Your family and friends mean well, but they are obviously uneducated. Fasting is a long-proven technique for cleansing and good health! You won't be hurting yourself by doing the MC. Drink plenty of juice and WATER and you will be fine! Relax and enjoy the ride. I found that fasting is a time of intense peace, so rest and do some quiet things you don't normally do - take walks and enjoy nature, watch a sunset, read a good book... God bless you on your journey!
P.S. I've posted a link below that has all kinds of great information on the benefits of fasting. Also, a google search will turn up tons more information for your "battle" against all the naysayers. You can also browse the forum for tips on dealing with those around us who mean well but simply don't know any better. :^)