NEURO(B)LOG For Patients

Food is not just fuel — it also affects thinking. Just the very thought of food activates areas of the brain that control the search for food. In the clinic, patients frequently ask me how to eat and which dietary supplements to take. The market is flooded with over-the-counter products and dietary supplements promising better memory or dementia prevention. Patients face massive marketing. In this text, I will summarize what science, preclinical animal studies, and clinical human trials say about what is safe and what actually makes sense to take.

Brain Development

The brain begins to form very early in pregnancy — as early as the 22nd day after fertilization, the neural tube develops, from which the brain and spinal cord form. In the seventh week after fertilization, cells inside the neural tube divide into neurons and supporting cells (neuroglia). A newly formed neuron travels to its specific brain region, where it continues to grow, forming projections (axons and dendrites) and creating synapses and connections with other neurons. During pregnancy and early childhood, adequate nutrition is therefore vital. Some of the most important nutrients include folic acid, iodine, vitamin D, vitamin A, vitamin B12, iron, copper, and essential fatty acids (omega-3 fatty acids) such as DHA (from fish or algae). These nutrients support neuron growth, synapse formation, and long-term cognitive development in children. Malnutrition is primarily an issue in developing countries or in families with low socioeconomic status.

Brain Metabolism

The brain consumes about 20% of the body's energy; neurons need it the most. For rapid energy recovery (ATP, adenosine triphosphate), creatine is important — the body produces it in the liver and kidneys, and a small part is also made in the brain. It is capable of crossing the blood-brain barrier in small amounts and can accumulate in the brain. For supplemented creatine to affect the brain, higher doses are often required than those used by people for building muscle mass. Creatine is a substance important for ATP resynthesis during increased metabolic demands, such as sleep deprivation, various mental health conditions, and certain neurological diseases.

• Omega-3 fatty acids (EPA, DHA) from fish and algae form the building blocks of brain cells and support their function. Conversely, a diet rich in sugars and saturated fats can reduce synaptic plasticity and impair cognitive function by increasing oxidative stress. 

• Hydration is also highly important: dehydration worsens alertness and working memory while increasing fatigue, tension, and anxiety. During overheating, the blood-brain barrier can even become temporarily disrupted, affecting overall brain function.

Supplements and Sports Performance

In athletes, researchers examine whether supplements improve endurance, quick decision-making, and accuracy. Laboratory tests often use standardized computer tasks, which might not accurately reflect real-world sports situations. While laboratory results are useful, they cannot always be directly translated into practice.

Fatigue, the Central Hypothesis, and Amino Acids

The feeling of fatigue also originates in the brain — this is known as the central fatigue hypothesis, which emerged around 1987. It was previously thought that an increase in serotonin during prolonged exercise played the main role; newer research shows that the ratio of serotonin to dopamine is also crucial. A drop in dopamine can increase feelings of lethargy. Examined supplements include BCAAs, tyrosine, carbohydrates, and caffeine. Tyrosine may help maintain performance and mood under stress, but study results are mixed. Laboratory studies with BCAAs have not provided clear evidence of reduced fatigue. The composition of the specific supplement matters — products vary, and this influences the overall effect.

• Creatine

Creatine is mainly known as a supplement for muscle mass gain (since about the 1990s), but its effects on the brain are also being studied. The body partially produces creatine on its own; when supplemented, a portion can reach the brain, but higher doses than those for muscles are usually needed for observable effects on the brain. Preliminary studies (mostly in animals – rats, mice) suggest that creatine may help mitigate the consequences of mild traumatic brain injury or concussion and may influence mood in certain models of depression. In humans, however, evidence is limited, and most clinical trials involve a small number of participants (some with only around a few dozen participants). Creatine is promising, but it cannot yet be claimed that it significantly improves memory or treats neurodegenerative diseases. If you are considering taking it, consult your doctor.

