Nutrition and cognition

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Relatively speaking, the 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. [1] Human bodily processes, including the brain, all require both macronutrients, as well as micronutrients. [2]

Contents

Insufficient intake of selected vitamins, or certain metabolic disorders, may affect 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 synaptic plasticity, or the ability to encode new memories. [1]

Macronutrients

The human brain requires nutrients obtained from the diet to develop and sustain its physical structure and cognitive functions. [1] [3] [4] Additionally, the brain requires caloric energy predominately derived from the primary macronutrients to operate. [1] [4] The three primary macronutrients include carbohydrates, proteins, and fats. Each macronutrient can impact cognition through multiple mechanisms, including glucose and insulin metabolism, neurotransmitter actions, oxidative stress and inflammation, and the gut-brain axis. [4] [5] [6] Inadequate macronutrient consumption or proportion could impair optimal cognitive functioning and have long-term health implications. [4] [6] [7] [8] [9] [10]

Carbohydrates

Through digestion, dietary carbohydrates are broken down and converted into glucose, which is the sole energy source for the brain. [5] [8] [11] Optimal brain function relies on adequate carbohydrate consumption, as carbohydrates provide the quickest source of glucose for the brain. [12] Glucose deficiencies such as hypoglycaemia reduce available energy for the brain and impair all cognitive processes and performance. [8] [12] [13] 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. [8]

Complex carbohydrates, especially those with high dietary fibre, are associated with increased cognitive performance and improved memory function. [4] This is because fibre regulates glucose metabolism, slowing the release of insulin and preserving insulin sensitivity. [4] 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 neurodegeneration. [4] 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 disability, depression, chronic disease, and decreased cognitive decline. [4]

Simple carbohydrates are associated with decreased global cognitive performance. [4] Simple carbohydrates negatively impact many essential cognitive processes, including attention, memory, reaction time, visual-spatial processing, mental processing speed, and executive functions. [4] Simple carbohydrates impair cognition through glucose and insulin metabolism dysfunction, as well as causing inflammation and oxidative stress within the brain. [4] Therefore, excessive or chronic consumption of simple carbohydrates is unanimously linked to negative health consequences. [4] [5] [11]

Proteins

Through digestion dietary proteins are broken down into individual amino acids and absorbed into the blood. [4] [5] The essential amino acids tyrosine and tryptophan are precursors for the neurotransmitters dopamine, serotonin, and norepinephrine, and these chemicals modulate neural activity and influence cognitive functioning. [4] [13]

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. [4] [8] [13] [14] Additionally, adequate and consistent consumption of tyrosine and tryptophan correlates to improvements in memory function. [4] [14] Tyrosine is also shown to improve convergent thinking processes through increased cognitive control. [15]

Fats

Through digestion dietary fats are broken down into individual fatty acids for utilization. Fatty acids are classified as saturated, trans, monounsaturated, polyunsaturated, and cholesterol. Each class has distinct affects on cognitive functioning and health. [4] Omega-3 polyunsaturated fatty acids are especially significant as they are critical cell membrane and structural components of the brain. [1] [4] [12]

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. [4] However, the adverse cognitive effects of cholesterol consumption appear to be reduced when combined with physical activity, which influences energy homeostasis and synaptic plasticity. [4]

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. [1] [4]

Micronutrients

Choline

Choline is an essential nutrient and its primary function within the human body is the synthesis of cellular membranes, [16] although it serves other functions as well. It is a precursor molecule to the neurotransmitter Acetylcholine which serves a wide range of functions including motor control and memory. Choline deficiencies may be related to some liver and neurological disorders. [17] 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. [16] Choline intakes from food for men, women and children may be below the Adequate Intake levels. [17] Women, especially when pregnant or lactating, the elderly, and infants, are at risk for choline deficiency. [17] Beef liver, wheat germ, and egg yolks are common foods providing choline. [16]

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: thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxin (B6), folic acid (B9), cobalamin (B12), and biotin. [18] B vitamins are not 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. [19] It is possible to identify broad cognitive effects of certain B vitamins, as they are involved in many significant metabolic processes within the brain. [2]

Vitamin B1 (thiamine)

This vitamin is important for the facilitation of glucose use, thus ensuring the production of energy for the brain, [2] and normal functioning of the nervous system, muscles and heart. [19] Thiamine is found throughout mammalian nervous tissue, including the brain and spinal cord. Metabolism and coenzyme function of the vitamin suggest a distinctive function for thiamine within the nervous system. [20]

