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Fish oil supplements, and even certain fish, may
hinder the effectiveness of cancer-fighting
chemotherapy, a new study suggests.
Researchers found that consuming the fish herring
and mackerel, as well as three kinds of fish oils,
raised blood levels of the fatty acid 16:4(n-3) in
cancer patients. Experiments in mice suggest that
fish oil may induce resistance to chemotherapy used
to treat cancer, according to a study published
online by JAMA Oncology.
Patients with cancer often adopt lifestyle changes
and those changes often include the use of
supplements. But there is growing concern about the
use of supplements while taking anticancer drugs and
the possible effect on treatment outcomes, according
to the study background.
A 2011 analysis has found that supplementing the
diet with fish oil may prevent muscle and weight
loss that commonly occurs in cancer patients who
undergo chemotherapy. Published early online in
Cancer, a peer-reviewed journal of the American
Cancer Society, the study indicates that fish oil
may help combat cancer-related malnutrition.
Emile E. Voest, M.D., Ph.D., of the Netherlands
Cancer Institute, Amsterdam, and coauthors examined
exposure to the fatty acid 16:4(n-3) after eating
fish or taking fish oil.
In the new study the authors examined the rate of
fish oil use among patients undergoing cancer
treatment, while researchers also recruited healthy
volunteers to examine blood levels of the fatty acid
after ingestion of fish oils and fish. The fish oil
portion included 30 healthy volunteers and the fish
portion included 20 healthy volunteers.
Among 118 cancer patients who responded to a survey
about the use of nutritional supplements, 35 (30
percent) reported regular use and 13 (11 percent)
used supplements containing omega-3 fatty acids,
according to the results.
The study found increased blood levels of the fatty
acid 16:4(n-3) in healthy volunteers after the
recommended daily amount of 10 mL of fish oil was
administered. An almost complete normalization of
blood levels was seen eight hours after the 10-mL
fish oil dose was given, while a more prolonged
elevation resulted after a 50-mL dose, according to
the results.
Eating 100 grams of herring and mackerel also
increased blood levels of 16:4(n-3) compared with
tuna, which did not affect blood levels, and salmon
consumption, which resulted in a small, short-lived
peak.
"Taken together, our findings are in line with a
growing awareness of the biological activity of
various fatty acids and their receptors and raise
concern about the simultaneous use of chemotherapy
and fish oil. Based on our findings, and until
further data become available, we advise patients to
temporarily avoid fish oil from the day before
chemotherapy until the day thereafter," the study
concludes.
For more information
American Cancer Society
Dietary Supplements: What Is Safe?
Dwight Kloth, Pharm.D, director, pharmacy, Fox Chase
Cancer Center, Philadelphia; Christine Metz, Ph.D.,
director, Laboratory of Medicinal Biochemistry,
Feinstein Institute for Medical Research, Manhasset,
N.Y.; Nagashree Seetharamu, M.D., medical
oncologist, North Shore-LIJ Cancer Institute, Lake
Success, N.Y.; Len Lichtenfeld, M.D., deputy chief,
medical officer, American Cancer Society; April 2,
2015, JAMA Oncology, online
Cancer
Fish Oil Fights Weight Loss Due to Chemotherapy -
February 28, 2011
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