption is enhanced by insulin. This function is important for muscle growth, repair, and overall protein synthesis within the body.

In contrast, while fibers are important for digestive health, they are not directly regulated by insulin. Vitamins and minerals are essential for various bodily functions, but they do not have their uptake or metabolism significantly influenced by insulin activity in the same way that proteins do. Therefore, the correct answer reflects the critical interactions between insulin and protein metabolism, highlighting its broader role in nutrient regulation.