HEALTH MATTERS
Why You Need Vitamin A
By Kepha Nyanumba
Micronutrient deficiencies are of great public health and socioeconomic importance worldwide . They affect low-income countries but are also a significant factor in health problems in industrialized societies with impacts among wide vulnerable groups in the population , including women , children , the middle-aged , and the elderly .
Micronutrients are dietary components , often referred to as vitamins and minerals , which although only required by the body in small amounts , are vital to development , disease prevention , and wellbeing . They perform a range of other functions , including enabling the body to produce enzymes , hormones and other substances needed for normal growth and development .
Micronutrients are not produced in the body and must be derived from the diet . Deficiencies in micronutrients such as vitamin A can have devastating consequences . According to World Health Organization ( WHO ), Vitamin A deficiency is a public health problem in more than half of all countries , especially in Africa and South-East Asia , hitting hardest young children and pregnant women in low-income countries .
Globally , 1 in 3 pre-school aged children and 1 in 6 pregnant women are vitamin A deficient due to inadequate dietary intake . An estimated 250 million preschool children are vitamin A deficient with half of vitamin A deficient children who become blind dying within 12 months of losing their sight .
Vitamin A is a fat-soluble vitamin that is naturally present in many foods . There are two different types of vitamin A . The first type , retinoids ( retinol ), is found in meat , poultry , fish , and dairy products . The second type , carotenoids ( provitamin A ) is found in fruits , vegetables , and other plant-based products .
The only type of vitamin A the body can readily use is retinol . When you get carotenoids ( provitamin A ) from plant sources , your body must convert the carotenoids into bioavailable retinol .
There are a number of factors that inhibit your body ’ s ability to absorb carotenoids
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Globally , 1 in 3 pre-school aged children and 1 in 6 pregnant women are vitamin A deficient due to inadequate dietary intake . An estimated 250 million preschool children are vitamin A deficient with half of vitamin A deficient children who become blind dying within 12 months of losing their sight . and convert them into retinol . This includes genetics , digestive problems , alcohol use , certain medicines , toxic exposures , and medical conditions that interfere with the digestion of fat ( including cystic fibrosis , pancreatic enzyme deficiency , and gallbladder and liver disease ).
Vitamin A Benefits Your Vision
Vitamin A is very important for good vision . Lutein and zeaxanthin are particularly crucial for preventing age-related macular degeneration , the most common cause of blindness among the elderly .
Vitamin A affects vision primarily by regulating gene expression , but in order for this to occur , it must be activated in a two-step process , converting from retinol to retinal , and finally to retinoic acid .
Retinal binds to a protein known as opsin , forming a vitamin-protein complex known as rhodopsin . Each photon of light that enters our eye and collides with rhodopsin causes the retinal to change shape and release itself from the complex .
This event then translates into an electrical impulse that our optic nerve transmits to our brain . The brain synthesizes myriad such electrical impulses at every moment and interprets them as vision .
While the function of opsin is to help generate visual images by binding and releasing vitamin A , opsin can only maintain its proper shape and function when it is bound to zinc . In addition , zinc supports the conversion of retinol to retinal , the form of vitamin A that binds to opsin .
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