Thiamine (Vitamin B1) Deficiency: The Overlooked Key to Energy, Brain Health, and Metabolism
Most people are unknowingly walking around with a vitamin B1 (thiamine) deficiency, and the consequences are far-reaching. Thiamine is essential for energy production, brain function, and nervous system integrity. Yet, modern diets, stress, and lifestyle factors leave many of us running on empty.
Without enough B1, metabolism slows, gut health declines, and a cascade of dysfunction unfolds, from poor glucose control to neurological imbalances and cardiovascular strain. Worse, conventional medicine rarely tests for it properly, meaning countless individuals suffer from "mystery symptoms" without ever identifying the root cause.
In this article, we’ll explore the critical role of thiamine, the hidden signs of deficiency, and the best strategies to restore optimal levels.
Let’s get into it. (10-minute read)
What is Thiamine (Vitamin B1)
Thiamine (Vitamin B1) is a water-soluble B vitamin essential for energy metabolism, brain function, and nervous system health. It acts as a coenzyme in critical metabolic pathways, helping convert food into ATP, the body’s cellular fuel.
Without sufficient B1, energy production stalls, leading to fatigue, brain fog, and metabolic dysfunction. Thiamine-dependent enzymes like pyruvate dehydrogenase and transketolase drive mitochondrial function, making B1 crucial for glucose metabolism, neurotransmitter balance, and overall vitality.
Unlike fat-soluble vitamins, B1 isn’t stored in large amounts, meaning daily intake is essential. Yet, modern diets, stress, and anti-nutrients rapidly deplete it.
Why is Vitamin B1 important?
Thiamine is essential for metabolism, brain function, and nervous system integrity. Without it, energy production grinds to a halt, and a cascade of dysfunction follows, including gut issues, halting detoxification, crashing hormones, and more.
Conventional and even functional medicine don't discuss the benefits of vitamin B1 or its potential to be functionally deficient (conventional testing is poor sensitivity).
More so, even in my nutritional therapist training, I was never taught much about vitamin B1 until I started dissecting the mitochondria and bioenergetics for myself (how we utilise food or hydrocarbons, break them down, and make ATP + water and light to regenerate, create order, and offset entropy).
Thiamine plays a pivotal role in:
Brain & Nervous System Neurotransmitter balance, nerve myelination, and autonomic function. The brain and nervous system rely on glucose and lactate as its primary fuel, and thiamine-dependent enzymes (e.g., pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, transketolase) drive mitochondrial ATP production. The health benefits alone of Vitamin 1 bioenergetically are powerful.
A lack of thiamine leads to energy deficits in neurons, contributing to brain fog, poor focus, and fatigue. Severe deficiency can cause Wernicke’s encephalopathy.
Thiamine is essential for synthesizing acetylcholine, a neurotransmitter that supports memory, learning, and neuromuscular function. Vitamin B1 influences dopamine and serotonin metabolism, impacting mood stability, motivation, and mental clarity.
Thiamine is crucial for maintaining the myelin sheath, the protective covering around nerves that ensures fast and efficient nerve transmission. Low thiamine can lead to peripheral neuropathy, which causes symptoms such as numbness, tingling, and muscle weakness.
Thiamine helps regulate autonomic nervous system function, preventing dysautonomia (dizziness, poor circulation, and fatigue).
Cardiovascular Health Vagal Tone & HRV – Thiamine supports the parasympathetic nervous system, enhancing vagal tone and heart rate variability (HRV) for better autonomic balance and stress resilience.
Electrolyte Balance – Regulates sodium, potassium, and magnesium transport, preventing arrhythmias, muscle cramps, and fluid imbalances.
Vasodilation & Circulation – Supports nitric oxide (NO) production, promoting blood vessel relaxation, oxygen delivery, and blood pressure regulation.
Heart Energy & Mitochondria – Essential for ATP production in cardiac cells, ensuring efficient heart function and preventing oxidative stress-induced damage.
Gut Function—Thiamine deficiency can contribute to slow digestion, bloating, gut dysbiosis, and malabsorption, making it crucial for optimal gut health.
Vagus Nerve & Moility: Thiamine supports the gut-brain axis, enhancing vagal tone and regulating peristalsis to prevent constipation and bloating.
Microbiome Balance influences gut bacteria, with some microbes producing and utilising thiamine for metabolic processes. Thiamine deficiency may contribute to dysbiosis and SIBO.
Digestive Enzyme Production is essential for HCl and pancreatic enzyme secretion, aiding protein and fat digestion. Low thiamine can lead to poor nutrient absorption and malnutrition.
Gut-Inflammation Link: Supports immune function and energy metabolism, helping to reduce intestinal inflammation and leaky gut risk.
Glucose Metabolism – Insulin sensitivity, carb tolerance, body composition, and energy regulation.
Thiamine supports glucose metabolism: B1 is required for pyruvate dehydrogenase (PDH) and α-ketoglutarate dehydrogenase, which facilitate carbohydrate oxidation in mitochondria. When thiamine is deficient, glucose metabolism shifts toward anaerobic glycolysis, increasing lactate production and insulin resistance.
