View source for Philosophy:Nutrition and cognition

{{short description|Biological relationship}}
Relatively speaking, the [[Biology:Brain|brain]] consumes an immense amount of energy in comparison to the rest of the body. The mechanisms involved in the transfer of energy from foods to neurons are likely to be fundamental to the control of brain function.<ref name="alpha" /> Human bodily processes, including the brain, all require both [[Earth:Nutrient|macronutrients]], as well as micronutrients.<ref name= bravo>{{cite journal | vauthors = Bourre JM | title = Effects of nutrients (in food) on the structure and function of the nervous system: update on dietary requirements for brain. Part 1: micronutrients | journal = The Journal of Nutrition, Health & Aging | volume = 10 | issue = 5 | pages = 377–385 | year = 2006 | pmid = 17066209 }}</ref>

Insufficient intake of selected vitamins, or certain metabolic disorders, may affect [[Cognition|cognitive processes]] by disrupting the nutrient-dependent processes within the body that are associated with the management of energy in neurons, which can subsequently affect [[Biology:Synaptic plasticity|synaptic plasticity]], or the ability to encode new [[Memory|memories]].<ref name="alpha">{{cite journal | vauthors = Gómez-Pinilla F | title = Brain foods: the effects of nutrients on brain function | journal = Nature Reviews. Neuroscience | volume = 9 | issue = 7 | pages = 568–578 | date = July 2008 | pmid = 18568016 | pmc = 2805706 | doi = 10.1038/nrn2421 }}</ref>

== Macronutrients ==
The human brain requires [[Earth:Nutrient|nutrient]]s obtained from the diet to develop and sustain its physical structure and [[Cognition|cognitive functions]].<ref name="alpha" /><ref>{{cite journal | vauthors = Costello SE, Geiser E, Schneider N | title = Nutrients for executive function development and related brain connectivity in school-aged children | journal = Nutrition Reviews | volume = 79 | issue = 12 | pages = 1293–1306 | date = November 2021 | pmid = 33355357 | doi = 10.1093/nutrit/nuaa134 }}</ref><ref name=":0" /> Additionally, the brain requires [[Calorie|caloric energy]] predominately derived from the primary macronutrients to operate.<ref name="alpha" /><ref name=":0" /> The three primary macronutrients include [[Chemistry:Carbohydrate|carbohydrate]]s, [[Biology:Protein|protein]]s, and [[Chemistry:Fat|fat]]s. Each macronutrient can impact [[Cognition|cognition]] through multiple mechanisms, including glucose and insulin metabolism, neurotransmitter actions, oxidative stress and inflammation, and the gut-brain axis.<ref name=":0">{{cite journal | vauthors = Muth AK, Park SQ | title = The impact of dietary macronutrient intake on cognitive function and the brain | language = English | journal = Clinical Nutrition | volume = 40 | issue = 6 | pages = 3999–4010 | date = June 2021 | pmid = 34139473 | doi = 10.1016/j.clnu.2021.04.043 | s2cid = 235470536 }}</ref><ref name=":1">{{cite book | vauthors = Robinson JL | date = 2022 | chapter = Macronutrients | title = Salem Press Encyclopedia of Health | publisher = Salem Press; Research Starters }}</ref><ref name=":7">{{cite journal | vauthors = Gutierrez L, Folch A, Rojas M, Cantero JL, Atienza M, Folch J, Camins A, Ruiz A, Papandreou C, Bulló M | display-authors = 6 | title = Effects of Nutrition on Cognitive Function in Adults with or without Cognitive Impairment: A Systematic Review of Randomized Controlled Clinical Trials | journal = Nutrients | volume = 13 | issue = 11 | pages = 3728 | date = October 2021 | pmid = 34835984 | pmc = 8621754 | doi = 10.3390/nu13113728 | doi-access = free }}</ref> Inadequate macronutrient consumption or proportion could impair optimal cognitive functioning and have long-term health implications.<ref name=":0" /><ref name=":7" /><ref>{{cite journal | vauthors = Zamroziewicz MK, Barbey AK | title = Nutritional Cognitive Neuroscience: Innovations for Healthy Brain Aging | journal = Frontiers in Neuroscience | volume = 10 | pages = 240 | date = 2016 | pmid = 27375409 | pmc = 4893495 | doi = 10.3389/fnins.2016.00240 | doi-access = free }}</ref><ref name=":3">{{cite journal | vauthors = Dye L, Lluch A, Blundell JE | title = Macronutrients and mental performance | journal = Nutrition | volume = 16 | issue = 10 | pages = 1021–1034 | date = October 2000 | pmid = 11054612 | doi = 10.1016/S0899-9007(00)00450-0 }}</ref><ref>{{cite journal | vauthors = Klimova B, Dziuba S, Cierniak-Emerych A | title = The Effect of Healthy Diet on Cognitive Performance Among Healthy Seniors - A Mini Review | journal = Frontiers in Human Neuroscience | volume = 14 | pages = 325 | date = 2020 | pmid = 32848680 | pmc = 7433394 | doi = 10.3389/fnhum.2020.00325 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Solon-Biet SM, Mitchell SJ, de Cabo R, Raubenheimer D, Le Couteur DG, Simpson SJ | title = Macronutrients and caloric intake in health and longevity | language = en-US | journal = The Journal of Endocrinology | volume = 226 | issue = 1 | pages = R17–R28 | date = July 2015 | pmid = 26021555 | pmc = 4490104 | doi = 10.1530/JOE-15-0173 }}</ref>

