The health benefits of vitamins embody their skill to stop and deal with numerous illnesses including coronary heart problems, excessive cholesterol levels , eye problems, and pores and skin problems. An RAE can’t be instantly transformed into an IU without knowing the source(s) of vitamin A. For example, the RDA of 900 mcg RAE for adolescent and adult males is equivalent to 3,000 IU if the food or supplement supply is preformed vitamin A (retinol).
The varied types of vitamin A are solubilized into micelles within the intestinal lumen and absorbed by duodenal mucosal cells 5 Both retinyl esters and provitamin A carotenoids are converted to retinol, which is oxidized to retinal after which to retinoic acid 2 A lot of the physique’s vitamin A is stored within the liver in the type of retinyl esters.
Effectively-recognized human vitamin deficiencies contain thiamine ( beriberi ), niacin ( pellagra ), 32 vitamin C ( scurvy ), and vitamin D ( rickets ). 33 In a lot of the developed world, such deficiencies are uncommon; this is because of (1) an ample supply of meals and (2) the addition of vitamins and minerals to widespread foods ( fortification ). 8 18 In addition to these classical vitamin deficiency ailments, some proof has additionally suggested links between vitamin deficiency and various completely different issues.
Until the mid-1930s, when the primary commercial yeast-extract vitamin B complex and semi-artificial vitamin C supplement tablets have been sold, vitamins have been obtained solely via food consumption, and changes in eating regimen (which, for example, may occur throughout a specific growing season) often vastly altered the kinds and quantities of vitamins ingested.
Although extra preformed vitamin A can have important toxicity (referred to as hypervitaminosis A ), giant quantities of beta-carotene and different provitamin A carotenoids will not be associated with major adversarial results 37 The manifestations of hypervitaminosis A depend on the size and rapidity of the excess intake.