Which mineral is applied to the navel of newborns to fight disease?

The correct answer is iodine, which is applied to the navel of newborns, particularly in livestock such as calves and lambs. This practice is important because iodine is a powerful antiseptic and helps reduce the risk of infections that could occur when the umbilical cord is cut.

Using iodine on the navel decreases the chances of bacteria entering the bloodstream through the exposed area, thereby protecting the newborn's immune system as it is still developing. This is a critical step in managing the health of newborn animals in farming and veterinary practices.

While calcium, sodium, and magnesium are essential minerals for various bodily functions, they do not serve the specific purpose of preventing infections in the same way iodine does in this context. Calcium plays a key role in bone health and muscle function, sodium is crucial for fluid balance and nerve transmission, and magnesium is important for many biochemical reactions in the body. However, none of these minerals are used topically to combat disease in newborns like iodine is.