I have done long fasts, including 59 days last summer. I did The Master Cleanse
for 48 days, then continued on fruit/veg juices to day 59. The Master-Cleanse
supported me beautifully until about day 45, and when I started juices I was again very well supported nutritionally. I took no additional supplements excepting an occasional tablespoon of blackstrap molasses for extra potassium/iron. No additional supplements should be necessary. I am certainly living proof that even after two months on juices you will certainly not starve or waste away!
I fast with supervision of my wonderful naturopath/nutritionist for the main purpose of colon cleansing. UNLESS you have specific medical issues like hypo or hyperglycemia, diabetes etc., or are very underweight, a limited fast should be perfectly safe. If you have any questions I highly recommend discussing them with a qualified natural health professional to outline your goals and the best and safest way to reach them.
A ten day juice fast (even a mono juice like the MC) should be perfectly safe for a person in good health with no supervision and no supplements other than the natural contents of fresh juices.
Best to all,