Body composition - Body Composition
Supports mitochondrial function and fat oxidation: Thiamine is required for efficient ATP production, and poor mitochondrial function can lead to fat storage rather than fat burning. Impaired glucose oxidation leads to increased lipid accumulation and metabolic inefficiency.
Impacts muscle mass: Since thiamine is crucial for energy production, low levels can reduce ATP availability, impairing muscle protein synthesis and performance.
Stress Resilience – Governs the stress response alongside magnesium. Supports the HPA Axis – Thiamine regulates the hypothalamic-pituitary-adrenal (HPA) axis, preventing cortisol dysregulation and adrenal fatigue.
Due to the connections with energy production, the nervous system, and gut regulation - there's a greater systemic resilience. Stress is not the problem. The inability to handle stress is, and that’s why vitamin B1 is a powerful dealbreaker.
Oxidative stress - The importance of Thiamine is shown in transketolase, which underpins a metabolic pathway called the pentose phosphate pathway, with NADPH activity, which recycles glutathione. Without sufficient thiamine, transketolase function declines, leading to oxidative stress and impaired detoxification.
Signs and Symptoms of Thiamine Deficiency
The early signs of deficiency are often mistaken for unrelated health woes: "Everything is normal." Yet, if you have 2 or more of the following, low thiamine status could be the culprit, and there are signs of thiamine deficiency.
Swollen feet and ankles
Gut motility issues (bloating and constipation)
Poor tolerance to carbohydrates
Low heart rate variability (HRV) and a flatlined stress response
Anxiety, agitation, and poor serotonin/GABA function
Chronic fatigue and low energy
Dealt with mycotoxins or candida issues
Humans are highly susceptible to thiamine depletion. “If intake is insufficient, it takes 18 days to become deficient”—think of it as your body's metabolic emergency brake.
Furthermore, nowadays, it is rare that people consume enough or meet the demand for vitamin B1, as psychological and physiological stress burns through our vitamin B1 stores and demands… just like magnesium.
Causes of Thiamine Deficiency
You might think that nowadays, with our plentiful food supply, fortification practices, and opportunity to supplement, a deficiency in B vitamins would be impossible. Indeed, our diets can meet the somewhat pathetic 1mg recommended daily intake.
However, vitamin B1 deficiency causes more than meets the eye.
Poor metabolic health - what came first, the chicken or the egg? B1 deficiency or insulin resistance? Your body requires energy to get itself out of a whole metabolically. The utilisation of B1 is reduced in poor health/metabolic states, requiring further nutrient repletion due to the losses and wastage such as absorption, uptake, and transport.
Consumption of refined foods (protein, fats, and carbs), especially, which deplete our functional vitamin B1 stores.
Vitamin B1 is a water-soluble vitamin-like magnesium, a hydrophilic mineral. If our cells and mitochondria are dehydrated and lose water, the B vitamins like thiamine will be washed out.
Certain foods can disrupt the absorption of thiamine and rob you of this hero nutrient without you knowing it.
Thiamine-Depleting Offenders:
White rice – Stripped of its B-vitamin-rich bran
Empty calorie food - think white/beige and adulterated by humans.
Tea & coffee – Polyphenols inhibit B1 absorption
Alcohol – Blocks thiamine uptake and transport
Raw fish – Contains thiaminase, an enzyme that destroys B1
Chronic stress – Increases demand but depletes stores faster
Medications: such as Metformin, which competes with cellular uptake, starving the cells of B1. Other medications, such as calcium blockers and PPIs, also contribute.
Certain bacterial species - produce thiaminase, destroying B1. Antibiotics can further add more fuel to the fire with this.
Vitamin B1 Deficiency: A Hidden Epidemic
Thiamine (B1) deficiency is more common than most realise, especially in conditions that increase metabolic demand or impair absorption.
Diabetes (Type 1 & 2) – Up to 76% are thiamine deficient due to altered transport function.
Chronic Liver Disease – 58% of patients show a deficiency, impairing detoxification and metabolism.
Obesity – At least 33% of obese individuals have low B1, affecting energy production and insulin sensitivity.
Elderly (Acute Care Patients) – 48% are deficient, increasing the risk for cognitive decline, frailty, and heart issues.
Post-Bariatric Surgery – Deficiency rates climb to 49%, affecting nerve function and metabolism.
Pregnancy – Up to 38% of women lack adequate B1, impacting fetal brain development and energy metabolism.
Mycotoxins/Mold Exposure and Vitamin B1
A typical scenario with clients with fatigue and other B1-related symptoms appears after dealing with mold exposure and mycotoxin burden. Why Mycotoxins Increase Thiamine Demand – Mycotoxins create oxidative stress, increasing the need for NADPH (which depends on thiamine via the pentose phosphate pathway) to make more glutathione to mop up the mess, which also includes.
Gut Microbiome Disruption – Mold exposure can alter gut bacteria, reducing thiamine-producing microbes and impairing absorption.
Enzyme Inhibition – Some mycotoxins may inhibit thiamine-dependent enzymes (like pyruvate dehydrogenase), impairing energy production and mitochondrial function.
