Vitamin A Overdose

Vitamin A Overdose

Vitamin A is a fat-soluble vitamin that is found in many food sources, including fish, liver, dairy products, eggs and carrots. It is also available as a dietary supplement. Vitamin A is essential for good vision, healthy skin and mucous membranes (gastrointestinal tract), growth and development of bones and teeth. It also helps to prevent night blindness.

There are two forms of vitamin A: retinol and beta-carotene. Retinol can be toxic if taken in large doses; therefore it is not recommended for regular consumption. Beta-carotene is considered safe for human consumption in moderate doses because it cannot be converted into retinol by the body.

Symptoms of vitamin A overdose include nausea, vomiting, abdominal pain and headache. The effects of an overdose may take up to three weeks to appear since it takes that long for vitamin A to leave the body after ingestion.

Vitamin A Overdose

Vitamin A excess (toxicity) can be sudden (acute), usually due to accidental ingestion by children, or chronic.

• Consuming too much vitamin A causes hair loss, cracked lips, dry skin, weakened bones, headaches, elevations of blood calcium levels, and an uncommon disorder characterized by increased pressure within the skull called idiopathic intracranial hypertension.
• The diagnosis is based on symptoms and blood tests.
• Most people recover completely when they stop taking vitamin A supplements.

Vitamin A (retinol) is necessary for the function of light-sensitive nerve cells (photoreceptors) in the eye’s retina and thus helps maintain night vision. It also helps keep the skin and the lining of the lungs, intestine, and urinary tract healthy and protects against infections. Good sources of vitamin A include fish liver oils, liver, egg yolks, butter, cream, and fortified milk. (See also Overview of Vitamins.)

Carotenoids, such as beta-carotene, are pigments in fruits and vegetables that give them their yellow, orange, or red color. Once consumed, carotenoids are slowly converted to vitamin A in the body. Carotenoids are best absorbed from cooked or homogenized vegetables served with some fat or oil. Good sources of carotenoids are dark green, yellow, and orange vegetables and yellow and orange fruits.

Drugs related to vitamin A (retinoids) are used to treat severe acne and psoriasis. Whether taking vitamin A, beta-carotene, or retinoids helps reduce the risk of certain types of skin cancer is being studied. However, the risk of certain cancers may be increased after taking high doses of beta-carotene supplements.

Too much vitamin A can have harmful effects (toxicity). For example, taking daily doses 10 times the RDA (recommended daily allowance) or greater for a period of months can cause toxicity. Sometimes toxicity results from taking special formulations of high-dose vitamin A to treat severe acne or other skin disorders. A smaller dose can cause toxicity in infants, sometimes within a few weeks. If children accidentally take a very high dose, toxicity may develop quickly.

Consuming large amounts of carotenoids (which the body converts to vitamin A) in food does not cause toxicity because carotenoids are converted to vitamin A very slowly. Usually, no symptoms occur. However, when very large amounts of carotenoids are consumed, the skin may turn a deep yellow (called carotenosis), especially on the palms and soles.

High-dose supplements of beta-carotene may increase the risk of cancer, but carotenoids consumed in fruits and vegetables do not seem to increase this risk.

Symptoms of Vitamin A Excess

Most people with vitamin A toxicity have a headache and rash.

Consuming too much vitamin A over a long period of time can cause coarse hair, partial loss of hair (including the eyebrows), cracked lips, and dry, rough skin. Chronic consumption of large doses of vitamin A can cause liver damage. It can also cause birth defects in a fetus.

Later symptoms include severe headaches and general weakness. Bone and joint pain are common, especially among children. Fractures may occur easily, especially in older people. Children may lose their appetite and not grow and develop normally. Their skin may itch. The liver and spleen may enlarge.

Did You Know…

Taking very high doses of vitamin A or isotretinoin (a drug derived from vitamin A used to treat severe acne) during pregnancy can cause birth defects.

Consuming very large amounts of vitamin A all at once can cause drowsiness, irritability, headache, nausea, and vomiting within hours, sometimes followed by peeling of the skin. Pressure within the skull is increased, particularly in children, and vomiting occurs. Coma and death may occur unless vitamin A consumption is stopped.

Taking isotretinoin (a vitamin A derivative used to treat severe acne) during pregnancy may cause birth defects. Women who are or who may become pregnant should not consume vitamin A in amounts above the safe upper limit (3,000 micrograms) because birth defects are a risk.

