This is an interesting topic in that it is hard to find conclusive across the board recommendations from Japanese sites. Many sites stress only doing this with organic teas, especially a particular type of high grade gyokuro, because you are injesting the leaves, thus any pesticides with it. Yet not all matcha is organic...then some say only use organic matcha. It is a very convoluted and complicated subject full of a lot of gray areas.
I use matcha in cooking all the time...but I have not taken to eating Japanese tea leaves that have been used. But I expect that I will.