Vitamin D generates many extraskeletal effects due to the vitamin D receptor (VDR) which is present in most tissues throughout the body. The possible role of vitamin D in infections is implied from its impact on the innate and adaptive immune responses. A significant effect is also the suppression of inflammatory processes. Because vitamin D could be acknowledged as a “seasonal stimulus”, as defined by R. Edgar Hope-Simpson, it would be crucial to prove it from a potential easy and cheap prophylaxis or therapy support perspective as far as influenza infections are concerned. The survey of the literature data generates some controversies and doubts about the possible role of vitamin D in the prevention of influenza virus. The most important point is to realise that the broad spectrum of this vitamin’s activity does not exclude such a possibility. According to most of the authors, more randomized controlled trials with effective, large populations are needed to explore the preventive effect of vitamin D supplementation on viral influenza infections.

The importance of vitamins in the prevention of cancer has attracted the attention of consumers, nutritionists and scientists for decades. The mechanisms of carcinogenesis, extended in the context of the function of vitamins, i.e. regulation of and participation in metabolic processes in the cell, suggest a substantial impact of these compounds on the initial stages of carcinogenesis. One-carbon metabolism involving folic acid, vitamins B2, B6 and B12, and folate metabolism doesn't only generate methyl groups, thus determining epigenetic processes, modifications of the genome and carcinogenesis. It also provides the compounds involved in the DNA synthesis and repair processes, especially the synthesis of purines and pyrimidines and the conversion of dUMP (2-deoxyuridine monophosphate) to dTMP (2-deoxythymidine monophosphate). In light of these pathways, folate, together with vitamins B2, B6 and B12, became a subject of interest as compounds whose deficit or surplus can potentially have an impact on the processes of carcinogenesis. Literature reports, however, do not fully confirm that the influence on the synthesis of nucleotides is connected with the inhibition of carcinogenesis. The impact of individual vitamins involved in one-carbon metabolism on carcinogenesis and their role in the prevention of these conditions depend on the type of cancer and the dose administered. Nevertheless, the research conducted makes it possible to conclude a considerable and probably long-underestimated role of these compounds in the prevention of serious, difficult to treat or incurable diseases.