Yes I struggle with this doubt sometimes and do realize that there are predators in ALL aspects of "medicine" to include supplements. It is vital to "trust your source" and use your best judgement (eg when I first started to increase my Vit D I was struggling to get it to go up lab wise and had to change to Natures Made which made a huge difference.) Here's the deal. ALL THINGS ARE TOXIC if you purify it and snort it in large quantities. And you can die from WATER overdose. Please keep in mind that reading the MSDS on a product must be taken with the caveat that this is the worst side effects of an ingestion of a purified substance. OF COURSE ingesting pure cholecalciferol will kill you. SO WILL LARGE DOSES OF WATER. It is dosed in MICROGRAMS for a reason. All things are poison in concentrations not intended for direct ingestion. What is amazing about this world is that someone figured out how to purify things or chemically make them so that they can benefit people who are no longer able to get good nutrition from the food we eat because it has been destroyed.