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Simon Parrott – Vitacuity Ltd
Thiamine, or vitamin B1, is a nutrient your body cannot make and cannot store for long. It acts as a helper molecule that converts carbohydrates into energy, which your brain especially needs since it burns more energy than any other organ. Without enough thiamine, serious conditions can develop, including beriberi (nerve damage and heart problems) and Wernicke’s encephalopathy (confusion, memory loss, and potentially permanent brain damage).
Thiamine deficiency is far more common today than most people realize, especially in those eating lots of processed foods high in refined carbohydrates. That type of diet actually increases your body’s thiamine demand. High-risk groups include people with alcohol dependency, digestive surgery, eating disorders, or diabetes. Most research confirms thiamine is essential, though human studies on its potential role in Alzheimer’s disease are still early.
If you eat a varied diet with whole grains and proteins, you likely have enough. If not, supplementing is safe because excess thiamine is simply excreted. Benfotiamine is a more absorbable form if you want better results, and magnesium is necessary for thiamine to work properly in your body.
Verdict: Thiamine is a foundational nutrient for brain and nerve health that is worth paying attention to, especially if your diet skews toward processed foods.
What if one of the most important discoveries in the history of brain medicine came from a flock of chickens eating the wrong rice?
It sounds absurd. But in the 1880s, a Dutch physician working in Java named Christiaan Eijkman noticed something strange. Chickens fed polished white rice developed a creeping leg paralysis. Chickens fed brown, unpolished rice did not. That observation, seemingly trivial, almost accidental, set in motion a chain of discoveries that would fundamentally reshape how we understand the relationship between nutrition and the human brain [13].
At the time, the scientific establishment believed beriberi was caused by miasmas rising from wet soil, or by some unknown infectious organism. The idea that a missing substance in food could devastate the nervous system and the heart was, frankly, unthinkable [13]. Yet here we are, more than a century later, with 1.77 million research papers in the Vitacuity database and a growing body of evidence suggesting that thiamine, vitamin B1, the molecule hiding in rice bran, may be more important to brain health than most of us ever realised.
Here’s what decades of research has taught us.
To understand why thiamine matters so much, you need to understand what it actually does. Thiamine is a water-soluble vitamin that your body cannot manufacture on its own, it must come entirely from food [11]. And unlike fat-soluble vitamins, it cannot be stored in significant quantities. The body’s reserves are depleted within weeks of inadequate intake [8].
Once absorbed, thiamine acts primarily as a coenzyme, a molecular helper, in several critical metabolic processes. Most importantly, it is essential for converting carbohydrates into usable energy, specifically the conversion of glucose into ATP, the fuel that powers every cell in your body. It acts as a catalyst in the Krebs cycle, the central engine of cellular energy production [11].
For the brain, this matters enormously. The brain is the most energy-hungry organ in the body, almost entirely dependent on glucose for fuel. Without adequate thiamine, that fuel conversion breaks down. Neurons begin to fail. The consequences range from subtle cognitive fogginess all the way to catastrophic neurological collapse [7].
But thiamine’s role goes further than energy metabolism alone. It is also involved in the synthesis of neurotransmitters and plays an active part in maintaining the central and peripheral nervous systems [11]. More recently, researchers have identified that thiamine and its derivatives appear to have anti-inflammatory and antioxidant properties that may operate through mechanisms entirely separate from its coenzyme function, opening up new and genuinely exciting lines of research [2].
Evidence grade: Strong, well-established clinical and historical data across multiple populations
The story begins with beriberi itself. The word has been in use for centuries, originating from a Sinhalese phrase meaning “I cannot, I cannot”, a grimly accurate description of the progressive weakness that defines the disease [9].
Beriberi presents in two main forms. “Dry” beriberi causes polyneuropathy, a progressive damage to the peripheral nerves, producing weakness, numbness and paralysis, particularly in the legs. “Wet” beriberi attacks the heart and circulatory system, causing fluid accumulation, heart enlargement and, if untreated, heart failure [3].
The breakthrough came in stages. Eijkman’s chicken observations in the 1880s pointed the finger at something missing from polished rice [13]. His successor, Gerrit Grijns, reached the correct conclusion: there were unknown substances in food essential for the peripheral nervous system [13]. In 1926, Barend Jansen and Willem Donath isolated and crystallised the active substance from rice polishings that cured polyneuritis in pigeons. Robert Williams synthesised thiamine in 1936, and the vitamin era was fully underway [13].
