Deficiency diseases occur when the body lacks essential nutrients, leading to health problems. These nutrients include vitamins, minerals, proteins, and carbohydrates. Common deficiency diseases include scurvy, caused by a lack of vitamin C, and rickets, resulting from insufficient vitamin D and calcium. Preventing deficiency diseases involves a balanced diet rich in fruits, vegetables, whole grains, and proteins. In some cases, supplements may be necessary to ensure adequate nutrient intake. Awareness of these diseases is crucial for maintaining overall health and well-being, especially in vulnerable populations like children and the elderly.