The Daily Telegraph today reported that “a vegan, low-fat diet combined with yoga and exercise can help fight prostate cancer”. They say that a new study has found that “combining a diet low in fat and rich in fruit and vegetables with regular moderate exercise seems to switch on genes that fight disease, while effectively turning off others that can promote cancer”.
It is essential to point out that this study did not actually look at the effects of lifestyle changes on the progression of prostate cancer. It only looked at the effects of lifestyle changes on the activity of different genes in prostate tissue, and only included men with very low-risk prostate cancer. Although the study did identify changes in the activity of some genes, it is not possible to ascertain whether the changes were the result of the lifestyle changes. It is also not possible to say what effect, if any, these changes had on the progression of the men’s prostate cancer.
Men with prostate cancer should discuss appropriate treatments with their doctors, and should under no circumstances refuse treatment in the belief that these lifestyle changes alone will help them beat cancer. A healthy lifestyle, including a good diet and exercise, has known benefits, and all people should aim to achieve this goal.
Where did the story come from?
Dr Dean Ornish and colleagues from the University of California and the Preventive Medicine Research Institute carried out the research. The study was funded by the Department of Defense/U.S. Army Medical Research Acquisition Activity Grant; Henry M. Jackson Foundation for the Advancement of Military Medicine; the Pritzker, DeJoria, Lederhausen, Walker, Wachner, Kaye, Ellison, Ito, Fisher, Gallin, Bucksbaum, Koch, Resnick, Safeway, Zimmer, Bodine, Hubbard, Bahna, Rohde, Talbott, Groppe, Gegax, PepsiCo, California HealthCare, George, Hartford, and Prostate Cancer Foundations; National Center for Complementary and Alternative Medicine; National Cancer Institute; the Kerzner Foundation; the Bernard Osher Foundation and the Walton Family Foundation.
The study was published in the peer-reviewed medical journal Proceedings of the National Academy of Sciences USA .
What kind of scientific study was this?
In this case series, called the Gene Expression Modulation by Intervention with Nutrition and Lifestyle (GEMINAL), the researchers looked at the effects of an intensive nutrition and lifestyle programme on the activity of genes in the prostate of men with low-risk prostate cancer.
The researchers recruited 31 men with prostate cancer, which was at low-risk of tumour metastasis (cancer spread), and who did not want immediate surgery, hormone therapy, or radiotherapy. The men agreed to make comprehensive lifestyle changes, including eating a low-fat, whole food, and plant-based diet, taking moderate exercise (using stress management techniques) and taking part in a psychosocial support group.
The men were closely monitored to see if their tumours progressed. Their weight, blood lipids (fats), blood pressure, and abdominal obesity were also monitored. The researchers took a series of needle biopsies of normal prostate tissue from the men’s prostates at the start of the study and after three months. They then compared the activity of different genes in the prostate tissue taken before and after the study.
What were the results of the study?
The men adhered well to the lifestyle changes over the three-month period. They reportedly consumed about 12% of their daily calories from fat, exercised over three-and-a-half hours a week, and used stress management for about four-and-a-half hours per week.
By the end of the study, the men had reduced their body mass index, blood pressure, waist circumference, and blood lipids. The researchers identified 48 genes that were more active and 453 genes that were less active after the intervention. Some of these genes are involved in tumour formation.
What interpretations did the researchers draw from these results?
The researchers concluded that an intensive nutritional and exercise programme may alter gene activity in the prostate, and that this information may help to develop effective ways of preventing and treating prostate cancer. They suggest that larger studies are needed to confirm their findings.
What does the NHS Knowledge Service make of this study?
This small pilot study has identified some of the changes to the prostates of men taking part in an intensive lifestyle change. There are a number of points to bear in mind when interpreting this study:
- The study did not include a control group who had made no lifestyle changes to which this group could be compared. Therefore it is not possible to ascertain whether the gene expression changes observed were related to the lifestyle changes.
- The study did not look at whether the lifestyle changes affected the progression of the men’s prostate cancer. Future studies would need to examine the relationship between changes in gene activity and cancer progression to confirm that these two events are linked.
- In order to investigate whether these lifestyle changes have an effect on prostate cancer progression, a randomised controlled trial would need to be carried out.
- Although the genes identified in this study may have functions involved in tumour formation, they also have roles in the cells’ normal functions. Therefore it is impossible to say with certainty that they have either “disease-preventing” or “disease-promoting” effects, as implied in some of the news reports.
Men who have prostate cancer should discuss appropriate treatment options with their doctors, and should under no circumstances refuse treatment in the belief that these lifestyle changes alone will help them beat cancer.
Sir Muir Gray adds…
High fat diets increase the risk of cancer; this may be the mechanism by which this happens.