2 years ago I tried doing a "supplement vacation". After a few days I started getting lots of "skipped heart beats". I knew that those had previously been improved by adding magnesium to my list. I stopped by a supplement store, bought a bottle of magnesium, and took two magnesiums on the spot. About an hour afterwards my skipped beats disappeared. I'm a magnesium believer now.
Otherwise, supplements aren't like drugs, they work over MONTHS/YEARS...NOT days.
That being said, the human body DOES build up a level. Magnesium is one of those supplements, but it can quickly decline, especially with heavy sweating and exercise.
Different supplements do different things.
Anti-Inflammatories such as curcumin, fish oil, boswellia, Vit D can work over a few days. It depends how "inflamed" you are, if you need to continue those. These CAN modulate the amount of inflammation someone gets when they're doing something like...walking all day, everyday for a month.
Classically, hikers take a lot of ibuprofen, but that's tough on your body.
You'd think you wouldn't need Vit D because you're in the sun all day. But most people only have their hands and face exposed to the sun (and even those are covered with sunscreen), so Vit D may be worth it to carry.
Joint Supplements like Glusosmine, condroitin, MSM work over the LONG term, not days. They're not going to help over the course of days.
Electrolytes (including magnesium) are definitely a must if you're sweating alot or drinking lots of water.
Bringing your normal Multi-Vitamin is probably a good idea.
What I do is repackage the daily vitamins
into little baggies, so there's as little hassle as possible.
THE PROBLEM IS, most box stores and pharmacies carry the CHEAPEST supplements
ever made. So it just depends whether you can even buy a decent version of your normal supplement on the road.