Just like minerals have decreased due to farming activity, so have vitamins. Also, our microbiome used to supply us with some Bs as well. With the increase use of antibiotics, etc these are obviously compromised too. Sometimes supraphysiologic doses are needed to fix deficiencies especially when you flood the system with a high dose of one vitamin, B1 for example. Doing this will put more strain on B2. B2 is needed for many things like methylation so this will stress B12 for example.
All of the Bs are important for proper metabolic activity (PPP, TCA, ETC, glycolysis, etc). Restoring ATP and CO2 production is what causes the cytoplasm to be structured correctly. When it is, protein synthesis, DNA folding, all fundamental cellular processes work appropriately. This is what makes sure enough ferritin, ceruloplasmin, etc are made. And this is why B1 (and other vitamins and minerals but especially B1 because of much it’s needed as a rate limiting step in these processes) helps get Fe out of the body.
It’s something to watch out for. My edema clears up immediately with B1. But if I don’t take B2 with it then my POTs continues. I eat liver, use bee keepers naturals b powered, and take a ton of the ancestral supplements organs.