Consuming too many vitamins can cause vitamin toxicity, or hypervitaminosis. Vitamins absorbed from food rarely lead to toxicity, but taking too many supplemental vitamins can. While the body generally excretes excess water-soluble vitamins, fat-soluble vitamins are stored in the liver and fatty tissues, and excesses can lead to serious health problems. Vitamins A, D, E and K are fat soluble.
Vitamin A
The National Institutes of Health Office of Dietary Supplements, or ODS, warns that acute hypervitaminosis A can cause nausea, vomiting, headaches, dizziness, blurred vision and a loss of coordination. Chronic hypervitaminosis A can lead to birth defects, liver abnormalities, neurological disorders and loss of bone mineral density, which can result in osteoporosis. The established daily upper intake levels for vitamin A are 600 mcg for children under age 3, 900 mcg for children ages 4 to 8, 1,700 mcg for children age 9 to 13, 2,800 mcg for teenagers age 13 to 18, and 3,000 mcg for adults, including pregnant and lactating women.
B-Complex Vitamins
Consuming too much vitamin B6 and niacin can have negative consequences. Symptoms of excessive vitamin B6 consumption include acne, photosensitivity, gastrointestinal distress, abnormal liver function tests, headaches, and tingling or numbness in the arms and legs. Fetal seizures may result from high maternal consumption of vitamin B6. MayoClinic.com recommends that adults limit daily vitamin B6 consumption to 100 mg.Symptoms of excess niacin consumption include cramps, nausea, vomiting and abnormal liver function tests.
Vitamin C
Vitamin C is generally not considered to be toxic at high levels, but can cause diarrhea, nausea and abdominal cramping in large amounts, according to the ODS.
Vitamin D
Hypervitaminosis D causes nausea, vomiting, anorexia, constipation, weakness and weight loss, according to the ODS. Because vitamin D plays a role in regulating blood calcium levels, hypervitaminosis D can cause elevated blood calcium levels, which can cause confusion and cardiac arrhythmia. Tolerable daily upper level vitamin D limits are 25 mcg for infants under age 1 and 50 mcg for children over age 1 and adults, including pregnant and lactating women.
Vitamin E
Large doses of vitamin E are generally considered to be safe, but may cause nausea and gastrointestinal disorders.
Vitamin K
There are no side effects associated with overconsumption of vitamin K.
References
- Colorado State University: Fat-Soluble Vitamins
- National Institutes of Health Office of Dietary Supplements: Dietary Supplement Fact Sheet: Vitamin A and Carotenoids
- MayoClinic.com: Vitamin B6
- Colorado State University: Water-Soluble Vitamins
- National Institutes of Health Office of Dietary Supplements: Vitamin C
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