Prof Bruce Ames proposed some years ago in 2010 that providing additional nutrients to diminish the adverse consequences of cellular triage (A system used to allocate a scarce commodity, such as food, only to those capable of deriving the greatest benefit from it), would result in diminished mutagenesis. Very presciently he concluded his review paper by stating:
Optimising micronutrient intake could have a major effect on the prevention of cancer and other degenerative diseases of aging.
After a series of conflicting reports about whether vitamin pills can stave off chronic disease or worse, can promote it, researchers announced on October the 17th 2012 that a large clinical trial of nearly 15,000 older male doctors followed for more than a decade found that those taking a daily multivitamin experienced 8% fewer cancers than the subjects taking placebo pills.
While many studies have focused on the effects of high doses of particular vitamins or minerals, such as calcium and vitamin D, this clinical trial examined whether a common daily multivitamin had an effect on overall cancer risk. A randomised, double-blinded clinical trial, the kind considered the most rigorous type of study, it was one of the largest and longest efforts to address questions about vitamin use. Some, 14,641 male US physicians initially aged 50 years or older (mean [SD] age, 64.3 [9.2] years), including 1,312 men with a history of cancer at randomisation, enrolled in a common multivitamin study that began in 1997 with treatment and follow-up through June 1, 2011.
Multivitamin use had no effect on the incidence of prostate cancer, which was the most common cancer diagnosed in the study participants. But when researchers looked at the effect of vitamin use on all other cancers, they found a 12% reduction in occurrence. Overall cancer deaths were reduced among vitamin users, but the difference was not statistically significant.
Whilst there are always flaws in studies that produce both positive and negative outcomes, this was a large number of well managed professional male Drs who were considered very compliant. Although multivitamins were not apparently effective in reducing prostate cancer they did limit others, showing an overall 8% reduction in risk.
Prof. Ames would probably suggest that dosing needs to be increased further to achieve the optimal intake, and whilst over consumption may have limited increased benefit the incidence of reduction may be pushed higher yet if they also included minerals
 J. Michael Gaziano, MD, MPH; Howard D. Sesso, ScD, MPH; William G. Christen, ScD; Vadim Bubes, PhD; Joanne P. Smith, BA; Jean MacFadyen, BA; Miriam Schvartz, MD; JoAnn E. Manson, MD, DrPH; Robert J. Glynn, ScD; Julie E. Buring, ScD Multivitamins in the Prevention of Cancer in MenThe Physicians’ Health Study II Randomized Controlled Trial JAMA. 2012;():1-10. doi:10.1001/jama.2012.14641. View Full Paper