Chole She’ein Bo Sakanah, which the Ramah defines as Choleh Kol Gufo or Nafal Lamishkav (you have to lie down) is allowed to do anything that is Assur Mishum Refuah. Vitamins are probably a Ma’achal Bri’im, though if they had existed at the time of Chazal then Chazal would have most likely extended the Gezeirah to them because they are often crushed.
My opinion is that because the fear of shchikas samemonim nowadays is virtually nonexistent, it is permissible to be meikel in most situations. On the other hand, for those who require the situation of nafal lemishkav, this does not mean that one has to lie down, but rather that one cannot get up. In the olden days, nafal lemishkav meant that one was bedridden, and not simply felt the need to lie down for a while.
Old man: I have heard that needing to stay in bed for most of the remainder of the day counts as “bedridden”. And there are many countries that still give out medicines which require grinding. In some places it’s virtually nonexistant (like the US), but there are places where it’s a legitimate fear. Many Poskim do use that Svara to be Meikil though.
You can’t be Mevatel a Gazeira. Your Svara works for things that aren’t Nahug, that we don’t have to try to re-establish thr old Gezeira. Unless you are saying that you use the Svara to look for Kulos, and to view it lightly.
Nafal l’mishkov dosent mean you are actualy bedridden. It means you would lie down if you have the option to do so. (e.g. a mother who has to take care of young kids but feels bad enough that if someone would be avalible to take over the kids she would lie down then she is aloud to take a refuah)