• Ketone Bodies

Ketone bodies are substances the body produces during a state called ketosis (e.g., during fasting or a very low-carbohydrate diet). They serve as an alternative energy source for the brain when glucose availability is low. In certain situations (e.g., in some metabolic disorders or with special diets), they can help maintain brain function, but their use should be managed and consulted with a specialist.

• Caffeine

Caffeine acts as a stimulant because it blocks the action of adenosine (and has a structure similar to adenosine) in the brain. It is fat-soluble, easily crosses the blood-brain barrier, and increases the activity of certain neurotransmitters, including dopamine. Low to moderate doses (approximately 0.5–4 mg/kg of body weight) improve alertness, attention, and reaction time. In people not used to caffeine, side effects such as heart palpitations, dizziness, or digestive issues may occur. Use caffeine in moderation, monitor your individual reactions, and do not combine high doses with medication or use it in conditions where caffeine is unsuitable (e.g., certain heart problems).

• Omega-3 Fatty Acids

These include alpha-linolenic acid (ALA) and long-chain acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). ALA is essential (we must obtain it from food) — it is found in flaxseed and rapeseed oils, walnuts, and leafy green vegetables. EPA and DHA are mainly present in fatty fish and certain algal supplements.DHA is a structural component of brain cells and synapses, supporting neuron membrane function. EPA and DHA also contribute to heart health, better blood vessel function, and the integrity of the blood-brain barrier, which indirectly benefits the brain. Some studies also suggest a favorable effect on mood and depression. It is worth noting that estrogen receptors are located throughout the brain, and these are of interest in research regarding the decline of estrogen during menopause in women and its effect on the brain. During menopause, women suffer from a range of unpleasant symptoms, including night sweats, worsened sleep, impaired memory, and the occurrence of depression. Current results from clinical trials suggest that EPA and DHA could have a positive effect on easing menopausal symptoms, though further research is required.It is better to eat fish 1–2 times a week or take verified fish oils if you do not eat fish. Supplements can help, but they are not miraculous — the effects depend on the dose, the EPA:DHA ratio, and the duration of use. Consult your doctor if you take blood-thinning medications.

• Plant Extracts Polyphenols 

are plant substances with antioxidant effects. They include flavonoids (in fruit, green tea, chocolate, berries, coffee, parsley, celery, citrus fruits, soy, green tea, red wine) and non-flavonoids (e.g., chlorogenic acid in apples, kiwi, plums, blueberries, and resveratrol in grapes and peanuts).They can reduce oxidative stress and inflammation, support memory and learning, and show neuroprotective effects in animal experiments. In humans, however, the evidence is still preliminary — some studies show improvements in attention and episodic memory, while others do not.It is sensible to eat a varied diet rich in fruit, vegetables, tea, and berries. For supplements, the rule applies: the effect depends on the specific substance and dose; sufficiently large clinical studies are lacking.

• Cocoa and Cocoa Flavanols

Cocoa flavanols are polyphenols found in dark chocolate and cocoa products.Some studies have shown that cocoa flavanols can improve memory and increase brain oxygenation by dilating blood vessels (via nitric oxide). If you like dark chocolate, a small amount with a high cocoa content can have a beneficial effect. Beware of the sugar and calories in regular chocolate — the effect depends on the amount of flavanols, which varies across products.

• Beetroot Juice (Nitrates)

Beetroot contains nitrates, which are converted into nitric oxide (NO) in the body. It functions in the body as a vasodilator and neuromodulator. NO improves blood vessel (endothelial) function, lowers blood pressure, and can improve blood flow to the brain as well as other organs. NO is also a key factor enabling erections by relaxing smooth muscle in the penis and increasing blood flow. In athletes, it improves performance during high-intensity exercise; in healthy individuals and older adults, it can improve cognitive performance during demanding tasks. Drinking beetroot juice can provide short-term benefits for blood flow and performance; people with low blood pressure or those taking certain medications should consult a doctor.

