Can we get enough B1 by just diet alone? It seems a lot of foods either have in naturally or are fortified with it. Why the need for extra supplements?
Back in the day when we were all doing enough work (men, women, children) to need over twice our base-metabolic-rate number of calories per day, and eating whole foods, particularly red and white offal and leafy greens like collard and beet greens, steamed and roasted, we got enough of these mesonutrients and micronutrients.
Twice your BMR is about 5000 Cal/day for an adult male. You need to do eight hours' physical work (shoveling, threshing, chopping, sawing, lifting, doing the laundry by hand, etc.) to burn off the extra.
Now, the hypothesis says, we are deficient in many of these nutrients because we simply do not eat enough food, only 2500 Cal/day and a lot of that is from vegetable oils and low-nutrient animal fats.
I have no investment in the hypothesis. Just reporting it.
Edit: Vegemite and Marmite are high in vitamin B1. Possibly Bovril also. Spread it thinly on your toast and grill it.
e.g. tomatoes have lost most flavor and nutrition over past few decades, some efforts are underway to hybridize them with older variants to get the best of both worlds.
can't speak for nutrition (nor do you provide support for that claim) but as to flavour, you clearly haven't been round long! Old fashioned tomatoes were shite I can testify (at least those available in the UK).
Apparently the mechanisms for absorbing it depend on having sufficient B1, and can get "stuck" in a deficient mode if you went through a period of deficiency, which can then be "unblocked" (kickstarted) with a megadose.
Take this with a grain of salt, it's supposedly based in research, but I didn't check any papers about it yet.
And if you aren't eating a lot of enriched flour you might not be consuming it in fortified foods at all.