Not everyone has a tough time digesting dairy products, but there is a huge amount of the population who suffer from lactose intolerance without realizing it. Aside from creating unpleasant bathroom issues, it can also get in the way of detoxing. “Dairy tends to build up mucus and slow down liver function,” says Dr. Bravin. For some people, like New York Times food writer Mark Bittman, eliminating dairy is paramount to a miracle. Recently, he wrote about giving it up after a doctor suggested he “take a vacation from certain foods.” Just 24 hours later the discomfort that he’d felt for a lifetime had virtually disappeared.