Berries function to reduce the amount of genetic (DNA) damage produced in these tissues by chemical carcinogens, including carcinogens in tobacco smoke and in the diet. They also reduce the growth rate of precancerous cells, in part, by reducing the expression of genes associated with cell growth. Berries also inhibit the expression of other genes associated with cancer development including genes involved in inflammatory processes and in the formation of new blood vessels (angiogenesis).
In a preliminary trial in humans, berries were found to be well tolerated at doses similar to those used in animals. They reduced cellular damage caused by oxidative radicals which is consistent with their anti-oxidant potential. In view of these results, several human clinical trials are ongoing to determine the ability of freeze-dried berries to inhibit the development of precancerous lesions in the oral cavity, esophagus and colon of humans. Preliminary results suggest that berries influence the expression of many of the same genes in humans as they do in animals. An apparent advantage of this “food-based” approach to disease prevention is the relative absence of toxicity associated with the long-term consumption of berries by humans.