Vitamins are chemical substances which are essential for cell functioning. Humans have discovered 13 of them so far. Scientists have grouped them into two categories:

1- Four Fat-soluble Vitamins: these are vitamins  A, D, E & K which get stored in the human body’s fatty tissue.

2- Nine Water-soluble Vitamins: these types of vitamins leave the body through urine. Among them is vitamin B12 which can stay in the human liver for several years.

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