What makes this story remarkable is that beriberi was not simply a disease of historical poverty. A 2025 clinical review confirms that beriberi remains underdiagnosed today, particularly in high-income countries where physicians rarely consider it. The condition can be life-threatening if not recognised promptly, and clinical doses of 100–300 mg daily are typically sufficient to produce significant improvement in symptomatic patients [3].
Evidence grade: Strong, well-established clinical data; RCT evidence for treatment protocols remains limited
Perhaps the most alarming consequence of thiamine deficiency is Wernicke’s encephalopathy (WE), an acute neuropsychiatric emergency characterised by confusion, abnormal eye movements and loss of coordination. Left untreated, it can progress to coma, death, or a permanent form of dementia known as Korsakoff syndrome, defined by devastating and irreversible memory loss [7].
A 2006 paper published in the context of global thiamine research makes for sobering reading: Wernicke-Korsakoff syndrome is frequently undiagnosed, and in populations at risk, primarily but not exclusively people with alcohol dependency, the damage accumulates silently before it is caught [6].
The tragedy is that this is an entirely preventable condition. Thiamine supplementation works. Treatment with thiamine “generally results in a dramatic clinical improvement” when administered promptly, but delays, even short ones, can cause permanent damage [5]. A 1998 review noted bluntly that thiamine treatment “remains inadequate or delayed” across clinical settings, decades after the science was clear [5].
A 2020 review in *Therapeutic Advances in Psychopharmacology* underscores that our understanding of optimal dosing, timing and route of administration for WE treatment remains incomplete. Randomised controlled trial evidence is “virtually absent,” meaning clinical practice relies heavily on inference from basic science [7]. This is an honest and important caveat, the clinical consensus on treatment is strong, even if the RCT evidence for specific protocols is not.
Evidence grade: Strong for high-risk groups; Promising for broader population prevalence
Here is where the history intersects uncomfortably with the present. Thiamine deficiency was, for most of the 20th century, considered a problem of extreme poverty and alcoholism in developing nations. That framing is now recognised as dangerously incomplete.
A 2022 review is direct on this point: vitamin B1 deficiency is “an under-diagnosed disease because it is less frequently suspected in high income countries,” yet its risk factors, including alcohol consumption, poor diet quality, diabetes, malnutrition and congestive heart failure, are common across modern populations [10]. A 2015 review echoes this, explicitly arguing that thiamine deficiency occurs in “a world of abundance,” affecting people whose caloric intake appears adequate but whose diet is nutritionally poor [11].
One mechanism deserves particular attention. Thiamine is essential for glucose metabolism. A diet high in refined carbohydrates and simple sugars dramatically increases the body’s demand for thiamine, what one researcher describes as “high calorie malnutrition” [9]. In other words, the more processed carbohydrates you consume, the more thiamine you require, and the more likely you are to run short.
This insight reframes thiamine deficiency not as a relic of rice-dependent colonial populations but as a genuine risk in the modern Western diet.
Evidence grade: Promising, strong mechanistic and preclinical data; early-stage human evidence
This is where the research becomes genuinely fascinating, and where intellectual honesty demands we distinguish between what we know and what we hope.
A 2016 review in *Annals of the New York Academy of Sciences* draws a striking parallel between thiamine deficiency and Alzheimer’s disease (AD). Both conditions are associated with cognitive deficits and a measurable reduction in brain glucose metabolism [12]. Thiamine-dependent enzymes, the molecular machinery that thiamine activates, are critical components of glucose metabolism, and these enzymes are found to be reduced in the brains of Alzheimer’s patients [12].
In animal and cell culture models, reducing thiamine produces AD-like changes: memory deficits, neuritic plaques and hyperphosphorylation of tau protein, one of the defining hallmarks of Alzheimer’s pathology [12]. Conversely, excess thiamine in these models appears to diminish AD-like pathologies [12].
This does not mean thiamine supplementation prevents or treats Alzheimer’s disease. The human trial evidence is not there yet. But the mechanistic case is compelling enough that researchers are actively pursuing it, and the fact that the brain of an Alzheimer’s patient appears “functionally thiamine deficient”, even without classical dietary deficiency, is a finding that demands further investigation [12].
Evidence grade: Promising, human trial data exists but samples are small; animal and lab evidence is more extensive
Standard thiamine supplements have one notable limitation: bioavailability. Thiamine is absorbed through a saturable transport system, meaning there is a ceiling on how much the gut can take up at any one time [2].
Enter benfotiamine, a fat-soluble synthetic precursor of thiamine that crosses cell membranes more efficiently and achieves higher tissue concentrations than standard thiamine supplements [2]. A 2023 review describes benfotiamine as having demonstrated antioxidant and anti-inflammatory properties, improvements in complications of type 2 diabetes, and beneficial effects in mouse models of neurodegenerative disease [2].
