"Parents who let kids romp in the mud and eat food that has fallen on the floor could be helping to protect them against maladies like heart disease later in life, a US study showed Wednesday..."
(This reminds me of my friend's recent wedding reception, which took place in a bar. There was a little girl eating nuts. I watched her drop one on the floor, then bend down to pick it up and pop it in her mouth - all in front of her dad. My instinctive reaction was to try and stop her, but her dad just said "Eh... it's good for you.")