I am very confused right now.

A few years ago, I learned that multivitamins are ineffective, according to research. At that point, I have heard of the benefits of many of them, they were individually praised like some would praise anything that's good enough to take by itself, so I was thinking that multivitamins should be something ultra-effective that only irrational people won't take. When I learned they were ineffective, I hypothesized that vitamins in pills simply don't get processed well.

Recently, I was reading a few articles about Vitamin D - I thought I should definitely have it, because the sources were rather scientific and were praising it a lot. I got it in the form of softgels, because gwern suggested it. When they arrived, I saw it's very similar to pills, so I thought it might be ineffective and decided to take another look at Wikipedia/Multivitamins. Then I got very confused.

Apparently, the multivitamins DO get processed! And yes, they ARE found to have no significant effect (even in double-blind placebo trials), But at the same time, we have pages saying that 50-60% of the people are deprived from Vitamin D and that it seriously reduces the risk of cancer, among with other things (including a heart disease). Can anyone explain what's going on?