In a pre-clinical test-tube study, researchers said they found grape seed extract can attack colon cancer, but more study must be done before the chemicals found in the seed can be tested as a cancer treatment for humans, WebMD.com said

Researchers said they thought antioxidants called proanthocyanidins were the reason for successful preliminary tests, WebMD.com said.

In their study, researchers tested different dosages of the grape seed extract on cancerous cells from the human colon. The growth cycle of cancer cells treated with the grape seed extract was retarded and the cells died, compared to cells not treated with the extract.

Researchers inject human colon cancer tumors under the skin of mice and fed the extract to the mice, WebMD.com said. The tumors grew more slowly in the mice receiving the extract than in those that didn't. During the eight-week study, mice getting the grape seed extract maintained their normal weight, experienced no diet changes and didn't exhibit other side effects, the medical site said.