Extra
Fruits and Veggies May Not Protect Cancer Survivors
While a healthy diet remains a mainstay of cancer
prevention, eating more than the recommended amounts of fruits, vegetables,
and fiber will not give you added protection against breast cancer
recurrence, says a study in the Journal of the
American Medical Association (JAMA).
This study of breast cancer survivors and cancer
recurrence found no meaningful benefit for women who followed a diet
that encouraged eating at least eight servings of vegetables and fruits,
at least 30 grams of fiber, and no more than 15 percent to 20 percent
of fat.
"These were healthy breast cancer survivors who
were already eating at least five servings of fruits and vegetables,” says
study author John Pierce, Ph.D., at the University of California, San
Diego.
Dr.
Pierce and his team wanted to know “what
happened when you really ramped that up. Some women ate 12 or more
servings of fruits and vegetables a day," he says.
"Clearly, there's a threshold for prevention,” explains
Dr. Pierce. “You don't have to go overboard. The national guidelines
are good enough."
October is National Breast
Cancer Awareness Month. Breast cancer accounts for about one
in three of all cancers diagnosed in women, according to the American
Cancer Society.
More than 200,000 women are diagnosed with breast
cancer in the US each year. More than 40,000 American women die from
breast cancer annually.
Many previous studies have suggested that a diet
full of fruits, vegetables, and fiber, but low in fat, can reduce the
risk of certain cancers.
To assess whether or not improving the diet over
and above what is already recommended could provide a more significant
benefit, Dr. Pierce recruited more than 3,000 women who had already
been diagnosed with and treated for early-stage breast cancer.
The women were between the ages of 18 and 70 and
had no evidence of recurrent breast cancer at the start of the study.
The volunteers were randomly assigned to one of
two groups.
The intervention group included 1,537 women who
were given telephone counseling along with cooking classes and newsletters
that recommended five servings of vegetables, one serving of vegetable
juice, three servings of fruit, at least 30 grams of fiber, and no
more than 15 percent to 20 percent of daily calories from fat.
A comparison group included 1,551 women who were
given printed materials that recommended the current national guidelines
of five servings of fruits and vegetables a day.
Throughout the study, the women were periodically
asked to recall their diet in the past 24 hours. The researchers also
checked for changes in certain substances in the blood that indicate
fruit and vegetable intake. The average follow-up time was 7.3 years.
After four years, the researchers found that vegetable
intake had increased in the intervention group by 65 percent, while
fruit consumption was up by 25 percent.
Fiber intake was also increased, by as much as 30
percent, and fat intake was down 13 percent.
Even with this healthy diet during the study, there
were no significant differences in the rates of breast cancer recurrence.
During the study period, 16.7 percent of women in
the intervention group versus 16.9 percent of women in the comparison
group received a diagnosis of invasive breast cancer.
There were also no statistically significant differences
in mortality. In the intervention group, 10.1 percent of the women
died compared to 10.3 percent in the comparison group.
Does that mean eating well will not help prevent
cancer from returning?
"For women with breast cancer, the answer is out
on whether or not there's a single constituent in the diet that will
help,” says Susan Gapstur, Ph.D., at Northwestern University,
who wrote an editorial in the journal.
“But, for overall health, maintaining a healthy
weight and eating a healthy diet is always good," she notes.
Dr. Gapstur points out that the women in the study
were not able to meet the suggested reduction in fat intake.
Additionally, she says that there appeared to be
some discrepancy in the number of calories consumed. By the end of
the study, the average number of reported calories consumed in the
intervention group was 180 less per day.
Dr. Gapstur says that such a change would have resulted
in weight loss instead of the slight increase that the women experienced.
Rather than just one aspect of diet or lifestyle,
Dr. Gapstur says she believes the next question researchers have to
answer is all of these factors as a whole.
"We have to address the full spectrum - diet, physical
activity, and obesity," she says.
In
the meantime, she notes, "At the
end of the day, it's never wrong or bad to eat healthfully."
Dr. Pierce adds that exercise patterns are also
important and suggested that women exercise moderately for about 30
minutes a day.
Always consult your physician for more information.
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