Study finds widespread vitamin and mineral use among cancer survivors
February 1, 2008Use of vitamin and mineral supplements among cancer survivors is widespread, despite inconclusive evidence that such use is beneficial, according to a comprehensive review of scientific literature conducted by researchers at Fred Hutchinson Cancer Research Center and published Feb. 1 in the Journal of Clinical Oncology.
“Can vitamin and herbal supplements reduce the adverse effects of cancer treatment, decrease the risk of cancer recurrence or improve a patient’s chances of survival? We don’t really know. Research into these matters has been minimal,” said senior author Cornelia (Neli) Ulrich, Ph.D., an associate member of the Hutchinson Center’s Public Health Sciences Division. “While supplement use may be beneficial for some patients, such as those who cannot eat a balanced diet, research suggests that certain supplements may actually interfere with treatment or even accelerate cancer growth,” she said.
In reviewing 32 studies conducted between 1999 and 2006, Ulrich and co-author Christine Velicer, Ph.D., formerly a postdoctoral fellow at the Hutchinson Center (now an epidemiologist at Merck Research Laboratory in North Wales, Pa.), found that many of the nation’s 10 million adult cancer survivors use nutritional supplements.
They found 64 percent to 81 percent of cancer survivors overall reported using vitamins or minerals (excluding multivitamins), whereas in the general population only 50 percent of adults reported taking dietary supplements.
Survivors of breast cancer reported the highest use (75 percent to 87 percent), whereas prostate-cancer survivors reported the least (26 percent to 35 percent). Factors associated with the highest level of supplement use overall included a higher level of education and being female.
The researchers also found that many people initiate the use of vitamins and supplements after cancer diagnosis; between 14 percent and 32 percent start taking them after learning they have cancer.
“Cancer survivors report that they hope to strengthen their immune system with supplement use or gain a sense of control and empowerment,” Ulrich said. However, many cancer survivors who use supplements do not let their doctors know; 31 percent to 68 percent of cancer patients and survivors who use supplements may not disclose this information or their doctors may fail to record it in their charts.
“This is disconcerting and suggests that many physicians may not recognize the importance of understanding whether their patients are taking supplements,” Ulrich said.
Knowing about supplement use is crucial, she continues, because of potential adverse effects. “Evidence clearly suggests the need for caution,” Ulrich said. “Some vitamins, such as folic acid, may be involved in cancer progression while others, such as St. John’s wort, can interfere with chemotherapy. However, we really need more research to understand whether use of these supplements can be beneficial or do more harm than good.”
Until research clarifies the effects of vitamin use in cancer survivors, the authors urge health care professionals to communicate openly with their patients about supplement use. “A simple explanation that medical studies show supplement use may not always be beneficial may help cancer survivors make well-informed decisions,” the authors wrote.
Source: Fred Hutchinson Cancer Research Center
Aug 11, 2009 |
not rated yet |
0
The accumulation of excess free radicals which cause oxidative damage to cells is one of the contributing factors in ageing and has been implicated in many diseases, including cancer. Cancer treatment by radiation and anticancer drugs reduces inherent antioxidants and induces oxidative stress, which increases with disease progression.
While clinical studies on the effect of anti-oxidants in modulating cancer treatment are limited in number and size, experimental studies show that antioxidant vitamins and some herbs selectively induce apoptosis (cell death) in cancer cells but not in normal cells and prevent angiogenesis and metastatic spread, suggesting a potential role for antioxidants as adjuvants in cancer therapy. There is no evidence that antioxidant supplements interfere with the therapeutic effects of chemotherapy agents.
The human immune system is a collection of mechanisms that protects against disease by identifying and killing pathogens and tumor cells. The body's immune system attacks and eliminates not only bacteria and other foreign substances but also cancer cells. Much of the body's protection against cancer is carried out directly by cells of the immune system rather than by antibodies circulating in the bloodstream. For example, the presence of tumor antigens on cancer cells can activate certain white blood cells (lymphocytes, and to a lesser degree, monocytes), which carry out an immunological surveillance, looking for cancer cells and destroying them.
The immune system and antioxidant activity becomes weaker and less efficient with age. This reduced effectiveness helps to explain the rising incidence of cancer and life threatening infections in older people. It is thought that antioxidant supplements could help maintain bodily processes and prevent a significant number of degenerative diseases, especially those involving the immune, cardiovascular and liver functions.
Cancer is much more common in immunosuppressed people. Is the cancer a result of immunosuppression or does the cancer occur as a result of the same thing which caused the immunosuppression? The immune system is obviously very important, it is a natural approach to cancer therapy. Indeed, antioxidant supplementation has shown a remarkable ability to forestall age related changes to the immune system and even reverse many aspects of immune function damage.
Sources:
Block Center for Integrative Cancer Treatment (2007, April 27).
ScienceDaily (Antioxidants May Aid Chemotherapy Patients).
Journal Cancer Treatment Reviews (May, 2007)