=== Carbohydrates ===
Through digestion, dietary [[Chemistry:Carbohydrate|carbohydrate]]s are broken down and converted into [[Chemistry:Glucose|glucose]], which is the sole energy source for the brain.<ref name=":1" /><ref name=":3" /><ref name=":2">{{cite book | vauthors = Casirola DM | date = 2019 | chapter = Carbohydrates | title = Salem Press Encyclopedia of Science | publisher = Salem Press; Research Starters }}</ref> Optimal brain function relies on adequate carbohydrate consumption, as carbohydrates provide the quickest source of glucose for the brain.<ref name=":5">{{cite journal | vauthors = Wahl D, Cogger VC, Solon-Biet SM, Waern RV, Gokarn R, Pulpitel T, Cabo R, Mattson MP, Raubenheimer D, Simpson SJ, Le Couteur DG | display-authors = 6 | title = Nutritional strategies to optimise cognitive function in the aging brain | journal = Ageing Research Reviews | volume = 31 | pages = 80–92 | date = November 2016 | pmid = 27355990 | pmc = 5035589 | doi = 10.1016/j.arr.2016.06.006 }}</ref> Glucose deficiencies such as [[Medicine:Hypoglycemia|hypoglycaemia]] reduce available energy for the brain and impair all cognitive processes and performance.<ref name=":3" /><ref name=":5" /><ref name=":6">{{cite journal | vauthors = Leigh Gibson E, Green MW | title = Nutritional influences on cognitive function: mechanisms of susceptibility | journal = Nutrition Research Reviews | volume = 15 | issue = 1 | pages = 169–206 | date = June 2002 | pmid = 19087403 | doi = 10.1079/NRR200131 | s2cid = 24862318 | doi-access = free }}</ref> Additionally, situations with high cognitive demand, such as learning a new task, increase brain glucose utilization, depleting blood glucose stores and initiating the need for supplementation.<ref name=":3" />

Complex carbohydrates, especially those with high dietary fibre, are associated with increased cognitive performance and improved memory function.<ref name=":0" /> This is because fibre regulates glucose metabolism, slowing the release of [[Biology:Insulin|insulin]] and preserving insulin sensitivity.<ref name=":0" /> An improperly functioning glucose and insulin metabolism is a primary mechanism for cognitive impairment, and general metabolic dysfunction, as it can cause inflammation and oxidative stress within the brain, potentially leading to [[Medicine:Neurodegeneration|neurodegeneration]].<ref name=":0" /> Therefore, complex carbohydrates with high fibre can improve glucose and insulin metabolism, which decreases inflammation and oxidative stress, and leads to improved brain aging as measured by the absence of [[Social:Disability|disability]], [[Medicine:Depression (mood)|depression]], chronic disease, and decreased cognitive decline.<ref name=":0" />

