I honestly cannot tell you why 30 days seems so.... right.
It just does. The time factor is even and balanced.
People fast 3 days, 1 week, 10 days, 2 weeks, 3 weeks, 1 month, 60 days, etc., what's next?
I've done three 30 day fasts and many 2 week fasts am about to embark on a 60 day juice fast.
I don't believe there is a scientific reason behind 30 days specifically... but I do know first hand that 30 days juice fasting is a dynamic modality to radiant, glowing, rebalanced and rejuvenated well being.
Think. It took you ten, twenty, thirty years to get to the health problems you have, you cannot expect to reverse the illnesses and dis-eases (dissing your ease) in the blink of an eye. But you can on a 30 day juice fast.