Nutrients to support brain and vision

Let’s protect our brain

The number of functions of our brain is incredible and we use a multitude of them every second of our life (memory, speech, learning, reasoning, autonomous body regulations…). Unfortunately, as we get older, these brain functions diminish. This phenomenon is on the one hand normal, because our cells repair themselves less and create less new networks, but on the other hand, an inflammatory environment or an environment deficient in certain essential elements prevents the correct functioning of our cells. For example, certain molecules seem to be lacking in people suffering from cognitive problems such as Alzheimer’s disease and their supplementation could play a protective role. Vitamins A, B, C, D, E, as well as other molecules such as flavonoids or omega-3s, affect many brain functions such as antioxidation, energy production, neuroplasticity, neurotransmitter secretion, cell death, vasodilatation and inflammation. ^1–3

Let’s keep our eyes healthy

Vision is one of the senses we use the most. With age, inflammation and oxidative stress may have had time to take hold, which can cause one of many diseases, such as cataract, diabetic retinopathy or age-related macular degeneration (AMD). Fortunately, studies show that certain nutrients, such as vitamins C and E, carotenoids (lutein, zeaxanthin, β-carotene), zinc, omega-3 (DHA, EPA), copper… can reduce the risk of developing these diseases.^4,5,6

 

Omega-3 DHA

Omega-3s, belonging to the polyunsaturated fatty acids, are essential for a large number of physiological functions (cardiovascular, neurological, etc.). There are 3 types involved in our functioning: α-linoleic acid, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). DHA²⁷ is a powerful protector of our body: it can reduce the synthesis of pro-inflammatory cytokines and oxidative stress, maintain neuronal functions and the integrity of cell membranes, increase the production of certain phospholipids such as phosphatidylserine²⁸, inhibit cell death (apoptosis), limit angiogenesis and modulate metabolic functions.^4,29 The grey matter of the brain and the eyes, especially the retina, have a very high concentration of DHA, which allows neural signals and vision to function properly. A lack of DHA will lead to poor cognitive and visual performance, especially if it occurs during pregnancy or early childhood.³⁰ On the contrary, taking omega-3 is neuroprotective and can have benefits on cognition and dementia. High blood levels of DHA have been associated with better thinking, mental flexibility, memory and verbal performance. It also limits the decline in neuronal plasticity that accompanies age-related omega-3 loss. Alzheimer’s patients are often deficient in DHA, and some studies even suggest a reduction in cognitive plaques and symptoms after taking omega-3.^{2,31, 32,33} Due to its high concentration in the retina, DHA intake is important for the health of the eye, including phototransduction, photoreceptor membranes, retina integrity and visual function.^4,29,34 For example, DHA is useful for people with dry, inflamed eyes,^35,36 or incipient macular degeneration, diseases in which inflammation and neovascularisation play a major role.⁴ In addition, omega-3s appear to be essential for maintaining cardiovascular health,³⁷ reducing, for example, blood pressure (hypertension) and heart rate.³⁸ Finally, despite some contradictory studies, they could also have a positive effect on hypertension, arthritis, atherosclerosis, depression, strokes, diabetes and certain cancers. ^39,40,41 The only way to get omega-3s is through diet. Omega-3s are found in fish oil and some oilseeds or algae, but they are rarely sufficient to meet the recommended daily intake, so omega-3 supplementation is an effective strategy for maintaining the health of our eyes and brain.⁴ Omega-3s contribute to “the normal development of the eyes and maintenance of normal vision”, “maintenance of normal brain function” and “normal blood pressure and heart function”.*

Lutein and zeaxanthin

Lutein and zeaxanthin are carotenoids and although they cannot act as vitamin A (unlike β-carotenes), they are powerful antioxidants. They can limit oxidative stress damage by defusing free radical energy and facilitating glutathione synthesis (GSH). Lutein and zeaxanthin also have anti-inflammatory properties, by inhibiting the cytokine cascade, and can modulate immunity. Daily supplementation of lutein and zeaxanthin can significantly improve dementia and cognitive performance such as spatial and long-term memory, complex attention, reasoning abilities, executive functions… High concentrations of lutein and zeaxanthin have been associated with neuronal efficiency in many areas of the brain such as visual perception, decision-making, motor coordination… ^17,18

They may even be able to protect against certain neurodegenerative diseases such as Alzheimer’s, as they can, for example, stimulate neuronal stem cells, reduce oxidative stress and improve the functions of mitochondria (the energy-producing part of the cells).² Lutein and zeaxanthin are particularly concentrated in the macula (the central region of the retina), hence their nickname macular pigment. They are important structural molecules in cell membranes and prevent oxidative damage to the retina by absorbing blue light. Studies have shown that they can improve optical pigment macular density (MPOD), visual acuity, contrast sensitivity, as well as visual memory and visual processing speed by decreasing the signal-to-noise ratio.^19,20 

