The scientists administered the grape seed extract to two different human colon carcinoma cells and recorded an inhibition of cell growth dependent on time and dose.
"Beneficial effects were correlated with how much extract was used and how long it was used for," said lead researcher Rajesh Agarwal, Ph.D., professor in the Department of Pharmaceutical Sciences at the University of Colorado Health Sciences Center in Denver, adding that there was a 92 percent reduction in live cells when the highest dose was administered to one cell line for two days.
The researchers then implanted mice with advanced human colorectal cancer cells, and fed the mice grape seed extract at the same time. After eight weeks, the tumor volume dropped by 44 percent compared to controls. The dose was comparatively larger than what a human would consume, admitted Agarwal, but no toxic side effects were observed.
Not only did researchers observe the decrease in colorectal tumors in the mice, but they also documented for the first time the molecular mechanism grape seed extract uses to inhibit cancer growth: an increase of the availability of critical protein Cip1/p21 in tumors causes the cell cycle to freeze and often self destruct.
"With these results, we are not suggesting that people run out and buy and use grape seed extract," Agarwal said. "That could be dangerous since so little is known about doses and side effects. The value of this preclinical study is that it shows grape seed extract can attack cancer, and how it works, but much more investigation will be needed before these chemicals can be tested as a human cancer treatment and preventive."
Next, the team plans to structure a study to determine the lowest effective dose of grape seed extract and the highest non-toxic dose in mice.
"Grape seeds contain miraculous medicines for protecting the human body from heart disease and cancer," said Mike Adams, author of "The Seven Laws of Nutrition." "But guess what's been removed from all the grapes sold at grocery stores: the seeds, of course. Luckily, healthy consumers know to buy grapes with seeds, then chew and swallow the seeds."
Colorectal cancer is the second most common malignancy in Americans, and the second leading cause of cancer-related deaths.