Vitamin A is a very important nutrient for healthy skin and eyes, immunity and good general health but just how much vitamin A is too much and can an overdose be toxic?
Vitamin A Toxicity and Overdose
A vitamin A intake of more than 25,000 IU for adults and 10,000 IU for children a day for several months may be toxic to the human body. Children are more vulnerable to vitamin A toxicity than adults so keep vitamin supplements well out of their reach.
Chronic vitamin A toxicity is usually only seen with a very high intake of preformed vitamin A supplements over a long period. Hypervitaminosis A is the term given for the condition caused by vitamin A overdose and symptoms can include loss of appetite; dizziness; headaches; dry, itchy skin; hair loss; blurred vision and reduced bone mineral density, leading to joint pain and even eventually osteoporosis. Severe cases of hypervitaminosis A, while very rare, may lead to liver damage and hemorrhage.
To avoid vitamin A overdose read the labels on any health supplements containing synthetic preformed vitamin A and keep your intake under 10,000 IUs a day. Most vitamin supplements do not exceed 10,000 IUs when taken at the recommended dosage.
Also remember that beta-carotene, often used in multivitamin supplements, is a carotenoid and will not be converted to vitamin A once the body has what it needs. While many supplements will list beta-carotene as vitamin A, it isn’t really until it’s converted, and this is conversion is estimated to be at a ratio of at least 12 to 1 of beta-carotene into vitamin A. From this perspective, the whole practice of listing beta-carotene as Vitamin A is actually pretty misleading.
Women who are pregnant should discuss their vitamin A needs with a healthcare professional to avoid getting either too much or too little preformed vitamin A retinol. People with liver disease, those at risk of osteoporosis, smokers and those who regularly drink a lot of alcohol should also be careful about ingesting too much vitamin A from vitamin supplements.
A high quality cod liver oil, with a good balance of natural vitamin A to vitamin D, is a much more effective way to get your fat soluble retinol than the isolated synthetic retinyl palmitate in many multivitamin capsules. While you definitely don’t want excessive doses of either, avoiding getting too much vitamin A actually has a lot to do with getting it in the correct vitamin A to vitamin D ratio as well.
Photo credit with thanks: nathanmac87