Final answer:
Magnesium is the mineral that directly aids in the function of insulin by improving insulin sensitivity and glucose utilization, and it is involved in various cellular activities related to insulin action.
Step-by-step explanation:
The mineral that directly aids in the function of insulin is magnesium. Magnesium plays a critical role in the body's metabolism and has several actions or effects related to insulin. For instance, magnesium supplementation can decrease fasting circulating insulin concentrations and improve insulin sensitivity, highlighting its role in glucose utilization and insulin action. Moreover, magnesium has been shown to have a positive impact on cellular activity, including the regulation of secretion of certain peptide hormones and maintaining magnesium homeostasis. Relevant studies, such as those by Djurhuus et al. (1995) and Chacko (2011), support the view that magnesium is vital for the optimal activity of insulin.