Multi-vitamins do not help. I had a few doctors come out and give me that unsolicited advice.
Do not help what?
I'm just saying that if your diet sucks, supplements help prevent deficiencies. Ever heard of scurvy? That's an extreme example, but the theory is sound; humans need macros & micros just like plants. Natural is better, but there are other options, depending on your situation.
Some people take vitamins then stop because they "don't feel any different than before".
Yep. That's how it is supposed to work. As I said earlier, you can't turn back the clock -- but you can slow it down.
Wouldn't it be awesome if you felt the same in ten years? Aging is so gradual that most people only notice it on special events, like birthdays. Truth is, you age a little every day. If your body is deficient, it ages a little faster.
Just like money, every little bit counts -- and it adds up over time.
BTW: I've had a LOT of experience with doctors, including specialists. Most of them have proven to be... "unhelpful". (I am being kind.)