Signs of a nutrient deficiency in a diet can vary but often include symptoms such as fatigue, weakness, hair loss, and compromised immune function. Specific deficiencies may show unique signs, for example, iron deficiency can lead to anemia, characterized by pale skin and shortness of breath, while vitamin D deficiency can result in bone pain and muscle weakness. These deficiencies often prompt individuals to seek dietary changes or supplements, underscoring the importance of a balanced diet rich in essential nutrients.