Is it true that you can become lactose intolerant if you eat lactose free products for a long period of time?

No: Lactose intolerance develops with age - the older you get, the higher the chance that your body starts making less lactase enzymes which helps break down lactose to prevent the symptoms of lactose intolerance. Interestingly, it is also dependent upon ethnicity - african americans, asians, hispanics - develop lactose intolerance earlier in life.

No: You either have the genetics for it or don't. Most will have the enzyme in infancy because breastmilk contains this sugar, but it is lost as an unneeded factor with age. Many with lactose intolerance begin selectively avoiding lactose containing products at a young age without ever knowing the label, just because their body steers them away from what makes them cramp/feel bad.