Hi Friend
Thiamine (vitamin B1) is emerging as a hidden player in Ehlers-Danlos Syndrome (EDS), POTS, and Mast Cell Activation Syndrome (MCAS). Once associated only with severe malnutrition, deficiency is now being recognised as surprisingly common in people with complex chronic illness — and a January 2026 landmark study has added a powerful new piece to the puzzle, linking thiamine metabolism directly to IBS and gut motility for the first time.
WHY YOU MIGHT BE DEFICIENT WITHOUT KNOWING IT
Thiamine is water-soluble, stored for only 18–20 days, and depleted by sugar-heavy diets, coffee and tea, diuretics, metformin, chronic stress, and gut dysfunction. Standard blood tests are unreliable — many patients are told their levels are "normal" while their cells are running on empty. Functional testing such as whole blood thiamine or the erythrocyte transketolase assay (ETKA) gives a far more accurate picture and is worth requesting specifically.
THE POTS CONNECTION
The autonomic nervous system — dysregulated in POTS — is heavily dependent on thiamine for energy production in the brainstem and hypothalamus. A 2017 study found measurable deficiency in a subset of POTS patients, with symptom improvement on supplementation. A 2024 case report showed a patient's autonomic symptoms resolve within one hour of intravenous thiamine. Clinicians Lonsdale and Marrs have long argued that thiamine deficiency is one of the most underappreciated drivers of dysautonomia.
THE EDS CONNECTION
More than 70% of EDS respondents in a Health Rising patient survey reported significant improvements from high-dose thiamine, particularly in fatigue, brain fog, and pain. Thiamine also supports myelin sheath maintenance and nerve conduction — relevant to the peripheral and small fibre neuropathy increasingly recognised in EDS. Gut dysmotility, gastroparesis, and SIBO — all common in EDS — simultaneously increase thiamine demand and impair its absorption.
BREAKING RESEARCH: THIAMINE AND IBS (January 2026)
A study published in Gut on 20 January 2026 analysed genetic data from 268,606 people and uncovered a previously unrecognised role for thiamine in controlling gut motility. Two thiamine-related genes — SLC35F3 (a thiamine transporter) and XPR1 (essential for thiamine activation) — were shown to have direct causal effects on bowel transit speed. Higher dietary thiamine intake was strongly associated with more frequent bowel movements, and a person's genetic profile at these two genes determined how much benefit they got from that intake.
The study confirmed a causal genetic link between gut motility and IBS, and found overlaps with gastrointestinal, psychiatric, and cardiovascular traits. The researchers concluded they had found "a previously unrecognised role for vitamin B1 in gut motility, highlighting a biologically plausible and modifiable axis with potential for nutritional or pharmacological intervention."
A 2025 Frontiers in Nutrition review added further weight, formalising the concept of "gastrointestinal beriberi" — thiamine deficiency manifesting as nausea, constipation, reflux, SIBO, and abdominal distension. SIBO is present in up to 78% of IBS cases and is strongly linked to EDS.
For the hypermobile triad community, this is significant: some people may be genetically predisposed to process thiamine less efficiently, meaning normal intake and even normal blood levels may be insufficient — and their gut dysfunction may be both a cause and a consequence of that impaired thiamine metabolism.
THE MCAS CAUTION
Many MCAS patients report improvement with thiamine, but a meaningful subset experience worsening — possibly because thiamine may act as a histamine liberator and inhibit DAO (the enzyme that breaks down histamine) at higher doses. ⚠ Start low, go slow, and avoid trialling during an active flare.
FORMS OF THIAMINE
Standard HCl and mononitrate forms rely on gut transport mechanisms that are often impaired in this population. TTFD (available as allithiamine or Thiamax) bypasses these transporters, crosses the blood-brain barrier, and is the preferred form for autonomic and CNS symptoms. Benfotiamine is useful for peripheral nerve support but does not reach the brain.
KEY TAKEAWAYS
Standard serum testing is unreliable — request functional testing.
Thiamine deficiency is directly linked to POTS and dysautonomia.
Over 70% of EDS patients in one survey improved with high-dose thiamine.
A January 2026 study confirms thiamine metabolism genes directly control gut motility and IBS risk.
Some people are genetically predisposed to process thiamine inefficiently regardless of intake.
"Gastrointestinal beriberi" reframes IBS, SIBO, and gastroparesis as potentially thiamine-responsive.
MCAS patients: start at the lowest dose and avoid active flares.
TTFD/allithiamine is the preferred form for autonomic and CNS symptoms.
Always take with magnesium, potassium, and a B-complex.
Expect a temporary paradoxical worsening at first — titrate slowly.
The appts for the mend clinic will be opening again soon, join the priority list here.
Stay Well
Dr Ahmed
This newsletter is for informational and educational purposes only. It does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before making any changes to your supplements, medications, or treatment plan.
