Heart-Healthy Diet May Be Prostate Cancer Healthy Too

Nick Mulcahy

June 10, 2013

UPDATED June 13, 2013 — A diet that reduces carbohydrates and animal fat intake and boosts vegetable fat consumption could benefit men with prostate cancer, a new observational study concludes.

This dietary-fat mix mirrors a heart-healthy diet and was associated with better overall and prostate-cancer-related mortality in a large cohort of men, report the authors, led by Erin Richman, ScD, from the Department of Epidemiology and Biostatistics at the University of California, San Francisco.

"Overall, our findings support counseling men with prostate cancer to follow a heart-healthy diet in which carbohydrate calories are replaced with unsaturated oils and nuts to reduce the risk of all-cause mortality," write the authors.

Nuts and vegetable oils (such olive and canola oil) were the 2 sources of vegetable fats associated with reduced overall and disease-specific mortality.

The study was published online today in JAMA Internal Medicine.

In practical terms, the findings mean that men with prostate cancer "should have olives or nuts for an appetizer instead of bread" and should "skip the croutons on their salad but have more oil-based dressing," Stephen Freedland, MD, from the Department of Urology at Duke University in Durham, North Carolina, told Medscape Medical News.

Dr. Freedland explained that Americans consume most of their vegetable fats in food items such as margarine, mayonnaise, and salad oil — not vegetables. "Asparagus does not have much vegetable fat," he noted.

The study is not conclusive about dietary fat because it is not a randomized controlled trial, Dr. Freedland noted. However, he leans toward agreeing with Dr. Richman and colleagues on a major point. "A heart-healthy diet is probably a prostate-healthy diet," he writes in an accompanying commentary. Heart disease and prostate cancer share causal factors such as inflammation, high cholesterol, and obesity, he explains.

Dr. Freedland counsels prostate cancer patients that obesity is the only known modifiable risk factor linked to prostate cancer mortality. But this study suggests that "substituting healthy foods (i.e., vegetable fats) for unhealthy foods (i.e., carbohydrates) may have a benefit," he writes. "When eating an egg-salad sandwich, skip the bread and go heavy on the egg salad," he said, offering another everyday food example.

A groundbreaking trial being conducted at Duke University, led by Dr. Freedland, could soon clarify just how detrimental carbohydrate consumption can be for men with prostate cancer and whether carbohydrate restriction is associated with better outcomes.

The trial participants will have "failed" primary therapy for prostate cancer, as evidenced by a rising prostate-specific antigen (PSA) score after surgery, and will have experienced disease progression.

The study will randomize men to either a low-carbohydrate diet (<20 g/day) or usual care. The outcome measure is PSA doubling time or change in PSA over the 6-month study period.

Cut Carbs, Increase Vegetable Fats

In their study, Dr. Richman and colleagues prospectively examined the dietary-fat intake of 4577 men with nonmetastatic prostate cancer enrolled in the Health Professionals Follow-up Study, conducted from 1986 to 2010.

The men, who are dentists, optometrists, and other professionals, but not physicians, completed a series of food frequency questionnaires over time.

The researchers looked at the men's intake of saturated, monounsaturated, polyunsaturated, trans, animal, and vegetable fat after a diagnosis of prostate cancer.

They observed 315 events of lethal prostate cancer and 1064 deaths (median follow-up, 8.4 years).

When the researchers calculated the crude rate of lethal prostate cancer per 1000 person-years, they found that men who ate more vegetable fat had lower prostate cancer mortality than men who ate less vegetable fat. No other fats were significantly associated with lethal prostate cancer.

Table. Prostate Cancer and All-Cause Mortality per 1000 Person-Years by Quintile of Fat Intake

Mortality by Type of Fat Highest Quintile Lowest Quintile
Prostate cancer (crude rate)    
   Saturated 7.6 7.3
   Monounsaturated 6.4 7.2
   Polyunsaturated 5.8 8.2
Trans 8.7 6.1
   Animal 8.3 5.7
   Vegetable 4.7 8.7
All-cause    
   Saturated 28.4 21.4
   Monounsaturated 20.0 23.7
   Polyunsaturated 17.1 29.4
Trans 32.4 17.1
   Animal 32.0 17.2
   Vegetable 15.4 32.7

 

The team also performed modeling exercises on data of carbohydrate consumption from the study.

They found that replacing 10% of calories from carbohydrates with vegetable fats was associated with a 29% lower risk for prostate cancer death (hazard ratio [HR], 0.71; P = .04) and a 26% lower risk for all-cause death (HR, 0.74; = .001).

In statistical modelling, when 5% of energy from carbohydrates was replaced with saturated fat after diagnosis, all-cause mortality was significantly higher (HR, 1.30; = .02). It was also higher when 1% of energy from carbohydrates was replaced with trans fat (HR, 1.25; = .01).

This work was supported by the National Institutes of Health, the Department of Defense, and the Prostate Cancer Foundation. The authors and Dr. Freeland have disclosed no relevant financial relationships.

JAMA Intern Med. Published online June 10, 2013. Abstract, Commentary

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