According to the study published in the journal Nature, the AHR -- aryl hydrocarbon receptor -- is a protein found at barrier sites like the gut and the lung. Natural molecules in cruciferous vegetables -- such as kale, cauliflower, broccoli, or cabbage -- are dietary “ligands” for AHR, meaning that once eaten, they activate AHR to target several genes. Some of the genes targeted switch off the AHR system, allowing it to self-regulate.