Simple carbohydrates are associated with decreased global cognitive performance.<ref name=":0" /> Simple carbohydrates negatively impact many essential cognitive processes, including [[Philosophy:Attention|attention]], [[Memory|memory]], reaction time, visual-spatial processing, mental processing speed, and [[Philosophy:Executive functions|executive functions]].<ref name=":0" /> Simple carbohydrates impair cognition through glucose and insulin metabolism dysfunction, as well as causing inflammation and oxidative stress within the brain.<ref name=":0" /> Therefore, excessive or chronic consumption of simple carbohydrates is unanimously linked to negative health consequences.<ref name=":0" /><ref name=":1" /><ref name=":2" />

=== Proteins ===
Through digestion dietary proteins are broken down into individual [[Chemistry:Amino acid|amino acid]]s and absorbed into the blood.<ref name=":0" /><ref name=":1" /> The [[Chemistry:Essential amino acid|essential amino acid]]s [[Chemistry:Tyrosine|tyrosine]] and [[Chemistry:Tryptophan|tryptophan]] are precursors for the [[Biology:Neurotransmitter|neurotransmitter]]s [[Biology:Dopamine|dopamine]], [[Chemistry:Serotonin|serotonin]], and [[Biology:Norepinephrine|norepinephrine]], and these chemicals modulate neural activity and influence cognitive functioning.<ref name=":0" /><ref name=":6" />

Dietary protein can improve cognition by increasing reaction time and inhibition control during mentally demanding and physically stressful situations, as tyrosine and tryptophan will replenish exhausted neurotransmitter levels.<ref name=":0" /><ref name=":3" /><ref name=":6" /><ref name=":4">{{Cite journal | vauthors = Lieberman HR |date=2003-06-01 |title=Nutrition, brain function and cognitive performance |url=https://www.sciencedirect.com/science/article/pii/S0195666303000102 |journal=Appetite |language=en |volume=40 |issue=3 |pages=245–254 |doi=10.1016/S0195-6663(03)00010-2 |pmid=12798782 |s2cid=22347097 |issn=0195-6663}}</ref> Additionally, adequate and consistent consumption of tyrosine and tryptophan correlates to improvements in memory function.<ref name=":0" /><ref name=":4" /> Tyrosine is also shown to improve [[Convergent thinking|convergent thinking]] processes through increased cognitive control.<ref>{{cite journal | vauthors = Colzato LS, de Haan AM, Hommel B | title = Food for creativity: tyrosine promotes deep thinking | journal = Psychological Research | volume = 79 | issue = 5 | pages = 709–714 | date = September 2015 | pmid = 25257259 | doi = 10.1007/s00426-014-0610-4 | s2cid = 16999404 }}</ref>

=== Fats ===
Through digestion dietary fats are broken down into individual [[Chemistry:Fatty acid|fatty acid]]s for utilization. Fatty acids are classified as [[Chemistry:Saturated fat|saturated]], [[Chemistry:Trans fat|trans]], [[Chemistry:Monounsaturated fat|monounsaturated]], [[Chemistry:Polyunsaturated fatty acid|polyunsaturated]], and [[Chemistry:Cholesterol|cholesterol]]. Each class has distinct affects on cognitive functioning and health.<ref name=":0" /> Omega-3 polyunsaturated fatty acids are especially significant as they are critical [[Biology:Cell membrane|cell membrane]] and structural components of the brain.<ref name="alpha" /><ref name=":0" /><ref name=":5" />

Cholesterol is an unsaturated alcohol commonly found in eggs, meat, and dairy. Studies on dietary cholesterol have indicated both positive and negative effects on global cognitive functioning.<ref name=":0" /> However, the adverse cognitive effects of cholesterol consumption appear to be reduced when combined with physical activity, which influences [[Biology:Energy homeostasis|energy homeostasis]] and synaptic plasticity.<ref name=":0" />

Saturated fatty acids are typically solid at room temperature with common sources including butter, cheese, and meat. Trans fatty acids occur naturally in some meat and dairy products, however the majority are artificially created by hydrogenating vegetable oils and are present in many processed foods. Saturated and trans fatty acids decrease cognitive functioning and specifically impact memory and learning performance.<ref name="alpha" /><ref name=":0" />

