Vitamin A

Vitamin A isn’t a single vitamin, rather it's a group of fat-soluble chemical compounds with similar structures. Vitamin A plays a role in skin, bone and eye health. Getting adequate vitamin A is also critical for supporting immune function.Both animal and plant-based foods contain vitamin A. However, the forms of vitamin A found in plants, carotenoids, need to be converted to the bioactive form retinol before the human body can use them.Deficiency of vitamin A is relatively uncommon in developed countries. It’s more common in pregnant women and children in developing countries.

The traditional Benefits of Vitamin A

Vitamin A has been shown to help immune health, structural support, and fitness support.

What is Vitamin A Used For?

Vitamin A may have numerous benefits to the body, including the following: Promotes Eye Health, Supports Immunity, May Help Prevent Cancer, Acts as an Antioxidant, Can Lead to Weight Loss, And Improves Bone Health.

Benefits of Vitamin A

Vitamin A has various benefits related to the eyes, skin and immune system. Because carotenoids can act as an antioxidant, supplementation may lower cancer risk. Vitamin A promotes eye health. The most well-known benefit of vitamin A is its ability to protect the eyes. Beta-carotene may reduce symptoms of age-related macular degeneration, which is a common cause of blindness in old age. One Italian study(1) found patients treated with lutein and zeaxanthin had their symptoms stabilize compared to non-treated patients .Vitamin A supports immunity Vitamin A prevents infections from developing. When the body is deficient in vitamin A, immune cells are severely weakened. It’s thought that vitamin A supports the regeneration of mucus(2), which lowers the chances of viruses making it into the body. Vitamin A Prevents Cancer. A diet including foods high in vitamin A can have anti-carcinogenic benefits. In vitro studies(3) show that vitamin A can block the growth of skin, bladder, prostate and lung cancer. One study(3) found that supplemental vitamin A reduced the risk of melanoma. However, results are still controversial. Vitamin A acts as an antioxidant Besides being a precursor to retinol, beta-carotene also acts as an antioxidant to reduce oxidative stress caused by cellular metabolism. This antioxidant property reduces inflammation throughout the body. Reducing inflammation(4) can lower the risk of developing cancer and cardiovascular disease. Vitamin A preserves skin health Vitamin A can have benefits for a wide range of skin disorders including psoriasis, eczema and acne(5). Vitamin A’s benefits for skin health are due to its anti-inflammatory properties.Weight lossVitamin A doesn’t directly affect metabolism, but many of its other effects indirectly lead to weight loss. Supporting immunity can reduce the frequency of sickness. Vitamin A’s anti-inflammatory benefits may reduce joint pain and make exercising less painful. Bone Health Vitamin A intake above and below the RDA can cause issues with bone health. One study(6) examined the effect of retinol on the bone health of women with osteoporosis. The study found that retinol had a bone-sparing effect. Plasma levels of all carotenoids except for lutein were lower in women with osteoporosis than in woman without osteoporosis.

How to Use Vitamin A

A diet high in organ meats, dairy products and fish may provide enough retinol without supplementation. However, people who don’t eat many leafy greens or animal products can take retinol as an oral supplement. Retinol is also a common ingredient in multivitamins. Some supplements may also include alpha or beta-carotene. Vitamin A can also be used topically for skin conditions such as eczema or acne. It’s often added to cosmetic products like sunscreen and moisturizers. According to the Institute of Medicine Panel of Micronutrients, the Recommended daily dosage of vitamin A for an adult man (or boy over 14 years) is 900μg RAE.Adult man (or boy over 14 years) is 900μg RAE.Adult women and girls over 14 should get 700μg RAE per day. Women who are pregnant need more vitamin A. The RDA is set at 770μg RAE per day. Children between the ages of 9-13 need 600μg RAE per day. Children from 1-3 need 300μg RAE per day and children 4-8 need 400μg RAE per day. All the RDAs use RAE so if vitamin A intake comes primarily from carotenoids, a higher amount of total vitamin A needs to be consumed. There is no RDA set for beta-carotene, the form of vitamin A found in sweet potato and carrots. There’s also no upper limit set for beta-carotene, but mega-dosages may negatively affect health. Epidemiological evidence(7) shows that taking large amounts of beta-carotene from supplements increases the risk of developing lung cancer and heart disease in smokers.

