Vitamin A is a vital nutrient in our diet. It supports vision, the immune system, and all of our major organs. It's important for reproduction, growth, and our development. You might be familiar with retinol, preformed vitamin A, which comes from animal-based foods such as liver, some types of fish, and eggs. Carotenoids, or the provitamin A, is found in plant-based foods, and not always bioavailable to us. We have to turn this into vitamin A.
The body absorbs at least 75% of the vitamin A from animal-based foods, but only about 10 to 30% of the vitamin a from plant-based foods. Cooking the plant-based foods helps them better absorb into your body and eating a little bit of fat helps as well. We need about 700mcg a day, although men require a little more, at about 900mcg (Hodge & Taylor, 2023). Deficiency in the United States is rare, more related to Crohn's disease or Celiac disease.
Vitamin A is fat-soluble, meaning the body can store it so when the diet is void of vitamin A or deficient, symptoms aren't acutely available, but this also means that toxic levels can be stored in the liver and body fat (Carazo et al., 2021). Carotenoids are yellow-to-orange-to-red in color and have significant antioxidant activities. Some of the more well-known cartenoids are B-carotene, a-carotene, lutein, lycopene, and cryptoxanthin. Carrots, spinach, and tomato products are probably the most common contributors to B-carotene, while B-cryptoxanthin is mostly obtained from citrus fruits such as persimmons, mandarins, tangerines, clementines, oranges, chili peppers, red peppers, papaya, mango, and apricots. Some vitamin A can also be found in some medicinal plants and herbs, cereals, and some vegetable oils.
How much vitamin A in plants depends on the deepness of the color of the fruit or vegetable, as well as its ripeness (Carazo et al., 2021). Where the fruit was grow and cultivated also makes a difference, but if these fruits and vegetables, even spices are dried, then upwards of 90% of the vitamin A is lost, more sun when sun-dried.
Milk and dairy products, as well as meat and its products, are the largest contributors of vitamin A to our diet. Eggs and fish are also good sources. The amount here does depend on season and livestock species, although the higher the fat content, typically the higher the retinol content (Carazo et al., 2021). Liver oil has some of the highest content of vitamin A, including shark liver oil and cod liver oil. Fish eggs and chicken egg yolks are additional sources. Quail eggs have about twice as much as chicken eggs.
Clinician Perspective on Evaluating Vitamin A
Acne (Kotori, 2015), dermatitis (Yang et al., 2020), and follicular hyperkeratosis are all evident when vitamin A deficiency occurs. Photophobias are also associated with vitamin A deficiency (Pereira et al., 2023) and eyes can become dry, called xerophthalmia. Vision gets increasingly more poor at night, and one's eyes become less shiny, bright, and moist (Carazo et al., 2021).
Three months of treatment with low dose, synthetic vitamin A has been found to be effective in the treatment of moderate acne, with low risk of side effects (Kotori, 2015). Eye concerns though do need followed by an ophthalmologist. While vitamin A deficiency is rare in developed countries, there are case reports of autistic children with very restricted diets having skull-based bone changes that impacted vision (Pereira et al., 2023).
Prompt treatment of xerophthalmia can resolve ocular manifestations without long-term consequence if found early. Studies have even found that many of these symptoms can be resolved within 2 months of treatment, even improvement in night vision (Carazo et al., 2021). Zinc supplementation is also encouraged with vitamin A is deficient.
Gingivitis can be the result of vitamin A deficiency, as can enlarged tonsils in the child. Dry skin, rough and bumpy skin on the back of the arms, psoriasis, increased vascularization, crusting, increased pigmentation, thickened and inelastic skin, as well as fissured skin, especially when exposed to the sun are also related to deficiency in vitamin A (Carazo et al., 2021). Skin may also become scaly, dry, inflamed in the folds, easily traumatized, darkening and redness around the neck when exposed to sun, increased pigmentation around the eyes, and impaired wound healing. Bone and joint pain can also be associated with vitamin D deficiency.
References
Carazo, A., Macakova, K., Matousova, K., Krcmova, L. K., Protti, M., & Mladenka, P. (2021). Vitamin A update: forms, sources, kinetics, detection, function, deficiency, therapeutic use and toxicity. Nutrients, 13(5), 1703.
Hodge, C. & Taylor, C. (2023). Vitamin a deficiency. StatPearls.
Kotori, M. G. (2015). Low-dose vitamin A tablets-treatment of acne vulgaris. Medical Archieves, 69(1), 28-30.
Pereira, A., Adekunle, R. D., Zaman, M., & Wan, M. J. (2023). Association between vitamin deficiencies and ophthalmological conditions. Clinical Ophthalmology, 17, 2045-2062.
Pereira, A., Ertl-Wagner, B., Tumber, A., Vincent, A., & Wan, M. J. (2023). Bilateral compressive optic neuropathy and outer retinopathy due to optic canal hyperostosis in a child with isolated vitamin a deficiency. Doc Ophthalmology, 146(2), 173-180.
Yang, H., Chen, J-S., Zou, W-J., Tan, Q., Xiao, Y-Z., Luo, X-Y., Gao, P., Fu, Z., & Wang, H. (2020). Vitamin A deficiency exacerbates extrinsic atopic dermatitis development by potentiating type 2 helper T cell-type inflammation and mast cell activation. Clinical Exp Allergy, 50(8), 942-953.
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