Are food supplements really safe and effective?

There are different food supplements being offered today. One of them is Aloe Vera products. There are studiesabout Aloe Vera and its benefits , but can those really be true for the Aloe Vera food supplements? Though you can find information online, like examples of personal statements and sample admission essay for example, and Aloe Vera benefits and side effects, are there any facts for the specific products? One can quote studies easily, but these studies are about Aloe Vera in general and not the food supplement itself. And with lax government regulation on food supplements, how can you tell which ones are really safe?