It's also untrue. Before you shell out your hard-earned money on running shoes, you should know a bit about your feet and feet mechanics. What you want to do is choose the shoe that will match and complement your feet. Pronation is the inward roll of the foot that allows the body to absorb shock and adapt to uneven surfaces. It occurs as soon as the heel touches the ground.
Supination is the slight outward roll which makes the foot more rigid and ready for push-off.
It occurs as your body weight moves over your foot from the midfoot to the forefoot. Injuries can occur when one's foot either pronates or supinates excessively. Those who are predisposed to excessive pronation strike the ground on the outside portion of their heel to the extent that their foot continues to roll in past the point where it should stop. This flattens the arch of the foot. An unstable foot can and will cause shin pain, knee pain and low back pain.