You assume a lot of competence on the part of these large actors to collude and conspire at the macro level.

Let’s assume, for sake of argument, the conclusion of your assertion is true in that we are being poisoned and offered medication to mitigate the effects of said poison. This is more likely the effects of independent actors acting upon their respective self-interests.

Food companies try to drive costs down to sell cheaper products at the same price, which may end up having poor health consequences by virtue of untested substances having mass exposure. Pharmaceutical companies respond to market forces by developing drugs they can get funding for, which usually ends up being ailments that a lot of people have. There are way more efficient ways for them to team up and make money, this is just a side-effect of large institutions acting in self-interest.