Symptoms of a Vitamin A Deficiency

All of the symptoms of vitamin A deficiency may have other causes. However, anybody experiencing multiple of the following symptoms should have their vitamin A levels checked. Dry skin and eyesThere are many causes of dry skin that have nothing to do with vitamin A status. However, vitamin A is needed for fibroblasts to create new skin cells. Vitamin A also protects the skin from UV damage by acting as an antioxidant. Vitamin A deficiency can cause eczema and acne, which is why many skin creams contain vitamin A. Abnormal dryness of the eyes is another common symptom of vitamin A deficiency. One case study(8) of an 88-year-old in Australian woman found that she developed itchy eyes from a vitamin A deficiency. Because of dietary restrictions, her diet consisted exclusively of rice porridge, canned tuna and vitamin B supplements. Nyctalopia (Night Blindness) Vitamin A deficiency is a common cause of blindness in developing countries. According to the World Health Organization, over 13.8 children in developing countries have vision problems caused by vitamin A deficiency. In particular, vitamin A deficiency can cause problems with night vision. Vitamin A deficiency inhibits the pigment found in the retina used for seeing in low light. The pigment is composed primarily of retinal. The body cannot create retinal in large amounts so it must be consumed through food or supplements. InfertilityVitamin A deficiency can lead to infertility in both men and women. Vitamin A deficiency can also lead to a higher risk of miscarriage in women(9). Children who don’t receive adequate vitamin A may have stunted growth or delayed growth. Research shows that supplementing children in developing countries with vitamin A can help restore their growth(10). A study(11) in Indonesia found that children who took vitamin A grew 0.15 inches more than children taking a placebo. Poor wound healing Poor vitamin A status can slow the healing of wounds(12) and injuries. Vitamin A promotes the production of collagen, which is the most common protein in the body. Research in humans(12) shows that elderly men treated with vitamin A had a 50 percent reduction in the size of wounds after taking a vitamin A cream compared to men who did not use the cream. Vitamin A is fat-soluble. Fat-soluble vitamins accumulate in the liver and when levels of the vitamin are too high there can be health complications. Vitamin A overdose is known as hypervitaminosis A. The upper limit of vitamin A is 3000μg RAE for adults.Vitamin A toxicity is unique to retinol. Beta-carotene and other provitamin A supplements seem to be safe in mega-dosages of 20-30mg/day. Taking too high of a daily dose of a retinol supplement is the most common cause of vitamin A toxicity. However, early arctic explorers(13) overdosed from vitamin A found in polar bear liver. The livers of moose and seals also contain a dangerous amount of retinol. Excess intake of vitamin A can lead to side effects such as dizziness, headaches, nausea, skin irritation, joint pain, coma and potential death in extreme cases. Diets high in beta-carotene can cause carotenoderma, which is a condition where the skin turns orange. Carotenoderma is harmless and is reversed when beta-carotene intake is lowered. Overdosing on vitamin A can be especially dangerous for pregnant women. Excess vitamin A intake over the upper limit is linked to birth defects.

