Why a human in space would freeze?

basically the space between objects is a void of nothingness apart from dense regions such as nebulae and possibly asteroid belts, but even still, unless your touching an object there is still a vacuum. what im wondering is that although the shaded space is about 280 C below zero, if there is no particles for heat to travel through, why does the coldness of space suck the heat out of the human body? what object is the heat being absorbed by? dark matter?