The Positive Effects of Monounsaturated
Fat on Prostate Cancer
In both the US and Canada, prostate cancer is the
most commonly diagnosed non-dermatological cancer among men. A relatively
low incidence of prostate cancer has been found amongst southern European
men who traditionally consume what nutritionists often refer to as a
typical "Mediterranean" diet.
It is believed that this interesting observation is
due to the unique characteristics of this diet that includes low intakes
of fat from animal sources, a high proportion of monounsaturated fats
(MUFAs)(ie. oleic acid) from vegetable oils such as canola oil and olive
oil, as well as the consumption of relatively high levels of fruits
and vegetables. Two recent studies have investigated the effect of dietary
monounsaturated fatty acids on the survival rate of individuals with
prostate cancer, as well as on the risk of developing prostate cancer.
In a study by Norrish and coworkers, the diets of
317 individuals with prostate cancer were compared to diets of 480 control
subjects who did not have the disease. The study was conducted in Auckland,
NZ. A food frequency questionnaire was used to collect data on MUFA
consumption, as well as other dietary variables. The very positive results
indicated that increasing dietary levels of MUFA-rich vegetable oils
such as canola oil, was associated with a significant reduction in prostate
cancer risk. In addition, it was observed that those participants who
consumed more than 5.5 mL of MUFA-rich vegetable oils per day also had
a high dietary intake of vegetables, lycopene, vitamin E, selenium,
and omega-3 fish oils. These dietary factors may also have contributed
to the reduction in prostate cancer risk.
The association between dietary caloric, fat, and
vitamin A intakes and survival from prostate cancer was assessed in
207 and 201 prostate cancer patients from Toronto and Vancouver, Canada,
respectively, by Kim and co-workers. The researchers reported a strong
significant inverse relationship between MUFA intake and the relative
risk of dying from prostate cancer.
With regard to dietary intraventions aimed at reducing
prostrate cancer, it is important to note that although these findings
were highly significant in terms of MUFA consumption and prostate cancer
risk and survival, the authors state that other parameters must be considered.
First, it is hypothesized that the consumption of vegetable oils high
in MUFA also implies the consumption of plant constituents such as polyphenols
that provide antioxidant activity. Antioxidants within the oil may have
a protective effect on prostate cancer that is independent of the MUFA
content. Second, hormones are believed to be intimately involved in
the pathogenesis of prostate cancer, and dietary factors including MUFA
intake may influence hormonal levels. And finally, it has been found
that diets high in MUFAs are correlated with higher dietary fruit and
vegetable intake, as well as lower consumption of animal fat, which
in turn may also contribute to the positive effects found. Regardless
of the mechanism of action, it is apparent that increasing dietary MUFA
from vegetable oils such as canola oil can only result in beneficial
effects with regard to prostate cancer risk and survival.
Norrish, A.E., et. al. C. 2000. Men who consume vegetable
oils rich in monounsaturated fat: their dietary patterns and risk of
prostate cancer (New Zealand). Cancer Causes and Control. 11(7): 609-615.
Kim, D.J., et. al. T.E. 2000. Premorbid diet in relation
to survival from prostate cancer (Canada). Cancer Causes and Control.
11(1): 65-77
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