No, lactose intolerance, specifically caused by lactase nonpersistence, is a real thing. What this means is that your body stops producing the enzyme required to digest milk. If you consume dairy without producing lactase, you'll get pain and cramping and diarrhea because your gut bacteria will try to break down the lactose instead, and that produces a lot of gas. It's worth noting that this form of lactose intolerance CAN be overcome by subjecting yourself to a heavy dairy diet and simply dealing with the symptoms. From what I've heard, after a few weeks, the balance of bacteria in the gut will change to favor ones that can easily digest the lactose without causing problems, meaning you've effectly outsourced your lactase production to your gut bacteria.