Identify a common symptom of vitamin D deficiency.

Bone pain or muscle weakness is a common symptom of vitamin D deficiency due to the vitamin's crucial role in maintaining bone health and muscle function. Vitamin D is essential for the absorption of calcium and phosphorus, which are vital minerals for bone structure. When there is a deficiency, the body may struggle to maintain adequate calcium levels, leading to weakened bones and discomfort.

Furthermore, insufficient vitamin D can result in a condition known as osteomalacia in adults and rickets in children, both of which are characterized by bone pain and weakness. The muscles also rely on proper levels of vitamin D for optimal function; therefore, individuals with low vitamin D often report muscle weakness along with bone pain.

In contrast, increased energy levels, improved immune function, and enhanced mood and mental clarity are not directly associated with vitamin D deficiency. Lack of vitamin D typically leads to the opposite effects, such as fatigue and a decreased immune response.