Yes, I think caffeine pills can't be a food. I think it's kind of supplement. = Yes, I think caffeine pills can't be food. I think it's kind of a supplement.
Also, it can't be a medicine because it's not for patients and it can't treat them. = Also, it can't be a medicine because it's not for patients, and it can't treat them.
I think there should be a regulation about caffeine pills.
If not, some people could eat more than allowance and it leads to health problem. =  If not, some people could eat more than their allowance, and it leads to health problems.