Thiamine deficiency: the silent epidemic of the modern world

B1: an energy conductor

Imagine that every cell in your body is a factory running on electricity. Thiamine (B1) is not the fuel: it is the electrical transformer that makes the fuel usable. Without it, the mitochondrial power plant slows, overruns, or partially breaks down, depending on the organs affected.¹

More concretely: thiamine is the limiting cofactor of three fundamental enzymes of energy metabolism: pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and transketolase.²³

History: a century of ignored warnings

Thiamine deficiency has been known since the era of beriberi linked to polished rice, documented from the late 19th century in Asia.⁴⁵⁶

From the 1970s–2000s, Dr Derrick Lonsdale published dozens of papers showing that subclinical thiamine deficiency is widespread in the United States and linked to behavioural disorders, developmental problems, and chronic disease, while remaining largely ignored.⁷

In 2021, a review in Nutrients (Hiding in Plain Sight: Modern Thiamine Deficiency) emphasized that no current data on thiamine deficiency rates in the United States is available, not because the problem has been resolved, but simply because thiamine is not being measured.²

“TD is believed to be rare in developed, food-secure countries […] As a result of this perception, thiamine is not consistently assessed in healthcare practice or in the nutritional surveys that guide policy.”²

Demystifying: B1 is not “easy to obtain”

Officially, the recommended intake (≈1.1–1.2 mg/day) would be easily achieved through diet, but numerous modern factors destroy or deplete B1: cereal refining, high-temperature cooking, coffee/tea containing thiaminases, alcohol, diuretics, metformin, PPIs, stress, and chronic hyperglycaemia.^5891011

Body stores cover only 2–3 weeks, with a half-life of 9 to 18 days, so any increase in demand (infection, pregnancy, surgery, high carbohydrate intake) can unmask functional deficiency.²

The carbohydrate paradox

Sugar consumed

Thiamine is indispensable to carbohydrate metabolism: several key steps of glycolysis and the Krebs cycle are B1-dependent.²³

The higher the diet in refined carbohydrates, the greater the thiamine requirement, creating a double trap: ultra-processed foods are both poor in B1 and major consumers of B1.²³

“Among the most common contributors to thiamine deficiency is the regular consumption of a high carbohydrate/highly processed food diet.”³

This phenomenon particularly affects type 2 diabetics, obese individuals in “high-calorie malnutrition,” and children raised on ultra-processed products.¹²¹³

Sugar produced

The paradox is not only dietary. A person in chronic hyperinsulinemia and central adiposity carries a metabolism running at high throughput between meals as well as during them. Compensatory hyperinsulinemia drives sustained glycolytic flux. Adipose tissue is engaged in continuous cycles of lipolysis, re-esterification, and gluconeogenesis from released glycerol and free fatty acids. Muscle work at a higher body weight imposes a higher basal energetic cost. Each of these engages the thiamine-dependent enzymes of central carbon metabolism: pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, transketolase. The overweight metabolism is thiamine-hungry in a way that eating white bread only reproduces episodically.

The pharmaceutical load that often accompanies the metabolic phenotype compounds the depletion. Metformin, loop and thiazide diuretics for hypertension, proton pump inhibitors, and higher-than-average coffee intake all lower thiamine stores by the mechanisms flagged above.

The clinical consequence is that fatigue, cognitive fog, and the sense of running on empty in overweight adults are not always primarily a caloric or macronutrient problem. They can express a thiamine deficit driven by a body doing too much of the work of glycolysis and lipid recycling at once. In the practitioner case literature, the energy response to thiamine repletion in this population is often rapid and subjectively pronounced. It belongs to the small class of nutritional interventions that show themselves to the person taking them, on a short time scale, without a laboratory test.

Who is really at risk?

Contrary to the myth that confines B1 to alcoholics and low-income countries, measurable deficits have been observed in: psychiatric patients, pregnant women, emergency department patients, obese individuals (especially pre-bariatric surgery), dialysis patients, heart failure patients on diuretics, the elderly, people with chronic illness, and patients on artificial nutrition.¹⁰¹³¹⁴

“The number and variety of symptomatic thiamine-deficient adults identified in this review demonstrates that thiamine deficiency is not exclusive to LMICs and, in high-income settings, is not exclusive to alcoholic patients.”¹⁰

Genetics: when B1 meets its transporters

Polymorphisms in the SLC19A2 and SLC19A3 genes (THTR1 and THTR2 transporters) can reduce absorption or utilization of thiamine and predispose to early-onset diabetes, chronic inflammation, or neurological disorders.¹⁵¹⁶¹⁷

In these individuals, a “normal” intake may be insufficient, lowering the clinical deficiency threshold and modifying the response to supplementation.

