How many grams you should eat in a day?
You should eat just enough; but never, ever, eat too many.
If you're taking a fiber supplement, read the instructions on the package. You don't want to end up with nasty diarrhea! If that's not what you mean, it doesn't matter how much fiber you eat per meal. Nutritional recommendations say that women should consume 25 grams of fiber per day, and men should eat 38 grams of fiber per day.