Energy Metabolism, Nerve Health, and the Hidden Deficiency

Evidence Review

Mechanisms and deficiency syndromes — Smith et al., 2021 [1]

This clinical perspective published in the Annals of the New York Academy of Sciences provides a comprehensive map of thiamine deficiency disorders (TDDs). The authors describe how TDDs affect a far broader spectrum of systems than the classic neurological picture suggests: metabolic (lactic acidosis), cardiovascular (wet beriberi, high-output heart failure), respiratory, gastrointestinal, and musculoskeletal manifestations all appear. They emphasize that a low threshold for empirical thiamine supplementation is warranted because: (a) serum levels are unreliable proxies for tissue status, (b) the consequences of untreated deficiency are irreversible in some cases (Wernicke's without treatment progresses to Korsakoff's), and (c) therapeutic thiamine is safe even at high doses. The authors document that in high-income countries, risk groups extend well beyond alcoholism to include bariatric surgery patients, people with eating disorders, heavy diuretic users, and those dependent on ultra-processed food diets.

Pathophysiological mechanisms — Isenberg-Grzeda et al., 2014 [2]

This review details the biochemical cascade triggered by thiamine depletion. The three TPP-dependent enzymes — pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and transketolase — are rate-limiting steps in aerobic energy production. When these enzymes slow, cells switch toward anaerobic glycolysis, lactate accumulates, and oxidative stress increases. Neurons are particularly vulnerable because they cannot store significant glycogen and rely almost entirely on oxidative phosphorylation. The review also addresses why serum thiamine poorly predicts intracellular status: red blood cell transketolase activity (or erythrocyte TPP) is a more reliable functional marker, though rarely used in clinical practice.

High-dose thiamine for fibromyalgia — Costantini and Pala, 2013 [3]

Three patients with fibromyalgia — a condition characterized by widespread musculoskeletal pain, severe fatigue, and sleep disturbance — received thiamine at doses determined by body weight, ranging from 600 to 1,800 mg per day orally. All three experienced significant, sustained improvement in fatigue scores and pain within 20 days, with no adverse effects. Normal serum thiamine levels at baseline suggested the benefit was not simply correcting classic deficiency but rather overcoming impaired intracellular transport through mass-action diffusion. The authors emphasize this is a case series with limited generalizability, and propose that a subset of fibromyalgia cases may represent a functional mitochondrial thiamine insufficiency rather than a systemic inflammatory disorder. Larger, controlled trials have not yet been conducted.

Thiamine, pyridoxine, and diabetic neuropathy — Stracke et al., 1996 [4]

In a controlled trial involving patients with symptomatic diabetic peripheral neuropathy, daily supplementation with thiamine (25 mg) plus pyridoxine (50 mg) produced measurable symptom relief: 82.5–89.7% of patients reported improvement in pain, numbness, and paraesthesia at four weeks, compared with 11.1–40.5% in the control group. Peripheral neuropathy severity scores also decreased more in the treated group (48.9% vs. 11.4%). While the doses used were relatively modest, the results suggest that correcting mild B vitamin insufficiency may be clinically meaningful in this population. The study predates modern standards for diabetic neuropathy trials and lacks placebo blinding, which limits the strength of conclusions.

Thiamine supplementation in chronic heart failure — Liu et al., 2024 [5]

This updated meta-analysis of randomized controlled trials examined whether thiamine supplementation improves cardiac outcomes in patients with chronic heart failure. The pooled analysis confirmed that thiamine supplementation reliably corrected thiamine deficiency status across studies. Effects on ejection fraction and other cardiac function markers were not statistically significant in aggregate, likely because study populations were heterogeneous and many patients were not profoundly deficient at baseline. The authors conclude that correcting documented deficiency is appropriate, and that loop diuretics create a physiologically plausible mechanism for depletion (increased urinary excretion) that warrants routine monitoring in this patient group.

Global prevalence — Whitfield et al., 2018 [6]

This report from a global expert working group estimates that thiamine deficiency is far more prevalent than acknowledged in nutrition surveys. In Southeast Asia, deficiency rates in infants and young children exceed 50% in some regions, contributing substantially to infant mortality. In high-income countries, the shift toward ultra-processed foods — which are low in thiamine even when nominally fortified — is creating pockets of subclinical deficiency. The authors advocate for better biomarker assessment and note that the gap between estimated dietary reference intakes and actual intake in vulnerable populations is larger than standard nutritional surveys capture. The review provides context for why thiamine deficiency remains clinically underrecognized even in settings with abundant food.