Deficiency

Deficiency is the state of lacking something necessary for normal function, health, or maintenance. In medicine and nutrition, a deficiency refers to an insufficient amount of a nutrient or other essential factor, such as vitamins, minerals, proteins, or hormones, resulting in impaired function or disease. Deficiencies can be primary, caused by inadequate intake, or secondary, due to poor absorption, increased requirements, or losses from illness or medications.

Nutritional deficiencies are the most common type. Micronutrient deficiencies involve vitamins and minerals and can affect many body systems. For example, iron deficiency can cause anemia; vitamin D deficiency can result in bone problems; iodine deficiency can affect thyroid function; vitamin A deficiency can impair vision; zinc deficiency can affect growth and immunity. Macromutrient deficiencies, such as protein-energy malnutrition, occur with insufficient dietary protein or overall calories.

Causes and risk factors include restricted diets, poverty, certain medical conditions (malabsorption syndromes, inflammatory diseases), pregnancy or lactation, chronic illnesses, medications, and alcohol use. Symptoms depend on the nutrient but may include fatigue, weakness, impaired growth, skin or hair changes, skeletal problems, neuropathy, or immune dysfunction. Diagnosis uses dietary history, clinical examination, and laboratory tests showing low nutrient levels or functional disturbances.

Treatment and prevention involve correcting the underlying cause, providing targeted supplementation or fortification, and improving overall diet. Public health strategies include fortifying staple foods, supplementation programs, and screening in at-risk populations. Early detection and appropriate management can prevent progression to severe disease.