Black Raspberry Diet Partially Restores Normal Gene Expression

Freeze-drying the berries concentrates these elements about 10 times and allows more precise dietary control.

Investigators from Ohio State University College of Medicine (Columbus, OH, USA) fed rats either a normal diet or a diet containing 5% black-raspberry powder. During the third week, half the animals in each diet group were injected three times with a chemical carcinogen, N-nitrosomethylbenzylamine. The animals continued consuming the diets during the week of carcinogen treatment. After the third week, the investigators analyzed the expression of 41,000 genes in esophageal tissue removed from the animals.

Results published in the August 1, 2008, online issue of the journal Cancer Research revealed that the carcinogenic treatment caused dysregulation of 2,261 genes. However, the raspberry diet restored 462 of these genes to normal expression. These results complement previous results that 1,323 genes were protected when animals were fed phenylethyl isothiocyanate (PEITC).

After comparing the data, it was found that a group of 53 genes was restored by both diets. These 53 common genes included genes involved in oxidative damage, oncogenes, and tumor-suppressor genes that regulate apoptosis, cell cycling, and angiogenesis. Since both PEITC and black raspberries maintained near-normal levels of expression of these 53 genes, their dysregulation during the early phase of induced esophageal cancer may be especially important in the genesis of the disease.

"We have clearly shown that berries, which contain a variety of anticancer compounds, have a genome-wide effect on the expression of genes involved in cancer development,” said first author Dr. Gary D. Stoner, professor of pathology, human nutrition, and medicine at the Ohio State University College of Medicine. "This suggests to us that a mixture of preventative agents, which berries provide, may more effectively prevent cancer than a single agent that targets only one or a few genes.”

"What is emerging from studies in cancer chemoprevention is that using single compounds alone is not enough,” said Dr. Stoner. "And berries are not enough. We never get 100% tumor inhibition with berries. So we need to think about another food that we can add to them that will boost the chemopreventive activities of berries alone.”

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Ohio State University College of Medicine