Which symptom could indicate a vitamin C deficiency in a patient?

A symptom that could indicate a vitamin C deficiency is receding gums. Vitamin C plays a crucial role in the health of connective tissues, including the gums. It is vital for collagen synthesis, which is integral to the structure and integrity of gums. A deficiency can lead to gum disease, characterized by receding gums, bleeding, and inflammation.

Frequent headaches, insomnia, and muscle cramps are not typically associated with vitamin C deficiency. While they could suggest other health issues or deficiencies, they do not specifically point to the lack of vitamin C in the body as objectively as the symptoms related to oral health. Thus, receding gums is the most indicative symptom of vitamin C deficiency within the context provided.