“Munching chocolate can help fight cancer,” the Daily Star reported. It added that “chomping on Mars bars - which famously ‘help you work rest and play’” could be the best way to beat the disease”. The Daily Express also covered the story and said that scientists had investigated the chemical GECGC, a man-made version of antioxidants called procyanidins, which naturally occur in cocoa beans. They found that it “halved the rate at which tumours grew, leaving healthy cells untouched”. The scientists added GECGC to 16 different types of cancer cells and found that it slowed growth in four, with the greatest effect seen in two types of bowel cancer cells.
Although GECGC reduced the growth of five of the human cancer cells lines tested, it is far too early to suggest that it may be used to treat or prevent human cancer. It is not clear whether this compound would have similar effects on cancer cells in a living organism, or what side effects it would have. This study cannot be taken as evidence that eating chocolate, and specifically Mars bars, will reduce your risk of bowel cancer, or any other type of cancer, or that it is “good for you”.
Where did the story come from?
Dr Min Kim and colleagues from the Georgetown University School of Medicine and Thomas Jefferson University in the US carried out the research. The study was funded by the National Institutes of Health, the Pennsylvania Department of Health and Dr. Ralph and Marian C. Falk Medical Research Trust. The chemical being tested in the study (GECGC) was provided as a gift from Mars Inc. The authors also acknowledge grant support from Mars Inc. The study was published in the peer-reviewed scientific journal Cell Cycle .
What kind of scientific study was this?
This was a laboratory study which looked at the effects of the chemical procyanidin [3-O-galloyl]-(-)-epicatechin-(4β,8)-(+)-catechin-3-O-gallate (GECGC) on the growth of normal human cells and cells from a variety of human cancers. Procyanidins are chemicals found in cocoa beans as well as other fruits and vegetables. The GECGC used in this study was chemically synthesised rather than extracted from cocoa beans or other sources.
The researchers used 16 different types of cells which had been taken from eight different types of human cancers and grown in the laboratory over a period of time, called cell lines. The cell lines were from cancers of the breast (five cell lines), colon (two cell lines), lung (three cell lines), prostate, ovary, cervix, kidney, central nervous system, and blood (leukaemia). They also used six cell lines derived from the following normal (non-cancerous) human tissues: umbilical cord, skin, breast and lung.
The researchers added GECGC in a range of concentrations to the different cells lines for 12, 24 or 48 hours, and looked at its effect on cell growth compared to cells not treated with GECGC. They then took the cells whose growth was affected by GECGC and looked at how it had this effect.
What were the results of the study?
The researchers found that five of the 16 cancer cell lines were sensitive to GECGC. This means that the chemical could inhibit the growth of these cell lines at relatively low concentrations. The five cells that were sensitive to GECGC came from colon cancer (two cell lines), cervical cancer, leukaemia, and lung cancer (although two other lung cancer cell lines were not sensitive to GECGC). None of the cell lines from normal non-cancerous human tissues were sensitive to GECGC.
What interpretations did the researchers draw from these results?
The researchers concluded that chemically synthesised GECGC selectively reduces the growth of human cancer cells. They say that their results show that GECGC warrants further investigation as a possible preventative or treatment for human cancers.
What does the NHS Knowledge Service make of this study?
It is far too early to suggest that GECGC can be used to treat or prevent any human cancers. Although GECGC has been shown to slow the growth of five of the human cancer cells lines tested in the laboratory, it is worth noting that the other 11 cancer cell lines tested were not sensitive to the chemical.
It is far from clear whether this compound would have similar effects on cancer cells in a living organism, or what side effects it would have. Substantial further testing in the laboratory and in animals will be needed, and GECGC will have to be shown to be safe and effective in these experiments before ever being tested in humans, a hurdle that the majority of chemicals fail to overcome.
This study cannot be taken as evidence that eating chocolate, and specifically Mars bars as mentioned in The Daily Star, will reduce your risk of bowel cancer, or any other type of cancer, or that it is “good for you”. Maintaining a healthy weight by exercising and eating a healthy balanced diet, including at least five servings of fruit and vegetables a day, are the best ways to aim for good health.
Sir Muir Gray adds...
Chemotherapy or chocolate? I would take the chemo for a cure and the chocolate for taste.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
Daily Express, 27 June 2008
Links to the science
Cochrane Database Syst Rev 2002, Issue 1
Cochrane Database Syst Rev 2008, Issue 1
Cell Cycle 2008; 7: 1648–1657