The really good supplements seem to be hard to find and I don't really comprehend this. If they are by prescription why do some vitamin stores carry them but not the big vitamin shops and health food stores? Right now I take Pure Encapsulations but I am looking into others like Thorne, Allergy Research, etc that seem to be very good. I am just wary as to why I don't see these more widely available. How can I trust them if they are small companies? Which "good" vitamin companies do you trust?