Do our bodies produce enough vitamins or do we need to take multivitamins?

We don't make them: Vitamins by definition are vital elements of our bodies building blocks that we do not make.We can extract many from dietary intake and others as supplements. Those following a well balanced and diverse diet need fewer supplements than those on a narrow or restricted diet. In the us it is hard to find foods that don't have various vitamin fortifiers added. We usually eliminate any excess daily.

Multivitamins: Of you eat a healthy well-balanced diet, there is little need to take a multivitamin. However, if you have a certain condition such as osteoporosis, for example, then supple metal calcium and vitamin d are in order.

You don't make vits: With the exception of vitamin d your body does not make vitamins. You need to ingest them. Whether or not you choose to get them from a supplement or diet is up to you.