@holyshineball I need to add a few things:
When someone has a thiamine deficiency/functional blockage, they cannot convert make ATP (cellular energy) via oxidative metabolism properly. Normally, the process of oxidative metabolism burns glucose in the presence of oxygen and the end product is carbon dioxide. Thiamine acts as a cofactor for several enzymes in the process. If Thiamine is not available, then the process is derailed and lactic acid is the end product instead of carbon dioxide.
Lactic acid build up is known as lactic acidosis, which is extremely painful. Thiamine supplementation is known to resolve (quickly) lactic acidosis. This is how thiamine supplementation resolves the pain.
As people age, their ability to absorb thiamine through the intestinal wall doesn't work as well as when they were younger. This is why older people are more likely to run into trouble with thiamine deficiency. Thiamine deficiency is implicated in many chronic diseases seen in old age, including all the dementias.
I hope you find this information helpful.
Here are additional links for your consideration:
https://www.mercuryfreekids.org/mercury101/2018/1/21/thiamine-saves