I give 600-700 ml each month like clockwork due to Phlebotomies. Due to high rbc and have had it well before i started juice, it has been a way of life.
I always use this as an extra calorie day and have experienced zero issues with digestion cramping etc. I have been doing this for years now...
I dont go crazy, but carbs are good on these days, i give almost double of a blood donation and i will be tired the afternoon of donation and the next day as well, i use this time as days off also, 400 ml would be less an issue i believe..