Vitamin A is not a single compound but actually comprises a fat-soluble family of molecules that includes retinol, retinal, retinoic acid, and retinyl ester. The term vitamin A also includes certain plant carotenoids called provitamin A because they are dietary precursors of retinol.
Vitamin A is essential for normal vision and eyeball health, a properly functioning immune system, gene regulation, reproduction, embryonic development, health and protection of all the tissues that line the body, including skin and mucosa of the lungs, digestive tract, urinary tract, and genital tract, bone metabolism and normal growth and strong teeth in children.
Vitamin A Deficiency
The United States National Institutes of Health recommends testing vitamin A levels in people with celiac disease at diagnosis. This is because vitamin A deficiency is common in celiac disease. Deficiency can result from incomplete digestion, absorption, or metabolism.
Normal absorption of vitamin A first requires digestion, or releasing, from food protein in the stomach. Then it is converted to retinol and bound to albumin protein in the small intestine for transport through the intestinal lining and absorption with fatty acids via the lymph system into the body. In the blood plasma, maintaining proper retinol levels depends on having adequate levels of amino acids and zinc.
Vitamin A deficiency can develop in celiac disease in the following ways. Upper digestive problems, such as low stomach acid, can fail to dissolve vitamin A out of food sources. Protein deficiency impairs absorption transport through the intestinal lining while fat malabsorption impairs vitamin A absorption into the lymph. Finally, the liver cannot mobilize stored vitamin A to maintain adequate blood levels when blood protein and zinc levels are low.
Vitamin A deficiency can persist or develop after diagnosis and treatment with a gluten-free diet if the diet does not include adequate amounts of vitamin A, protein, zinc and fat.
Vitamin A deficiency…
- Impairs maintenance of eye tissue of the conjunctiva and cornea.
- Alters visual function of the retina due to depletion of rhodopsin, a pigment located in the rod cells of the retina, needed to distinguish light and dark.
- Impairs development and maintenance of skin and mucus membranes, resulting in skin thickening and poor defense against infection.
- Alters immune response, impairing the numbers and responsiveness of white blood cells to bacterial, viral and fungal infections.
- Alters gene regulation resulting in adverse growth and development of tissues in general.
- Impairs reproduction for conceiving and producing children and fertility in both sexes, and
- Impairs bone and tooth growth in children.
1. Sight problems:
Nightblindness, or difficulty seeing in dim light such as twilight is the earliest sign.
- Difficulty adjusting from light area to dark area.
- Excessive sensitivity to light (photophobia).
2. Eye problems:
- Dry eyes (dry, sandy feeling) due to lack of adequate tear production.
- Eye redness (conjunctivitis).
- Blepharitis (inflamation of the eyelid).
- Bitot’s spots following thickening of conjunctiva and lack of tears.
- Blurry vision due to dryness of cornea.
- Xerophthalmia develops from softening of the cornea in advanced stage of dryness and thickening and advances to blindness.
2. Skin problems:
- Dry, rough, scaly skin.
- Plugged hair follicles, or dry, bumpy skin “goose flesh,” called follicular hyperkeratosis.
3. Low mucus production
- Dryness in digestive tract, lungs, urinary tract and genital tract.
- Poor protection against microbe invasion.
4. Digestive problems:
- Dry mouth.
- Poor digestion.
5. Immunity problems:
- Repeat infections such as sinusitis, ear infections, candidiasis, fungal infections, and particularly, respiratory infections.
- Poor recovery from infections such as flu and colds or sores.
6. Reproductive problems:
- Impairment of sperm formation in males.
- Spontaneous abortion in females.
- Impaired development of embry
7. Failure to grow, or growth retardation, is the most common sign in children.
Food Sources of Vitamin A in Animals
Excellent: Liver, chicken giblets, oysters, cod, halibut.
Good: Milk, cheese, butter, eggs and other fish.
Food Sources of Vitamin A in Plants (Carotenoids)
Very good: Carrot juice, sweet potato with peel, pumpkin, carrots.
Good: Dark green leafy vegetables such as spinach, collards, kale, beet greens, turnip greens.
Recommended Daily Dietary Allowances for Vitamin A:
Children 1 to 3 years: 600 micrograms (2,000 IU)
Children 4 to 8 years: 900 micrograms (3,000 IU)
Children 9 to 13 years: 1,700 micrograms (5,666 IU)
Males and females 14 to 18 years: 2,800 mcg (9,333 IU)
Males add females 19 years and older: 3,000 mcg (10,000 IU)
Pregnant and breastfeeding females 18 and older: 2,800 mcg (9,333 IU)
Pregnant and breastfeeding females 19 and older: 3,000 mcg (10,000 IU)
Getting Your Daily Intake
In addition to consuming foods rich in vitamin A and carotenoids as a part of your healthy diet, consider taking a multivitamin containing up to, but not more than, 100% RDA in order to make up for any shortfall. Do not give vitamin A or any other supplement to a child without the advice of your doctor.
If you take medicine, there is a potential for side effects and interactions with all supplements. Discuss your optimum dose of vitamin A with your doctor.
Drugs that are used to reduce cholesterol also alter vitamin A in the body. Drugs that increase blood levels of vitamin A include Lescol, Mevacor, Provachol and Zocor, while those that interfere with vitamin A absorption include Cholestyramine and Colestid.
Contraceptives may increase blood levels of vitamin A. Neomycin, an antibiotic, may decrease the absorption of vitamin A.
Impact of Storage, Processing, and Cooking
Vitamin A is unaffected by light, heat and usual cooking methods. It is destroyed by oxidation (exposure to air), drying, very high temperatures and ultraviolet light. Keep food wrapped to protect it from air and sunlight.
Excessive vitamin A may interfere with vitamin K absorption.
Persistent high doses of vitamin A (not carotenoids) of over 14,000 IU in infants or 33,000 IU in adults overcomes the liver’s ability to store it and can produce toxicity. Children and people with kidney failure are at high risk of toxicity and should always inform their physician of any supplement use. Excessive alcohol consumption increases toxicity. Toxic effects of vitamin A (in the form of retinoic acid) exceeding 10,000 IU when used as a supplement by pregnant women or as the active ingredient in acne products like Accutane have been shown to cause malformations such as spina bifida in their developing fetuses.
Symptoms of vitamin A toxicity include dry lips is an early sign, followed by dryness of the nasal tissues. Later signs include dryness, redness, scaling, and peeling of skin, hair loss and nail fragility. Other symptoms can include vomiting in infants and children, headache, nausea, bone pain, fractures, fatigue and muscle pain.
1. Cleo J. Libonati. Recognizing Celiac Disease, Fort Washington, PA, USA: GFW Publishing, 2007. www.recognizingceliacdisease.com
2. Kathleen Mahan and Sylvia Escott-Stump, ed. Krause’s Food, Nutrition, & Diet Therapy, 10th Edition. Philadelphia, PA, USA: W.B. Saunders Company, 2000.
3. National Acadamies Press http://books.nap.edu/openbook.php?record_id=10026&page=82