• Ginseng (Panax)

Ginseng (e.g., Panax ginseng, Panax quinquefolius) is traditionally used against fatigue and stress, particularly in Chinese medicine. Clinical results are mixed. Some standardized extracts show short-term improvements in memory or attention in healthy adults, while other studies found no effect. Differences may be caused by various types of ginseng, ginsenoside content, and dosage. It can interact with medications (especially anticoagulants, certain psychiatric drugs, and cholesterol-lowering medications). If you are considering taking it, consult a doctor.

• Ginkgo Biloba

Recently, herbal preparations containing ginkgo biloba have been promoted, promising to improve memory and cognitive functions. In the short term, P. ginseng can have a positive effect on memory accuracy in young, healthy adults at doses around 200–400 mg; P. quinquefolius repeatedly shows benefits for working memory and attention. The results are inconclusive — some studies report small benefits for attention or memory, while others show no effect, especially with long-term use. The effect depends on the type of extract and the dose.Ginkgo can increase the risk of bleeding and interact with anticoagulants and certain other medications. Do not use without consulting a doctor if you take blood thinners or are planning surgery.

L-Theanine: What is it? 

A non-protein amino acid found mainly in green tea. L-theanine alone does not have consistently proven effects, but combined with caffeine (as in tea), it improves attention and alertness during demanding tasks while simultaneously easing the jitters caused by caffeine. If you drink tea, the combination of L-theanine and caffeine can be pleasant for focus without excessive stimulation. For dietary supplements, consult a doctor if you take medications affecting the brain.

Guarana (Paullinia cupana)

A plant containing caffeine, theobromine, theophylline, and other bioactive substances. Some studies suggest a small improvement in reaction speed, mood, and a reduction in mental fatigue; the effects are often similar to caffeine. Combined with vitamins and minerals, it can improve performance in short-term cognitive tasks. 

• Side effects: at higher doses, it can cause heart palpitations, insomnia, and digestive issues. It can interact with medications (anticoagulants, psychiatric drugs, etc.). 
• Guarana can help short-term with alertness, but monitor the dose and possible interactions; do not exceed the recommended amount of caffeine.

Rhodiola Rosea

This plant extract is widely used in Chinese medicine (containing salidroside, rosavin), traditionally against fatigue and stress and to restore vitality. 

• What it does: Preclinical studies in mice and rats, along with some clinical papers, suggest that it can reduce the perception of fatigue, improve endurance, and lower mental tension. Mechanisms may involve effects on the stress axis (HPA - hypothalamus-pituitary-adrenal) and neurotransmitters.
• Clinical results in humans are mixed; the effect depends on the quality of the extract and the dose. It can interact with antidepressants and anticoagulants. 
• Rhodiola can help with temporary fatigue or stress, but it is not a universal solution; choose standardized products and consult your doctor before use.

Magnesium L-Threonate

A form of magnesium described in 2010 in the journal Neuron as being more bioavailable to the brain than some other forms of magnesium. In humans, it is found in plasma, vitreous humor, urine, and the brain as an endogenous compound (a metabolite of ascorbic acid). Preclinical studies suggest memory improvement in healthy adults in short-term studies. Magnesium is vital for nervous function in general. 

• Where to find it in food: in some fruit juices, canned mushrooms, and processed meat; a regular diet also contributes to magnesium intake. If you are considering magnesium supplementation for memory, magnesium L-threonate is an option, but the evidence is not definitive; consult a doctor, especially if you have kidney disorders or take medication.

