Hypervitaminosis A, or vitamin A toxicity, occurs when a person consumes too much vitamin A, typically from supplements or animal sources like liver and fish oil. Symptoms include nausea, vomiting, altered mental states, and hair loss. Carotenemia, caused by excessive ingestion of carotenes, can also occur but is not harmful. Treatment involves stopping vitamin A intake and staying hydrated.
Vitamin A toxicity is the effect of a person taking too much vitamin A. Also known as hypervitaminosis A, consuming too much vitamin A can lead to a number of harmful effects and is typically the result of someone taking too many dietary supplements. Vitamin A toxicity is rarely fatal, but can have unpleasant effects, such as nausea, vomiting, altered mental states, drowsiness, body aches, and in chronic cases can lead to hair loss, insomnia, and anemia.
The form of vitamin A found in vitamin supplements and animal sources, such as liver and fish oil, is called retinol. It is this type of vitamin A that can cause toxicity. Retinol is fat soluble, meaning that a person has no way of excreting excessive amounts from within the human body, unlike water soluble vitamins which are typically removed from the body through urination.
Acute toxicity of vitamin A is caused by a single ingestion of excessive amounts of vitamin A. Chronic toxicity is caused by excessive ingestion over a longer period of time. Most multivitamins contain vitamin A doses of less than 10,000 international units (IU). Acute toxicity is estimated to occur only after 25,000 IU or more of vitamin A has been ingested, so the recommended dosage of most multivitamins should not cause toxicity.
Eating animal liver and fish oil could potentially pose a threat of causing vitamin A toxicity when consumed in extraordinarily large amounts, but it’s unlikely. Most animal livers do not contain enough vitamin A to cause toxicity, although some animals such as polar bears, huskies, seals and walruses have extreme amounts of vitamin A in their livers and will eat the liver of such an animal it would probably cause a vitamin A overdose. Plant sources, such as carrots, contain vitamin A precursors known as carotenes that only selectively convert to retinol within a person’s body, meaning that ingesting vegetables does not cause vitamin A toxicity. Excessive ingestion of carotenes can cause a condition called carotenemia in which a person’s skin takes on a yellow-orange pigmentation. Aside from the cosmetic effects, however, carotenemia does not cause particularly harmful effects or vitamin A toxicity due to limited conversion to retinol.
While vitamin A toxicity is harmful, it is easily treated by stopping ingestion of vitamin A until symptoms subside. Toxicity can cause vomiting and diarrhea, so there is a risk of dehydration. Anyone experiencing such symptoms should make sure they drink plenty of water. Like any disease or disorder, however, anyone experiencing vitamin A toxicity should see a doctor immediately to be sure there have been no long-term effects, especially in chronic cases.
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