If you look at all the vitamin studies done on groups of more than a thousand people in the last few decades, many of them have shown that taking vitamin supplements is correlated with an increased risk of diseases such as cancer and produces little benefit to health. Some of these results were statistically significant, but some were not. The interactions of supplements and the body are very complex, but a simple explanation may be that the body likes to create free radicals to attack “bad” cells, including cancerous ones. If you block that mechanism by taking copious amounts of vitamins, especially those touted as antioxidants, you block your body’s natural ability to control itself. You block a physiological process. You disrupt a system we don’t fully understand yet.
Simply put, we cannot expect a pill or packaged food product to satisfy our nutritional needs in the same way real food can. I don’t care what the label says, go for the foods that don’t come with labels! And stop taking vitamins.