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Can Nutrition Help Fight Cancer?
July 18, 2006 -- CancerCancer patients spend billions a year on vitamins and dietary supplements, but there is no proof that these products -- or other nutritionnutrition strategies -- are effective for treating or preventing the disease, a new analysis shows.
Researchers who reviewed 59 previous studies assessing a wide range of diet-related approaches found little evidence that specific vitamins, supplements, or foods had any impact on disease-free survival, mortality, or cancer recurrence.
The impact of diet on cancer was either disappointing or could not be determined because most studies conducted to date have been of poor quality, the researchers concluded.
"There is no evidence that dietary modification by cancer patients improves survival and benefits disease prognosis," they wrote.
Antibiotics vs. Diet Supplements
The analysis was one of two reports on nutrition and cancer, published in the July 10 issue of the Journal of the National Cancer Institute.
In an original study from the National Cancer Institute and China's Peking University, researchers assessed various interventions thought to prevent stomach cancerstomach cancer or precancerous lesions in Chinese people of Linqu County in Shandong Province, where stomach cancer causes 42% of cancer deaths.
The long-time use (around seven years) of either garlic or vitamin E, vitamin C, and selenium supplements did not result in a reduction in precancerous lesions or in stomach cancers. But a two-week course of antibiotics given to kill Helicobacter pylori bacteria in the stomach was associated with a reduction in precancerous lesions.
H. pylori infection is known to be a major cause of stomach ulcersulcers, and it is believed to play a critical role in the development of stomach cancer.
Researchers concluded that the H. pylori treatment reduced the occurrence of precancerous stomach lesions, which could prevent stomach cancers.
Studies Show No Impact
The analysis of previous nutritionnutrition and cancercancer studies included 25 studies in patients with cancer and 34 studies in patients with precancerous conditions.
Steven Thomas, MD, PhD, and colleagues from the U.K.'s University of Bristol concluded that the vast majority of the studies they looked at were poorly designed or poorly executed.
With this caveat, they reported that none of the interventions studied appeared to have an impact on cancer one way or the other.
Specifically, vitamin A supplementation did not appear to be beneficial in studies involving patients with lung, cervical, head and neck, and skin cancers, and leukemialeukemia.
Other studies examined multivitamins use by patients with a variety of cancers: beta carotene supplementation in patients with skin, stomach, cervical, mouth, and colorectal cancers; fiber for colorectal cancercolorectal cancer; and green tea for esophageal cancer.
"We did not find any conclusive benefit or harm for any of these interventions," Thomas tells WebMD.
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