Vitamins are a key element in having the body function properly. When a person does not receive enough vitamins, he can develop deficiencies that cause problems in the way the body functions. Vitamins are either water-soluble or fat-soluble. Any excess of a water-soluble vitamin is excreted in the urine. Fat-soluble vitamins are stored in the liver and fatty tissues until the body needs them. Because fat-soluble vitamins are stored, they can be toxic to the body in excessive quantities, writes Frances Sizer and Ellie Whitney in their book "Nutrition Concepts and Controversies."
Vitamin A
Taking more than 3,000 International Units, or IUs, of vitamin A can be toxic to a person. According to Sizer and Whitney, signs and symptoms of toxic amounts of vitamin A include abdominal pain, hair loss, joint pain, stunted growth, and soreness in the bones and muscles. In women, cessation of menstrual period can be a symptom of too much vitamin A. Nausea, rashes, diarrhea, liver damage and enlargement of the spleen are also signs and symptoms of too much vitamin A. Healthy people can consume foods that naturally contain vitamin A in large amounts and not experience toxic levels.
Vitamin D
According to Sizer and Whitney, vitamin D is the most potentially toxic of all vitamins. Signs and symptoms of toxic levels of vitamin D include increase in blood calcium levels, kidney stones, excessive thirst, headaches, irritability, loss of appetite and nausea. Calcification of soft tissues can occur, as well as thinning of tooth enamel with toxic levels of vitamin D. The Tolerable Upper Intake Level for vitamin D is 50 micrograms, or 2,000 IUs a day.
Vitamin C
Many people take extra vitamin C to help prevent colds, but too much vitamin C can cause health problems. According to MayoClinic.com, when vitamin C is taken in excess, signs and symptoms of toxicity can include nausea, abdominal cramping, diarrhea, excessive urination, headache, fatigue, insomnia, rashes and kidney stones. Sizer and Whitney report that the Dietary Reference Intake for vitamin C is 90mg for men and 75mg for women.
Consult with Medical Professionals
Before a person purchases vitamins, she should consult her doctor about the type of vitamin, whether she actually needs to take a supplement and the correct dosage. Some vitamins can be more toxic than others, and the person may not even need to be taking a supplement. The doctor can do blood work if a person or the doctor believes she is deficient in a nutrient. If the person is deficient, then the doctor will prescribe the correct dosage for that individual.
Vitamins From Natural Sources
A person should receive most, if not all, vitamins from the foods he eats. Sources of vitamin A can be found in dark-green leafy vegetables, broccoli, apricots, cantaloupe, carrots, sweet potatoes and pumpkin. Vitamin D comes from sunlight and some foods such as milk, liver, sardines, salmon and shrimp. Vitamin C is found in citrus fruit, dark green vegetables, tomatoes and potatoes.
References
- Mayo Clinic: Too Much Vitamin C
- "Nutrition Concepts and Controversies (10th Edition)"; Frances Sizer and Ellie Whitney; 2006
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