From pills to powder to gummies, there are just so many vitamin options these days. If you're wondering what those supposedly magical substances actually are, you are definitely not alone. As Catherine Price, author of Vitamania, told us a few months ago, "It turns out there’s no chemical definition of a vitamin. They were all lumped together by historical happenstance when they were discovered around the same time," she said. "The Polish biochemist Casimir Funk came up with the word 'vitamine' before anyone had isolated a vitamin. Now, 104 years later, we’re still calling these things vitamins." What actually are they, then? Well, they're all different chemical compounds, and all necessary to keep our bodies functioning properly. We tend to talk about vitamins, minerals, and other supplements as if they were the same kind of thing. But, there are only 13 essential vitamins. These vitamins are also all things your body can't make on its own, meaning you need to get some help from your environment or food. For instance, your body can only make the vitamin D your muscles need after some time in direct sunlight, but you usually get your vision-enhancing vitamin A from dairy products and, of course, immune-boosting vitamin C from citrus fruits. Whether you need to take vitamin supplements is still somewhat up for debate. If you have a vitamin deficiency, then yes, supplementing is essential. But, for those of us who aren't deficient, taking extra vitamins has shown mixed results. For instance, recent studies have found that taking excessive amounts of vitamins E and A can actually increase cancer risk. There's other evidence to suggest that taking too much of a vitamin can tax the liver and cause a variety of other problems — yes, you can actually overdose on vitamins. To complicate matters even further, Price explained that the recommended daily allowance for vitamins is often too high for most of us because they're meant to cover everyone's needs. Therefore, unless you're addressing a specific deficiency, there's really no need to get more than 100% of your RDAs. Still, some supplementing is recommended for certain groups of people, such as folic acid (a B vitamin) for women who are pregnant. And, the recommended amounts change once you hit 50 and your body's ability to absorb some vitamins decreases. The bottom line is: As along as you're getting your sunshine and eating a healthy, varied diet, you probably don't need to supplement with extra stuff. And, you certainly don't need to go overboard.