I have a veritable medicine cabinet of supplements I use, in part because I have an appalling diet due to Avoidant-Restrictive Food Intake Disorder (an Autism related eating disorder where it doesn't have anything to do with self image, rather I have sensory aversions to many foods, a heavily restricted diet to 'safe foods' and a general disinterest in eating - I view it as a chore - as well as a tendency to feel full very quickly. So I need to supplement my diet heavily with a bunch of stuff.)
At the moment I take: Magnesium, Vitamin D, Vitamin C, and a Multivitamin (I'm soon replacing these three with a more expensive but better Multivitamin which contains all three of them in appropriate amounts), Fish Oil tablets, Fish Oil liquid, Coloxyl (a laxative due to being on Buprenorphine injections), Gut Relief powder (morning), Intestamine (a gut supplement - night time), a 5 strain Probiotic, Calm Relax turpines (for anxiety), Biotene mouth spray (again, due to dry mouth from Buprenorphine injections and Dexamphetamine to keep my dental hygiene in the clear, which has been working since last week I went to the dentist and for the first time in a year I've not needed any fillings and he was happy with everything), sleep drops, and high dose Melatonin.
I don't recommend that everyone take this many supplements, but to give an idea of what my diet can be like when I did a food diary to be referred to a dietician it went something like this:
Breakfast: handful of skittles
Lunch: Up n Go (caramel milk drink)
Dinner: bag of crisps
Soooooo, yeah. That's the reason I don't have scurvy. My GP is constantly astounded that my blood results come back perfect each time. Not just good, but perfect. I put it down to the supplement regiment. He often jokes that it's highly unfair that my bloods come back as good as they do when he has patients who have an amazing diet but can't get their bloods under control yet I eat shit and have great results.
However, I now have a support worker I meal prep with once a week to learn how to cook and have frozen meals to reheat, and my diet is improving. Last week we cooked chicken alfredo and I really liked it, and on Tuesday this week I had salmon for the first time ever and it wasn't terrible.
Supplements can be useful, if you need them and are lacking in them for some reason. But if you have a fine diet and you get enough sun, eat fruit and vegetables (I don't really) and exercise, there really isn't much point.