Vitamin B3 (niacin)

Vitamin B3, also known as niacin, includes both nicotinamide as well as nicotinic acid, both of which function in many biological oxidization and reduction reactions within the body. Niacin is involved in the synthesis of fatty acids and cholesterol, known mediators of brain biochemistry, and in effect, of cognitive function. [21]

Vitamin B9 (folic acid)

Folate and vitamin B12 play a vital role in the synthesis of S-adenosylmethionine, which is of key importance in the maintenance and repair of all cells, including neurons. [22] 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. [23] Concentrations of blood plasma folate and 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. [24]

The link between levels of folate and altered mental function is not large, but is sufficient to suggest a causal association. [23] Deficiency in folate can cause an elevation of homocysteine within the blood, [24] as the clearance of homocysteine requires enzymatic action dependent on folate, and to a lesser extent, vitamins B6 and B12. Elevated homocysteine has been associated with increased risk of vascular events, as well as dementia. [25]

Intake of the vitamin has been linked to deficits in learning and memory, particularly within the elderly population. [23] 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. [26] Because neurulation may be completed before pregnancy is recognized, it is recommended that women capable of becoming pregnant take about 400 μg of folic acid from fortified foods, supplements, or a combination of the two in order to reduce the risk of neural tube defects. [23] These major anomalies in the nervous system can be reduced by 85% with systematic folate supplementation occurring before the onset of pregnancy. [27] 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. [22]

Vitamin B12

Also known as cobalamin, B12 is important for the maintenance of neurological function. [28] B12 deficiency, also known as hypocobalaminemia, often results from complications involving absorption into the body. [29] An assortment of neurological effects can be observed in 75–90% of individuals of any age with clinically observable B12 deficiency. Cobalamin deficiency manifestations are apparent in the abnormalities of the spinal cord, peripheral nerves, optic nerves, and cerebrum.

People who are deficient in B12 despite normal absorption functionality may be treated through oral administration of at least 6 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 B12. Strategy for treatment is dependent on the person's level of deficiency as well as their level of cognitive functioning. [29] Treatment for those with severe deficiency involves 1000 μg of B12 administered 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. [28] People who become demented usually show little to no cognitive improvement with the administration of B12. There is risk that folic acid administered to those with B12 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 B12 deficiency-related anemia, which are not associated with anemia related to folate deficiency. [30]

Vitamin A deficiency

Vitamin A is an essential nutrient for mammals which takes form in either retinol or the provitamin 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 central nervous system and vision.[ citation needed ]

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 neurotoxicity causing oxidation and modification of lipids, proteins, carbohydrates, and DNA. [31] Hypoxic conditions in severely anemic individuals may cause brain damage resulting in cognitive impairment. [32] 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. [33] [34] 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. [31] 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. [34] Decreased iron concentration results in a reduction of neurotransmitter levels, in turn leading to poor myelination and delayed neuromaturation. [32]

See also

Related Research Articles

<span class="mw-page-title-main">Riboflavin</span> Vitamin, dietary supplement, and yellow food dye

Riboflavin, also known as vitamin B2, is a vitamin found in food and sold as a dietary supplement. It is essential to the formation of two major coenzymes, flavin mononucleotide and flavin adenine dinucleotide. These coenzymes are involved in energy metabolism, cellular respiration, and antibody production, as well as normal growth and development. The coenzymes are also required for the metabolism of niacin, vitamin B6, and folate. Riboflavin is prescribed to treat corneal thinning, and taken orally, may reduce the incidence of migraine headaches in adults.

<span class="mw-page-title-main">Vitamin</span> Nutrients required by organisms in small amounts

Vitamins are organic molecules that are essential to an organism in small quantities for proper metabolic function. Essential nutrients cannot be synthesized in the organism in sufficient quantities for survival, and therefore must be obtained through the diet. For example, vitamin C can be synthesized by some species but not by others; it is not considered a vitamin in the first instance but is in the second. Most vitamins are not single molecules, but groups of related molecules called vitamers. For example, there are eight vitamers of vitamin E: four tocopherols and four tocotrienols.

