Answer:
Conflict.
Step-by-step explanation:
The given sentence discusses the 'conflict' of the essay as it talks about the key disagreement('many other award-winning doctors do not agree that eating organic foods definitely prevents cancer') that opposes the main idea of the essay('organic foods prevent cancer'). This establishes a conflict or struggle between the two combating or incompatible ideas which must be resolved by presenting sufficient evidences to justify the central argument. However, this conflict also helps the audience to have an objective outlook of the issue and consider the another aspect as well.