I'm going to try to not nerd out too much and keep this as simple as possible.
Synthetic vs Natural sources of Vitamins
The universe is made of molecules. No two things made of molecules are alike, as no two people are alike. There are even chiral isomers that are identical images of the same molecule that absolutely do NOT function alike. An example is glucose. There are different forms of glucose such as d-glucose and l-glucose. While they are mirror images of each other, d-glucose is sugar and can be used as a sweetner. But l-glucose is poison and can kill you. So something may look the same, but it's definitely not the same. That being said, let's get into vitamins.. first you need to understand how they are formed before you can understand the differences and make decisions about which ones and how many of them you want in your body.
Synthetic vitamin supplements and additives are made in a lab. Scientists have very strict guidelines they adhere to when creating them. They have to mimic the molecule identically. So you are actually getting an identical replica of a natural vitamin molecule. And "molecule" is the key word here: you're getting only that one single vitamin molecule... with a filler. Vitamin C sold in stores is usually nothing more than ascorbic acid. In nature, ascorbic acid isn't the "vitamin part" of the vitamin.
Getting vitamins naturally from food works differently than simply getting ascorbic acid into your system. In nature, ascorbic acid in vitamin C actually only carries the vitamin C complex through the body and acts as a "shell" or protective covering for that entire vitamin complex.
I'll use an heirloom tomato as an example. An organic, heirloom tomato contains natural vitamin C. But this tomato also contains other things like co-factors and compounds. Together, these compounds and other chemicals work together along with the vitamin C molecule to form a biological complex. Vitamins in nature are not single molecules with fillers added to them. They are biological complexes.
These co-factors and compounds present in the shell of the vitamin complex found in a tomato play an extremely important role. They allow that vitamin C molecule to break down and get absorbed by the body correctly. And every food that contains vitamin C has its own complex that is different and allows the vitamin C of that particular food to work with the other chemicals in it to break down and move properly. Vitamin C complex in tomatoes is different than vitamin C complex in peppers. And each vegetable brings its own set of nutrients to the table, working to supply your body with minerals it needs to heal and bond human body molecules together correctly. This is why getting synthetic supplements isn't as great as getting natural vitamin complexes from foods. And in addition to getting the vitamin complex from a vegetable, you're also getting p factors as well from it.. those are things like antioxidants and other mineral complexes. But that all gets into something even more complicated. Let's stick to simple vitamins.
Now don't stop taking supplements if you're not getting enough good food - synthetic vitamins do have their benefits. It's better than not getting any part of a vitamin at all and going into full on depletion. If you can't get enough to eat, definitely take a supplement. If you're body building or are athletically extreme, take a supplement. If you're sick or going into surgery soon, take a supplement. But don't replace supplements for real food. And there in the name is your eye opener.. "Supplement".
It is never a good idea to think you're getting all the vitamins you need simply from taking a multivitamin every day. A lot of companies even use sugar in the fillers for vitamins. You absolutely need to eat good food as well. You will become nutritionally depleted over time without healthy fruits and vegetables, and that absolutely leads to cancer. Things like smoking and sun damage do not give you cancer. They are just things that help cause it. Cancer is a result of many different things going wrong in the body, and some of those factors are things like not having the ability to fight off infection, depletion/malnutrition, and hereditary dna mutations (which sometimes come from bad farming and slaughtering processes). As simple and stupid as it may sound to say it, we need good food to survive. We need natural, non-modified sources of vitamins. And for some reason, a lot of us are forgetting that very elementary idea. Cells turn cancerous when there are mutations within those cells. And mutations can occur when the body is trying to compensate for a lack of nutrients. Think of it this way: We, as human beings, do everything we can to survive. We sometimes get into desperate situations where we're depleted of basic things we need, like food and shelter. And when we find ourselves in this situation, we are likely to do some crazy, abnormal and desperate things to obtain the things we don't have. Well, the cells in our bodies are no different. They are alive and active, like little creatures in the big city streets of anatomy. They're fighting to survive. And when they find themselves without, they make desperate attempts to get what they need. Some develop mutations, or learn to adapt to their situation in order to make up for what they're lacking. And as with humans, those mutations are not always the best idea. Even nature isn't perfect; especially when she's been influenced by a toxic environment.
I know that is a weird way of looking at it, but I'm just trying to make it easier to visualize. The bottom line here is eat good food and don't rely on vitamin supplements for good health.