Dietary Supplements in Relation to Mental Focus and Memory
Researched and written by Alison Smith Ph.D.
Cultivating the capacity for strong mental focus promotes successful performance at work, school, and athletics. Mental focus is defined as the ability to concentrate and to become absorbed in an activity 1.
There are motivational strategies to help enhance mental focus; however, can specific supplements strengthen mental focus as well?
This paper will provide an overview of the current scientific literature regarding the use of L-theanine, vitamins B6 and B12, choline, vitamins C and D, and magnesium to support the neurophysiological processes that influence mental focus, including: attention, concentration, cognitive performance, memory formation and retrieval, information processing, abstract thinking, as well as stress mediation and emotional well-being.
There are over 500 different amino acids found in nature2. Of those 500, humans require only twenty amino acids to sustain life. Theanine (also known as gamma-glutamylethylamide) is a type of non-protein amino acid that is not one of the twenty required by the human body; however, it does provide health benefits, and for that reason, scientists have been studying it for over sixty years.
Theanine was first discovered in 1949 when Japanese researchers extracted it from Camellia sinensis tea leaves, used to make green, black, white, and oolong teas. In fact, theanine accounts for 50% of the total amino acid content in tea and provides a 25-60 mg dose in a 200 mL cup of tea3.
Theanine is also found in trace amounts in Camellia japonica and sasanqua leaves and one edible mushroom species called Xerocomus badius4. In tea, the main form of theanine is its L-isomer form called L-theanine––the most common form of theanine also found in supplements5.
The health benefits of theanine are attributed to the L-isomer form (L-theanine) rather than its D-isomer form (D-theanine). Therefore, when purchasing a theanine supplement, it is important to choose one that contains L-theanine only.
To ensure consumer access to a pure form of L-theanine, Suntheanine® was developed by a brand called Taiyo Kagaku. Suntheanine® is a patented and purified form of L-theanine5 available in supplements like new Calm Balance (coming soon) and Calmful Sleep by Natural Calm. It provides a pharmaceutical dose of L-theanine allowing consumers to enjoy the benefits of L-theanine without having to drink copious amounts of tea6.
L-theanine crosses the blood-brain barrier and influences neuronal activity within 30-minutes following ingestion14. Research has demonstrated that Suntheanine® (L-theanine) improves mood7, cognitive and mental performance3,8, stress9, alertness10, and alpha brain waves 11,12 without any adverse side effects13.
Essentially, 50-200 mg of L-theanine promotes a relaxed yet alert mental state by stimulating the production of alpha brainwaves3,12 and gamma-amino-butyric acid (GABA): a neurotransmitter that relaxes the nervous system6. Alpha activity is associated with the ability to ignore distractions, which ultimately improves attention and focus. It also improves visual acuity and the ability to respond to visual stimuli faster11.
Interestingly, these beneficial effects seem to be more pronounced in healthy subjects who typically experience chronic anxiety15––pointing to the potential importance of L-theanine to help anxious people to relax and focus.
There are eight water-soluble B vitamins, all of which act as coenzymes in a myriad of physiological processes16. Vitamin B6 (pyridoxine), in its bioactive form pyridoxal 5’-phosphate (P5P), is an essential cofactor in the functioning of over 140 separate enzymes responsible for the production, degradation, and interconversion of amino acids16. Its concentration is one hundred times greater in the brain than the blood17 ––pointing to how important this vitamin is for cognitive function.
Through its involvement in amino acid function, vitamin B6 plays a direct role in the production of neurotransmitters that mediate mental focus and attention, including: gamma-aminobutyric acid (GABA), dopamine, noradrenalin, and serotonin18.
GABA allows us to maintain attention and to pick the right responsive behaviour in a timely manner19, and a reduced concentration of GABA in the central nervous system is related to mental focus issues observed in disorders like attention-deficit/hyperactivity disorder (ADHD)20; dopamine regulates attention particularly through the mesocorticolimbic pathway 21, and a reduction in dopamine activity results in ADHD 22.
