Solving the Diet-Cancer Mystery:
Scientific Studies Provide Clues
Epidemiological: Cohort Studies
Cohort studies gather data on a large group of healthy people and then follow that group over many years. Study participants may keep daily food diaries or fill out questionnaires about what they eat.
As some people in the study develop cancer, researchers zero in on how their diets differed from the people who remained healthy. Did the people who stayed cancer-free eat more blueberries or soy products than the people who developed cancer? What they ate might provide a clue.
Strengths of Cohort Studies
Cancer doesn’t just “pop up.” Cohort studies let researchers study people over the long period of time that it takes for cancer to develop. They have an advantage over case-control studies because they ask people to keep track of what they’re eating while they're still healthy, rather than waiting until they develop cancer and then asking what they ate in the past (pre-diagnosis). A strength of cohort studies is that many different types of cancer (or other diseases) can be studied using the same cohort.
Weaknesses of Cohort Studies
As in any kind of dietary investigation, to pack real scientific and statistical punch, cohort studies also need to be extremely large and participants followed over a long period of time.