Vitamin B<sub>6</sub> Class of chemically related vitamins

Vitamin B6 is one of the B vitamins, and is an essential nutrient for humans. The term essential nutrient refers to a group of six chemically similar compounds, i.e., "vitamers", which can be interconverted in biological systems. Its active form, pyridoxal 5′-phosphate, serves as a coenzyme in more than 140 enzyme reactions in amino acid, glucose, and lipid metabolism.

<span class="mw-page-title-main">Folate</span> Vitamin B9; nutrient essential for DNA synthesis

Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing and storage. Folate is required for the body to make DNA and RNA and metabolise amino acids necessary for cell division and maturation of blood cells. As the human body cannot make folate, it is required in the diet, making it an essential nutrient. It occurs naturally in many foods. The recommended adult daily intake of folate in the U.S. is 400 micrograms from foods or dietary supplements.

A nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excreted by cells to create non-cellular structures such as hair, scales, feathers, or exoskeletons. Some nutrients can be metabolically converted into smaller molecules in the process of releasing energy such as for carbohydrates, lipids, proteins and fermentation products leading to end-products of water and carbon dioxide. All organisms require water. Essential nutrients for animals are the energy sources, some of the amino acids that are combined to create proteins, a subset of fatty acids, vitamins and certain minerals. Plants require more diverse minerals absorbed through roots, plus carbon dioxide and oxygen absorbed through leaves. Fungi live on dead or living organic matter and meet nutrient needs from their host.

<span class="mw-page-title-main">Human nutrition</span> Nutrients supporting human health

Human nutrition deals with the provision of essential nutrients in food that are necessary to support human life and good health. Poor nutrition is a chronic problem often linked to poverty, food security, or a poor understanding of nutritional requirements. Malnutrition and its consequences are large contributors to deaths, physical deformities, and disabilities worldwide. Good nutrition is necessary for children to grow physically and mentally, and for normal human biological development.

Vitamin deficiency is the condition of a long-term lack of a vitamin. When caused by not enough vitamin intake it is classified as a primary deficiency, whereas when due to an underlying disorder such as malabsorption it is called a secondary deficiency. An underlying disorder can have 2 main causes:

<span class="mw-page-title-main">Choline</span> Chemical compound and essential nutrient

Choline is a cation with the chemical formula [(CH3)3NCH2CH2OH]+. Choline forms various salts, such as choline chloride and choline bitartrate. It is an essential nutrient for humans and many other animals, and is a structural part of phospholipids and cell membranes.

B vitamins are a class of water-soluble vitamins that play important roles in cell metabolism and synthesis of red blood cells. They are a chemically diverse class of compounds.

<span class="mw-page-title-main">Nootropic</span> Compound intended to improve cognitive function

Nootropics, colloquially brain supplements, smart drugs and cognitive enhancers, are natural, semisynthetic or synthetic compounds which purportedly improve cognitive functions, such as executive functions, attention or memory.

<span class="mw-page-title-main">Malabsorption</span> Abnormality in absorption of food nutrients across the gastrointestinal tract

Malabsorption is a state arising from abnormality in absorption of food nutrients across the gastrointestinal (GI) tract. Impairment can be of single or multiple nutrients depending on the abnormality. This may lead to malnutrition and a variety of anaemias.

<span class="mw-page-title-main">Cat food</span> Food for consumption by cats

Cat food is food specifically formulated and designed for consumption by cats. As obligate carnivores, cats have specific requirements for their dietary nutrients, namely nutrients found only in meat or synthesized, such as taurine and Vitamin A. Certain nutrients, including many vitamins and amino acids, are degraded by the temperatures, pressures and chemical treatments used during manufacture, and hence must be added after manufacture to avoid nutritional deficiency. Cat food is typically sold as dry kibble, or as wet food in cans and pouches.

Food fortification or enrichment is the process of adding micronutrients to food. It can be carried out by food manufacturers, or by governments as a public health policy which aims to reduce the number of people with dietary deficiencies within a population. The predominant diet within a region can lack particular nutrients due to the local soil or from inherent deficiencies within the staple foods; the addition of micronutrients to staples and condiments can prevent large-scale deficiency diseases in these cases.

