Aug. 12, 2008 -- Dietary supplement use among long-term cancer survivors aged 65 and older is very common, according to a new study. But researchers say the practice may pose risks, even though the goal is often to prevent cancer recurrence.
"When you supplement, particularly one specific type of nutrient, you can upset the metabolic balance, how the body processes those nutrients," says Denise Snyder, RD, the clinical trials manager at the Duke University School of Nursing and a study co-author. "Maybe you have too much of one thing, not enough of something else, and that may put your cells at risk."
For the study, published online in the Journal of Cancer Survivorship, Snyder and colleagues asked 753 cancer survivors who were five years or more out from their diagnosis of breast, prostate, or colorectal cancer to answer questions by telephone about their dietary habits and their use of supplements.
Supplements for Cancer Survivors
Seventy-four percent of the survivors reported taking dietary supplements. Of these:
- 80% took a multivitamin.
- 50% took calcium, vitamin D, or both.
- 41% took antioxidants such as vitamins C and E, carotenoids, selenium, and combinations.
- 29% took fish oil or fatty acid supplements.
- 19% took glucosamine, chondroitin, and combinations.
- 18% took botanicals or herbs.
Ninety percent of those who used supplements reported using at least one formulation for more than a year.
The numbers taking supplements were a surprise, Snyder says. "We kind of expected it would be at least half," she tells WebMD.
Supplement use was tied into diet habits and other lifestyle factors, Snyder's team found. In general, the healthier the lifestyle, the more likely the survivors were to take supplements.
Those who ate a high amount of fruits, vegetables, and fiber and less saturated fat than the others tended to use supplements. Nonsmokers and the more highly educated participants were also more likely to report supplement use.
Supplements for Cancer Survivors: Analysis
Turning to dietary supplements after cancer treatment is understandable, says Snyder. Cancer survivors tend to look for something they hope will reduce the odds of recurrence or a new cancer, she says.
"They have often reached out to supplements as a backup to a healthy diet," she tells WebMD. The researchers didn't ask why the cancer survivors took the supplements, she says.
Supplements OK for Cancer Survivors?
While dietary supplements may help fill in nutrients lacking in a person's diet -- particularly in the diets of seniors, which can fall short -- Snyder warns that risks are also associated with supplement use.
"I'm recommending that people not self-supplement," Snyder tells WebMD. The supplements may backfire in preventing cancer recurrence, she says.
The American Institute for Cancer Research and the World Cancer Research Fund recommend against supplements to protect against cancer.
The bottom line, Snyder says: "Talk to your doctor or meet with a registered dietitian, someone who can help you evaluate whether you need a supplement or not."
Supplements for Cancer Survivors: Use Caution
Having a conversation with your health care professional about whether you need a supplement or not is wise, whether you are a cancer survivor or not, says Len Lichtenfeld, MD, deputy chief medical officer for the American Cancer Society.
Because the people in the study were all five years removed from their cancer diagnosis, he says, "there is no need to treat cancer survivors at this point in their journey any differently" than non-survivors.
More study is needed on supplement use among survivors, he says. "What isn't known is supplement use's effect on cancer relapse; that is up in the air."
Many of the supplements taken by the survivors, such as multivitamins, calcium, vitamin D and fish oil, probably pose little risk when not taken in large doses, says Christine Gerbstadt, MD, RD, a spokeswoman for the American Dietetic Association. "If you really think you need a supplement, you probably can't go wrong taking a multivitamin, calcium and D, and fish oil. But if you are eating two to three fish servings a week, you probably don't need the fish oil."
There are little data on the role of supplements in helping cancer survivors remain cancer free, says Andrew Shao, PhD, vice president of scientific and regulatory affairs for the Council for Responsible Nutrition, a trade group based in Washington, D.C. “Most of the data on nutrient intake in cancer risk is on primary prevention,” that is, preventing a first cancer, he tells WebMD.
For that reason, he says, “The Council does not have a specific recommendation on supplements for cancer survivors.”
But he agrees with Lichtenfeld that at the five-year mark the advice is probably no different for survivors than for the general population.
Of the supplements used by the older cancer survivors in the study, he says: “There is no reason to think these would be harmful.”