A: Amino acids:
Your body cannot synthesise all of the 20 amino acids. Nine of them can only be obtained through food, including tryptophan and phenylalanine. These two amino acids, along with tyrosine, are the biosynthetic precursors for the neurotransmitters serotonin, dopamine, and norepinephrine. The amino acids glutamate and aspartate are themselves neurotransmitters as well. However, they are not taken up into the brain from the diet. Regular meals containing aspartate and glutamate have no effect on the levels of these neurotransmitters in the brain. The brain is only affected when glutamate is administered alone in extremely large doses [1]. Meat, fish, eggs, dairy products and legumes are rich in protein and thus, amino acids.
B: B complex vitamins
A typical component of dietary supplements for the brain are vitamin B complexes, which include Vitamin B6, B12 and folic acid. Vitamin B6 is a cofactor in the production of cysteine and vitamin B12 is a cofactor needed in folic acid metabolism. Folate promotes the regeneration of methionine from homocysteine. They all work by reducing levels of homocysteine and their deficiency leads to hyperhomocysteinemia. This can lead to DNA damage, increase the generation of reactive oxygen species, contribute to excitotoxicity and cause mitochondrial dysfunction which may lead to apoptosis [2]. Further, vitamin B12 deficiency and high levels of homocysteine double your risk for brain atrophy and cognitive decline [3, 4]. Taking vitamin B6, B12, and folic acid can reduce brain atrophy and improve brain function [5]. Vitamin B6 can be found in dairy products, meat and fish, but also in cabbage, beans, whole meal products, nuts, yeast, avocados and bananas. Foods with high folate content are dark green leafy vegetables like spinach, avocado, liver, asparagus, brussel sprouts, nuts, beans, dairy products and eggs. Animal products are the best source of vitamin B12; you find it especially in liver, but also in eggs and dairy products. For vegans it is difficult to get enough B12. A recent study suggests that dried purple laver (Nori) could be a good source of B12 for vegans and vegetarians [6].
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| Brainfoods by Claudia Willmes |
C: Calcium
This is one of the most important messengers in neurons. Indeed, only a few neuronal functions are immune to the influence of calcium! A transient rise in cytoplasmic calcium concentration allows activation of a large number of Ca2+-binding proteins that start signalling cascades. As calcium participates in the transmission of the depolarizing signal and contributes to synaptic activity, calcium deficiency impairs many neurological functions. Milk and dairy products as well as green vegetables, sesame seeds and nuts are an excellent source of calcium.
C: Chromium
Chromium is a trace mineral found in many nutritional supplements, especially in weight-loss and muscle-building pills. The use of chromium-containing dietary supplements is controversial, owing to the absence of any verified biological beneficial effect on healthy people [7]. However, eating some chromium should not hurt. Food sources of chromium are broccoli, grapes, whole-wheat products and potatoes.
F: Fat
Many people avoid eating fat because they are afraid of gaining weight, but never underestimate their necessity for a functioning brain! Fatty acids are structural components of myelin. Both prenatal and postnatal fatty acid deficiency in rodents reduces the amount and alters the composition of myelin [8]. Avocado, olives and coconut oil are an excellent source of essential fatty acids. Very often, omega 3 fatty acids are found in dietary supplements. There are two main omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The latter shields against age-related mental decline and improves both learning and memory in older adults [9]. People with low DHA levels actually have smaller brains and exhibit more cognitive impairment than those with adequate levels [10]! The best sources of omega-3 are animal products: cold-water fish such as salmon, as well as dairy products from animals on a grass-fed diet. Plants only contain the fatty acid precursor alpha-linolenic acid (ALA), of which a tiny amount eventually gets converted to EPA and DHA in the body. If you are vegan, eat pumpkin seeds, walnuts, soy beans and seaweed.
G: Glucose
This is the second important addition in neuro-drinks and the brain's primary energy source. Blood glucose levels influence mood and attention span. Glucose administration also improves performance in cognitively demanding tasks [11]. The brain cannot store glucose and needs a steady supply, but this does not mean you should constantly be sipping soda! To ensure a constant glucose supply to your brain, eat food with high fiber carbohydrates such as carrots, beets, potatoes or dark fiber-rich whole wheat bread.
I: Iodine
The body cannot produce iodine, so it is an essential part of your diet. This trace element is required for producing thyroid hormones [12] which, in turn are required for brain development. Iodine deficiency in utero or during early postnatal development results in impaired cognitive and motor development [12]. Pregnancy, smoking and increased alcohol intake are risk factors for iodine deficiency. Great sources for iodine are saltwater fish and seafood, milk and dairy products, and, of course, iodized salt.
I: Iron
Iron is an important mineral for neurodevelopment and neuronal function. It plays a fundamental role in neurotransmitter synthesis, myelination and ensures oxygenation and energy production in the brain. Iron deficiency appears to alter the metabolism of the monoamines dopamine and norepinephrine [13] and decreased iron intake is associated with reduced myelination [14]. Iron deficiency is linked to attention-deficit/hyperactivity disorder and abnormal development of cognitive functions. Iron deficiency is particularly common in women and is associated with depression [15]. Rich sources of dietary iron include red meat, fish, legumes such as lentils and chickpeas, leafy vegetables and whole-grain products.