==Micronutrients==

===Choline===
[[Chemistry:Choline|Choline]] is an essential nutrient and its primary function within the human body is the synthesis of [[Biology:Cell membrane|cellular membranes]],<ref name="lpi">{{cite web|url=http://lpi.oregonstate.edu/infocenter/othernuts/choline|title=Choline|publisher=Micronutrient Information Center, Linus Pauling Institute, Oregon State University|date=1 January 2015|access-date=22 October 2019}}</ref> although it serves other functions as well. It is a precursor molecule to the [[Biology:Neurotransmitter|neurotransmitter]] [[Chemistry:Acetylcholine|Acetylcholine]] which serves a wide range of functions including motor control and memory. Choline deficiencies may be related to some liver and [[Medicine:Neurological disorder|neurological disorder]]s.<ref name="Zeisel SH, da Costa KA">{{cite journal | vauthors = Zeisel SH, da Costa KA | title = Choline: an essential nutrient for public health | journal = Nutrition Reviews | volume = 67 | issue = 11 | pages = 615–623 | date = November 2009 | pmid = 19906248 | pmc = 2782876 | doi = 10.1111/j.1753-4887.2009.00246.x }}</ref> Because of its role in cellular synthesis, choline is an important nutrient during the prenatal and early postnatal development of offspring as it contributes to brain development.<ref name=lpi/> Choline intakes from food for men, women and children may be below the Adequate Intake levels.<ref name="Zeisel SH, da Costa KA"/> Women, especially when pregnant or lactating, the elderly, and infants, are at risk for choline deficiency.<ref name="Zeisel SH, da Costa KA"/> Beef liver, [[Biology:Wheat germ|wheat germ]], and egg yolks are common foods providing choline.<ref name=lpi/>

===B vitamins===
[[Chemistry:B vitamins|B vitamins]], also known as the B-complex, are an interrelated group of nutrients which often co-occur in food. The complex consists of: [[Physics:Thiamine|thiamine]] (B<sub>1</sub>), [[Biology:Riboflavin|riboflavin]] (B<sub>2</sub>), [[Chemistry:Niacin (substance)|niacin]] (B<sub>3</sub>), [[Chemistry:Pantothenic acid|pantothenic acid]] (B<sub>5</sub>), [[Biology:Vitamin B6|pyridoxin]] (B<sub>6</sub>), folic acid (B<sub>9</sub>), cobalamin (B<sub>12</sub>), and [[Chemistry:Biotin|biotin]].<ref>{{cite book |title=Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline |year=1998 |publisher=National Academy Press |location=Washington, DC |isbn=978-0-309-06554-2 |url=http://www.nal.usda.gov/fnic/DRI/DRI_Thiamin/27-40_150.pdf |access-date=2012-03-21 |archive-url=https://web.archive.org/web/20150906184801/http://www.nal.usda.gov/fnic/DRI//DRI_Thiamin/27-40_150.pdf |archive-date=2015-09-06 |url-status=dead }}{{page needed|reason=was " page=27 & pages=1–541". which is it?|date=July 2012}}</ref> B vitamins are not [[Biology:Biosynthesis|synthesized]] in the body, and thus need to be obtained from food. B-complex vitamins are water-soluble vitamins, which means that they are not stored within the body. In consequence, the B vitamins need ongoing replenishment.<ref name= charlie/> It is possible to identify broad cognitive effects of certain B vitamins, as they are involved in many significant [[Biology:Metabolism|metabolic processes]] within the brain.<ref name="bravo" />

===Vitamin B<sub>1</sub> (thiamine)===
This vitamin is important for the facilitation of glucose use, thus ensuring the production of energy for the brain,<ref name="bravo"/> and normal functioning of the nervous system, muscles and heart.<ref name= "charlie">{{cite journal | vauthors = Thompson J | title = Vitamins, minerals and supplements: part two | journal = Community Practitioner | volume = 78 | issue = 10 | pages = 366–368 | date = October 2005 | pmid = 16245676 }}</ref> Thiamine is found throughout mammalian nervous tissue, including the brain and [[Biology:Spinal cord|spinal cord]]. Metabolism and coenzyme function of the vitamin suggest a distinctive function for thiamine within the [[Biology:Nervous system|nervous system]].<ref name= foxtrot>{{cite journal | vauthors = Cooper JR, Pincus JH | title = The role of thiamine in nervous tissue | journal = Neurochemical Research | volume = 4 | issue = 2 | pages = 223–239 | date = April 1979 | pmid = 37452 | doi = 10.1007/BF00964146 | s2cid = 22390486 }}</ref>

