I will not give you the exact name or brand name of the supplement but will give you a general idea. This website contains more than just supplements, it contains also a detailed review of the supplement industry.
The first thing to do before you take a supplement is read the labels. The label says something along the lines of: "This product is not approved by the FDA or USDA, and may not be used by pregnant or nursing women." But you can easily find supplements that meet those requirements. The other thing to remember is that supplements are sold to people. If you buy it from a store, the store owner is not legally bound to provide a scientific evidence of any kind. And if he or she doesn't provide any, then you have no way of knowing that the product you are taking is a good one. I recommend you read the labels of the supplements you buy to see if they do or don't contain a "proven" ingredient. If you aren't sure, you may be better off asking the store owner about it. The supplements that are available for purchase on the Internet also have the added disadvantage of being free from scientific evidence.