Vitamin A helps keep your skin, teeth, mucus membranes, soft tissues and skeletal tissues healthy, according to MedlinePlus. It also promotes healthy vision in low light. Vitamin A is fat-soluble, meaning your body stores vitamin A in its tissues rather than flushing it out on a daily basis. Because of this, taking large amounts of it can be poisonous.
Causes
Vitamin A toxicity is caused by eating too much preformed vitamin A -- or retinol --
rather than the beta-carotene form you can find in vegetables such as carrots dark leafy greens. Preformed vitamin A is primarily found in fortified cereals, dietary supplements and animal foods such as fatty fish, liver and eggs. Although it is possible to overdose from short-term high exposure, you are more likely to experience negative effects if you take more than 8,000 to 10,000 mcg, or 25,000 to 33,000 IU, per day over a long period of time, according to the Linus Pauling Institute at Oregon State University. As a reference point, dietary supplements contain about 1,500 mcg, or 5,000 IU, of vitamin A, 1 tsp. of cod liver oil contains about 1,350 mcg, or 4,500 IU, and one serving of fortified cereal contains 130 to 230 mcg, or 500 to 767 IU, of vitamin A.
Symptoms
If you take too much vitamin A over a short period of time and develop vitamin poisoning, you may experience symptoms such as headache, fatigue, dizziness, appetite loss, dry skin and fluid in the brain. If you have chronic poisoning, you may have similar symptoms but are also at risk of bone and joint pain. In infants, vitamin A poisoning may cause the "soft spots" on the head to bulge.
Complications
Vitamin A poisoning can cause calcium levels to creep dangerously high, which may lead to kidney damage. Extreme cases of vitamin A poisoning may also result in hemorrhage, liver damage and coma. If you're pregnant, taking too much vitamin A may lead to abnormal development in your baby, according to PubMed Health. Infants are especially sensitive to high levels of vitamin A. If they consume a toxic amount, they may be diagnosed with failure to thrive and have long-lasting growth and development retardation.
Avoiding Overdose
Avoid vitamin A poisoning by taking no more than the recommended daily amount. Infants between 0 and 6 months should get no more than about 400 mcg, or 1,320 IU, per day, and infants 7 to 12 months should have only 500 mcg, or 1,650 IU, per day, according to MedlinePlus. Children 1 to 3 should have only 300 mcg, or 1,000 IU; kids 4 to 8 should have 400 mcg, or 1,320 IU, and children 9 to 13 should have no more than 600 mcg, or 2,000 IU. Males 14 and over can have about 900 mcg, or 3,000 IU, per day, and females 14 and over can have about 700 mcg, or 2,310 IU, per day. However, you may be at higher risk of toxicity if you are elderly, a chronic user of alcohol or if you have a genetic predisposition to high cholesterol levels. Ask your doctor to recommend the proper dose for you.
References
- MedlinePlus: Vitamin A
- PubMed Health: Hypervitaminosis A
- Linus Pauling Institute at Oregon State University: Vitamin A
- MedlinePlus: Hypervitaminosis A
- Office of Dietary Supplements: Vitamin A and Carotenoids
- National Institute of Arthritis and Musculoskeletal and Skin Diseases: Vitamin A and Bone Health
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