Your body requires adequate amounts of each of the essential vitamins to function properly. Vitamin deficiencies can lead serious medical problems, ranging from weak bones to anemia. Although the amounts of vitamins typically obtained from your diet or a daily multivitamin prove safe, taking high doses of vitamin supplements can lead to adverse side effects or toxicity. Overdoses of the fat-soluble vitamins are particularly dangerous because your body stores these micronutrients and a toxic level can build up over time.
Hypervitaminosis A
Vitamin A is a fat-soluble substance, stored primarily in your liver. Vitamin A toxicity, or hypervitaminosis A, may occur if you take too much vitamin A. The Institute of Medicine of the National Academies recommends taking no more than 3,000 micrograms of vitamin A per day. Signs and symptoms of hypervitaminosis A include nausea, vomiting, loss of appetite, dizziness, drowsiness, irritability, headaches, blurred vision, bone pain, hair loss, dry or peeling skin, itching and yellow skin discoloration.
Severe hypervitaminosis A can cause liver damage, potentially leading to liver failure. Excess vitamin A intake during pregnancy may lead to birth defects. The Office of Dietary Supplements of the National Institutes of Health reports that hypervitaminosis A may contribute to osteoporosis, a condition characterized by weak bones and reduced bone mineral content.
Hypervitaminosis D
Vitamin D, a fat-soluble vitamin, can accumulate to toxic levels with excessive supplementation, leading to hypervitaminosis D. Because vitamin D increases calcium absorption from your small bowel, excess supplementation can lead to an abnormally elevated blood calcium level. Symptoms of vitamin D toxicity include vomiting, loss of appetite, irritability, increased thirst, increased urinary volume and frequency, constipation and muscle weakness. Hypervitaminosis D increases your risk of developing kidney stones. As of 2010, the Institute of Medicine recommends consuming no more than 50 micrograms of vitamin D daily to prevent the development of hypervitaminosis D.
Bleeding Risk
Taking more than 1,000 mg of vitamin E daily may lead to an increased risk of bleeding, especially if you take blood-thinning or antiplatelet medication, "The Merck Manual for Healthcare Professionals" reports. The risk of bleeding associated with excess vitamin E intake increases if you have a low intake of vitamin K, which is used by your liver to manufacture blood clotting factors.
Heartburn and Diarrhea
Vitamin C is a water-soluble vitamin that is not stored by your body. Large doses of vitamin C, however, can lead to stomach upset, heartburn and diarrhea, the Mayo Clinic reports. The Institute of Medicine recommends that you take no more than 2,000 mg of vitamin C daily.
References
- Institute of Medicine of the National Academies: Dietary Reference Intakes: Vitamins
- MedlinePlus: Hypervitaminosis A
- National Institutes of Health, Office of Dietary Supplements: Vitamin A
- Oregon State University Linus Pauling Institute: Vitamin A
- MedlinePlus: Hypervitaminosis D
- National Institutes of Health, Office of Dietary Supplements: Vitamin D
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