Confusing Research Findings About Diet and Cancer
by Pamela A. Popper, Ph.D., N.D
The Journal of the
National Cancer Institute published
an article online[i] in which
researchers reported eating more servings of fruits and vegetables daily
did not significantly reduce the risk of cancer.
Researchers obtained data
on 478,478 men and women in ten European countries and then followed them for
an average of 8.7 years. They
assessed the association between cancer risk and fruit and vegetable consumption. The researchers concluded that “high
intake of vegetables, and fruits and vegetables combined, was associated with a
small reduction in overall cancer risk.”
I’m not surprised at these
results, and I actually agree with the findings of the researchers. The problem is not that the conclusions
are incorrect; the problem is that the interpretation and reporting of the
results are very misleading.
The term “high intake” as
applied to the fruit and vegetable consumption of the study participants might
lead one to believe that the participants were eating a plant-based diet. But this was not the case.
Scientific American
included this comment in its online article covering the study: “The
researchers concluded that if the results of the analysis can be broadly
applied, upping daily fruit and vegetable consumption by about 150 grams
(equivalent to about one cup of cherry tomatoes or 1.5 medium bananas), from
most dietary levels, could prevent about 2.5% of cancers in most populations.” This is true; an extra serving of
vegetables or fruit daily is not enough to improve anyone’s health outcomes.
This study’s structure and
conclusions are indicative of a major problem plaguing research studies that
attempt to establish a relationship between diet and health. Scientists tend to structure studies
that evaluate the effects of individual nutrients or foods, or small variations
in less-than-optimal diets on health, instead of looking at the totality of the
diet. This is a very important
limiting factor.
Those of us who are
recommending a well-structured plant-based diet as a means for preventing,
stopping the progression of, and even reversing disease, are achieving
spectacular results by teaching people to make sweeping changes in their diets, not by adding or restricting one
food, or by making small changes in their eating patterns. These changes include the elimination
of dairy products; reducing or eliminating the consumption of all other animal
foods (the upper limit being 10% of calories); reducing fat and eliminating
oils; and eating a diet comprised of high-fiber, nutrient-dense, whole plant
foods. Studies have shown that
such a diet is not only protective, but can actually stop the progression of
and even reverse disease.[ii],[iii],[iv]
In this case, the researchers
were attempting to isolate the protective effects of what turned out to be very
small differences in the amounts of fruits and vegetables consumed on cancer
incidence. Although they did factor in consumption of alcohol and smoking, they
did not take into consideration other very important dietary factors. Animal protein has been proven to be a
powerful cancer promoter.[v] Dietary fat, including monounsaturated
and polyunsaturated fat, is also a significant factor in cancer risk.[vi] And the consumption of dairy products
has been linked to several forms of cancer, particularly prostate cancer.[vii] But these factors were not considered.
The dietary habits in this
study were self-reported, and researchers acknowledge limitations in
self-reported information. Without intentionally trying to mislead, subjects
will often misrepresent their eating patterns. People often do not remember what they ate, and are sometimes
hesitant to report consumption of desserts, large portions, second helpings,
and other habits that they think are unhealthy. They will also tend to over-estimate consumption of foods
like fruits, vegetables and whole grains.[viii]
The unfortunate result of studies
of this type is that they confuse people, perpetuating the idea that diseases
like cancer are largely unpreventable and that their diets do not really
matter. This turns people into
helpless victims rather than empowering them to take control of their health.
A well-structured
plant-based diet is effective in reducing the risk of common degenerative
diseases, and has been proven to be a powerful tool in helping sick people to
regain their health. Much research
has already been conducted and published proving this relationship, and medical
journals and the media need to report this information to the general public.
[i] Boffeta, P,
Couto, E, Wichman J, et al. “Fruit and Vegetables Intake and Overall Cancer
Risk in the European Prospective Investigation into Cancer and Nutrition.” JNCI
published online April 6 2010; doi:10.1093/jnci/djq072
[ii] Esselstyn,
CB. Ellis SG, Mendendorp SV et al. “A strategy to arrest and reverse coronary
artery disease: a 5-year longitudinal study of a single physician’s
practice.” J Family Practice 41 (1995):560-568
[iii] Esselstyn
CJ. “Introduction: more than coronary artery disease.” Am J Cardiol. 83 (1998):5T-9T
[iv] Swank RL.
“Effect of low saturated fat diet in early and late cases of multiple
sclerosis.” Mancer 336 (1990):91-103
[v] Campbell,
TCC, The China Study Ben Bella Books
2004 pp 51-67
[vi] Kenneth K
Carroll “Dietary Fats and Cancer.” Am J Clin Nutr 1991;53:1064S-7S
[vii] Chan JM and Giovannucci EL. “Dairy products,
calcium and vitamin D and risk of prostate cancer.” Epidemiol. Revs.
23 (2001):87-92
[viii]
Lee RD, Nieman DC. Nutrition Assessment, 2nd edition. St. Louis, MO Mosby 1996
