Abstract
B group vitamins represent essential micronutrients for myriad metabolic and regulatory processes required for human health, serving as cofactors used by hundreds of enzymes that carry out essential functions such as energy metabolism, DNA and protein synthesis and other critical functions. B vitamins and their corresponding vitamers are universally essential for all cellular life forms, from bacteria to humans. Humans are unable to synthesize most B vitamins and are therefore dependent on their diet for these essential micronutrients. More recently, another source of B vitamins has been identified which is derived from portions of the 1013 bacterial cells inhabiting the gastrointestinal tract. Here we review the expanding literature examining the relationship between B vitamins and the immune system and diverse cancers. Evidence of B vitamin’s role in immune cell regulation has accumulated in recent years and may help to clarify the disparate findings of numerous studies attempting to link B vitamins to cancer development. Much work remains to be carried out to fully clarify these relationships as the complexity of B vitamins’ essential functions complicates an unequivocal assessment of their beneficial or detrimental effects in inflammation and cancers.
Highlights
B vitamins (B1, thiamine, B2, riboflavin, B3, niacin, B5, pantothenic acid B6, pyridoxine, B7, biotin B9, folate and B12, cobalamin) are essential micronutrients for all cellular life
One-carbon metabolism balances the flux of one-carbon units toward either the folate cycle that generates nucleotides for DNA and RNA synthesis and energy metabolism or alternatively, toward the methionine cycle for methionine generation where it serves as precursor of SAM, which is required for the methylation of DNA, RNA, histones and proteins impacting gene expression
Evidence for some B vitamins having a protective role in various cancers remains elusive, begging the question, why? The answers are likely to be complex, owing to the number of variables associated with any B vitamin such as absorption, bioactivity and variability of vitamer generation to name a few
Summary
A.A. Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, 119991 Moscow, Russia. Immunity and Pathogenesis Program, Infectious and Inflammatory Diseases Center, Sanford Burnham. Tumor Microenvironment and Cancer Immunology Program, Sanford Burnham Prebys Medical Discovery. Received: 13 October 2020; Accepted: 2 November 2020; Published: 4 November 2020
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