Vitamins are compounds that the body needs only in very small amounts, but they’re essential for health since the body can’t make them in adequate quantities. Vitamin deficiencies can have serious health repercussions, particularly if they exist over a long period of time. On the other hand, getting too much of some vitamins in supplemental form can be a problem too. One example is vitamin A. How much is too much vitamin A – and what happens when you get excessive amounts of it?
How Much is Too Much Vitamin A?
The recommended daily allowance of vitamin A for adults is 5,000 international units. You can get vitamin A directly from animal foods, but also by eating plant foods that are high in carotenoids – such as carrots, sweet potatoes, apricots, and squash. The carotenoids in fruits and vegetables are called pro-vitamin A, because a portion of them are converted by the liver to vitamin A.
Excess vitamin A, particularly supplemental vitamin A, isn’t healthy since it’s a fat-soluble vitamin that can be stored by the liver – so excessive vitamin A in the diet, or in the form of supplements, can build up in the body – leading to toxicity.
What Happens if You Get Too Much Vitamin A?
Vitamin A excess usually comes from taking supplements. It’s difficult to get enough vitamin A through diet alone to cause toxicity – although too much pro-vitamin A in the form of carotenoids, can cause a benign, self-limited condition called carotenemia, where the skin turns orange.
To reach toxic levels of vitamin A, a person would need to consume at least four to five times the recommended daily allowance every day for six months or longer. This is difficult to do through diet alone. For people who take supplements, vitamin A excess can be more of a problem.
Symptoms of Excess Vitamin A: Vitamin A Toxicity
Excess vitamin A causes a variety of symptoms, mostly due to its effects on bone metabolism – and on the liver. Too much vitamin A over long periods of time can lead to bone fractures, bone pain, joint discomfort, and liver abnormalities. Bone fractures occur because vitamin A and vitamin D compete for the same receptor, so too much vitamin A interferes with vitamin D’s bone-preserving benefits.
Other symptoms of excess vitamin A include nausea, abdominal pain, weakness, loss of hair, brittle nails, weight loss, headache, blurred vision, dry mucous membranes, fever, sweating, and personality changes. People who have liver disease are more prone to vitamin A toxicity.
How Much Vitamin A is Too Much: The Bottom Line?
The best way to avoid getting excess vitamin A is to get it from dietary sources. Vitamin A is found mostly in meat and dairy foods, although carotenoids, some of which are converted to vitamin A, are found in orange-colored fruits and vegetables. For safety purposes, don’t take vitamin A supplements except under a doctor’s care.
Emedicine website. “Vitamin A Toxicity”
Merck Manual. Eighteenth Edition.