Thiamine HCl
into brain
The common water-soluble form, also added to processed foods. It crosses the blood–brain barrier poorly.
The inner ear needs a lot of energy to hear. When it runs short, the brainstem turns up its sensitivity, and you hear that as ringing in your ears.
Hair cells have high energy demand and almost no reserve. They depend on a constant supply from the blood, so an energy shortfall shows up here first.
When the inner ear lacks energy, the brainstem amplifies auditory signals.
The amplified signal is heard as a phantom sound. Low GABA plays a role too: it is the inhibitory neurotransmitter, and when it is low it dampens the amplification less.
Why it isn’t in the ear: in severe cases the auditory nerve used to be cut. Patients lost their hearing, but the ringing stayed. So the sound is generated in the brain, not the ear.
The common water-soluble form, also added to processed foods. It crosses the blood–brain barrier poorly.
Better absorbed. Its brain penetration is debated, but some research has shown effects on the central nervous system.
A synthetic derivative of allithiamine from garlic, sold under the name Allithiamine. It reaches the brain best, which is why it is the form used for tinnitus.
Well above the recommended daily intake (under 2 mg). B1 has very low toxicity; EFSA has not set a tolerable upper intake level for it.
Threonate is the only form of magnesium shown by research to raise magnesium directly inside neurons. B1 doesn’t work without magnesium — magnesium is its essential cofactor. Magnesium deficiency is common, and a standard blood test detects it poorly. That may explain why B1 doesn’t help everyone.