Dietary deficiency occurs when a person's diet lacks essential nutrients, such as vitamins, minerals, or proteins, needed for optimal health. This can lead to various health issues, including weakened immunity, fatigue, and impaired growth. Common deficiencies include a lack of vitamin D, iron, and calcium, which can affect bone health and overall well-being. People at higher risk for dietary deficiencies include those with restrictive diets, such as vegetarians or vegans, and individuals with certain medical conditions that affect nutrient absorption. Addressing these deficiencies often involves dietary changes or supplementation to ensure the body receives the necessary nutrients for proper function.