B1, the “great imitator”: dysautonomia, SIBO, fatigue

The brainstem and autonomic nervous system, highly dependent on mitochondrial ATP, are particularly vulnerable to thiamine deficiency, which can cause dysautonomia (POTS, tachycardia, exercise intolerance, vasomotor disturbances), anxiety, and brain fog.¹⁸¹⁹

At the digestive level, B1 is necessary for acetylcholine synthesis for the vagus nerve; its deficiency can lead to gastroparesis, constipation, reflux, and presentations confused with SIBO or IBS.¹⁸²⁰

“The gastrointestinal tract is one of the main systems that can be affected by a deficiency of thiamine […] often non-responsive to antimicrobial treatments. Yet, sometimes the issues improve greatly with vitamin B1 repletion.”¹⁸

The testing problem: a false sense of security

Serum thiamine poorly reflects tissue stores and can remain “normal” despite functional deficiency.²¹

Measurement of TDP (thiamine diphosphate) in whole blood is more relevant but remains limited by the absence of standardised thresholds and inter-laboratory variations; some data also suggest increased vulnerability of certain populations (e.g. Black subjects) at lower concentrations.²²²³²⁴

Functional tests such as ETKAC also have important technical limitations; a study in thiamine-sensitive children showed that no biomarker could reliably identify them individually.²³²⁵

In practice, several authors conclude that it is often rational to supplement empirically when the clinical picture is compatible, since thiamine is very safe and inexpensive.¹¹⁰

Health authorities vs scientific reality

Official fact sheets (NIH, WHO, national agencies) state that thiamine deficiency is rare in developed countries and easily prevented through diet and fortification, but acknowledge not having recent data on actual deficiency rates.²⁸

Independent reviews show on the contrary that modern deficiency is widely underestimated, poorly measured, and affects a much broader spectrum of populations than just alcoholics or low-income countries.²¹⁰²⁶

The researchers who have sounded the alarm

• Derrick Lonsdale (1924–2024): more than 50 years of work on thiamine, author of Thiamine Deficiency Disease, Dysautonomia, and High Calorie Malnutrition; three of his papers are cited by the WHO on sudden infant death syndrome.⁷²⁷
• Chandler Marrs (PhD): co-author of the reference book and founder of HormonesMatter.com, a platform documenting hundreds of clinical cases and thiamine effects.²⁸
• Elliot Overton (EONutrition): functional medicine practitioner who developed high-dose thiamine protocols (ThiamineProtocols), used by thousands of patients and carers.²⁹³⁰³

Benfotiamine and its cousins: the derivatives with the trial base

Thiamine hydrochloride, the standard supplement form, is water-soluble. It is absorbed by two intestinal mechanisms: a high-affinity carrier system (the SLC19A2 and SLC19A3 transporters) that saturates at around 5 mg per single oral dose, and a passive diffusion pathway that continues to admit thiamine at higher intraluminal concentrations but at a much lower percentage efficiency. The historical high-dose oral protocols developed by Lonsdale and taken up by Costantini and Overton, in the 100 to 1500 mg per day range, exploit the passive route: a small fraction of a large dose still delivers useful amounts of thiamine to the circulation and to the tissues that need it. The lipid-soluble derivatives were developed as an alternative route to the same end. They bypass the carrier system entirely and deliver substantially more intracellular thiamine per milligram administered, at more moderate oral doses.

Benfotiamine: chemistry and mechanism

Benfotiamine (S-benzoylthiamine O-monophosphate) is a synthetic S-acyl derivative of thiamine, developed in Japan in the 1950s. Unlike thiamine hydrochloride, it crosses the intestinal wall by facilitated diffusion, is dephosphorylated at the brush border, and enters the circulation as S-benzoylthiamine. Once in the bloodstream it is hydrolysed to free thiamine, which is then taken up into tissues and phosphorylated to thiamine diphosphate, the active cofactor. The route delivers substantially higher intracellular thiamine concentrations in muscle, nerve, kidney, and retina than equimolar oral thiamine HCl. Its penetration of the central nervous system, however, is limited.³¹

The mechanistic case for benfotiamine in metabolic disease was made in 2003 by Hans-Peter Hammes and colleagues in Nature Medicine.³² Chronic hyperglycemia was known to drive four biochemical pathways of tissue damage: the polyol pathway, the hexosamine pathway, protein kinase C activation, and the formation of advanced glycation end products (AGEs). Hammes showed that benfotiamine, by activating the thiamine-dependent enzyme transketolase, shunts excess glycolytic intermediates into the pentose phosphate pathway and thereby blocks three of the four pathways at once. The finding gave a single molecule plausibly capable of preventing the microvascular complications of diabetes, at a cost of pennies per day. It also opened a broader hypothesis relevant to the right to measure insulin: any state of chronic hyperinsulinemia and hyperglycemia, well before frank diabetes, engages the same damage pathways, and the same transketolase intervention may partially interrupt them.