Phosphatidylserine and Magnesium-Related Vitamins

• Phosphatidylserine is a component of neuronal cell membranes and is involved in nerve impulse transmission and myelin formation. It is capable of crossing the blood-brain barrier. It can help protect nerve cells, but clinical evidence of significant memory improvement is limited. 
• Vitamin B6 and Vitamin D: B6 supports the absorption of magnesium from the intestines; vitamin D helps retain magnesium in the body (reabsorption by the kidneys) and improves its absorption. Maintain a balanced intake of magnesium and vitamins B6 and D; when supplementing, monitor your overall regimen and consult with a doctor.
• B-Complex Vitamins (Especially B6, B9 – Folate, and B12)They play a crucial role in cellular energy metabolism, DNA synthesis and repair, and the regulation of homocysteine levels — processes that are also important for the brain. B12 is additionally essential for maintaining myelin (the protective sheath of nerve fibers) and for proper nerve function.
• When they make the most sense: Supplementation of B vitamins provides the greatest benefit where there is a proven deficiency (e.g., in older adults, individuals on a vegan diet, or those with malabsorption disorders) or where homocysteine in the blood is elevated. In these situations, folate and B12 supplementation can contribute to improving or slowing cognitive decline.In healthy adults with normal B vitamin levels, routine use of large doses is not proven to be effective as a prevention against dementia or for significantly improving memory. The effect is usually small and depends on the baseline nutritional status.

Safety and Practical Advice: 

• Before you start taking B vitamins, have your B12 and folate levels tested, and potentially homocysteine as well.
• If a deficiency is proven, supplementation according to a doctor's recommendation is justified.
• Avoid long-term high doses without medical supervision (e.g., very high doses of B6 can cause neurological problems with prolonged use).

B vitamins are best taken as part of a comprehensive approach:

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If you are interested in the role B vitamins play in the nervous system, read also the article:👉 Myths and Facts About B Vitamins in Neurological Diseases

NAD+ (Nicotinamide Adenine Dinucleotide)

• NAD⁺ is a key coenzyme for energy, DNA repair, and mitochondria in the brain;
• Supplementation with NAD⁺ precursors (NR, NMN, NAM, niacin, or NAD⁺/NADH) shows promising neuroprotective and cognitive effects in preclinical animal models, but evidence in humans is still limited and inconclusive; well-controlled clinical studies are needed.Supplements (precursors): some of the most common include NR (nicotinamide riboside), NMN (nicotinamide mononucleotide), NAM (nicotinamide), and niacin. These substances increase NAD⁺ levels in the blood. 
• Consult a doctor before taking them (due to interactions, chronic diseases, or pregnancy). 
• Risks: gastrointestinal difficulties, changes in blood parameters, potential drug interactions; long-term safety is not fully known.

PRACTICAL SUMMARY

What Has the Strongest Support and Why to Try It

• Omega-3 (EPA, DHA) — important for neuron structure and vascular health; it is recommended to eat fatty fish 1–2 times a week or take a verified fish/algal oil, especially if you do not eat fish.
• Hydration and essential nutrients in pregnancy — folate (folic acid), iron, iodine, vitamin D, B12, and DHA are crucial for fetal brain development and young children.
• Caffeine (in moderation) — short-term improvement in alertness and reaction time; beware of insomnia and cardiac symptoms in sensitive individuals.
• Beetroot juice (nitrates) and cocoa flavanols — can temporarily improve brain blood flow and performance in demanding tasks; suitable as a supplement, not as a primary treatment.
• B-complex vitamins (B6, B9/folate, B12) - supplementation makes the most sense in individuals with a proven deficiency (e.g., older adults, vegans, those with absorption disorders, or bariatric surgery patients) or with elevated homocysteine; in these cases, folate and B12 replenishment can support cognition. In healthy individuals without deficiency, there is no evidence for routine high-dose supplementation as dementia prevention. I recommend first checking B12 and folate levels and consulting a doctor before starting supplementation.

In some patients, nutritional factors, such as vitamin D deficiency, can play a role in the development of various conditions. 

You can read more about this connection in the article Vitamin D and Its Role in the Development and Treatment of Neurological Disorders

If you are interested in how magnesium levels can affect migraines and neurological functions, also read the article Magnesium: Worth Its Weight in Gold? How Is It Absorbed and Used?

