Well, I am not a doctor but I do know that I have taken it without problems over the past 4 years on and off and know of others who have used it long term. I know my doctor (who is also a good friend of mine) doesn't feel concerned about people taking this as needed but you have to do what you feel comfortable with. I think if you bring it in to your doctor she can maybe call a colleague from the US or do some web research to help you find the answers!
Glad it is working for you though!
Lecia