Q. What is the difference between fat-soluble and water-soluble vitamins? Why can fat-soluble vitamins cause harm when ingested in excess?
Water-soluble vitamins are those vitamins that are soluble in water. Fat-soluble vitamins are those soluble in oil that is lipids and fat.
Vitamin C and the vitamins of the B complex are types of water-soluble vitamins. Vitamins A, D, E and K are types of fat-soluble vitamins.
Fat-soluble vitamins, since they aren't soluble in water cannot easily be excreted by the body so they tend to accumulate in tissues with toxic effect when they are ingested in amounts over what is necessary.