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Definition: Vitamin deficiency means a shortage of vitamins in the body. Vitamins are essential compounds for our bodily functions, but cannot be created by the body itself. We therefore need to take vitamins in through our diet. A deficiency in vitamins can therefore be solved by improving diet or with vitamin supplements.


We refer to vitamins as the group of organic compounds that are essential for normal and healthy growth and are required from diet, because they cannot be synthesized by our body. Vitamins are classified into two groups depending on their solubility.

Fat-soluble vitamins are required for various body functions, such as bone metabolism, blood coagulation, immune response, antioxidant activity and other actions needed for the prevention of many diseases. Water-soluble vitamins are essential for metabolism, participating in several metabolic pathways and are involved in energy production, redox reactions and the transfer of carbon units [1].

Vitamins play multiple functions within the central nervous system, which may help to maintain brain health and optimal cognitive functioning. Recent studies have suggested supplementation of the diet with various vitamins as a way of maintaining cognitive function, or even of preventing dementia, in later life [2]. Thus, diet and lifestyles (also sunlight-exposure) are very important to maintain a healthy status in many ways [3].

Vitamin deficiencyWithin fat-soluble vitamins, Vitamin D deficiency is characterized by blood plasma levels of circulating 25-hydroxy vitamin D [25(OH)D] below 20 ng/mL and is associated with some chronic diseases, such as insulin resistance, metabolic syndrome [4], atherosclerosis, obesity and mental diseases [5]. In aging, vitamin needs are higher, so elderly people have a higher risk of being vitamin deficit. This group is also at risk of mental illnesses such as dementia, stages of mild cognitive impairment and cognitive decline and flexibility [6], although a direct link between old age, vitamin D deficiency and cognitive decline has not yet been proven. ]. Recent studies have shown evidence demonstrating the widespread presence of vitamin D receptors and 1α-hydroxylase (the enzyme responsible for the formation of the active vitamin) in the human brain. Vitamin D directly upregulates expression of tyrosine hydroxylase, an enzyme important for the regulation of the neurotransmitter dopamine) [7]. It is also suggested that vitamin D is involved in the synthesis of serotonin in the brain. Serotonin is a neurotransmitter that plays critical roles in brain function, and so maintaining vitamin D levels is associated with their correct synthesis in elderly people [8]. 

As for water-soluble vitamins, B complex vitamins act as coenzymes involved in many biochemical pathways necessary for proper tissue and organ function. Current studies are investigating whether B complex vitamin supplementation can reduce the symptomatology of depression [9], cognitive impairment, dementia, even insomnia in later life [10]. There are many studies that try to determine if vitamin supplementation improves the symptoms of these disorders., Although there are no conclusive results regarding the cognitive effects of vitamin supplementation, it is considered essential to maintain vitamins at appropriate levels for proper functioning and healthy aging  [11].


[1] Thomas-Valdés S, Tostes MDGV, Anunciação PC, da Silva BP, Sant’Ana HMP. Association between vitamin deficiency and metabolic disorders related to obesity. Crit Rev Food Sci Nutr. 2017 Oct 13;57(15):3332-3343. doi: 10.1080/10408398.2015.1117413. Review.

[2] Rutjes_AWS, Denton_DA, Di Nisio_M, Chong_LY, Abraham_RP, Al-Assaf_AS, Anderson_JL, Malik_MA, Vernooij_RWM, Martínez_G, Tabet_N, McCleery_J. Vitamin and mineral supplementation for maintaining cognitive function in cognitively healthy people in mid and late life. Cochrane Database of Systematic Reviews 2018, Issue 12. Art. No.: CD011906. DOI: 10.1002/14651858.CD011906.pub2.

[3] Bierens, M. 2019.

[4] Wieder-Huszla S, Jurczak A, Szkup M, Barczak K, Dołęgowska B, Schneider-Matyka D, Owsianowska J, Grochans E. Relationships between Vitamin D₃ and Metabolic Syndrome. Int J Environ Res Public Health. 2019 Jan 9;16(2). pii: E175. doi: 10.3390/ijerph16020175.

[5] Khoshbakht Y, Bidaki R, Salehi-Abargouei A. Vitamin D Status and Attention Deficit Hyperactivity Disorder: A Systematic Review and Meta-Analysis of Observational Studies. Adv Nutr. 2018 Jan 1;9(1):9-20. doi:10.1093/advances/nmx002.

[6] Aarts E, van Holstein M, Cools R. Striatal Dopamine and the Interface between Motivation and Cognition. Front Psychol. 2011 Jul 14;2:163. doi:10.3389/fpsyg.2011.00163.

[7] Cui X, Pertile R, Liu P, Eyles D. Vitamin D regulates tyrosine hydroxylase expression: N-cadherin a possible mediator. Neuroscience 2015;304:90–100.

[8] Patrick RP, Ames BN. Vitamin D and the omega-3 fatty acids control serotonin synthesis and action, part 2: relevance for ADHD, bipolar disorder, schizophrenia, and impulsive behavior. FASEB J 2015;29(6):2207–22. doi: 10.1096/fj.14-268342.

[9] Gorlova A; Veniaminova E. 2019.

 [10] Djokic G, Vojvodić P, Korcok D, Agic A, Rankovic A, Djordjevic V, Vojvodic A, Vlaskovic-Jovicevic T, Peric-Hajzler Z, Matovic D, Vojvodic J, Sijan G, Wollina U, Tirant M, Thuong NV, Fioranelli M, Lotti T. The Effects of Magnesium – Melatonin – Vit B Complex Supplementation in Treatment of Insomnia. Open Access Maced J Med Sci. 2019 Aug 30;7(18):3101-3105. doi: 10.3889/oamjms.2019.771.

[11] Ford AH, Almeida OP. Effect of Vitamin B Supplementation on Cognitive Function in the Elderly: A Systematic Review and Meta-Analysis. Drugs Aging. 2019 May;36(5):419-434. doi: 10.1007/s40266-019-00649-w.

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About the author

Rebeca Fernández-Carrión began her professional career in Human Food and Nutrition (2013), and a Master in Food Quality and Safety (2015). Currently she is a PhD Student within the Medicine program of the University of Valencia, Spain, focusing on Nutritional Genomics. She also works as Senior Research Support Technician for the Valencia Regional Government (PROMETEO 17/2017) and Nutritionist in the PREDIMED Plus study. PREDIMED-Plus is one of the studies participating in the Eat2beNICE project, coordinated at Radboud University, The Netherlands. She is also a researcher member in CIBER of the Pathophysiology of Obesity and Nutrition (ciberobn).

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