What Is Vitamin A?
Vitamin A is a family of fat-soluble compounds that are essential for health, vision, protection of the body, reproduction, and normal growth of children before and after birth.
Q: What is the family of vitamin A ?
A: The natural vitamin A  family members are called retinoids. Retinoids are found only in animal food sources. They include retinol (alcohol form), retinal (aldehyde form), and retinoic acid (acid form).
In the plant kingdom, pigments called carotenoids can yield retinoids on metabolism in the body. Carotenoids that can converted to retinol include β-carotene, α-carotene, and β-cryptoxanthin.1 
There are hundreds of various carotenoids although only a few have been researched including beta-carotene, lycopene, lutein and zeaxanthin.
Fruits and vegetables that are a rich source of carotenoids are thought to provide health benefits by decreasing the risk of various diseases, particularly eye diseases and certain cancers (esophageal, stomach, pancreatic, bladder and cervical). In this respect, research shows that the regular consumption of fruits and vegetables may prevent 20% of most types of cancers.2 
In part, the beneficial effects of carotenoids are thought to be due to their role as antioxidants. Lutein and zeaxanthin may be protective in eye disease because they absorb damaging blue light that enters the eye.3 
The antioxidant effects appear to be highest in fresh fruit as compared to preserved fruit. A study of fresh peach pulps and peel in animals demonstrated highest antioxidant and anti-inflammatory effects in fresh fruits preventing against induced damage in animal tissues.4 
A study investigating the specific anti-inflammatory and anti-oxidant micronutrients that reduce oxidative stress showed that adolescents with metabolic syndrome (MetS) had consistently lower carotenoid concentrations compared with their counterparts without MetS. MetS prevalence was estimated at 7% among boys and 3% among girls.5 
What Is Vitamin A Deficiency In Celiac Disease and/or Gluten Sensitivity?
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Maggio M, de Vita F, Lauretani F, et al. Relationship between Carotenoids, Retinol, and Estradiol Levels in Older Women. Nutrients. 2015 Aug 5;7(8):6506-19. doi: 10.3390/nu7085296. ↩ 
Gasparotto J, Somensi N, Bortolin RC, Moresco KS, Girardi CS, Klafke K, Rabelo TK, Morrone Mda S, Vizzotto M, Raseira Mdo C, Moreira JC, Gelain DP. Effects of different products of peach (Prunus persica L. Batsch) from a variety developed in southern Brazil on oxidative stress and inflammatory parameters in vitro and ex vivo. J Clin Biochem Nutr. 2014 Sep;55(2):110-9. doi: 10.3164/jcbn.13-97. Epub 2014 Sep 1. ↩ 
Krinsky NI1, Johnson EJ. Carotenoid actions and their relation to health and disease. ((Mol Aspects Med. 2005 Dec;26(6):459-516. ↩ 
Gasparotto J, Somensi N, Bortolin RC, Moresco KS, Girardi CS, Klafke K, Rabelo TK, Morrone Mda S, Vizzotto M, Raseira Mdo C, Moreira JC, Gelain DP. Effects of different products of peach (Prunus persica L. Batsch) from a variety developed in southern Brazil on oxidative stress and inflammatory parameters in vitro and ex vivo. J Clin Biochem Nutr. 2014 Sep;55(2):110-9. doi: 10.3164/jcbn.13-97. ↩ 
TGBeydoun MA, Canas JA, Beydoun HA, Chen X, Shroff MR, Zonderman AB. Serum antioxidant concentrations and metabolic syndrome are associated among U.S. adolescents in recent national surveys. J Nutr. 2012 Sep;142(9):1693-704. doi: 10.3945/jn.112.160416. ↩