Foods that Contain Vitamin A

The best sources of carotenoids are fruits and vegetables with bright orange or red flesh. Dark, leafy greens also contain a considerable number of carotenoids. Organ meats, dairy products and fish are the best sources of retinol. Some people have trouble converting carotenoids into retinol. These people may benefit from increasing their vitamin A intake. Here is a list of foods with more than 10 percent of the daily value of vitamin A intake per 100g. Animal Sources: Cod Liver Oil 3333 percent DV Cow Liver 1049 percent DV Lamb Liver 832 percent DV Bluefin Tuna 84 percent DV Butter 76 percent DV Goat Cheese 45 percent DV King Mackerel 28 percent DV Cheddar Cheese 27 percent DV Salmon 17 percent DV Eggs 17 percent DV Plant Sources Sweet Potato 116 percent DV Carrot 95 percent DV Winter Squash 62 percent DV Cantaloupe 19 percent DV Red Pepper 17 percent DV Apricot 11 percent DV

Citations and Sources

1. Piermarocchi S, Saviano S, Parisi V, et al. Carotenoids in Age-related Maculopathy Italian Study (CARMIS): two-year results of a randomized study. Eur J Ophthalmol. 2012;22(2):216-225. [PubMed] 2. Semba R. Vitamin A, immunity, and infection. Clin Infect Dis. 1994;19(3):489-499. [PubMed] 3. Doldo E, Costanza G, Agostinelli S, et al. Vitamin A, cancer treatment and prevention: the new role of cellular retinol binding proteins. Biomed Res Int. 2015;2015:624627. [PubMed] 4. Hunter P. The inflammation theory of disease. The growing realization that chronic inflammation is crucial in many diseases opens new avenues for treatment. EMBO Rep. 2012;13(11):968-970. [PubMed] 5. Chivot M. Retinoid therapy for acne. A comparative review. Am J Clin Dermatol. 2005;6(1):13-19. [PubMed]6. Maggio D, Polidori M, Barabani M, et al. Low levels of carotenoids and retinol in involutional osteoporosis. Bone. 2006;38(2):244-248. [PubMed] 7. Goralczyk R. Beta-carotene and lung cancer in smokers: review of hypotheses and status of research. Nutr Cancer. 2009;61(6):767-774. [PubMed] 8. Lee M, Sarossy M, Zamir E. Vitamin A Deficiency Presenting with “Itchy Eyes”. Case Rep Ophthalmol. 2015;6(3):427-434. [PubMed] 9. Simşek M, Naziroğlu M, Simşek H, Cay M, Aksakal M, Kumru S. Blood plasma levels of lipoperoxides, glutathione peroxidase, beta carotene, vitamin A and E in women with habitual abortion. Cell Biochem Funct. 1998;16(4):227-231. [PubMed] 10. Ramakrishnan U, Aburto N, McCabe G, Martorell R. Multimicronutrient interventions but not vitamin a or iron interventions alone improve child growth: results of 3 meta-analyses. J Nutr. 2004;134(10):2592-2602. [PubMed] 11. Hadi H, Stoltzfus R, Dibley M, et al. Vitamin A supplementation selectively improves the linear growth of indonesian preschool children: results from a randomized controlled trial. Am J Clin Nutr. 2000;71(2):507-513. [PubMed] 12. Hunt T. Vitamin A and wound healing. J Am Acad Dermatol. 1986;15(4 Pt 2):817-821. [PubMed] 13. Rodahl K, Moore T. The vitamin A content and toxicity of bear and seal liver. Biochem J. 1943;37(2):166-168. [PubMed] 14. Mactier H, Weaver L. Vitamin A and preterm infants: what we know, what we don’t know, and what we need to know. Arch Dis Child Fetal Neonatal Ed. 2005;90(2):F103-8. [PubMed]15. Oliveira-Menegozzo J, Bergamaschi D, Middleton P, East C. Vitamin A supplementation for postpartum women. Cochrane Database Syst Rev. 2010;(10):CD005944. [PubMed] 16. Graham-Maar R, Schall J, Stettler N, Zemel B, Stallings V. Elevated vitamin A intake and serum retinol in preadolescent children with cystic fibrosis. Am J Clin Nutr. 2006;84(1):174-182. [PubMed] 17. Borowitz D, Baker R, Stallings V. Consensus report on nutrition for pediatric patients with cystic fibrosis. J Pediatr Gastroenterol Nutr. 2002;35(3):246-259. [PubMed]

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