Smaller doses of resveratrol, a chemical found in red grapes, are more effective at preventing colorectal cancer in mice than high doses, according to new research published in Science Translational Medicine (2015; doi:10.1126/scitranslmed.aaa7619).

Previous research looked at high doses of purified resveratrol to study its potential to prevent cancer. This is the first study to look at the effects of a lower daily dose, the equivalent to the amount of resveratrol found in one large (approximately 250 mL) glass of red wine, and compare it with a dose 200 times higher.

Results from colorectal cancer-prone mice given the smaller dose showed a 50% reduction in tumor size while the high dose showed a 25% reduction. Lower doses of resveratrol were twice as effective as the higher dose in stopping tumor growth, although this effect was only seen in animals fed a high-fat diet.

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Tumor samples from patients with colorectal cancer given different doses of resveratrol showed that even lower doses can get into cancer cells and potentially affect processes involved in tumor growth.

Resveratrol is a naturally occurring chemical found in grape skins and other plants. Laboratory studies have suggested that it may have anticancer properties, although results from human trials have been mixed.

This study opens up new avenues for the role of purified resveratrol in preventing cancer, but suggests that it may only be effective for people with a specific genetic make-up, particular diets, and lifestyles.

Also, it does not mean drinking red wine reduces cancer risk, as drinking alcohol increase the chances of developing the disease.

“For the first time, we’re seeing that less resveratrol is more. This study shows that low amounts may be better at preventing tumors than taking a high dose,” said corresponding author Karen Brown, PhD, professor of translational cancer research at the University of Leicester in England.

“The same might be true for other plant-derived chemicals and vitamins that are also being studied for cancer prevention. There should be more research looking at the effects of low doses. But this is early laboratory research and the next stage is for clinical trials to confirm whether resveratrol has the same effects in people at high risk of bowel cancer.”

Julie Sharp, PhD, Cancer Research UK’s head of health information, said, “This research doesn’t mean that having a glass of red wine will reduce your risk of cancer because you can’t separate the resveratrol from the alcohol. And the increase in cancer risk linked to alcohol outweighs any possible benefits of the resveratrol.

“It’s a fascinating study but we need much more research to understand all the pros and cons of someone taking resveratrol to prevent bowel cancer. However, we do know that keeping a healthy weight along with a balanced diet low in red and processed meat with lots of fiber including fruit and vegetables can stack the odds in your favor to lower your risk of developing the disease.”