Vitamins are a group of organic substances that are essential for the normal functioning of the human body. Vitamins are classified into two groups: water-soluble and fat-soluble. The water-soluble vitamins (vitamins C and B complex) are not stored in the body and need to be replenished daily. The fat-soluble vitamins (vitamins A, D, E and K) are stored in the liver and fatty tissues and can last for weeks or months without being replaced.
Vitamin A is important for growth, reproduction and cell differentiation. Vitamin D is essential for calcium absorption and bone health. Vitamin E functions as an antioxidant, protecting cells from damage caused by free radicals. Vitamin K is necessary for blood clotting.
The B vitamins include thiamine (vitamin B1), riboflavin (vitamin B2), niacin (vitamin B3), pantothenic acid (vitamin B5), pyridoxine (vitamin B6), biotin (vitamin B7), folic acid (vitamin B9) and cobalamin (vitamin B12). These vitamins are involved in energy metabolism, nervous system function, red blood cell production and DNA synthesis.
A balanced diet usually provides enough of these vitamins but some people may require supplements due to poor absorption or increased needs during pregnancy, lactation or illness. Megadoses of certain vitamins can be toxic so it is important to consult a healthcare professional before taking any supplements.