===Vitamin B<sub>3</sub> (niacin)===
Vitamin B<sub>3</sub>, also known as niacin, includes both [[Chemistry:Nicotinamide|nicotinamide]] as well as nicotinic acid, both of which function in many biological [[Chemistry:Redox|oxidization and reduction reactions]] within the body. Niacin is involved in the synthesis of fatty acids and [[Chemistry:Cholesterol|cholesterol]], known mediators of brain biochemistry, and in effect, of cognitive function.<ref>{{cite journal | vauthors = Yehuda S, Rabinovitz S, Mostofsky DI | title = Essential fatty acids are mediators of brain biochemistry and cognitive functions | journal = Journal of Neuroscience Research | volume = 56 | issue = 6 | pages = 565–570 | date = June 1999 | pmid = 10374811 | doi = 10.1002/(SICI)1097-4547(19990615)56:6<565::AID-JNR2>3.0.CO;2-H | s2cid = 26274561 }}</ref>

===Vitamin B<sub>9</sub> (folic acid)===
Folate and vitamin B<sub>12</sub> play a vital role in the synthesis of [[Chemistry:S-Adenosyl methionine|S-adenosylmethionine]], which is of key importance in the maintenance and repair of all cells, including neurons.<ref name= oscar>{{cite journal | vauthors = Hauck MR | title = Cognitive abilities of preschool children: implications for nurses working with young children | journal = Journal of Pediatric Nursing | volume = 6 | issue = 4 | pages = 230–235 | date = August 1991 | pmid = 1865312 }}</ref> In addition, folate has been linked to the maintenance of adequate brain levels of cofactors necessary for chemicals reactions that lead to the synthesis of serotonin and catecholamine neurotransmitters.<ref name= november>{{cite book |title=Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline |year=1998 |publisher=National Academy Press |location=Washington, DC |isbn=978-0-309-06554-2 |url=http://www.nal.usda.gov/fnic/DRI/DRI_Thiamin/196-305_150.pdf |access-date=2012-03-21 |archive-url=https://web.archive.org/web/20130515073832/http://www.nal.usda.gov/fnic/DRI/DRI_Thiamin/196-305_150.pdf |archive-date=2013-05-15 |url-status=dead }}{{page needed|reason= was "page=196, pages=1–541". which is it?|date=July 2012}}</ref> Concentrations of blood plasma folate and [[Chemistry:Homocysteine|homocysteine]] concentrations are inversely related, such that an increase in dietary folate decreases homocysteine concentration. Thus, dietary intake of folate is a major determinant of homocysteine levels within the body.<ref name= quebec>{{cite journal | title = Dose-dependent effects of folic acid on blood concentrations of homocysteine: a meta-analysis of the randomized trials | journal = The American Journal of Clinical Nutrition | volume = 82 | issue = 4 | pages = 806–812 | date = October 2005 | pmid = 16210710 | doi = 10.1093/ajcn/82.4.806 | doi-access = free | author1 = Homocysteine Lowering Trialists' Collaboration }}</ref>

The link between levels of folate and altered mental function is not large, but is sufficient enough to suggest a causal association.<ref name="november"/> Deficiency in folate can cause an elevation of homocysteine within the blood,<ref name="quebec"/> as the clearance of homocysteine requires enzymatic action dependent on folate, and to a lesser extent, vitamins B<sub>6</sub> and B<sub>12</sub>. Elevated homocysteine has been associated with increased risk of [[Medicine:Stroke|vascular events]], as well as dementia.<ref>{{cite journal | vauthors = Quadri P, Fragiacomo C, Pezzati R, Zanda E, Forloni G, Tettamanti M, Lucca U | title = Homocysteine, folate, and vitamin B-12 in mild cognitive impairment, Alzheimer disease, and vascular dementia | journal = The American Journal of Clinical Nutrition | volume = 80 | issue = 1 | pages = 114–122 | date = July 2004 | pmid = 15213037 | doi = 10.1093/ajcn/80.1.114 | doi-broken-date = 31 January 2024 }}</ref>

