Over just 3 days, I would not worry about massive doses.
And what do you consider massive dose? This is a food.
I take 10 grams a day ALL the time.
Massive would be the likes of 40+ in my opinion and because of what it might do to your bowels (EXTREME activity) I would not use it for more than 3 days.
Actually you are better off at 20 grams for a few weeks and then stick with 10 grams.
In a pristine environement with perfect foods at your disposal, 5 a day would be enough, but 10-15 in major cities and with the types of foods we have is better.