Extra fruits, vegetables in diet
does not stop breast cancer return
19 July, 2007:
A diet low in fat and high in fruits
and vegetables may not necessarily
prevent the return of breast cancer.
A large, seven-year experiment
involving over 3,000 women,
commissioned by the United States
government, found no benefit from an
extra-large diet of vegetables and
fruits over the US-recommended
servings of five fruits and vegetables
a day – which is more than what most
Canada’s Food Guide recommends 7 to 10
servings a day for adults between 19
and 50 years of age.
Researchers noted that none of the
survivors of breast cancer lost weight
on either diet, leading some experts
to suggest that weight loss and
exercise should be the next frontier
for cancer prevention research.
The study appears in the July 18,
2007, issue of the Journal of the
American Medical Association.
“It sends us back to the drawing
board,” says Susan Gapstur of
Northwestern University’s Feinberg
School of Medicine, who was not
involved in the new study, but
co-wrote an accompanying editorial in
For now, the message for breast cancer
survivors is that they do not need to
eat too much vegetables and fruits,
The research was started by a
$5-million US grant from John Walton,
the late heir of Wal-Mart, and an
additional $30 million from the
National Cancer Institute.
Earlier research on whether a healthy
diet prevents breast cancer has shown
mixed results. The new study was
designed to be more rigorous.
In this experiment, all the women had
been successfully treated for
early-stage breast cancer. Their
average age was 53 when the study
In one group, 1,537 women were
randomly assigned to a daily diet that
included five vegetable servings,
three fruit servings, 16 ounces (about
500 ml) of vegetable juice and 30
grams of fibre. In most cases, a
serving equalled a half-cup (125 ml).
French fries and iceberg lettuce could
not be counted as vegetables.
The women were allowed to eat meat,
but were told to get no more than 15%
to 20% of their calories from fat, a
goal they ultimately were unable to
As a comparison, another 1,551 women
were assigned to get educational
materials about the importance of
eating five servings of fruits and
vegetables a day.
The women in both groups kept food
diaries regularly, but not daily,
throughout the study.
During the next seven years, the
cancer returned in about the same
proportion of women in both groups –
256 women (16.7%) of the women on the
special diet and 262 women (16.9%) in
the comparison group. During that
time, about 10% of the subjects in
both groups died, most of them from
According to the researchers, it did
not matter whether the breast cancer
was the most common type – fueled by
hormones – or not; the special diet
did not prevent the cancer from
returning. The results run counter to
a previous study by different
researchers that suggested low-fat
diets may help prevent the return of
the type of breast cancer that is not
linked to hormones.