If you're like me, in that your eating habits vary widely from day to day, then you're never sure if you're getting the full pharmacopoeia of beneficial vitamins and minerals that your body needs.
I can't manage take my vitamin supplement with any real level of consistency. If I do remember, then
I've got to actually eat something more substantial than a couple of Poptarts (tm) so that the vitamins don't make me queasy (Zinc).
So assuming that one changes his/her underwear with regularity, the underwear itself could slowly deliver the requisite daily vitamin and minerals through a dermal patch in the waistband. The slow delivery mechanism would help to prevent the empty-stomach queasiness and given that one is not likely to forget to change their underwear, the chance of not getting your vitamin fix is severely curtailed.
These could be disposable underwear (and panties) that could come in popular styles and colors of briefs, boxers, boxer briefs, and (I suppose) thongs. Okay, I admit that I don't know a single woman that would go for it. Maybe they could be edible too, so at least two people could benefit.
There could be recreational psychedelic party pants versions as well, or even prescription pants for people with specific needs.
I concede that perhaps this idea might be pared down to a special waistband insert for normal under garments, like a stretchy 'vitamin-band' type device that goes around the waist. In any case, it's more convenient and subtle than an adhesive dermal patch. And a person is likely to remember it by association when slipping on their underwear.
Now if there was a good way to deliver fiber... hmmm Fiber Pants? Perhaps this would prove too invasive. I have to think on it a bit.