While the role of fruits and vegetables is well established and known in protecting against major diseases and disorders of the cardiovascular, digestive, and endocrine systems, their protective role is less known and established with respect to radiation-induced cancer. Their role with respect to radiation appears to be a particular manifestation of their general role in preventing and/or inhibiting cancer. For purposes of this review, radiation encompasses X-rays and gamma-rays, neutrons, alpha and beta particles, high-speed electrons and protons, and other particles capable of producing ions; it does not include non-ionizing radiation such as radio waves or microwaves and visible, infrared, or ultraviolet light.
Since the dawn of the Nuclear Age, there have been concerted efforts to discover and/or develop radioprotectors, agents that inhibit the development of radiation-induced cancer either by blocking the DNA damage that initiates carcinogenesis or by arresting or reversing the progression of premalignant cells in which such damage has already occurred. It is important to make the distinction between natural radioprotectors such as fruits and vegetables and synthetic ones. While there has been a long history of research in synthetic radioprotectors and pharmacological agents, in toto, the results have been at best only equivocal. Much research has been devoted to the sulfhydryl compounds (synthetic sulfur-containing amino acid antioxidants) cysteine and cysteamine, which unfortunately are marked by toxicity and short active periods, and to biological response modifiers such as cytokines, polysaccharides, and prostaglandins.
Although combinations of radioprotective drugs acting via different mechanisms have been found to improve the degree of protection and keep toxicity to acceptable levels in small rodents, attempts to use such treatments in large mammals have been less successful, generally due to poorer protection and higher toxicity. There have also been long-term efforts by radiation oncologists and radiation biologists to develop synthetic chemical radiosensitizers to differentially spare normal tissues (as opposed to tumor cells) from radiation damage, but clinical exploitation has been slow in coming.1 In a review paper summarizing past, present, and future prospects of chemical radioprotection, Maisin2 stated that no radioprotective drug has all of the requisite qualities of an ideal radioprotector, and that it is questionable whether chemical radioprotection in humans has any future prospects. He did, however, hold out some future hope for non-toxic combinations of biological and chemical agents.2 With certain caveats, the prospects for natural radioprotective agents in general, and diets rich in fruits and vegetables in particular, have far greater efficacy. One caveat is that these natural agents would not necessarily be expected to exert a significant influence at high radiation doses and/or dose rates. However, as will be reviewed here, outside this caveat there appears to be mounting evidence that a diet rich in fruits and vegetables can play a positive and important role in both the prevention and amelioration of radiation-induced cancer.
