Bustrbrwn, if you google Ala you will find there are 2 forms, the R and the S. Some brands combine both and some are just 1 or the other. I recently read an in-depth article on the differences and the pros and cons of each. The brand I take combines the 2 but I also have the all R-Ala which I switch off to at times. I think the R is better since it is also more expensive. Helen