Vegetable Fats May Reduce Risk of Death in Prostate Cancer Patients

A new study shows that men diagnosed with prostate cancer may do better by substituting carbohydrates and saturated fats with plant-based fats such as those found in nuts and olive oil.

The prospective study of 4,577 men with non-metastatic prostate cancer showed that those men who consumed more vegetable fats after their diagnosis had a lower risk of developing metastatic prostate cancer and dying from the disease compared to men who consumed a diet with more saturated and animal fats. The results are reported in JAMA Internal Medicine.

The researchers tracked the study participants after they were diagnosed with localized prostate cancer as part of a large health workers study that started in 1986. Men were followed every 2 years with questionnaires on their dietary habits. Within a median of 8.4 years, 315 men died of their prostate cancer and 1,064 men died on the study from other causes.

Erin L. Richman, ScD, of the University of California, San Francisco (UCSF), and colleagues examined the connection between fat intake and prostate cancer and any-cause mortality.

Analysis of the participants based on lowest and highest fat consumption quartiles showed that replacing just 10% of calories from carbohydrates with those from vegetable fat was associated with a 29% lower risk of dying from prostate cancer (P = .04). This replacement translated to a 26% lower risk of dying from any cause. A similar association was found when 10% of saturated, animal fats were replaced with vegetable fats, although this result was not statistically significant.

Men who had the highest consumption of vegetable fats among the study participants had a 36%  lower risk of dying from their prostate cancer, but the differences were also not statistically significant.

Replacing just 5% of calories from carbohydrates with saturated fats or 1% with trans fats was linked to a 30% higher risk of dying during the period of the study (P = .02).

The potential benefit of vegetable fats for prostate cancer patients suggested by the study warrants further research, said the authors.

Previous smaller studies have suggested a link between prostate cancer death and animal fat intake. A Canadian study of 384 men, mentioned in the study by Richman and colleagues, showed saturated fat intake before diagnosis was associated with a higher risk of prostate cancer death. Conversely, a greater vegetable fat intake was linked to a lower risk of advanced prostate cancer at diagnosis.

The influence of diet and balance of vegetable and animal fat sources on prostate cancer initiation and progression still remains to be teased out. What type of meat and how it is cooked may influence patient outcomes and has been little studied. It is also not clear which components of vegetable fats are in fact beneficial. The authors suggest that vegetable oils and nuts are linked with lower insulin and inflammation and could account for the potential benefit. As suggested by Steven Stephen Freedland, MD, urologist at Duke University Medical Center in Durham, North Carolina, who wrote an accompanying commentary on the study, it is not clear if vegetable fats are in fact beneficial, whether carbohydrates are just harmful, or whether it is a combination of both. According to Freedland, future prospective trials should address this key issue.