The neuropathy trials: two decades of consistent signals, no phase III sponsor

The most substantial clinical evidence base for benfotiamine is in painful diabetic peripheral neuropathy. Winkler and colleagues, in 1999, reported dose-dependent improvement in Neuropathy Symptom Score at 320 mg/day of benfotiamine.³³ The BEDIP study (Haupt, Ledermann, Köpcke, 2005) confirmed the finding in a three-week placebo-controlled pilot.³⁴ The BENDIP trial (Stracke and colleagues, 2008), a three-arm randomised double-blind study in 165 patients over six weeks, demonstrated dose-dependent improvement at 600 mg/day, with vibration perception threshold also improving.³⁵ The trials are not large by pharmaceutical standards, but they are directionally consistent, mechanistically anchored, and use validated neuropathy endpoints. What they lack is the multi-thousand-patient phase III replication that would justify guideline inclusion. In the two decades since Hammes, no commercial actor has funded that trial.

Beyond neuropathy

Small trials at Weill Cornell Medicine, led by Gary Gibson, have tested high-dose benfotiamine in mild cognitive impairment and early Alzheimer’s disease, on the mechanistic hypothesis that thiamine-dependent enzymes are impaired in the Alzheimer brain.³⁶ Results are preliminary and mixed but sufficient to sustain a research programme. Diabetic nephropathy and diabetic retinopathy have been investigated in single-centre studies with promising but not conclusive findings. The pattern across the non-neuropathy literature is what one might expect for a molecule that is cheap, safe, and mechanistically attractive: committed investigators run small trials, no phase III sponsor materialises, the literature accumulates in the specialist journals.

Choosing the derivative by tissue target: TTFD, sulbutiamine

Benfotiamine is not the only lipid-soluble thiamine derivative in clinical use. Two others merit mention.

TTFD (thiamine tetrahydrofurfuryl disulfide), also called fursultiamine, is a synthetic derivative of allithiamine, the naturally occurring compound isolated by Fujiwara in 1954 from garlic bulbs stored with thiamine. TTFD crosses the blood-brain barrier substantially better than benfotiamine and is the derivative of choice when central nervous system involvement (dysautonomia, fatigue, cognitive symptoms, mood dysregulation) is prominent. The practitioner protocols developed by Overton and by Marrs use TTFD as the primary agent for these presentations.³⁷

Sulbutiamine, developed in France in the 1960s under the brand name Arcalion, is another lipid-soluble derivative with good CNS penetration. It has been prescribed for asthenia in France and francophone jurisdictions since the 1970s and has been studied in post-infectious fatigue.

The choice among the three is not arbitrary. Benfotiamine reaches peripheral tissues: nerve, kidney, retina, muscle. TTFD and sulbutiamine reach the central nervous system. The distinction is well documented in the practitioner literature and largely absent from routine clinical education.

Availability and regulatory status

In Germany, benfotiamine has been sold as a prescription drug since the 1980s (Milgamma, Benfogamma), with reimbursement in some diabetic neuropathy indications. Sulbutiamine is prescribed in France and several francophone jurisdictions. TTFD is available over the counter as a supplement in most of Europe and North America; in Japan it retained a prescription status for decades before liberalisation.

In most of Europe and in North America, benfotiamine is sold as a food supplement, without prescription and without insurance coverage. No mainstream diabetes society includes it in its neuropathy guidelines. No routine primary care encounter surfaces it. This is the pattern this resource names elsewhere: a mature, cheap, mechanistically targeted intervention with two decades of clinical trial data, structurally excluded from routine practice by the absence of a commercial actor with a stake in its adoption. See Behind Every Test, an Industry on the general mechanism, and The Seventy Years Task Force on the class of findings this failure produces.

The hope: a simple, safe, often transformative intervention

Thiamine combines three rare properties: high safety even at elevated doses, very low cost, and the potential for rapid reversibility of sometimes debilitating symptoms (extreme fatigue, mild to moderate dysautonomia, functional digestive disorders, paradoxical anxiety).¹⁰¹

“Treatment with intravenous thiamine resulted in partial or complete recovery from the symptoms (cardiac, neurologic, and metabolic disorders) for most patients.”¹⁰

Within the framework of the physiological rights this resource defends, this grounds a right to an optimal thiamine status: the right to recognition of subclinical deficiency, access to relevant tests where available, access to the specific derivatives whose trial base has been accumulating for twenty years, and safe, low-cost supplementation strategies to correct a deficit that today is, quite literally, hiding in plain sight.

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