Intake of the vitamin has been linked to deficits in [[Learning|learning]] and memory, particularly within the elderly population.<ref name="november"/> Elderly people deficient in folate may present with deficits in free recall and recognition, which suggests that levels of folate may be related to efficacy of episodic memory.<ref>{{cite journal | vauthors = Wahlin A, Hill RD, Winblad B, Bäckman L | title = Effects of serum vitamin B12 and folate status on episodic memory performance in very old age: a population-based study | journal = Psychology and Aging | volume = 11 | issue = 3 | pages = 487–496 | date = September 1996 | pmid = 8893317 | doi = 10.1037/0882-7974.11.3.487 }}</ref>
Because neurulation may be completed before pregnancy is recognized, it is recommended that women capable of becoming pregnant take about 400μg of folic acid from fortified foods, supplements, or a combination of the two in order to reduce the risk of neural tube defects.<ref name="november"/> These major anomalies in the nervous system can be reduced by 85% with systematic folate supplementation occurring before the onset of pregnancy.<ref name= papa>{{cite journal | vauthors = Moyers S, Bailey LB | title = Fetal malformations and folate metabolism: review of recent evidence | journal = Nutrition Reviews | volume = 59 | issue = 7 | pages = 215–224 | date = July 2001 | pmid = 11475447 | doi = 10.1111/j.1753-4887.2001.tb07013.x | doi-access = free }}</ref> The incidence of Alzheimer's and other cognitive diseases has been loosely connected to deficiencies in folate. It is recommended for the elderly to consume folate through food, fortified or not, and supplements in order to reduce risk of developing the disease.<ref name="oscar"/>

===Vitamin B<sub>12</sub>===
Also known as cobalamin, B<sub>12</sub> is important for the maintenance of neurological function.<ref name= sierra>{{cite book |title=Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline |year=1998 |publisher=National Academy Press |location=Washington, DC |isbn=978-0-309-06554-2 |url=http://www.nal.usda.gov/fnic/DRI/DRI_Thiamin/306-356_150.pdf |access-date=2012-03-19 |archive-url=https://web.archive.org/web/20120912181029/http://www.nal.usda.gov/fnic/DRI//DRI_Thiamin/306-356_150.pdf |archive-date=2012-09-12 |url-status=dead }}{{page needed|reason=was "page=306, pages=1–541". which is it?|date=July 2012}}</ref> B<sub>12</sub> deficiency, also known as hypocobalaminemia, often results from complications involving absorption into the body.<ref name= victor>{{cite journal | vauthors = Hvas AM, Nexo E | title = Diagnosis and treatment of vitamin B12 deficiency--an update | journal = Haematologica | volume = 91 | issue = 11 | pages = 1506–1512 | date = November 2006 | pmid = 17043022 }}</ref> An assortment of neurological effects can be observed in 75–90% of individuals of any age with clinically observable B<sub>12</sub> deficiency. Cobalamin deficiency manifestations are apparent in the abnormalities of the spinal cord, peripheral nerves, optic nerves, and [[Biology:Cerebrum|cerebrum]].

People who are deficient in B<sub>12</sub> despite normal absorption functionality may be treated through oral administration of at least 6&nbsp;µg/day of the vitamin in pill form. People who suffer from irreversible causes of deficiency, such as pernicious anemia or old age, will need lifelong treatment with pharmacological doses of B<sub>12</sub>. Strategy for treatment is dependent on the person's level of deficiency as well as their level of cognitive functioning.<ref name="victor"/> Treatment for those with severe deficiency involves 1000&nbsp;µg of B<sub>12</sub> administered [[Biology:Intramuscular injection|intramuscularly]] daily for one week, weekly for one month, then monthly for the rest of the person's life. The progression of neurological manifestations of cobalamin deficiency is generally gradual. As a result, early diagnosis is important or else irreversible damage may occur.<ref name="sierra"/> People who become demented usually show little to no cognitive improvement with the administration of B<sub>12</sub>. There is risk that folic acid administered to those with B<sub>12</sub> deficiency may mask anemic symptoms without solving the issue at hand. In this case, people would still be at risk for neurological deficits associated with B<sub>12</sub> deficiency-related anemia, which are not associated with anemia related to folate deficiency.<ref>{{cite journal | vauthors = Malouf R, Grimley Evans J | title = Folic acid with or without vitamin B12 for the prevention and treatment of healthy elderly and demented people | journal = The Cochrane Database of Systematic Reviews | issue = 4 | pages = CD004514 | date = October 2008 | pmid = 18843658 | doi = 10.1002/14651858.CD004514.pub2 }}</ref>

