By: Dan Sperling, MD
Prostate cancer is the second most common cancer among men. In the U.S., more than 27,000 deaths occur each year. A tremendous amount of research has been, and continues to be, done to identify lifestyle factors that may contribute to the risk of prostate cancer (PCa). Such research has the potential to help men understand what they can take control of to reduce the risk of PCa. Perhaps the most widely identified controllable factors that are hypothesized to influence PCa are diet/nutrition, exercise, stress and the environment. In most cases, there is a complex interplay of these factors. For example, obesity, which is associated with increased risk of aggressive PCa and recurrence, is connected with food intake and sedentary lifestyle. Knowing the most efficient and effective place to begin to change old habits is often elusive. Obese men continue to live under the cloud of increased PCa risk. However, a necessary first step is to document the relationship and impact of cancer contributors, so men can evaluate themselves and their choices.
Three new studies shed light on some aspects of obesity and nutrition in relation to PCa:
- “The Role of Dietary Fat Throughout the Prostate Cancer Trajectory” (Di Sebastiano et al.)[i]
- “Impact of obesity upon prostate cancer-associated mortality: A meta-analysis of 17 cohort studies” (Zhang et al.)[ii]
- “Nutrition, dietary interventions and prostate cancer: the latest evidence” (Lin et al.)[iii]
All three studies are derived from extensive reviews and analysis of published literature on the subject. This article presents an integration of key concepts from all of them.
Di Sebastiano paper
Consumption of dietary fats, particularly animal fat and saturated fats, is one of the causal factors that lead to obesity. Obesity itself puts a strain on many systems in the body, such as cardiovascular health and joint health. Not only is there a connection between obesity and increased risk for prostate cancer, the condition can make treatment such as surgery or radiation more difficult. It can complicate recovery, and as already mentioned, it increases the risk for PCa to recur. It has been observed that when people from a culture with a low rate of prostate cancer, such as Japan, move to the U.S. and begin consuming a Western-style diet, their body-mass index (BMI) tends to increase, and so does their risk of developing PCa. One of the naturally-occurring regulators of cell function is insulin-like growth factor (IGF). Dietary fat is associated with circulating levels of IGF and may lead to disruptions in the pathway that affects cell reproduction, differentiation, die-off and transformation. In turn, this may be related to either the origin of malignancy, or the inability of the body to switch off malignancy-causing mechanisms. Dietary fat can also disrupt androgen signaling; androgens pay an important part in the development of normal prostate tissue, but a specific androgen signaling receptor is the chief stimulant of prostate cancer becoming more aggressive. There is some thinking that dietary fat may work through secondary pathways to stimulate cancer proliferation (increase in number and spread of cells) and angiogenesis (development of cancer-specific blood supply to bring nutrients to tumor cells).
Because some early studies demonstrated that prostate cancer survivors who consume high levels of dietary fat have a lower rate of PCa-specific survival, some clinical studies have been designed to explore the converse: does consumption of low-fat diet decrease any aspects of PCa risk? There is, indeed, evidence that “healthy fats” (those low in saturated fat) consumed in moderation may diminish the chances of developing PCa, or progression of established disease, or recurrence following treatment.
Zhang et al performed a meta-analysis of 17 cohort studies involving a total of 3,569,926 individuals inclusively. Essentially, their work was a statistical calculation based on published data. While they did not discover a conclusive correlation between obesity and the onset (incidence) of prostate cancer, they found a significant increase in PCa-specific death, demonstrated by the low survival rates among obese PCa patients. They found ample evidence suggesting that “obesity is a significant risk factor for aggressive PCa and PCa-specific mortality.” The importance of this article lies in the amount of data the team amassed, based on a huge population size. It becomes virtually impossible to deny the link between obesity and the likelihood of developing a deadly cancer condition, in addition to the many other ways in which obesity compromises health and quality of life.
The Lin study is not specific to obesity, but looks at a “potential role for dietary intake on the incidence and progression of PCa.” By examining a range of nutrients and dietary patterns, the study gives a well-rounded perspective on food intake and disease profile. The team examined the role of carbohydrates, soy protein, omega-3 fatty acids, green tea, tomatoes and tomato products in relation to PCa. In contrast to the detrimental effects of dietary fat, especially animal fats and saturated fats, they found that a balanced combination of reducing carbohydrates, a shift toward omega-3 fats, consumption of green tea and tomato products “showed promise in reducing PCa risk or progression.” They recommend a nutritional pattern that is rich in fruits and vegetables while reducing cooked meats, refined carbs, and total fats. Their full article can be found at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4286914/.
As advances in prostate cancer detection, diagnosis and treatment continue, much still needs to be done to understand ways to minimize the risk of developing PCa, and reducing the chance of progression or recurrence. Developing healthy dietary programs is of prime importance for those men who undergo a focal treatment, such as focal laser ablation. A doctor can administer a treatment, but only the patient can optimize his own body’s response to it.