• Creatine — promising preclinical results in animals (concussions, mild brain injuries, mood); in humans, studies are still few and small; it cannot be considered an established therapy for memory or neurodegeneration.
• L-Theanine — combined with caffeine (e.g., in tea), it improves focus and reduces jitteriness; its standalone effect is less consistent.
• Guarana — effects often match its caffeine content; can briefly improve alertness and reaction time, but poses a risk of side effects at higher doses.
• Rhodiola Rosea — may reduce the perception of fatigue and stress; clinical results are mixed, and the effect depends on extract quality.
• Magnesium L-Threonate — preclinical studies suggest possible memory improvement; evidence in humans is limited.
• Phosphatidylserine — a component of neuron membranes; some studies show small benefits, but the evidence is not strong.
• Polyphenols (fruit, tea, berries) — generally beneficial for the brain due to antioxidant and anti-inflammatory effects; specific clinical effects vary by substance and dose.
• Ginseng and Ginkgo Biloba — study results are mixed; they may have a short-term effect on attention/memory in some people, but they are not a universal solution.

Experimental / Preclinical Animal Studies

• NAD⁺ Precursors (NR, NMN, NAM, niacin) — strong preclinical evidence in animals for neuroprotection and improved mitochondrial function; in humans, clinical results are still limited and inconclusive. They increase blood NAD⁺, but reliable cognitive improvement is not proven.
• Ketone Bodies / Ketogenic Diet — can serve as an alternative fuel for the brain (fasting, keto diet); useful in certain indications (e.g., refractory epilepsy), but not suitable for everyone without medical supervision.

Safety Recommendations (Practical)

• Consult a doctor or pharmacist before starting any dietary supplement if you take medications (especially anticoagulants, antidepressants, hypoglycemics, hypolipidemics) or have a chronic condition.
• Monitor dosage: "more" is not always better — higher doses can cause side effects (caffeine: palpitations; guarana: insomnia; niacin: flushing; high doses of nicotinamide: liver risks).
• Choose verified products: prefer products with a clear composition, standardized content of active substances, and laboratory quality testing.
• Be cautious with combinations (e.g., multiple stimulants at once) and long-term use without medical supervision.
• Do not expect miracles: supplements can help in specific situations (short-term fatigue, boosting alertness), but they are not a substitute for a healthy lifestyle.

Supplements — When Do They Make Sense and How to Use Them Safely

• When to consider supplementation: if you do not eat fish, have a laboratory-proven deficiency (vitamin D, B12), or are an older individual at risk of deficiency. In healthy adults without deficiency, the effect of omega-3 on global cognition is uncertain.
• Dosage: commercial products often contain around 1000 mg of EPA+DHA/day; clinical studies use a wide range; consult a doctor for a decision.

Bleeding Risk, Interactions, and Warnings (Important)

• Bleeding risk: omega-3, ginkgo, high doses of vitamin E, garlic, and certain herbs can increase the risk of bleeding or interact with anticoagulants (warfarin, NOACs). Consult a doctor or pharmacist before combining.
• Product quality: quality and active substance content vary among manufacturers; choose products with purity certification and declared EPA/DHA content.
• Do not exceed recommended doses without medical supervision; high doses of certain vitamins can be harmful.

Conclusion

Diet and certain dietary supplements, extracts, or foods can slightly influence alertness, mood, and specific aspects of memory, but no dietary supplement is a "miracle" cure for impaired cognition or dementia. The firmest foundation for a healthy brain remains a balanced diet, regular exercise, quality sleep, and control of risk factors (diabetes, high blood pressure, smoking, obesity).Certain dietary supplements — omega-3 (EPA/DHA), targeted B-vitamins in case of deficiency, L-theanine in tea, beetroot juice, a moderate dose of caffeine, or occasionally cocoa flavanols — can temporarily support alertness, mood, or certain aspects of memory. For other substances (creatine, magnesium L-theonate, rhodiola, NAD⁺ precursors, etc.), the evidence is currently preliminary within preclinical animal studies or mixed. Do not hesitate to consult your doctor or pharmacist before purchasing and taking dietary supplements. Even plant extracts can interact with the medications you take, increasing or decreasing their effectiveness, or causing unwanted side effects.

MUDr. Petra Mištríková, MBA

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