Another reason for avoiding protein shakes and eating our nutrients instead of drinking them is that they might make your menus top-heavy in protein unless you add fat alongside them.
Many of us use a programme like
www.fitday.com which analyses our food intake to make sure we stick around the 65% fat/30% protein/5% carbs that induciton menus work out to.
Remember, Atkins is a highfat/medium protein/low carb regime, not a high protein one! Excess protein can be converted into glucose according to Dr Atkins!