Vitamin A deficiency is a serious health issue that affects more than half of the countries in the world, particularly those in Africa and South-East Asia. It is caused by an inadequate dietary intake of vitamin A, which can be aggravated by high rates of infection, such as diarrhea and measles. This deficiency can lead to a variety of health problems, including lower birth weight, delayed child growth, and increased mortality. Natural sources of vitamin A include dark green leafy vegetables, orange vegetables, dairy products, liver, and fish.
It is absorbed in the duodenum after hydrolyzation by pancreatic and intestinal enzymes and is emulsified with dietary fats and bile acids. Most of it is then stored in the stellate cells of the liver, with significant amounts also stored in adipose tissue and pancreas. Vitamin A deficiency (VAD) can be evaluated through xerophthalmia and night blindness. Preterm infants are at risk of VAD due to their immature gastrointestinal tract, inefficient absorption of vitamin A, minimal storage of the vitamin, and increased needs during rapid development. Vitamin A supplementation alone or in combination with Fe supplementation has been shown to improve anaemia.
The World Alliance for Vitamin A (GAVA) guidelines provide guidance and information to district and national managers on the monitoring and reporting of vitamin A supplementation programs aimed at children aged 6 to 59 months. During the acute phase response, the protein that binds to retinol can be separated from the circulating RBP-TTR-Retinol complex, causing high and abnormal urinary losses of vitamin A. Vitamin A deficiency can also cause abnormal functions of the lungs, skin, and thyroid. It has been observed to increase susceptibility to infections, leading to a decrease in erythropoiesis. In addition, people with inflammatory bowel disease (IBD) are at risk for VAD due to chronic inflammation of the intestinal mucosa combined with a decrease in oral intake. Improving the vitamin A level of children with deficiencies (6 to 59 months) can reduce mortality rates from measles and diarrhea by 50% and 33%, respectively, and can reduce risk rates for all causes of death by 23%.
Beta-carotene, also known as provitamin A, is the vegetable source of retinol from which mammals produce two-thirds of their vitamin A. An adult's liver can store up to a year's worth of vitamin A stores, while a child's liver can have enough reserves to last only several weeks. Vitamin A deficiency is rarely seen in nutrient-rich first-world countries; however, it can affect people with IBD and after bariatric surgery. Results from randomized clinical trials document that vitamin A supplementation alone or in combination with Fe supplementation improves anaemia. The report includes a flowchart that provides a quick snapshot of the overall review process, as well as a detailed description of the review questions, the different scenarios encountered and how each of them is addressed.