In a newly published study, researchers at The University of Texas MD Anderson Cancer Center found that those with a localized prostate cancer diagnosis fared better over the course of their disease when they adhered to a standard Mediterranean diet (Cancer 2021; https://doi.org/10.1002/cncr.33182). After adjusting for things that may worsen cancer over time like age, prostate-specific antigen, and tumor volume, men that followed this diet had a reduced risk of their cancer growing or advancing to a point at which they would need active treatment.
After the men completed a food frequency questionnaire and the Mediterranean diet score was calculated for each participant, they were split into three groups according to their adherence to the diet: low, medium, and high. The researchers found that a high baseline diet score correlated with a lower risk of cancer progression.
They also found that the effects of this diet were more significant for the Black participants and others that identified as non-White. This is important to consider since the rate of prostate cancer is over 50 percent higher in Black men.
"There are a number of studies that suggest that behavioral factors, such as dietary quality, may be related to the risk of someone developing prostate cancer or of having prostate cancer return after it is treated," said Justin Gregg, MD, Assistant Professor of Urology at MD Anderson and lead author of the study. "However, research is limited on the effect of diet on prostate cancer progression in men whose tumors are actively monitored on a program of active surveillance. We hypothesized that diet quality may be associated with a lower risk of disease progression over time."
Diet Specifics
The Mediterranean diet consists of many things, and Gregg suggests taking a look at the methods section of the published paper for the full details of how they characterized the Mediterranean diet.
"In summary, vegetables, fish, fruit, legumes, whole grains and moderate alcohol consumption were considered 'consistent' with the Mediterranean diet," he noted, "while things like fatty meat, dairy, and a high fat intake ratio and no or high alcohol consumption were 'inconsistent.'"
So what exact elements of the Mediterranean diet do we now understand are helpful in slowing prostate cancer progression? Gregg says the short answer is that they don't know, but their hypothesis is that the Mediterranean diet may be beneficial because of its overall effect.
"In sum, it may lower systemic inflammation and/or circulating lipid levels that may be detrimental to health," he stated. "It would be nice to discover a single diet component that can directly affect health or cancer, though our limited data do not suggest that this is the case."
Gregg noted that, although these results don't necessarily surprise him, he does think that they are very encouraging. He said this is a somewhat underpowered retrospective study, so he would not use it to recommend to all men with prostate cancer to adhere to the diet.
"However, I think that it certainly is evidence that further work should be done investigating the use of Mediterranean diet in this setting, which is important given much stronger evidence that diet adherence likely helps other aspects of men's lives, such as risk of heart attack or stroke," he said.
There is a lot of room for more research on this subject. In fact, Gregg said that future studies validating their findings in external cohorts would be useful. "In addition, prospective studies, particularly if they are controlled by dietary type, may yield insights into how the Mediterranean diet can affect men with prostate cancer, including through studying specimens such as blood or tumor tissue."
Gregg said that it is difficult to say whether this diet could lead to better outcomes in patients with other types of cancers. "We only studied prostate cancer and can really only speak to this," he said. "However, in general, at times interventions or treatments that are effective for one cancer are found to be useful in other malignancies. If, in the future, we determine that something like dietary change is actually beneficial for men with prostate cancer, I think that it would be worthwhile to investigate similar changes in other cancers."
At the end of the day, this study is an encouraging step forward in figuring out if a good diet really does help those with prostate (or any other) cancer. "I think this study highlights the importance of work related to diet and prostate cancer risk," said Gregg. "And [it highlights] that future work will hopefully elucidate more clearly if and how men benefit from something like a change in diet following a cancer diagnosis."
Dillon Stickle is a contributing writer.