why is vitamin a deficiency common in developing countries
Vitamin A deficiency The major cause is roughage which include few animal sources of pre-formed vitamin A.[citation needed] In addition to dietary problems, there are other causes of VAD. Iron deficiency can affect vitamin A uptake. Excess alcohol consumption can deplete vitamin A, and a stressed liver may be more susceptible to vitamin A toxicity. People who consume large amounts of alcohol should seek medical advice before taking vitamin A supplements. In general, people should also seek medical advice before taking vitamin A supplements if they have any condition associated with fat malabsorption such as pancreatitis, cystic fibrosis, tropical sprue and biliary obstruction. Other causes of Vitamin A deficiency are inadequate intake, fat malabsorption, or liver disorders. Deficiency impairs immunity and hematopoiesis and causes rashes and typical ocular effects (e.g., xerophthalmia, night blindness).[17]
Blood type distribution by country Blood group B has its highest frequency in South Asia where it ranks first as the largest share of the earth's population. In Southeast Asia the share of the population is high, especially in Thailand and Indonesia, then in East Asia, Northern Asia and neighboring Central Asia, and its incidence diminishes both towards the east and the west, falling to single digit percentages in Netherlands, Norway, Portugal and Switzerland.[40][41] It is believed to have been entirely absent from Native American and Australian Aboriginal populations prior to the arrival of Europeans in those areas.[41][42]