What is the difference between water-soluble and fat-soluble vitamins? Why can fat-soluble vitamins cause harm when ingested in excess?
Water-soluble vitamins are those soluble in water. Fat-soluble vitamins are those soluble in oil (lipids, fat). Vitamin C and the vitamins of the B complex are instance of water-soluble vitamins. Vitamins A, D, E and K are examples of fat-soluble vitamins.
Fat-soluble vitamins, as they are not soluble in water, cannot simply be excreted by the body. So they tend to accumulate in tissues with toxic effect when they are ingested in amounts over what is essential.