A common symptom of a nutrient deficiency is fatigue or weakness, which can result from insufficient intake of essential vitamins and minerals. For example, deficiencies in iron can lead to anemia, causing tiredness and reduced energy levels. Vitamin D deficiency may also contribute to fatigue and muscular weakness. Other symptoms can include hair loss, brittle nails, and cognitive impairments, depending on the specific nutrient lacking. Recognizing these signs can prompt individuals to evaluate their diets and consider supplementation or dietary adjustments.