===Vitamin A deficiency===
[[Chemistry:Vitamin A|Vitamin A]] is an essential [[Earth:Nutrient|nutrient]] for mammals which takes form in either [[Chemistry:Retinol|retinol]] or the [[Chemistry:Provitamin|provitamin]] [[Chemistry:Beta-Carotene|beta-Carotene]]. It helps regulation of cell division, cell function, genetic regulation, helps enhance the immune system, and is required for brain function, chemical balance, growth and development of the [[Biology:Central nervous system|central nervous system]] and vision.{{Citation needed|date=December 2019|reason=removed citation to predatory publisher content}}

===Iron deficiency===
Oxygen transportation, DNA synthesis, myelin synthesis, oxidative phosphorylation, and neurotransmitter synthesis and metabolism are all biological processes that require iron; however, an iron imbalance can result in [[Chemistry:Neurotoxicity|neurotoxicity]] causing oxidation and modification of lipids, proteins, carbohydrates, and DNA.<ref name="pmid25231526">{{cite journal | vauthors = Ward RJ, Zucca FA, Duyn JH, Crichton RR, Zecca L | title = The role of iron in brain ageing and neurodegenerative disorders | journal = Lancet Neurol | volume = 13 | issue = 10 | pages = 1045–60 | date = October 2014 | pmid = 25231526 | pmc = 5672917 | doi = 10.1016/S1474-4422(14)70117-6 }}</ref> Hypoxic conditions in severely anemic individuals may cause brain damage resulting in cognitive impairment.<ref name="pmid31681682">{{cite journal | vauthors = Agrawal S, Kumar S, Ingole V, Acharya S, Wanjari A, Bawankule S, Raisinghani N | title = Does anemia affects cognitive functions in neurologically intact adult patients: Two year cross sectional study at rural tertiary care hospital | journal = J Family Med Prim Care | volume = 8 | issue = 9 | pages = 3005–3008 | date = September 2019 | pmid = 31681682 | pmc = 6820398 | doi = 10.4103/jfmpc.jfmpc_599_19 | doi-access = free }}</ref> When iron levels in the brain are disrupted neurophysiological mechanisms and cognition are affected, potentially resulting in long-term behavioral changes and may affect attention span, intelligence, sensory perception functions, mood, and behavior. <ref name="pmid23735056">{{cite journal | vauthors = Chen MH, Su TP, Chen YS, Hsu JW, Huang KL, Chang WH, Chen TJ, Bai YM | title = Association between psychiatric disorders and iron deficiency anemia among children and adolescents: a nationwide population-based study | journal = BMC Psychiatry | volume = 13 | issue = | pages = 161 | date = June 2013 | pmid = 23735056 | pmc = 3680022 | doi = 10.1186/1471-244X-13-161 | doi-access = free }}</ref><ref name="pmid25419131">{{cite journal | vauthors = Jáuregui-Lobera I | title = Iron deficiency and cognitive functions | journal = Neuropsychiatr Dis Treat | volume = 10 | issue = | pages = 2087–95 | date = 2014 | pmid = 25419131 | pmc = 4235202 | doi = 10.2147/NDT.S72491 | doi-access = free }}</ref> Neuropathies such as ADHD, autism, depression, anxiety, schizophrenia, and bipolar disorder are seen in iron deficient individuals. However, excessive iron accumulation can be seen in neurodegenerative diseases including Alzheimer’s and Huntington’s disease.<ref name="pmid25231526"/> Iron is needed to develop the central nervous system (CNS), endocrine system, autoimmune system, and brain. Iron is involved with the development and functioning of different neurotransmitter systems and large iron quantities are required for the myelination of white brain matter. Abnormal myelination of white matter due to iron deficiency during development may be related to the onset of psychological disorders in adolescents.<ref name="pmid25419131"/> Decreased iron concentration results in a reduction of neurotransmitter levels, in turn leading to poor myelination and delayed neuromaturation.<ref name="pmid31681682"/>

== See also ==
*[[Chemistry:Nootropic|Nootropic]]
*[[Biology:Nutrition|Nutrition]]
*[[Biology:Nutritional neuroscience|Nutritional neuroscience]]
*[[Medicine:Pellagra|Pellagra]]
*[[Medicine:Wernicke–Korsakoff syndrome|Wernicke–Korsakoff syndrome]]

== References ==
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[[Category:Cognition]]

{{Sourceattribution|Nutrition and cognition}}