A reduction in noradrenaline activity is also associated with ADHD, and medical intervention typically involves medications that maintain dopamine and noradrenalin levels to enhance attention and reduce hyperactivity22.
Serotonin level, on the other hand, is rarely treated in relation to ADHD22; however, it is directly involved in motivation and depression23: cognitive states that influence mental focus. Vitamin B6 is a cofactor in serotonin production through the tryptophan-serotonin pathway, and B6 deficiency is linked to depression, cognitive decline, dementia, and a lack of attention16,23,24.
There is inadequate statistical information regarding B6 deficiency in Canadian adults. The Canadian Community Health Survey reports that 18% of Canadian adult females fail to ingest the minimum requirement of B6 each day, but this could be a drastic underestimation since Health Canada does not track biochemical markers for B6 status. In the U.S., it’s reported that 40% of U.S. adult females are B6 deficient, which points to the need to look at B6 status in the Canadian population more closely25.
In terms of supplementation, the recommended upper limit of daily B6 intake is 100 mg/day16, according to Health Canada26. Toxicology studies report that it is safe to take a maximum of 500 mg per day; however, it is important to avoid taking more than that maximum dose because vitamin B6 in high doses is linked to sensory neuropathy and neurotoxicity27,28.
Vitamin B12 (cobalamin) plays a pivotal role in healthy brain function, particularly because of its interaction with folic acid and the production of SAMe (S-adenosylmethionine). Without vitamin B12, the circulating inactive form of folic acid called methyltetrahydrofolic acid could not convert into its bioactive form, tetrahydrofolic acid. Missing this synergistic interaction between B12 and folic acid deeply affects brain function by causing a decrease in neuronal cell DNA stability and repair, which causes demyelination of brain cells, a reduction in neurotransmitter production and nerve cell firing, hippocampal shrinking (memory storage decay), and subsequent cognitive decline16.
Vitamin B12 and folic acid also produce SAMe, a metabolite that helps to produce neurotransmitters like dopamine, serotonin, and epinephrine––all of which mediate mood, mental focus, attention, and clarity29.
A study by Asselt30 reports a significant improvement in brain and cognitive function in adults aged 64-89 who had low plasma B12 concentration. Improvements were observed after intramuscular hydroxocobalamin (B12) injections at 1000 micrograms weekly for 4 weeks and 1000 micrograms monthly for 4 months.
Adults over the age of 19 should consume at least 2.4 micrograms of vitamin B12 daily31. About 97% of the Canadian population successfully takes in enough daily B12; therefore, a B12 deficiency is uncommon for healthy adults 32; however, older adults (>50 years of age) are definitely at risk. With age, there is a reduction in vitamin B12 absorption through the intestine. Health Canada recommends individuals over the age of 50 to eat foods fortified with vitamin B12 or to take a daily supplement. Vegetarians and vegans are also at risk for B12 deficiency since dietary sources of B12 are typically animal based33.
A B12 deficiency is bad news not only for healthy brain function but for overall health as well. Vitamin B12 deficiency can cause pernicious anemia, reduce cognitive abilities, compromise the ability to think and concentrate, and to form memories33. Deficiency can also cause neuropsychiatric disorders––in fact, over one-third of psychiatric hospital admissions are caused by either a B12 or folic acid deficiency16.
Choline is a vital amine––a term used to describe an organic compound needed in small quantities to maintain health. The term vital amine eventually became the word vitamin34; however, choline is not a vitamin in the true sense of the word; it’s only vitamin-like35.
Choline is naturally produced by the human body, but not in adequate quantities; therefore, it must be taken in through the diet. It has an important interrelationship with methionine (an amino acid) and vitamins B12 (cyanocobalamin), B6 (pyridoxine), and B9 (folic acid)34. It plays a role in the production of phospholipid bilayers that surround and protect cells; it’s a component of the neurotransmitter, acetylcholine, used for nerve cell function; it provides a methyl group for various metabolic processes, and transports fats from the liver35. In fact, a choline deficiency can cause a pathological build-up of fats in the liver; consequently, choline is considered an essential nutrient36.