M: Magnesium
Magnesium is often listed as a supplement in brain-boosting drugs or drinks. It is involved in all the major metabolic pathways such as oxidation-reduction and ionic regulation. It also blocks the NMDA receptor, thereby preventing glutamate excitotoxicity. In magnesium deficiency, NMDA receptors become hyperexcitable, leading to excessive intracellular calcium. This can cause production of toxic reactive oxygen species and eventually lead to neuronal cell death. People with low magnesium are more susceptible to migraine attacks [16]. Parkinson's patients have low magnesium levels in the brain and rats with chronic low magnesium rapidly lose dopaminergic neurons [16]. Supplementary magnesium may thus be beneficial to prevent Parkinson's disease. Increased magnesium intake can also lead to improvement in patients with mania and depression [16]. The exact benefit of magnesium supplementation however is not yet definitive. Although whole grains contain magnesium, phytic acid in grains can inhibit its absorption. Therefore, the best sources of magnesium are dairy products, beans, leafy green veggies, and nuts.
V: Vitamin C:
This is an important antioxidant, serving as an electron donor in biological reactions. The brain has higher concentrations of Vitamin C compared to other organs [17]. It participates in neuronal maturation and myelin formation and supplies electrons for dopamine-β-hydroxylase, catalyzes the formation of norepinephrine from dopamine and is involved in presynaptic re-uptake of glutamate. Thus, it modulates the cholinergic, catecholinergic, and glutamergic systems [17]. Studies show that vitamin C levels are low in patients with dementia while research with animal models show that vitamin C supplementation can reduce cognitive decline [18]. Foods rich in vitamin C are citrus fruits, berries, bell peppers and sea buckthorn.
V: Vitamin D:
Although it's difficult to obtain from food, one thing you should definitely not get too little of is vitamin D. The best food source by far is cod liver oil (yuck!). Luckily, vitamin D is created when our skin is exposed to sunlight. Vitamin D has profound effects on the brain during all stages of life. Continuing to get adequate vitamin D throughout adult life can ward off cognitive decline, dementia, and Alzheimer’s disease [19, 20].
W: Water:
Obviously the most important thing for your brain is water. It helps the blood flow and consequently the oxygen supply of the brain. Thus, our advice: Try to drink 2 liters of water per day.
Z: Zinc:
The organ containing the highest amount of zinc is the brain, especially the hippocampus and cerebral cortex. Zinc acts as an antagonist of the NMDA receptor, induces BDNF gene expression and is a cofactor in the conversion of homocysteine to cysteine. Early postnatal zinc deficiency impairs neurogenesis, leading to learning and memory deficits persisting into adulthood [21]. Studies with rodent depression models and clinical studies have demonstrated the benefit of zinc supplementation in antidepressant therapy [22]. In animal models of depression, zinc treatment has antidepressant-like effects and dietary zinc insufficiency induces depressive behaviors [23]. Even though zinc has been associated with many psychological disorders, the nature of this relationship remains unclear. Seafood, beef, lamb, "variety meats" such as liver or brain, and some cheeses such as Emmental, Edam and Gouda are excellent sources of zinc. Plants provide us with zinc as well, but with lower bioavailability. Vegetarians and vegans should consume seeds, nuts, spinach, cocoa and beans to get enough zinc.
Our advice: Add these smart foods to your shopping list and go out for a picnic in the sun!
[1] Fernstrom, J Am Diet Assoc, 1994
[2] Kronenberg, Curr Mol Med, 2009
[3] de Jager, Neurobiol Aging, 2014
[4] Tangney et al, Neurology, 2011
[5] Douaud et al, PNAS, 2013
[6] Watanabe et al, Nutrients, 2014
[7] EFSA Panel, EFSA Journal, 2014
[8] Salvati et al, Dev Neurosci, 2000
[9] Yurko-Mauro et al, Alzheimers, 2010
[10] Tan et al, Neurology, 2012
[11] Brandt et al, Behav Neurosci, 2013
[12] Delange, Proc Nutr Soc, 2000
[13] Burhans et al, Nutr Neurosci, 2005
[14] Todorich et al, Glia, 2009
[15] Lozoff et al, Semin Pediatr Neurol, 2006
[16] de Baaij et al, Physiol rev, 2015
[17] Normann Hansen et al, Nutrients, 2014
[18] Harrison et al, Nutrients, 2014
[19] Lee et al, J Neurol Neurosurg Psychiatry, 2009
[20] Anastasiou et al, J Alzheimers Dis, 2014
[21] Chowanadisai, J Neurochem, 2005
[22] Nowak et al, Pharmacol Rep, 2005
[23] Swardfager et al, Neurosci Biobehav Rev, 2013
by Claudia Willmes, PhD Student AG Eickholt / AG Schmitz
This article originally appeared 2015 in CNS Volume 8, Issue 3, Food for Thought.
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