Whole foods or phytochemicals? Considerations for chemoprevention

CN05-01

Most scientists have now come to accept the views of Richard Doll and Richard Peto that a sizable fraction of cancer mortality is influenced by diet. However, acceptance of this epidemiologic reality leads to a most complex issue: Should part of a proactive strategy to address the prevention of cancer and chronic disease encourage a better diet and more exercise, or should it yield to the realities of reduced energy expenditure in the modern world? Should it support the rational development of supplements that might not require, for example, the consumption of at least five servings per day of fruits and vegetables? A large variety of phytochemicals have been identified, and mechanistic work on isolated compounds highlights multiple mechanisms for their cancer preventive activity. Bioavailability and efficacy of these compounds as components of whole foods are clearly impacted by complex interactions that are not yet well understood. There are three questions that are particularly perplexing, and although there is no consensus on any of them, it is proposed that they deserve to be the substrate for creative minds over the next decade: (1) When long-term prophylaxis is indicated, should persons at increased risk for particular cancers be encouraged to take (i) pharmaceuticals, (ii) food products or supplements enriched in potentially protective compounds, or (iii) whole foods? (2) Are there true synergies or matrix effects within the huge variety of concoctions, decoctions, preparations, elixirs, extracts, and tonics reported to have protective activities? There has been much descriptive work on the efficacy of these folk medicines, yet rigorous evaluation of the biological effects of these reported synergies is still an elusive goal. (3) Dogmatic approaches to protection from chronic disease frequently assume that one would need to attain high levels of protection in order for there to be value in this strategy. Whereas this may be the only paradigm that permits us to measure risk reduction using currently available tools, does it not also incorporate the flawed logic that the only good risk reduction is a large risk reduction?