Dr. Derrick Lonsdale is a name most patients have never heard, but his decades of work on thiamine deficiency changed how I evaluate a specific cluster of symptoms.
Thiamine, vitamin B1, is a cofactor for enzymes central to how your cells produce ATP through the citric acid cycle. Classic thiamine deficiency is beriberi, which most doctors were trained to picture as a historical disease. Lonsdale’s clinical work documented a subtler pattern: fatigue, gut motility problems, dizziness on standing, and autonomic symptoms that don’t fit neatly into a beriberi diagnosis but respond to thiamine repletion.
This overlaps heavily with what gets labeled dysautonomia or POTS in younger patients. Racing heart on standing. Gut that slows to a crawl. Brain fog that’s hard to describe.
High-carbohydrate, low-thiamine diets, chronic alcohol use, and gut absorption issues can all deplete thiamine status, and standard bloodwork rarely catches it because serum thiamine isn’t a reliable marker of tissue-level deficiency.
I want to be direct about where the evidence stands. This is not as extensively validated in large human trials. It’s clinical pattern recognition built over decades, and I treat it that way, not as settled science.
But when a patient has cycled through cardiology, GI, and neurology with no answers, thiamine status is one of the places I look next.
Struggling with dizziness on standing, gut motility issues, or unexplained fatigue no specialist has solved? Get my Free Balance Toolkit — comment BALANCE.
Research: Lonsdale D. “Thiamine and magnesium deficiencies: keys to disease.” Med Hypotheses. https://pubmed.ncbi.nlm.nih.gov/?term=Lonsdale+thiamine+deficiency+dysautonomia