Consuming more vegetable fat may cut prostate cancer mortality

Consuming more vegetable fat may cut prostate cancer mortality
Consuming more vegetable fat may cut prostate cancer mortality

HealthDay News -- Men with non-metastatic prostate cancer had a lower risk of dying of the disease as vegetable fat consumption increased, results form a large prospective cohort study indicate.

"Among men with nonmetastatic prostate cancer, replacing carbohydrates and animal fat with vegetable fat may reduce the risk of all-cause mortality," Erin L. Richman, ScD, of the University of California San Francisco, and colleagues reported in JAMA Internal Medicine.

For men who consumed the most vegetable fat prostate cancer mortality was 50% lower than those who consumed the least, they found. Vegetable fat intake was also inversely associated with all-cause mortality at 8.4 year follow-up.

Richman and colleagues examined the relationship between post-diagnostic fat intake and lethal prostate cancer and all-cause mortality among 51,529 men aged 40 to 75 years who participated in the Health Professionals Follow-up Study since 1986.

At baseline, information about diet, medication, height, weight, smoking and physical activity information was collected via questionnaire, and information on prostate-specific antigen (PSA) screening was added beginning in 1994.

The final analysis included 4,577 men who were cancer free at baseline and were diagnosed with nonmetastatic prostate cancer from 1986 to 2010. Participants were grouped into quintiles of fat intake, and were separated further based on animal fat, vegetable fat, monounsaturated fat, polyunsaturated fat and trans fat intake.

During a median follow-up of 8.4 years, the researchers identified 315 lethal cancer events (distant metastases or prostate cancer-specific death) and 1,064 deaths.

When comparing the highest versus the lowest quintiles of fat intake, they determined the following rates of lethal prostate cancer per 1,000 person-years:

  • Saturated -- 7.6 versus 7.3
  • Monounsaturated -- 6.4 versus 7.2
  • Polyunsaturated -- 5.8 versus 8.2
  • Trans -- 8.7 versus 6.1
  • Animal -- 8.3 versus 5.7
  • Vegetable -- 4.7 versus 8.7
The risks of lethal prostate cancer and all-cause mortality were significantly reduced with replacement of 10% of energy intake from carbohydrate with vegetable fat (hazard ratios, 0.71 and 0.74, respectively). No association was seen with other fats and lethal prostate cancer.

Higher all-cause mortality was seen with an increase in saturated and trans fats after diagnosis (replacement of 5% and 1% of energy from carbohydrates, respectively). Comparing the highest and lowest quintiles of fat intake, the researchers found a 28.4% vs. 21.4% unadjusted all-cause mortality per 1,000 person years for saturated fat (HR 1.30) and a 32.4% vs. 17.1% all-cause mortality for trans fat (HR 1.25).

“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," the researchers concluded. "The potential benefit of vegetable fat consumption for prostate cancer-specific outcomes merits further research.”

In an accompanying editorial, Stephen J. Freedland, MD, of the Duke University Medical Center, Durham, N.C., cautioned that "in the absence of randomized trial data," the study findings are  "not 'proof' that vegetable intake lowers prostate cancer risk."

He emphasized the importance of avoiding obesity, as it is the only known modifiable prostate cancer risk factor.

"Exactly how this should be done remains unclear, although the data by Richman et al suggest that substituting healthy foods (i.e. vegetable fats) for unhealthy foods (i.e. carbohydrates) may have a benefit. Determining whether this benefit is due to reduced consumption of carbohydrates or greater intake of vegetables will require future prospective randomized trials,” Freedland concluded.



References

  1. Richman EL et al. JAMA Intern Med. 2013; doi: 10.1001/jamainternmed.2013.6536.
  2. Freedland SJ. JAMA Intern Med 2013; doi: 10.1001/jamainternmed.2013.7744.
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