In this way, they could reduce the risk of diseases such as age-related macular degeneration, which is the primary cause of visual problems and blindness. There is a correlation between cognitive function, the amount of grey matter¹⁷ and the optical density of the macular pigment (eye), reflecting the importance of lutein and zeaxanthin in brain tissue in children, adults and the elderly. ^6,21,22,23 Lutein and zeaxanthin can have many properties in our bodies, such as lowering cholesterol and preventing cardiovascular disease, reducing the risk of cancer, or inhibiting bone resorption. Cataracts, retinopathy, uveitis, as well as heart disease and strokes may also be reduced, and skin and cognitive functions may also benefit.^24,25,26 On the contrary, low consumption of these carotenoids increases the risk of disease. ⁴ For example, they are found in kale and spinach, some cereals and egg yolk, but rarely in sufficient quantities. ^4,6,1

Lycopene

Lycopene belongs to the carotene family and is not synthesised by the body on its own. It has antioxidant properties, particularly by restoring the activity of superoxide dismutases, catalases and glutathione transferases.¹ For the brain, lycopene may be protective against neurodegenerative diseases, epilepsy and depression, and improves cognition and memory. In particular, it plays a role against oxidative stress, neuro-inflammation, cell death and maintenance of mitochondrial function.  For example, lycopene may be useful in reducing damage due to cerebral ischaemia (restriction of blood flow) due to its antioxidant properties that help limit the amount of free radicals and the activity of microglia (immune cells in the brain).² It may also limit cell death, inflammation and improve the integrity of the blood-brain barrier after a brain haemorrhage.³ In addition, lycopene may regulate blood lipid and cytokine levels, thereby limiting brain injury due to hyperlipidemia and releasing protective neurotransmitters.^4,5 Finally, it appears that, despite the heterogeneity of results, lycopene may limit dementia and cognitive decline, and decrease associated mortality.⁶ Pre-clinical studies have suggested that lycopene and vitamin E act synergistically to limit oxidative stress in Alzheimer’s mice, and that lycopene may inhibit the formation of brain plaques.^7,8,9 Lycopene is also highly concentrated in eye tissue and also helps to reduce the incidence and progression of cataract and macular degeneration.¹⁰ It is useful for many organs, for example for skin health⁸ or to prevent prostate cancer and some coronary heart disease.¹

Phosphatidylserine (PS)

Phospholipids are important constituents of our cells, especially neuronal membranes. With age, the lipid composition changes in the brain. Thus, phospholipid supplementation, especially phosphatidylserine (PS) – sometimes combined with omega3 – may be an effective therapy to prevent cognitive decline and improve cognitive performance and memory, even in people with mild dementia.^2,69 PS is well absorbed in our intestines and can cross the blood-brain barrier and can slow or even reverse biochemical and structural alterations in our neuronal cells, supporting our locomotor and cognitive functions, including memory, learning, concentration, reasoning, communication…⁷⁰ PS supplementation may even improve performance during intense physical exertion.⁷¹  Finally, the combined intake of PS and omega-3 may also be beneficial for people suffering from depression, notably by regulating their cortisol levels and correcting their circadian rhythm.⁷² PS may also reduce inflammation, which may limit the death of neurons in the retina.⁷³

Coenzyme Q10

Coenzyme Q10 is a cofactor present in mos mitochondria (the energy-producing part of the cell) and a strong antioxidant. It is a powerful neuroprotective agent, for example by preventing apoptosis (cell death) and by eliminating free radicals. Oral intake of coenzyme Q10 increases Q10 concentrations in the brain. Q10 improves mitochondrial function, which can be useful in the treatment of neurodegenerative diseases, where oxidative stress and mitochondrial dysfunction are often underlying. Despite the divergence of some clinical results, Q10 could thus be beneficial and dangerous for Parkinson’s disease, Huntington’s disease, Alzheimer’s disease, amyotrophic lateral sclerosis and Friedrich’s ataxia ^42,43,44 Q10 can also reduce eye damage: many studies have highlighted the importance of taking Q10 to slow or even reverse the progression of glaucoma (intraocular pressure destroying the optic nerve) leading to blindness. ^45,46 It may also limit cell damage and cell death due to UV or radiation.⁴⁷ One study has even highlighted that it may, in combination with certain vitamins, improve recovery of the visual field after a stroke in the occipital lobe.⁴⁸ Chronic cardiovascular disease and inflammation may also be relieved by the antioxidant power of Q10.⁴²  