Choline supplementation is related to better cognitive performance in older, healthy adults37, and a lack of cholinergic receptors in the brain is linked to ADHD and subsequent deficits in mental focus since acetylcholine and its action on cholinergic receptors is directly related to attention, learning, and memory. Without enough acetylcholine or cholinergic receptors, healthy cognitive function simply isn’t possible. Cholinergic projections link areas of the brain associated with sustaining attention to other areas in the cortex that allow us to perform cognitive and motor skills38.
Healthy mental focus requires adequate choline levels in the blood. The recommended adequate intake (AI) is 425 mg/day for women and 550 mg/day for men; however, these values are subject to change since there is a lack of scientific data on daily requirements for choline––it’s a new area of study39.
B Vitamins and the Homocysteine Hypothesis
There is a great deal of research investigating the link between cognitive decline, defined as a reduced ability to think clearly and to form or retrieve memories, and homocysteine levels in the blood. Homocysteine is a non-proteinogenic amino acid that is not acquired through the diet. Its presence is associated with vascular inflammation and cellular damage that can cause cerebrovascular disease. Recent research hypothesizes that high homocysteine levels may also cause a decline in cognitive function because of its neurotoxic effects: homocysteine causes brain cell injury and cell death40.
A high homocysteine level in the blood is caused by low levels of B6, B12, B9 (folic acid), or choline, and it is thought that with supplementation of these B vitamins or choline, homocysteine levels can be lowered, possibly improving or restoring cognition39,41,42. The jury is still out regarding the efficacy of this hypothesis; there are studies that have confirmed it and those that have not. For example, Riggs et al. 41 measured B-vitamin concentration (B12, B6, and B9) and homocysteine level in relation to cognitive ability and confirmed that homocysteine compromised cognitive ability. A study by Bryan et al.42 found that supplementation of B12, B6, and B9 improved the speed of information processing in the brain, recall, recognition, and verbal ability in women of various ages. And, Poly et al.37 report a significant improvement in cognitive ability in healthy adults who have a higher intake of dietary choline. Each of these three studies hypothesized that the cognitive improvements were attributed to a reduction in homocysteine from B12, B6, B9, or choline intake.
Vitamin C (ascorbic acid) is a powerful antioxidant; by donating electrons it neutralizes the damaging effects of free radicals, prevents compounds from being oxidized, protects DNA against mutation, and is essential for survival––a vitamin C deficiency, known and scurvy, is lethal if left untreated43.
In terms of brain health, vitamin C improves mood and cognitive ability in healthy older adults (aged 60-80)44. There is an association between blood plasma levels of vitamin C and intelligence (IQ) in teenagers45. It plays a vital role in brain and nerve cell development and myelin production. It mediates neurotransmitter and neural receptor function, in addition to glutamate reuptake by presynaptic neurons, which helps to reduce over-stimulation of the nervous system 46. Glutamate is an excitatory neurotransmitter and too much excitation is toxic to nerve cells; that’s why glutamate must be packed-up and put away after it has been used.
Humans cannot biosynthesize vitamin C from glucose like some other mammals; therefore, it must be taken in through the diet. The concentration of vitamin C in the brain and cerebrospinal fluid is 2-4 times that of the blood plasma–highlighting vitamin C’s vital importance as an antioxidant in the central nervous system46. To protect intellectual ability, adults should consume at least 150 mg of vitamin C, daily47; the Dieticians of Canada recommend an upper limit of 2000 mg per day48.
High blood serum concentration of vitamin C is behaviourally advantageous because it is associated with better memory performance49, and vitamin C supplementation potentially reduces cognitive impairment in the ageing population. It is thought that vitamin C helps to preserve cognitive ability by protecting the health of neuronal cell functioning and brain tissue through its antioxidative and tissue protecting actions47,50.
