vitamin deficiency vitamin deficiency vitamin deficiency is the condition of a long-term lack of a vitamin. when caused by not enough vitamin intake it is classified as a primary deficiency, whereas when due to an underlying disorder such as malabsorption it is called a secondary deficiency. an underlying disorder can have 2 main causes: metabolic causes: genetic defects in enzymes (e.g. kynureninase) involved in the kynurenine pathway of synthesis of niacin from tryptophan can lead to pellagra (niacin deficiency). lifestyle choices: lifestyle choices and habits that increase vitamin needs, such as smoking or drinking alcohol. government guidelines on vitamin deficiencies advise certain intakes for healthy people, with specific values for women, men, babies, children, the elderly, and during pregnancy or breastfeeding. many countries have mandated vitamin food fortification programs to prevent commonly occurring vitamin deficiencies. vitamin deficiencyother namesavitaminosis, hypovitaminosisspecialtyendocrinology conversely, hypervitaminosis refers to symptoms caused by vitamin intakes in excess of needs, especially for fat-soluble vitamins that can accumulate in body tissues. the history of the discovery of vitamin deficiencies progressed over centuries from observations that certain conditions – for example, scurvy – could be prevented or treated with certain foods having high content of a necessary vitamin, to the identification and description of specific molecules essential for life and health. during the 20th century, several scientists were awarded the nobel prize in physiology or medicine or the nobel prize in chemistry for their roles in the discovery of vitamins. defining deficiency a number of regions have published guidelines defining vitamin deficiencies and advising specific intakes for healthy people, with different recommendations for women, men, infants, the elderly, and during pregnancy and breast feeding including japan, the european union, the united states, and canada. these documents have been updated as research is published. in the us, recommended dietary allowances (rdas) were first set in 1941 by the food and nutrition board of the national academy of sciences. there were periodic updates, culminating in the dietary reference intakes. updated in 2016, the us food and drug administration published a set of tables that define estimated average requirements (ears) and (rdas). rdas are higher to cover people with higher than average needs. together, these are part of dietary reference intakes. for a few vitamins, there is not sufficient information to set ears and rdas. for these, an adequate intake is shown, based on an assumption that what healthy people consume is sufficient. countries do not always agree on the amounts of vitamins needed to safeguard against deficiency. for example, for vitamin c, the rdas for women for japan, the european union (called population reference intakes) and the us are 100, 95 and 75 mg/day, respectively. india sets its recommendation at 40 mg/day. individual vitamin deficiencies