From the Guidelines
Vitamin A can be toxic when consumed in excessive amounts, with acute toxicity developing after ingesting quantities above 300,000 IU in adults or > 60,000 IU in children within a few hours or days, as reported in the 2022 espen micronutrient guideline 1. The symptoms of vitamin A toxicity include increased intracranial pressure, nausea, headaches, pain in joints and bones, and can also cause hepatotoxic effects with prolonged intake of high doses.
- Key points to consider:
- Chronic toxicity results from the ingestion of daily amounts of >25,000 IU for more than 6 years or >100,000 IU for more than 6 months, with a high inter-individual variability 1.
- The IOM has set the UL for vitamin A at 3000 mg/d (10,000 IU) for women of childbearing age, highlighting the need for caution in this population 1.
- Vitamin A toxicity can be severe, and it is essential to be aware of the risks, especially for pregnant women, as excessive vitamin A can cause birth defects.
- A balanced diet can provide adequate vitamin A, and supplementation should be approached with caution, considering the potential for toxicity.
- Important considerations for supplementation:
- If supplements are needed, it is crucial to follow the recommended daily intake and be aware of the potential for toxicity, especially with prolonged use or high doses.
- The body's ability to store vitamin A, due to its fat-soluble nature, allows it to accumulate to harmful levels over time, emphasizing the need for careful supplementation practices.
From the Research
Vitamin A Toxicity Studies
- There are several studies that show vitamin A can be toxic in certain circumstances, including:
- A study published in The American journal of clinical nutrition in 2006, which found that high intakes of preformed vitamin A can lead to osteoporosis and hip fracture, even at levels only twice the recommended dietary allowance (RDA) 2.
- A case study published in Liver transplantation in 2006, which reported a case of vitamin A toxicity causing severe liver disease and liver failure in a 60-year-old male who had been taking large doses of vitamin A 3.
- A study published in Annals of neurology in 2002, which found that vitamin A levels were higher in the cerebrospinal fluid of patients with idiopathic intracranial hypertension, suggesting that vitamin A toxicity may play a role in the pathogenesis of this condition 4.
- A case study published in JGH open in 2020, which reported a case of liver toxicity caused by vitamin A in a 27-year-old female who had been taking high doses of vitamin A for over 18 months 5.
- A review published in Anais da Academia Brasileira de Ciencias in 2015, which discussed the neurotoxic effects of vitamin A and retinoids, including bioenergetics state dysfunction, redox impairment, and cell death or proliferation 6.
Key Findings
- High intakes of preformed vitamin A can lead to toxicity, even at levels only twice the RDA.
- Vitamin A toxicity can cause severe liver disease and liver failure.
- Vitamin A toxicity may play a role in the pathogenesis of idiopathic intracranial hypertension.
- High doses of vitamin A can cause liver toxicity.
- Vitamin A and retinoids can have neurotoxic effects, including bioenergetics state dysfunction and cell death or proliferation.