The Impact of Diet and Lifestyle on the Risk of Aggressive Prostate Cancer

This week’s 3-part blog detailed a recent, widely publicized study that suggested that fish and fish oil consumption caused aggressive prostate cancer. We pointed out several flaws in the study’s methodology that undermined this conclusion, and Dr. Block provided his recommendations for fish/fish oil, not only in light of this study, but in the context of other relevant research.  

Today’s blog will discuss a new prostate cancer study that shows a very different diet/lifestyle connection to aggressive prostate cancer than the study we reference above suggested.  The results may surprise you! (although they didn’t surprise us here at the Block Center!) 

A study published this summer by Lenore Arab and colleagues at UCLA assessed weight, diet, exercise, sodium and alcohol intake in over 2000 prostate cancer patients in Louisiana and North Carolina, with approximately an equal numbers of Caucasian and African-American men.  The particular concentration on African-American men was included because African-American men are diagnosed with prostate cancer at younger ages and have more aggressive disease than other ethnic groups.  The strategy of this study was to investigate what lifestyle factors are associated with aggressive versus low-grade prostate cancer by comparing the diet and exercise habits of prostate cancer patients to recommendations for cancer prevention made in 2007 by the World Cancer Research Fund, which are based on over 500 studies of lifestyle and cancer. 

The prostate cancer patients were interviewed to find out their diet and exercise habits, and then they were compared to the prevention recommendations.  Here are the recommendations that the study used:

1. Be as lean as possible without being underweight – your body mass index or BMI should be between 21 and 23 (most sources designate normal BMI as 20-25).
2. Engage in at least 60 minutes of moderate activity, or 30 minutes of vigorous activity daily.
3. Limit consumption of energy-dense (high calorie) foods.
4. Avoid sugary drinks, including fruit drinks and juices, sodas, and sugar in coffee or tea.
5. Eat at least 5 servings a day of nonstarchy vegetables and fruits daily (e.g., French fries don’t count towards you non-starch vegetable intake!).
6. Eat at least 25 grams of whole grains and cereals or legumes per day.
7. Eat less than 500 grams (about 1 pound) of red meat per week.
8. Limit alcohol to 2 drinks per day for men and 1 for women.
9. Limit sodium intake to less than 2.4 grams per day, about 1 teaspoon.

Based on their interviews, patients were awarded 1 point for each recommendation if they were completely in line with it.  In some cases, they could get half a point if they adhered partially to it, for instance, by getting 30 to 60 minutes of exercise daily, or 15 to 30 minutes of vigorous exercise.  If a patient adhered perfectly to each recommendation, they could get a total of 9 points.  The study didn’t mention how many patients received perfect scores, but it could not have been too many, since only 5% complied with the recommendation to maintain a BMI of 21-23, and the average amount of exercise was only 10 minutes per day! 

Once every patient had been scored, the study computed average adherences, and then compared the degree of adherence to the likelihood of having aggressive versus low-grade prostate cancer.    Overall, the result was definitely significant.  For every additional point in the adherence score, risk of aggressive prostate cancer declined by 13%.  The researchers also found that patients who had a total adherence score of less than 4 were 38% more likely to have aggressive prostate cancer than those whose scores were more than 4.  So, following cancer prevention guidelines does, in fact, help to prevent aggressive prostate cancer.  They also noted that smoking, which was not included in the adherence calculation for this study, was associated with aggressive cancer risk.

The researchers also analyzed which of the particular recommendations were the most relevant for reducing prostate cancer risk.  Three major risk factors were found in this analysis.  For both Caucasians and African-Americans, limiting the energy density of foods reduced risk of aggressive disease by 29%, and eating less than 500 grams of red meat reduced risk by 23%.  For the African-American patients, eating less red meat reduced risk even more, by 29%.  Eating less than a teaspoon of sodium was also significantly correlated with a 36% lower risk. 

Now, these authors don’t reduce the prostate cancer recommendations to energy density, red meat and sodium!  Their overall results don’t suggest that these are the only factors that are relevant to reducing prostate cancer risks, since it was the men who complied with fewer than 4 of the recommendations who had the really noticeable 38% increase in risk.  They point out that high consumption of vegetables, fruits, legumes and whole grains is likely a major reason why the men who ate less red meat wound up with lower risks of aggressive cancer.  Eating vegetables, fruits, legumes and whole grains is also a significant strategy for lowering the energy density of your diet, one of the major ways to reduce aggressive cancer risk.  Other ways to reduce energy density include avoiding foods that are high in fat (which has more calories per gram than protein or carbs) and excluding foods that are high in sugar and other refined carbs.  Avoiding red meat and excess salt are certainly important, but they are not the whole picture.  The whole picture is that men wishing to avoid aggressive cancers should try their best to adhere to as many of the prevention guidelines as they can.  We also suggest that these guidelines are appropriate for prostate cancer patients hoping to avoid progression of their disease.  While some factors, such as those causing genetic mutations, may not be as important once a cancer gets started, your biochemical environment, or terrain, can promote cancer growth through processes such as inflammation, stress hormones and excess blood sugar and insulin. 

A final note:  another study came out this week, which was a followup of an earlier randomized trial of the drug finasteride (Proscar) in preventing prostate cancer.  Like fish oil, finasteride was under suspicion for increasing risk of aggressive prostate cancer, although it decreased risk of low-grade disease by nearly 5% (10.5% low-grade disease in finasteride patients, 14.9% in the placebo group).  This study confirmed a slightly higher risk of aggressive prostate cancer in patients taking finasteride versus placebo patients (3.5% versus 3.0%).  However, interestingly, although there were differences in the incidence of prostate cancer, after 18 years of follow-up, there was no significant difference in survival of the finasteride and placebo groups, despite the slightly higher incidence of aggressive disease in the finasteride group.  Of course, there may have been much more distress, surgery and other medical intervention among men with aggressive disease as well.  Men who are interested in preventing prostate cancer through using finasteride should talk to their doctors about it, though, since significant side effects are possible from this drug, especially consequences on one’s sexual life.  On the other hand, though a lifestyle overhaul is certainly more difficult than simply popping a pill - and may not be quite as effective if it’s done half-heartedly – the major “side effects” of adhering to cancer prevention guidelines are a reduced risk of all cancers, and a reduced risk of cardiovascular disease as well!  And that’s a deal that should be attractive to all of us!

For more information on The Block Center for Integrative Cancer Treatment, call (847) 230-9107 or visit BlockMD.com.