Nervous System Stress – Mold toxins can trigger neuroinflammation, increasing thiamine depletion due to its role in nerve repair and neurotransmitter function.
Increased Urinary Loss – Chronic exposure may increase thiamine excretion, leading to deficiency symptoms like fatigue, brain fog, and autonomic dysfunction.
How to Fix Thiamine Deficiency
It is relatively simple. Increase your vitamin B1 content in your diet. Reduce the number of offenders that block absorption or rob your stores. Potentially, think about a vitamin B1 supplement.
Thiamine comes in two dietary forms:
Active & readily available: Organ meats, pork (most cuts), beef (animal foods like liver and heart)
Inactive & requires conversion: Peas, beans, nuts, brown rice (plant-based sources)
The best food sources of vitamin B1 (ranking highest first)
Pork (especially liver & muscle meat) – One of the richest sources of active thiamine.
Beef liver & heart – High in thiamine pyrophosphate (TPP), the active coenzyme form.
Egg yolks – Provide a bioavailable source of thiamine and other B vitamins.
Fish (trout, tuna, salmon) – Contains moderate amounts of thiamine.
Raw dairy (milk, cheese, yoghurt) – Contains small amounts, but fermentation may enhance absorption.
Nuts & Seeds (macadamia, sunflower, flax, sesame) are rich in thiamine but contain anti-nutrients that may reduce absorption.
Legumes (lentils, black beans, peas) are decent sources of thiamine but may be less bioavailable due to phytates.
Vegetables (asparagus, Brussels sprouts, spinach, squash) Provide some thiamine, but amounts are lower than animal sources.
Avoid these foods to improve Vitamin B1 Status
Refined carbohydrates - think white rice, pasta, cereal, bread, cakes, biscuits. They rob your B1.
Processed food/empty calories: To create energy in the body, we must acquire nutrients to help with the process - no nutrients, we can’t liberate energy from the food, and thus goes to our fat tissue.
Alcohol: Depletes vitamin B1 stores and impairs absorption, a massive net negative.
Phytic acid/polyphenols can interfere with the absorption. Drink or eat those foods at other times away from B1-high foods.
Vitamin B1 repletion tips
Whilst food should be the first strategy, some individuals may benefit from supplementation to indeed saturate in a shorter time, with a few caveats:
Pair with Magnesium – Thiamine and magnesium work together for mitochondrial energy production. My preferred magnesium is THIS, and a topical spray is HERE.
Timing Matters – Morning dosing may prevent nervous system overstimulation at night.
Dose Wisely – If sensitive, start with a low dose and titrate up.
Red light therapy - or sunlight - can augment the thiamine issue when restoration with food/supplement is in sync. The best Red light device out there that I recommend to clients worldwide and use myself.
Testing Vitamin B1 status?
Standard blood tests for B1? Practically useless. Since blood contains only 0.8% of total body free thiamine, it’s an unreliable marker.
Better Vitamin B1 assessments include:
Erythrocyte transketolase activity (ETKA) is rarely used and has conflicting scenarios/history associated with accuracy.
Organic Acid Test (OAT) – Elevated pyruvate & lactic acid hint at deficiency.
I use the OAT but also ask questions about symptoms and diet history - sometimes, even the OAT test is not needed to make an action.
Working with a health optimization nutritionist
I would always recommend working with clinicians who can think for themselves in a personalised fashion, connecting the dots. While this article outlines thiamine, there are further considerations and factors to focus on. Just taking a standard vitamin B1 might not work, as other parts of the system also require attention.
The Best Vitamin B1 Supplement
Thiamine Hydrochloride (HCL) – Readily available but less efficient
Benfotiamine – Lipid-soluble form, but doesn't cross the blood-brain barrier well
TTFD (Thiamine Tetrahydrofurfuryl Disulfide) – Crosses the BBB for neurological benefits - my preferred option HERE
I recommend and personally use it for my client’s TTFD. I have previously used and experienced all of them, but I have also discovered clinical differences with the forms. Thiamine HCL can be effective initially, but it lacks the power to move the needle. The TTFD is superior to all systems of the body and is effective in replenishing and regenerating your metabolism.
I recommend using the TTFD form of vitamin B1 from Objective Nutrition with the product Thiamax. Objective Nutrients is the leader in vitamin B1 research and brings knowledge and clinical supplement form.
I have extensively studied this form of thiamine, TTFD, from the vitamin B1 pioneer Derek Lonsdale. It is best absorbed, transported, and utilised in the brain and nervous system. The only caveat is sulphur sensitivities or reactions due to their intensity. Review the repleting tips above. Additionally, further resources on B1 can be found by my friend Elliot Overton, the founder of Objective Nutrients with the formulation of Thiamax. A few of the images are taken from Objective Nutrients.
Conclusion
Vitamin B1 (Thiamine) may be a small nutrient, but its impact on energy, brain function, and metabolic health is profound. In a world where stress, processed foods, and modern lifestyles deplete our vital resources, ensuring optimal B1 intake is a simple yet powerful step toward better health and vitality. First, optimise your diet with simple tweaks. That should be enough, but supplementation can also play a role, or you can work with a clinician like myself to further empower your health and beyond.
