Vitamin B1

Vitamin B1, also called thiamin or thiamine, is a water-soluble vitamin your body uses to turn carbohydrates into energy. The active form thiamine pyrophosphate sits inside enzymes that drive glucose metabolism in every cell. Nerve tissue and heart muscle depend on this supply most.^[1] Your body cannot store much thiamin. Reserves last two to three weeks without intake.

Severe deficiency causes beriberi. Historically this hit populations living on polished white rice. In high-income countries today it shows up most often as Wernicke's encephalopathy in people with alcohol use disorder. It also appears with severe pregnancy vomiting, after bariatric surgery, in heart failure on long-term diuretics. Symptoms include confusion, eye movement problems, unsteady gait. Untreated cases progress to permanent memory loss.^[6]

Forms of vitamin B1

Thiamin is supplemented in several chemical forms. They differ in stability, absorption, how easily they cross into nerve tissue.

Thiamin mononitrate is the standard form used in most multivitamins and food fortification. It is a stable salt of thiamin combined with nitric acid. It is non-hygroscopic so it survives well in tablet matrices. This is the form used in nōuxx Cycle Routine.^[1]

Thiamin hydrochloride is the other common pharmaceutical form. It is highly water-soluble. It is preferred for injectable preparations and liquid supplements. Bioavailability of mononitrate and hydrochloride is broadly comparable in healthy adults.^[1]

Benfotiamine is a fat-soluble synthetic derivative. It absorbs by passive diffusion rather than the saturable active transport that limits standard thiamin. Blood and tissue levels rise higher at the same oral dose. It is being studied for diabetic neuropathy and early Alzheimer's disease.^[5]

Sulbutiamine is another fat-soluble derivative used in France for asthenia. The evidence base is small.

How much you need

The European Food Safety Authority sets the population reference intake at 0.1 mg of thiamin per megajoule of energy intake. For most adult women this works out to about 0.9 mg per day. The US recommended intake for women is 1.1 mg per day.^[1]

Dietary sources include whole grains, legumes, pork, sunflower seeds, fortified breakfast cereals. Refined grains lose most of their thiamin during processing unless fortified. Heavy alcohol use depletes thiamin both by reducing intake and by impairing absorption. Coffee and tea contain compounds that destroy thiamin in the gut at very high intakes.^[1] nōuxx Cycle Routine contributes 2 mg per serving across all three phases.

The science on women's health

Energy and brain

Thiamin sits at the centre of glucose metabolism. The brain runs almost entirely on glucose so it is one of the first tissues to feel a shortfall. Even mild thiamin insufficiency has been linked to fatigue, irritability, slowed thinking. Outright deficiency in alcohol use disorder produces the cognitive damage of Wernicke-Korsakoff syndrome.^[5]

A 2025 systematic review of adults with alcohol use disorder found lower thiamin levels correlated with worse executive function, attention, memory. Supplementation improved cognition even when blood levels sat above the standard deficiency cutoff.^[5] A 2022 systematic review of B-vitamin supplementation and dementia reported a positive effect of thiamin on cognitive performance.^[4] Direct evidence in healthy non-deficient women is thin. Most trials are in older adults with cognitive complaints. The 2 mg in nōuxx Cycle Routine is a baseline insurance dose to prevent the gap, not a therapeutic intervention.

Pregnancy and dysmenorrhea

Pregnancy raises thiamin demand. A 2023 review in Frontiers in Nutrition documented increased requirements driven by maternal blood volume expansion and fetal growth. Severe early pregnancy vomiting can deplete reserves fast. Untreated maternal deficiency has been linked to cardiac, neurological, gastrointestinal complications in the infant.^[3] The authors noted that thiamin status is not routinely measured in antenatal care despite the consequences when she runs low.

For period pain, older trials suggested high-dose thiamin (100 mg per day) could reduce pain scores in primary dysmenorrhea, but no high-quality randomised trials have been published in the last decade. The mechanism may relate to improved muscle metabolism in the uterine wall. Until larger modern trials confirm an effect, the evidence remains too thin to draw firm conclusions about thiamin specifically for period pain.

EU authorised health claims

Under EU law, thiamine is officially authorised to carry the following health claims:

• Thiamine contributes to normal energy-yielding metabolism
• Thiamine contributes to normal functioning of the nervous system
• Thiamine contributes to normal psychological function
• Thiamine contributes to normal heart function^[2]

References

[1] National Institutes of Health, Office of Dietary Supplements. Thiamin: Fact Sheet for Health Professionals. ods.od.nih.gov/factsheets/Thiamin-HealthProfessional

[2] Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods. Official Journal of the European Union, 25 May 2012. eur-lex.europa.eu

[3] Kareem O, Nisar S, Tanvir M, Muzaffer U, Bader GN. Thiamine deficiency in pregnancy and lactation: implications and present perspectives. Frontiers in Nutrition 2023;10:1080611. doi.org/10.3389/fnut.2023.1080611

[4] Gil Martínez V, Avedillo Salas A, Santander Ballestín S. Vitamin supplementation and dementia: a systematic review. Nutrients 2022;14(5):1033. doi.org/10.3390/nu14051033

[5] Teixeira J, Pereira I, Castanho M, Simões do Couto F. What is the impact of thiamine deficiency on cognitive function in patients with alcohol use disorder? A systematic review. European Journal of Internal Medicine 2025;134:59-65. doi.org/10.1016/j.ejim.2025.01.008

[6] Cantu-Weinstein A, Branning R, Alamir M, et al. Diagnosis and treatment of Wernicke's encephalopathy: a systematic literature review. General Hospital Psychiatry 2024;87:48-59. doi.org/10.1016/j.genhosppsych.2024.01.005