Diagnosis of Vitamin A Excess

• Physical examination
• Blood tests

The diagnosis of vitamin A toxicity is based mainly on symptoms. To confirm the diagnosis, doctors may also do blood tests to measure the level of vitamin A.

Treatment of Vitamin A Excess

• Stopping vitamin A supplements

Treatment of vitamin A toxicity involves stopping vitamin A supplements. Most people recover completely.

how much vitamin a per day

The recommended daily amount of vitamin A is 900 micrograms (mcg) for adult men and 700 mcg for adult women.

Vitamin A (retinol, retinoic acid) is a nutrient important to vision, growth, cell division, reproduction and immunity. Vitamin A also has antioxidant properties. Antioxidants are substances that might protect your cells against the effects of free radicals — molecules produced when your body breaks down food or is exposed to tobacco smoke and radiation. Free radicals might play a role in heart disease, cancer and other diseases.

Vitamin A is found in many foods, such as spinach, dairy products and liver. Other sources are foods rich in beta-carotene, such as green leafy vegetables, carrots and cantaloupe. Your body converts beta-carotene into vitamin A.

As an oral supplement, vitamin A mainly benefits people who have a poor or limited diet or who have a condition that increases the need for vitamin A, such as pancreatic disease, eye disease or measles. If you take vitamin A for its antioxidant properties, keep in mind that the supplement might not offer the same benefits as naturally occurring antioxidants in food.

The recommended daily amount of vitamin A is 900 micrograms (mcg) for adult men and 700 mcg for adult women.

Evidence

Research on oral vitamin A for specific conditions shows:

• Acne. Large doses of oral vitamin A supplements don’t appear to affect acne.
• Age-related macular degeneration. A large clinical trial showed that people at high risk of advanced age-related macular degeneration reduced their risk of developing the condition by 25 percent by taking a specific combination of vitamins that included beta-carotene. It’s not entirely clear what role beta-carotene played.
• Cancer. The association between use of vitamin A supplements and reduced risk of lung, prostate and other types of cancer is unclear.
• Measles. Vitamin A supplements are recommended for children with measles who are at an increased risk of vitamin A deficiency. Research suggests that supplementation might reduce death due to measles.
• Vitamin A deficiency. People who have low levels of vitamin A appear to benefit most from vitamin A supplements. This kind of deficiency isn’t common in the United States. Vitamin A deficiency causes anemia and dry eyes.

Beyond use as an oral supplement, vitamin A is used in topical creams to reduce fine wrinkles, splotches and roughness and treat acne.

Our take

Caution

A healthy and varied diet will provide most people with enough vitamin A. If you’re interested in the antioxidant properties of vitamin A, food sources are best. It’s not clear if vitamin A supplements offer the same benefits as naturally occurring antioxidants in food. Too much vitamin A can be harmful and excess vitamin A during pregnancy has been linked to birth defects.

Safety and side effects

Too much vitamin A can be harmful. Even a single large dose — over 200,000 mcg — can cause:

• Nausea
• Vomiting
• Vertigo
• Blurry vision

Taking more than 10,000 mcg a day of oral vitamin A supplements long term can cause:

• Bone thinning
• Liver damage
• Headache
• Diarrhea
• Nausea
• Skin irritation
• Pain in the joints and bone
• Birth defects

If you are or might become pregnant, talk to your doctor before taking vitamin A. Excess use of vitamin A during pregnancy has been linked to birth defects.

Interactions

Possible interactions include:

• Anticoagulants. Oral use of vitamin A supplements while taking these medications used to prevent blood clots might increase your risk of bleeding.
• Bexarotene (Targretin). Taking vitamin A supplements while using this topical cancer drug increases the risk of the drug’s side effects, such as itchy, dry skin.
• Hepatotoxic drugs. Taking high doses of vitamin A supplements can cause liver damage. Combining high doses of vitamin A supplements with other drugs that can damage the liver could increase the risk of liver disease.
• Orlistat (Alli, Xenical). This weight-loss drug can decrease the absorption of food sources of vitamin A. Your doctor might suggest that you take a multivitamin with vitamin A and beta-carotene while taking this medication.
• Retinoids. Don’t use vitamin A supplements and these oral prescription drugs at the same time. This could increase the risk of high vitamin A blood levels.