Food is an important part of a balanced diet.
On that sentiment we can probably all agree; however, the details tend to be more elusive. For more than half a century, cancer epidemiologists and other scientists have attempted to understand the role of diet in the etiology of cancer, much of it focused on gastrointestinal (GI) cancers. Haenszel and Kurihara made groundbreaking observations on Japanese migrants to the United States, finding that the incidence of colorectal cancer in the migrants and their immediate offspring increased rapidly from the low rates in Japan to approach, and even exceed, the much higher rates in their new home. These large changes (approximately 250% in males) over a short period of time have been interpreted to reflect the importance of environmental exposures later in life in the etiology of colorectal cancer, perhaps via adoption of a more Western lifestyle, including dietary patterns. Similarly, studies of esophageal squamous cell carcinoma among migrants from high incidence (eg, China) to low incidence areas have indicated a change in incidence (in this case, reduction) among descendants over time toward that of the host country, with the speed of change depending somewhat on the country of origin and the prevalent risk factors in that country. In contrast, gastric cancer rates, which are quite high in Japan, change only very slowly among migrants in the direction of the new host country, taking multiple subsequent generations, suggesting that for gastric cancer, factors earlier in life (eg, Helicobacter pylori infection) and genetics are equally important. How far have we come since these early studies? A PubMed search showed more than 8000 publications related to diet and GI cancer, of which almost 2000 were in the past 5 years alone. Based on sheer numbers, it would seem that we already should have reached the promised land, where an individual in the general population or one at high risk for a specific GI cancer would be offered a simple chemopreventive pill, or a clear dietary recommendation, with the expectation of substantial beneficial results. Society also would be facilitating healthy nutrition choices. Unfortunately, we are not in such a land. What is taking so long?