In many peer-reviewed articles, the assertion that 30–40% of cancers can be prevented with a healthy lifestyle and appropriate dietary measures has become axiomatic. The information often is derived from an expert panel's opinion as opposed to hypothesis-driven research. Unquestionably, the single most effective and validated cancer prevention measure is to not smoke, or if one does, to cease. However, obesity avoidance reduces the risk of heart disease and diabetes and probably some cancers. While for some Americans the consumption of an unhealthy diet is by choice, for many it is driven by financial constraints and the search for calories of any kind. Regrettably, beyond that, there is little compelling evidence on how diet can be used to prevent cancer.