<span class="mw-page-title-main">Folate deficiency</span> Abnormally low level of folate (vitamin B9) in the body

Folate deficiency, also known as vitamin B9 deficiency, is a low level of folate and derivatives in the body. This may result in megaloblastic anemia in which red blood cells become abnormally large, and folate deficiency anemia is the term given for this medical condition. Signs of folate deficiency are often subtle. Symptoms may include fatigue, heart palpitations, shortness of breath, feeling faint, open sores on the tongue, loss of appetite, changes in the color of the skin or hair, irritability, and behavioral changes. Temporary reversible infertility may occur. Folate deficiency anemia during pregnancy may give rise to the birth of low weight birth premature infants and infants with neural tube defects.

Vitamin B<sub>12</sub> deficiency Disorder resulting from low blood levels of vitamin B12

Vitamin B12 deficiency, also known as cobalamin deficiency, is the medical condition in which the blood and tissue have a lower than normal level of vitamin B12. Symptoms can vary from none to severe. Mild deficiency may have few or absent symptoms. In moderate deficiency, feeling tired, headaches, soreness of the tongue, mouth ulcers, breathlessness, feeling faint, rapid heartbeat, low blood pressure, pallor, hair loss, decreased ability to think and severe joint pain and the beginning of neurological symptoms, including abnormal sensations such as pins and needles, numbness and tinnitus may occur. Severe deficiency may include symptoms of reduced heart function as well as more severe neurological symptoms, including changes in reflexes, poor muscle function, memory problems, blurred vision, irritability, ataxia, decreased smell and taste, decreased level of consciousness, depression, anxiety, guilt and psychosis. If left untreated, some of these changes can become permanent. Temporary infertility, reversible with treatment, may occur. A late finding type of anemia known as megaloblastic anemia is often but not always present. In exclusively breastfed infants of vegan mothers, undetected and untreated deficiency can lead to poor growth, poor development, and difficulties with movement.

Vitamin B<sub><small>12</small></sub> Vitamin used in animal cells metabolism

Vitamin B12, also known as cobalamin, is a water-soluble vitamin involved in metabolism. It is one of eight B vitamins. It is required by animals, which use it as a cofactor in DNA synthesis, and in both fatty acid and amino acid metabolism. It is important in the normal functioning of the nervous system via its role in the synthesis of myelin, and in the circulatory system in the maturation of red blood cells in the bone marrow. Plants do not need cobalamin and carry out the reactions with enzymes that are not dependent on it.

Vitamins occur in a variety of related forms known as vitamers. A vitamer of a particular vitamin is one of several related compounds that performs the functions of said vitamin and prevents the symptoms of deficiency of said vitamin.

<span class="mw-page-title-main">Nutritional neuroscience</span> Scientific discipline

Nutritional neuroscience is the scientific discipline that studies the effects various components of the diet such as minerals, vitamins, protein, carbohydrates, fats, dietary supplements, synthetic hormones, and food additives have on neurochemistry, neurobiology, behavior, and cognition.

<span class="mw-page-title-main">Vegan nutrition</span> Nutritional and human health aspects of vegan diets

Vegan nutrition refers to the nutritional and human health aspects of vegan diets. A well-planned vegan diet is suitable to meet all recommendations for nutrients in every stage of human life. Vegan diets tend to be higher in dietary fiber, magnesium, folic acid, vitamin C, vitamin E, and phytochemicals; and lower in calories, saturated fat, iron, cholesterol, long-chain omega-3 fatty acids, vitamin D, calcium, zinc, and vitamin B12.

In general, cognitive support diets are formulated to include nutrients that have a known role in brain development, function and/or maintenance, with the goal of improving and preserving mental processes such as attentiveness, short-term and long-term memory, learning, and problem solving. Currently, there is very little conclusive research available regarding cat cognition as standardized tests for evaluating cognitive ability are less established and less reliable than cognitive testing apparatus used in other mammalian species, like dogs. Much of what is known about feline cognition has been inferred from a combination of owner-reported behaviour, brain necropsies, and comparative cognitive neurology of related animal models. Cognition claims appear primarily on kitten diets which include elevated levels of nutrients associated with optimal brain development, although there are now diets available for senior cats that include nutrients to help slow the progression of age-related changes and prevent cognitive decline. Cognition diets for cats contain a greater portion of omega-3 fatty acids, especially docosahexaenoic acid (DHA) as well as eicosapentaenoic acid (EPA), and usually feature a variety of antioxidants and other supporting nutrients thought to have positive effects on cognition.

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