Vitamin C

Vitamin C is a particularly powerful antioxidant, which can also regenerate other antioxidants (e.g. vitamin E) and increase iron absorption. Vitamin C supplementation has been associated with improved cognitive performance and a reversal of age-related cognitive and motor decline, especially when combined with vitamin E and exercise. ^2,7 With its particularly high metabolic rate, the eye needs strong antioxidant protection. Vitamin C helps to prevent eye diseases and provides benefits to our eyes. ^4,6 It is found in citrus fruits, berries, tomatoes and broccoli, among others, but large amounts are needed to really limit the progression of eye and cognitive diseases.  Vitamin C contributes “to the normal functioning of the nervous system”, “to psychological functions”, “to the reduction of fatigue”, “to protection against oxidative stress”.*

Vitamin E

The term vitamin E describes a family of antioxidants comprising 4 tocopherols (α-, β-, γ- and δ-) and 4 tocotrienols (α-, β-, γ- and δ-) which are able to prevent the oxidation of lipids by attacking free radicals and participating in their metabolism. Oxidative stress is a major contributor to the deterioration of neuronal functions and the development of dementia. Thanks to its strong antioxidant power, vitamin E is often used for brain protection and the prevention and treatment of diseases. Many clinical trials encourage the intake of vitamin E to promote healthy aging of the brain and to delay cognitive decline. Although some results regarding its effectiveness for Alzheimer’s disease, cancer or heart disease are mixed, its safety and low cost make it a promising solution. ^2,8,9 The retina is particularly rich in fatty acids, making vitamin E particularly important.^4,10,6 Lack of vitamin E can lead to damage to the retina and loss of photoreceptors, but it has been shown that they can be limited by taking α-tocopherol.¹¹ Even a single oral dose of vitamin E can increase the concentration of vitamin E in the retina by up to 5x.⁴ Vegetable oils, nuts, wheat germ and some plants are rich in vitamin E, but we rarely get enough of it in our nutrition alone. Vitamin E contributes to “protection against oxidative stress”.*

Zinc

Zinc has important antioxidant and immune functions, and can therefore protect against the harmful consequences of free radicals (such as 3apoptosis of pericytes, capillary leakage, vascularisation). Zinc is also essential for the proper functioning of the brain, as it plays a role in cellular processes and synaptic transmission, particularly in the hippocampus (memory and spatial navigation). Indeed, deregulation of zinc homeostasis (too low or high) seems to characterise many neurodegenerative diseases and cognitive decline. Alcoholism, schizophrenia, Wilson’s disease, Pick’s disease and Alzheimer’s disease, for example, seem to be linked to zinc levels, and treatment with zinc can be beneficial. Zinc can also improve glycemic control in diabetics or increase recovery from head trauma. ^{2,12,13,14,15} Zinc is essential for maintaining the health of the retina, as it is an essential component of many proteins and cell membranes. It can prevent the onset of certain diseases such as macular degeneration or diabetic retinopathy.^4,16 Zinc intake is therefore necessary: a zinc deficiency can imply a higher risk of vision loss, whereas a zinc intake (10mg/d) helps to protect the retina. Zinc is found in oysters, meat, nuts, legumes and dairy products, but rarely in sufficient quantities on a daily basis.6 Be careful, however, as zinc can be toxic in large doses (more than 100mg per day).⁶ Zinc contributes to “normal cognitive function”, “maintenance of normal vision”, “protection against oxidative stress”, “protection against disease” and “protection against disease”.*

B-group vitamins

Vitamins are a group of organic compounds that are essential for the functioning of our body but are not produced by it. There are 8 B vitamins (thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), vitamin B6, biotin (B7), folate (B9) and vitamin B12) which play essential roles in many of our cells’ enzymatic reactions. In the brain, they are important for many functions, such as energy production, DNA repair, synthesis of neurochemical molecules… A healthy diet should provide sufficient amounts of these vitamins, but studies suggest that this is not the case for a large part of the population, which suffers from deficiency.

