I read somewhere that gut can only let around 80mg thiamine/day and gut gets saturated over time, so only IM/IV would work long-term.

> Is it possible to get anywhere near this much with dietary thiamine?

High thiamine food stuffs have a few milligram at most so it would take some effort. However, many B1 vitamin tablets have 100mg-300mg, although I wonder how well that is absorbed compared with an intramuscular shot - it would seem that you could consume the equivalent of 200mg a week.