Bs across the board
Niacin, same deal: an essential nutrient that has to be added back into the mix. Niacin is also known as vitamin B3, and without it, you’ll quickly develop weird weaknesses: anemia, headaches, dizziness, nausea, that kind of thing. Good! Add it back in, please.
Thiamine mononitrate is also an additive; it’s a version of thiamin, otherwise known as vitamin B1, though not a naturally occurring one. Thiamin is another nutrient kind of like niacin; it’s not that taking more of it makes you healthier, it’s that without it, you develop serious health problems. Thiamin deficiencies tend to affect the nervous and cardiovascular system.
Anyway, producers like Frito-Lay use thiamine mononitrate, a synthetic powder version of vitamin B1, to replace the regular vitamin B1 that grains like corn naturally contain before they’re bled out. It’s used instead of natural thiamin because it’s cheap and very stable and easy to use; it’s the thiamin replacement of choice for packaged goods.