This predisposes us to many health consequences and does not allow the optimal preservation of our brain. A deficiency of B vitamins can also lead to visual acuity problems, which can be reversed with multivitamin supplementation.⁵⁹ For example, there is some evidence that adequate intake may limit cognitive decline and the risk of dementia, and several studies have highlighted the improvement in psychological and cognitive function (performance and memory) after multi-supplementation.^2,60 In addition, supplementation with multivitamin B would reduce inflammation and oxidative stress in the brain, and improve energy storage and cellular metabolism.⁶¹

Thiamine (B1) is a neuromodulator in the acetylcholine system, acts as a cofactor during metabolic processes and contributes to the structure and function of cell membranes, especially neurons. Impairment can result in fatigue, irritability, gastrointestinal symptoms or pain, or even cerebral weakness. It is found in whole grains and green vegetables, but rarely at the recommended level. ⁶⁰ Riboflavin (B2) is essential for many cellular processes, the metabolism of fatty acids in the brain, the absorption and use of iron and the regulation of thyroid hormones. The deregulation of these processes due to a lack of riboflavin can have negative consequences on the functioning of the brain (weakness, personality change, brain dysfunction). Furthermore, it limits oxidative stress thanks to its antioxidant properties and its action on other molecules involved in redox cycles. Some of it can be found in dairy products, green vegetables or offal.^60,62 Riboflavin contributes to “normal energy-producing metabolism”, “normal functioning of the nervous system”, “maintaining normal vision”, “protecting cells from oxidative stress”, “reducing fatigue”.*

Many cellular functions in our body and brain are dependent on niacin (B3) derivatives such as NAD or NADP. These compounds are involved in energy production, antioxidant protection, DNA repair and gene expression, cell cycle and vitamin B9 metabolism. Niacin also appears to be crucial for neuronal health and survival. Niacin deficiency leads to skin problems, muscle weakness, anxiety or depression, and can be a risk factor for dementia, neurodegeneration, neurological or psychiatric deficits. On the contrary, taking niacin could modulate the immune system and reduce the restless sleep associated with Parkinson’s disease, and in animals it can improve Alzheimer’s, Parkinson’s and Huntington’s diseases, neuronal injuries and ischaemia (blocked circulation). It is found in small amounts in meat, fish and some whole grains.^60,63,64 However, consumption of more than 3g per day (the dosage for certain cardiovascular diseases) can lead to increased intraocular pressure and vision problems, which are reversible when niacin is stopped.^65,66

Pantothenic acid (B5) is involved in the synthesis of coenzyme A. It plays a role in oxidative stress, and contributes to the synthesis of cholesterol, amino acids, phospholipids and fatty acids. This structures and enables the proper functioning of neuronal cells, e.g. with neurotransmitters and steroid hormones. Numbness, skin problems or even behavioural changes or encephalopathy can be symptoms of a deficiency. Meat and wholegrain cereals can contribute to this.⁶⁰

Vitamin B6 is essential for the metabolism of amino acids, for example crucial for the synthesis of neurotransmitters (dopamine, serotonin, GABA, noradrenaline, melatonin…). It also has a direct effect on immune functions, gene expression and the regulation of cerebral glucose. By limiting inflammation, it reduces a risk factor for dementia and cognitive decline. A high intake of B6 has also been associated with a reduced risk of developing cataracts.⁶⁷ The main symptoms of B6 deficiency are anaemia or neurological changes (irritability, depression, cognitive decline, dementia…). Some of it can be found in meat, fish, vegetables or nuts.^2,60 Vitamin B6 contributes to “normal energy-producing metabolism”, “normal functioning of the nervous system”, “normal psychological functions”, “reduced fatigue”.*

Biotin (B7) is key in the metabolism and homeostasis of glucose, the main energy source of the brain. It also acts on insulin receptors and the pancreas. Its deficiency can lead to depression, lethargy or eczema. It can be found in eggs.⁶⁰

Folate (B9) is required for protein and DNA synthesis, making it particularly important for rapidly dividing cells during development. Folate supplementation has been associated with a reduced risk of developing macular degeneration.⁶⁸ Anaemia, behavioural changes, peripheral or cognitive neuropathies can be symptoms of a deficiency. They are found in green plants and citrus fruits.^2,60

Vitamin B12 is intimately intertwined with the folate and methionine cycles, so a lack of B12 can influence the functioning of the other cycles. Vitamin B12 deficiency can lead to anaemia or neuropsychiatric symptoms, such as behavioural or cognitive problems, neuropathies or spinal cord injuries. Cognitive deficits or depression can often be linked to a deficiency of vitamin B6, B9 and/or B12. Meat and fish contain the bacteria that produce B12.^2,60 Vitamin B12 contributes to “normal energy-producing metabolism”, “normal nervous system function”, “normal psychological functions”, “reduced fatigue”.*

 

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* official health claims of the EFSA (European Food Safety Authority).
An EFSA health claim is any statement concerning a relationship between a food and health. The European Commission allows various health claims as long as they are based on scientific evidence and are easily understood by consumers. The European Food Safety Authority (EFSA) is responsible for evaluating the scientific evidence supporting health claims.

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