Nutrient deficiency refers to a lack of essential nutrients, such as vitamins and minerals, in the body that are necessary for optimal health and functioning. This can occur due to inadequate intake of nutrients through diet, malabsorption issues, certain medical conditions, or increased nutrient needs (such as during pregnancy or illness). Common nutrient deficiencies include iron, vitamin D, vitamin B12, and calcium. Symptoms of nutrient deficiencies can vary depending on the specific nutrient lacking but may include fatigue, weakness, impaired cognitive function, and compromised immune function. Nutrient deficiencies can lead to a range of health issues and may require dietary changes, supplementation, or other interventions to correct.