Signs of nutrient deficiencies in an athlete may include fatigue, muscle cramps, poor immune function, and decreased performance. Specific deficiencies can manifest as hair loss, brittle nails, and skin issues, often tied to insufficient intake of vital nutrients like iron, calcium, and vitamins D and B12. Athletes should be vigilant regarding their diet to ensure adequate nutrient intake. Regular check-ups and blood tests can help identify deficiencies early, allowing for timely interventions to maintain optimal health and performance.