The vitamins are substances essential to the body classified into 13 families according to their specific physiological role. To go further in their categorization, two major classes can also be considered: vitamins soluble, which can dissolve in water and vitamins fat soluble which can dissolve in fat. In the end, if we consider the exhaustive list of vitamins, we find vitamin A or retinol, vitamin D or calciferol, vitamin E and vitamin K which are fat soluble then vitamins B1, B2, B3 or PP, B5 , B6, B8, B9, B12 and vitamin C or ascorbic acid which are water soluble.¹

Vitamins do not provide the body with any energy, in other words, they have no caloric value. However, each has an essential role for the functioning or the construction of the organism as long as the recommended intakes are respected. If these contributions must be reached to ensure the body to be in good health, they must not be exceeded: an excess of vitamins does not improve performance. In addition, a balanced diet must be able to provide each individual with the recommended daily dose of vitamins without resorting to food supplements. However, certain nuances must be made in certain cases, in particular for vitamin D for which certain populations are significantly deficient and vitamin B9 or folic acid, which is crucial in pregnant women for the optimal development of the fetus.²

Source: http://www.anses.fr/fr/content/que-sont-les-vitamines http://www.anses.fr/fr/content/vitamine-b9-ou-acide-folique