From the Guidelines
Vitamin A can be toxic when consumed in excessive amounts, with acute toxicity occurring at doses above 300,000 IU in adults and 60,000 IU in children, and chronic toxicity resulting from daily intake exceeding 25,000 IU for more than 6 years or 100,000 IU for more than 6 months 1.
Key Findings
- The European Society for Clinical Nutrition and Metabolism (ESPEN) guidelines highlight the risk of vitamin A toxicity, particularly with high doses or prolonged intake 1.
- Symptoms of vitamin A toxicity include increased intracranial pressure, nausea, headaches, pain in joints and bones, and in severe cases, liver damage 1.
- The Institute of Medicine (IOM) has set the upper limit (UL) for vitamin A at 3000 mg/d (10,000 IU) for women of childbearing age 1.
Recommendations
- To avoid vitamin A toxicity, it is essential to consider dietary intake when determining supplement dosing, and to choose beta-carotene forms rather than preformed vitamin A (retinol) when supplementing 1.
- Pregnant women should be especially cautious, as excessive vitamin A can cause birth defects, and should aim to achieve normal serum retinol concentrations through supplementation and dietary intake 1.
- Monitoring of serum vitamin A levels and adjustment of supplement dosing as needed can help prevent toxicity and ensure adequate vitamin A status 1.
From the Research
Vitamin A Toxicity Studies
- There are several studies that show vitamin A can be toxic in certain amounts, including:
- A 2006 study published in The American journal of clinical nutrition, 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 1989 study published in The Nurse practitioner, which described the common symptoms of vitamin A toxicity, including hypercalcemia, hepatomegaly, and dermatological and neurological effects 3.
- The toxicity of vitamin A can also lead to liver damage, as shown in a 2006 study published in Liver international, which found a significant positive correlation between the volume density of perisinusoidal fibrosis and the daily consumption of vitamin A 4.
- Additionally, vitamin A can interact with other substances, such as alcohol, to increase the risk of hepatotoxicity and carcinogenicity, as found in a 1999 study published in The American journal of clinical nutrition 5.
- A 2012 review published in Obstetrical & gynecological survey highlighted the potential adverse perinatal outcomes associated with excessive vitamin A intake, including teratogenic effects 6.
Key Findings
- High intakes of preformed vitamin A can lead to toxicity, even at levels only twice the RDA 2.
- Vitamin A toxicity can cause a range of symptoms, including hypercalcemia, hepatomegaly, and dermatological and neurological effects 3.
- The daily consumption of vitamin A is positively correlated with the severity of perisinusoidal fibrosis 4.
- Vitamin A can interact with alcohol to increase the risk of hepatotoxicity and carcinogenicity 5.
- Excessive vitamin A intake can have adverse perinatal outcomes, including teratogenic effects 6.