This recipe sounds pretty standard, however people can react differently. If you are new to Blasting and not used to eating as much fiber, then I'd suggest cutting back then slowly working your way back up. In this particular recipe cutting back on the flax and either choosing flax or chia could help. Also, make sure you're drinking plenty of fluids between Blasts. This helps move the fiber through your digestive system to help prevent it from blocking up (constipation). The back pain most likely isn't due to the fiber or the Blasts...if pain persists you should seek the advice of your Dr.