Overall, the classification of vitamins is based on such a criterion as their solvability. One can distinguish two broad groups, in particular, fat-soluble vitamins such as A or E and water-soluble vitamins like folate or biotin (Grosvenor & Smolin, 2012). Certainly, these organic compounds can be divided into other classes; for example, one can use such a criterion as the functions that they perform. However, the first approach is more widespread. Vitamins play a critical role for the growth and functioning of the body at various pre-natal and post-natal stages. For example, they are involved the chemical reactions that are vital for the formation of bones. In this case, one should speak primarily about vitamins D and K. In turn, its shortage of these chemical compounds can impair the development of a fetus. Secondly, vitamins are necessary for normal blood-clotting (Insel, Ross, McMahon, & Bernstein, 2010, p. 388). Apart from that, they are important for many cognitive functions such as memory or attention. For example, the shortage of B vitamins can impair the functioning of the brain. One should also remember that vitamins act as antioxidants that shield the organ from the detrimental effects of free radicals (Insel et al., 2010, p. 388). These examples indicate that these compounds are involved in various physiological processes. Overall, fat-soluble vitamins can be viewed as lipid-like molecules which can be solved in fat (Insel et al., 2010, p. 388). For instance, one can mention vitamins A, E, D, or K. These chemical substances can be derived from various types of food. For instance, vitamin A can be found in dairy products such as milk or butter. Additionally, fish is an important source of vitamins A and D. Moreover, vegetables like carrots or broccoli can contain fat-soluble vitamins. These are some of the main sources that can be identified. One can also discuss the specific role of fat-soluble vitamins. For example, vitamin A performs such roles as gene transcription, bone metabolism, and anti-oxidation. Its deficiency can lead to such problems as hyperkeratosis, night-blindness, and keratomalacia (McClatchey, 2002, p. 444). In turn, the toxicity of vitamin A takes place when the intake exceeds 500,000 milligrams per day. Its overdose is associated with such symptoms as nausea, intracranial pressure, or muscle weakness (McClatchey, 2002, p. 444). These are the main detrimental effects that can be mentioned. Apart from that, one can speak about vitamin D. One of its roles is to activate the innate immune systems. Secondly, it reduces the risk of a cardiovascular disease. Furthermore, its deficiency is associated with such as disorder as rackets (McClatchey, 2002, p. 445). Provided that a person ingests excessive amount of this vitamin, he/she can develop hypocalcaemia (McClatchey, 2002, p. 445). This is the main toxic risk that should be taken into account. Furthermore, one should speak about water-soluble vitamins. They are stored in the watery compartments of different foods. One of their distinctions is that they do not require lipoprotein carriers (Insel et al., 2010, p. 388). This group includes vitamins of the B group, and vitamin C. These nutrients can be found in meat, vegetables such as avocados or broccoli, fish, and dairy products. One can pr