Vitamin C also supports healthy brain function and cognitive ability by its influence on certain neurotransmitters. Vitamin C is required to convert dopamine into norepinephrine: an important neurotransmitter needed for attention, memory, and emotional stability51. Low levels of norepinephrine are associated with ADHD52.
Vitamin D is a fat-soluble vitamin that has hormone-like capabilities53. When thinking about vitamin D, we typically think of its integral involvement in bone health; however, in recent decades, research has indicated its importance in healthy nervous system function––vitamin D deficiency or inadequacy is associated with multiple sclerosis, and we are now beginning to understand how it affects cognition as well54.
In a study of 1766 adults aged 65+, Llewellyn et al.55 reported that vitamin D concentration in the blood was significantly associated with cognitive ability––lower vitamin D levels in the blood resulted in a performance decline on mental activities involving attention, orientation in time and space, and memory. In another study of 3369 men aged 40-79, Lee et al.56 reported that a low serum vitamin D level is correlated with a decrease in information processing speed, particularly in men 60 years and older.
Vitamin D is associated with our ability to problem-solve. Individuals aged 65+ are more able to do tasks involving attention skills, mental shifting, information updating, mental processing speed, recall, and language if vitamin D levels are adequate. Buell et al.57 reported that as vitamin D levels decrease, so too does the ability to think clearly and to make the right decisions, quickly. Studies in the rat model reported that vitamin D deficient rats have a hard time controlling impulsivity, holding attention, concentrating, and making good decisions58. Vitamin D deficiency is observed in those with ADHD59.
The Dieticians of Canada recommend men and women aged 19-70 to get a minimum of 600 international units (IU) of vitamin D per day, with a maximum of 4000 IU/day. Men and women aged 70+ should take a minimum of 800 IU/day, with a maximum of 4000 IU/day as well60.
Magnesium plays a crucial role in hundreds of physiological processes; as a consequence, it is considered an essential mineral for a healthy body, including a healthy brain61. Without adequate intake of magnesium, mental focus and memory are compromised: the nervous system becomes hyperexcitable62; the stress response is triggered63; the capacity to hold attention and to form new memories declines64, and anxiety and depression appear63. Magnesium is known as the original chill-pill, and without magnesium to bolster the capacity to stay calm, centred, and emotionally strong, razor-sharp mental focus fades.
Psychological stress causes the secretion of cortisol and norepinephrine––hormones that not only mediate the fight-or-flight response but also compromise attention and the ability to perform mental tasks optimally 64. Magnesium helps to reduce the stress response by inhibiting the secretion of cortisol and norepinephrine65.
Magnesium also sits on the surface of neurons and acts as a guard at a gate preventing calcium or the neurotransmitter, glutamate, from overstimulating NMDA receptors. NMDA receptor stimulation excites neurons, and without the presence of magnesium, neuronal stimulation by calcium and glutamate remains constant and behaviourally leads to anxiety and stress and physiologically to neuronal damage and cell death63. Moreover, magnesium binds to and stimulates GABA receptors. GABA (gamma-aminobutyric acid) is a neurotransmitter that calms the nervous system; without GABA, the brain becomes hyperexcitable, leading to anxiety and inattention62 ––reduced GABA concentration is also linked to ADHD66.
Magnesium also benefits learning and memory. Optimal levels of magnesium are associated with enhanced learning-related plasticity: the development of new neuronal connections in the brain, which solidify the creation of short and long-term memories67. In the rat model, Xu et al. found that magnesium protects cognitive function and neuronal plasticity in rats with Alzheimer’s disease (AD); leading to the thought that magnesium therapy may help those with AD and subsequent difficulties with learning and memory68.
There is a wealth of scientific data to support the use of certain nutritive supplements to support the neurophysiological processes underlying mental focus. Specifically, science supports the use of L-theanine, vitamins B6, B12, C, and D, in addition to choline and magnesium to enhance attention, concentration, alertness, information processing, clarity, cognitive function, healthy neuronal function, abstract thinking, and motivation, while reducing anxiety, depression, and stress, which could compromise mental focus.
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