What causes cancer? In 2015, researchers updated the landmark 1981 study from the U.S. Congress Office of Technology Assessment noting that the original estimates had “generally [hold] true for 35 years.” At 35% of the attributable risk, tobacco was the single largest contributor to cancer. But very close behind, was our diet, which researchers estimated contributed between 30–60% of the risk. Generally accepted as true, the far more contentious question is “What part of the diet contributed to the risk of cancer?”