I take mine in cranberry juice without food. It tastes good and doesn't bother my stomach. I couldn't find anything specifically about
eating first in Buhner's book but knowing that he said before a meal makes me wonder if it is better to take it first and not in the middle of a meal. The thing is I think that everyone is so individual that you have to listen to what your body is telling you and he emphasizes that repeatedly.
What you could do if it is making you sick is to divide the dosages to 3 times a day, that way you aren't taking so much at once. I believe they will work better that way because they will be in the body more consistently.