Most notably for brain health, a 2023 review of thiamine thioesters reports that benfotiamine has shown benefit on cognitive outcomes in patients with mild Alzheimer’s disease in human clinical studies, though it is critical to note these studies involve small samples and the evidence is promising rather than definitive [4]. A newer compound, O,S-dibenzoylthiamine (DBT), appears even more potent in laboratory settings, though human data is essentially absent at this stage [4].
The practical upshot: benfotiamine is an established, safe supplement used to support nerve health and healthy ageing, with a growing evidence base that warrants serious attention, just not unconditional enthusiasm yet [2].
Evidence grade: Promising, mechanistic evidence is strong; clinical trial data is limited
There is one nuance in the thiamine story that is rarely discussed in mainstream health writing: the role of magnesium.
Thiamine, once absorbed, must be phosphorylated, chemically activated, to perform its coenzyme functions. This activation requires magnesium as a cofactor [7]. A 2020 review notes that magnesium deficiency can effectively render thiamine supplementation partially ineffective, because without adequate magnesium, thiamine cannot be properly converted into its active form, thiamine diphosphate [7].
This means that someone supplementing thiamine while magnesium-deficient may not be getting the full benefit. Given that magnesium deficiency is itself extremely common in modern populations, this interaction is clinically and practically significant. The two nutrients are, in a meaningful biochemical sense, partners.
It would be dishonest to tell this story without acknowledging where the science still has gaps, and there are real ones.
The Alzheimer’s connection remains largely preclinical. The mechanistic case linking thiamine and Alzheimer’s disease is genuinely compelling, but the human trial evidence is early and incomplete. We know that thiamine-dependent enzymes are reduced in AD brains, and that thiamine depletion produces AD-like changes in animal models. We do not yet know whether correcting thiamine status meaningfully alters the course of Alzheimer’s disease in humans [12].
Optimal dosing for neurological conditions is poorly defined. A 2025 review candidly frames current thiamine supplementation protocols as a tension between “clinically driven rationality vs. biological commonsense”, acknowledging that the evidence base for specific doses in neurological contexts is thin, and that clinical practice often lags behind what basic science would suggest [1]. For acute conditions like Wernicke’s encephalopathy, randomised controlled trials are “virtually absent,” meaning treatment guidelines rest on expert consensus and inference rather than gold-standard trial data [7].
Who is truly at risk in the general population is unclear. While high-risk groups, people with alcohol dependency, malabsorption conditions, eating disorders, post-bariatric surgery patients, are well-established, the prevalence of subclinical thiamine inadequacy in otherwise healthy adults is not well-characterised [14]. We know it is more common than assumed; we don’t have precise population-level data.
Benfotiamine’s human evidence needs to grow. The animal and laboratory data for benfotiamine’s neuroprotective effects is strong and consistent. The human trial data, while promising, involves small numbers and short durations. Larger, longer trials are needed before we can make confident claims about cognitive outcomes [4].
The newly identified compounds need human testing. O,S-dibenzoylthiamine (DBT) and other thiamine thioesters appear more potent than benfotiamine in laboratory settings, but the research is almost entirely preclinical. The gap between “effective in cell culture” and “effective in a human being” is always vast, and it has not yet been bridged here [4].
Here is what a century of research, from Eijkman’s chickens in Java to modern Alzheimer’s laboratories, actually tells us.
Thiamine is not a trendy supplement. It is a foundational nutrient, and its deficiency is genuinely dangerous. The fact that it was discovered through one of the great detective stories in medical history, and that it reshaped our understanding of nutrition and brain disease, makes it no less important today.
If you are broadly healthy and eating a varied diet, you are likely getting enough thiamine, but the margin for error is smaller than most people assume. A diet high in refined carbohydrates actively depletes your thiamine reserves, because the more glucose you metabolise, the more thiamine your body needs [9]. If your diet skews toward processed foods, you may be running closer to the edge than you think.
Thiamine is a water-soluble B vitamin. Any excess is simply excreted in urine. There is no meaningful toxicity risk at normal supplemental doses [8]. This is important: the risk calculus here is almost entirely one-sided. The downside of mild, unrecognised thiamine insufficiency is real, cognitive fog, fatigue, nervous system strain. The downside of supplementing when you didn’t strictly need to is essentially nothing. For a water-soluble vitamin, supplementing daily is a safe, practical default and excess is simply excreted.
