Vitamins and minerals are essential nutrients for growth and development, reproduction, immune system function and energy metabolism. People take vitamin and mineral supplements for many reasons, including to obtain nutrients that they do not get in sufficient amounts from food and to prevent disease or manage a medical condition. Nonetheless, vitamins and minerals have dosage limits that, if exceeded, can increase the risk of health problems. Consult your doctor about dosage limits of vitamins and minerals.
Vitamin A
Vitamin A is a fat-soluble vitamin and antioxidant vital for cellular function, immune system stimulation, vision, reproduction and bone growth. A vitamin A deficiency is the leading cause of blindness in children and is associated with risk of infectious diseases. Vitamin A is found in fruits and vegetables, milk, liver and dietary supplements. The recommended dietary allowance for vitamin A is 3,000 international units for adult males and 700 IU for adult females, while the tolerable upper intake level is 10,000 IU for all adults. Exceeding this upper limit dosage can increase your risk of hypervitaminosis A, a toxic condition that can occur in a short period of time. The symptoms of vitamin A toxicity include nausea, loss of appetite, dizziness, dry itchy skin and joint pain.
Vitamin C
Vitamin C, also called ascorbic acid, is a water-soluble vitamin required to synthesize norepinephrine, carnitine and collagen. Norepinephrine is a neurotransmitter that affects mood and behavior. Carnitine is responsible for transporting fat into the mitochondria of cells where the fat is converted into energy. Collagen is a structural component of blood vessels, bones, tendons and ligaments. Vitamin C is also an antioxidant that stimulates your immune system to fight infections and protects your cells from harmful chemicals and toxins. The recommended dietary allowances for vitamin C are 90 mg for adult men and 75 mg for adult women, whereas the tolerable upper intake level is 2,000 mg for all adults. Exceeding 2,000 mg can increase your risk of rebound scurvy, genetic mutations, birth defects, kidney stones, erosion of dental enamel, cancer and atherosclerosis.
Calcium
Calcium is a mineral you need to produce and maintain healthy bones and prevent osteoporosis. The recommended daily intake of calcium is 1,000 mg for men and women ages 19 to 50 years and 1, 200 mg for men and women ages 51 years and older. The tolerable upper intake level for calcium is 2,500 mg for adults ages 19 to 50 years and 2,000 mg for adults ages 51 years and older. Overconsumption of calcium from foods and supplements can result in kidney stones, nausea, loss of appetite, abdominal pain, confusion, coma and even death.
Selenium
Selenium is a trace mineral that plays a vital role in assisting enzymes called selenoproteins that regulate cell growth and protect the cells in your blood vessels. The recommended daily allowance for selenium is 55 mcg, whereas the tolerable upper intake level is 400 mcg. Exceeding this dosage can result in gastrointestinal distress, hair loss and skin rashes.
References
- MedlinePlus; Vitamin A; April 2011
- World Health Organization; Vitamin a Deficiency; 2011
- Linus Pauling Institute at Oregon State University; Vitamin A; Victoria Drake; November 2007
- Linus Pauling Institute at Oregon State University; Vitamin C; Balz Frei; November 2009
- University of Maryland Medical Center; Calcium; March 2009
- Linus Pauling Institute at Oregon State University; Calcium; June Chan; June 2007
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