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Diet changes may not help fight cancer, studies find
July 23, 2006
Courtesy Journal of the National Cancer Institute
and World Science staff
Two new studies have found what their
authors say is scant evidence that changes in diet help cancer patients
survive longer or avoid recurrences of the disease.
Many cancer patients and their families see hope in foods popularly
believed to help fight cancer, including nutritional supplements. And
studies indicate that eating plenty of vegetables and fruits helps prevent
|Vegetables and fruit have been found to help
prevent certain cancers, but new research has found that healthy diets
don't significantly aid in treating the diseases. (Image courtesy NASA
While not disputing that healthy eating has major benefits, the authors of
one study said such diets may have little relevance in treating cancer
itself. Some nutritional supplements may even be harmful, they added.
The study consisted of an analysis of 59 previous studies of specific
dietary modifications. There was little relationship between diet and
survival or prognosis, the authors said.
The other study found that neither garlic nor vitamin supplements, both
popularly thought to help fight cancer, delays the progression of
pre-cancerous gastric lesions to cancer.
Both studies appear in the July 19 issue of the Journal of the National Cancer
In the first, Steven Thomas of the University of Bristol, U.K. and
colleagues investigated a range of dietary changes among patients
previously diagnosed with cancer or pre-cancerous lesions. The changes
included increased intake both of packaged nutritional supplements and of
foods generally considered healthy, such as high-fiber meals.
There was little evidence that these had any effect on disease-free
survival, mortality, or recurrence, Thomas’ team argued, adding that it
was hard to gauge the effects at all because of a dearth of high-quality
“The large personal expenditure on supplements and dietary modifications
by patients with cancer demonstrates an urgent need to understand their
effects on cancer outcomes. This vulnerable group of people need to be
better informed as diet is one of the few areas of their lives where they
may feel that they have some control,” the researchers wrote.
“Encouraging a healthy diet is certainly important because many patients
with cancer and preinvasive lesions will live a long time and may die of
other diseases related to diet,” they continued. But without better
evidence, they added, clinicians shouldn’t tell patients that a healthy
diet is “a priority in management of cancer itself.”
The second study found that garlic and vitamin supplements did not reduce
the prevalence of precancerous lesions or gastric cancer. But treatment to
kill the germ Helicobacter pylori, which causes the cancer, may
provide benefits, it found.
In Linqu County, China, gastic cancer causes 42 percent of all cancer
deaths, and the bacteria infect two-thirds of adults, said the scientists,
Wei-Cheng You of the Beijing Institute for Cancer Research and colleagues.
They tested 3,365 Chinese adults ages 35 to 64 in the county. The
researchers found that antibiotics reduced the severity and progression of
pre-cancerous gastric lesions. Long-term vitamin and garlic
supplementation, though, had no effect on the incidence of gastric cancer
or progression of pre-cancerous lesions, the researchers said.
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