The effects of vitamin A poisoning include:
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birth defects
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liver abnormalities,
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reduced bone mineral density that may result in osteoporosis
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Signs of acute toxicity include nausea and vomiting, headache, dizziness, blurred vision, and loss of muscular coordination.
Although vitamin A poisoning can occur when very large amounts of liver are regularly consumed, most cases of vitamin A toxicity result from an excess intake of vitamin A in supplements. Toxic symptoms can also arise after consuming very large amounts of preformed vitamin A over a short period of time.
The Institute of Medicine has established Daily Tolerable Upper Levels (UL) of intake for vitamin A from supplements that apply to healthy populations, in order to help prevent the risk of vitamin A toxicity. These levels for preformed vitamin A in micrograms (µg) and International Units (IU) are:
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0-3 years: 600 µg or 2000 IU
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4-8 years: 900 µg or 3000 IU
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9-13 years: 1700 µg or 5665 IU
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14-18 years: 2800 µg or 9335 IU
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19+ years: 3000 µg or 10,000 IU
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