Very high or prolonged doses can potentially cause:
- liver enzyme abnormalities
- liver injury
- headaches
- nausea
- bone problems
- dry or peeling skin
The risk mainly
applies to
high-dose supplements containing preformed vitamin A rather than beta-carotene naturally found in fruits and vegetables.
The NIH Office of Dietary Supplements specifically warns that excessive preformed vitamin A can damage the liver.
Be especially careful if:
- you take multiple supplements containing vitamin A
- you use high-dose retinol products
- you already have liver disease
- you regularly consume large amounts of alcohol
More vitamin A is not necessarily better.
2. Vitamin D
Vitamin D plays an important role in bones, muscles, immunity, and calcium regulation.
Vitamin D toxicity is
unusual from food
or sunlight. When it occurs, it is usually the result of taking very large amounts of vitamin D supplements for an extended period.
Excessive vitamin D can cause dangerously high calcium levels.
Possible symptoms include:
- nausea
- vomiting
- weakness
- confusion
- excessive thirst
- frequent urination
- dehydration
Very high vitamin D levels may lead to kidney stones and, in severe cases, kidney failure.
