The pile yarn of your carpet is made from short lengths of fibre which are spun together to form the rope-like yarn. Whenever this is cut some of the ends of these fibres will be too short to be held in the yarn and over time these will come loose and be picked up during vacuuming. Although the volume of these loose fibres may seem alarming they are only a small fraction of the total fibre weight of the carpet pile.
We recommend the use of an upright vacuum cleaner with beater bars for all cut pile carpets as these agitate the pile and allow the loose fibre to be removed more quickly than with a suction-only type cleaner. You cannot over-vacuum a carpet, and in fact the shedding will appear worse and for longer if an inefficient or suction-only cleaner is used.