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For someone who consumes a lot of vitamins, it's easy to have excess Vitamin A in the body because it's fat-soluble. I've read in a lot of credible places that Vitamin A over-consumption is dangerous, but I haven't found any quantitative figures.

For example, if someone consistently eats twice the RDI of Vitamin A by eating two large carrots a day, will he/she likely (in the long-term) suffer under adverse health effects from it?

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The quantitive figures for Vitamin A overdose are well established, and widely published.

The RDI in the United States (Different countries may have different values) is 900 micrograms for men, and 700 micrograms for females. 900 micrograms is approximately 3000 IU.

The acute toxic dose of vitamin A is 25,000 IU/kg, and the chronic toxic dose is 4000 IU/kg every day for 6-15 months.

A 1/2 cup of raw carrots contains about 9000 IU of Vitamin A. So if you are a 154 lb man, (70 kg), your toxic dose of Vitamin A is 1,750,000 IU, or right around 98 full cups of carrots for a toxic dose, or 15 cups a day for 6-16 months. I think you are perfectly fine eating two large carrots a day.

https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/

http://emedicine.medscape.com/article/819426-overview

  • Carrots don't contain vitamin A, though, they contain beta carotene, which is concerted into vitamin A in the liver. Your own source says "Although excess preformed vitamin A can have significant toxicity (known as hypervitaminosis A), large amounts of beta-carotene and other provitamin A carotenoids are not associated with major adverse effects" – YviDe Jan 16 '16 at 20:34
  • Source for plants not containing vitamin A directly: nlm.nih.gov/medlineplus/ency/article/002400.htm ods.od.nih.gov/factsheets/VitaminA-HealthProfessional – YviDe Jan 16 '16 at 20:50

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