If you are considering a thiamine supplement, standard thiamine (as found in most B-complex supplements) is perfectly reasonable for general nutritional support. If you are specifically interested in the neurological and cognitive research, benfotiamine, the more bioavailable fat-soluble form, is the version with the most relevant emerging evidence and an established safety record [2][4].
Don’t forget magnesium. If you are supplementing thiamine for brain or nerve health, adequate magnesium is biochemically necessary for thiamine to be fully activated. It is worth ensuring your magnesium intake is sufficient alongside any thiamine supplementation [7].
The groups who should pay particular attention include anyone with significant alcohol consumption, a history of digestive surgery, eating disorders, diabetes, or a diet that is heavy in refined carbohydrates and light in whole grains, legumes and animal proteins, the primary dietary sources of thiamine [3][11].
The discovery of thiamine did not just cure beriberi. It gave medicine its first proof of concept that a missing molecule, invisible, tasteless, present in food in vanishingly small quantities, could bring the human nervous system to its knees. And it opened the door to everything we now understand about nutritional neuroscience.
That is a remarkable legacy for a chicken that could not walk.
*Vitacuity has analysed over 1.77 million research papers to bring you evidence-graded insights like these. We read the science so you don’t have to, but we always show our working.*
[1] Protocols of Thiamine Supplementation: Clinically Driven Rationality vs. Biological Commonsense. (2025). DOI: 10.3390/jcm14113787 | https://pubmed.ncbi.nlm.nih.gov/40507549/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12156702/
[2] Thiamine and benfotiamine: Focus on their therapeutic potential. (2023). *Heliyon.* DOI: 10.1016/j.heliyon.2023.e21839 | https://pubmed.ncbi.nlm.nih.gov/38034619/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10682628/
[3] An Overview of Beriberi. (2025). DOI: 10.1159/000547719 | https://pubmed.ncbi.nlm.nih.gov/40753975/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12503715/
[4] Synthetic Thioesters of Thiamine: Promising Tools for Slowing Progression of Neurodegenerative Diseases. (2023). *International Journal of Molecular Sciences.* DOI: 10.3390/ijms241411296 | https://pubmed.ncbi.nlm.nih.gov/37511056/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10379298/
[5] Thiamine treatment today. (1998). https://pubmed.ncbi.nlm.nih.gov/9830340/
[6] Thiamine (vitamin B1) deficiency and associated brain damage is still common throughout the world and prevention is simple and safe! (2006). https://pubmed.ncbi.nlm.nih.gov/16987159/
[7] Wernicke’s encephalopathy – from basic science to clinical practice. Part 1: Understanding the role of thiamine. (2020). *Therapeutic Advances in Psychopharmacology.* DOI: 10.1177/2045125320978106 | https://pubmed.ncbi.nlm.nih.gov/33447357/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7780320/
[8] The role of thiamine in neurodegenerative diseases. (2015). https://pubmed.ncbi.nlm.nih.gov/26400895/
[9] A review of the biochemistry, metabolism and clinical benefits of thiamin(e) and its derivatives. (2006). *Evidence-Based Complementary and Alternative Medicine.* DOI: 10.1093/ecam/nek009 | https://pubmed.ncbi.nlm.nih.gov/16550223/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1375232/
[10] Thiamin: Simply a vitamin? (2022). *Revue Médicale Suisse.* DOI: 10.53738/REVMED.2022.18.801.2020 | https://pubmed.ncbi.nlm.nih.gov/36314092/
[11] Thiamine, “The Road Experience” of the Vitamin as a Manifestation of Deficiency in a World of Abundance. (2015). https://pubmed.ncbi.nlm.nih.gov/26742231/
[12] Vitamin B1 (thiamine) and dementia. (2016). *Annals of the New York Academy of Sciences.* https://pubmed.ncbi.nlm.nih.gov/26971083/
[13] The discovery of thiamin. (2012). *Annals of Nutrition and Metabolism.* https://pubmed.ncbi.nlm.nih.gov/23183292/
[14] Thiamin. (2018). https://pubmed.ncbi.nlm.nih.gov/29477220/
This article is for informational purposes only and does not constitute medical advice. Food supplements should not be used as a substitute for a varied and balanced diet and healthy lifestyle. If you are pregnant, breastfeeding, taking medication or have a medical condition, consult your doctor before taking any supplement. These statements have not been evaluated by the Food and Drug Administration (FDA) or the Medicines and Healthcare products Regulatory Agency (MHRA). This product is not intended to diagnose, treat, cure, or prevent any disease.
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