More than 80 percent of adults with cancer take at least one dietary supplement or use one or more as a complementary therapy. They include fish oil or omega-3 fatty acids, antioxidants, vitamins and minerals. Still, many physicians warn against supplementing during cancer treatment. What are the dangers, and what is the safest practice?
Oncology patients are at increased risk for weight and lean body mass losses, as well as nutrient deficiencies and not eating enough as a side effect of some therapies such as radiation, chemotherapy and surgery. Because nutritional status influences disease prognosis, tolerance of treatment and quality of life for those diagnosed with cancer, nutrition intervention should be the health professional's primary focus. If food interventions have proven inadequate, dietary supplements may be warranted.
Emerging research suggests some compounds in dietary supplements may help manage side effects of cancer treatment, helping to reduce discomfort caused by certain chemotherapy drugs and radiation.
The Academy of Nutrition and Dietetics' Evidence Analysis Library has found using supplements containing fish oil resulted in weight gain or stabilization in adult oncology patients who experienced weight loss because of treatment, although more research is needed to determine the optimal dose.
The omega-3 fatty acids eicosapentaenoic acid, EPA, and docosahexaenoic acid, DHA, provide anti-inflammatory effects that may help limit the neurotoxic effects of some chemotherapy drugs. However, caution is advised when taking omega-3 fatty acid supplements because side effects are possible, including an increase in bleeding and drug interactions.
Multivitamin and multimineral supplements that provide 100 percent of the Daily Value for nutrients can be considered safe for healthy individuals, but a person undergoing cancer treatment should be assessed by a physician or registered dietitian nutritionist to determine if this type of supplementation is needed based on symptoms and the amount of calories taken in from food. Certain minerals have been shown to reduce side effects of cancer treatment; strontium has been used to relieve bone pain associated with prostate and breast cancers.
Some research on antioxidant supplements has shown benefits, including reduced side effects, but many physicians fear these supplements may reduce the effectiveness of cancer treatment therapy. Study results remain mixed due to the variability in supplement dose, intake and treatment type. Curcumin (present in turmeric) has been shown to inhibit enzymes that stimulate inflammation; preliminary research suggests taking a dietary supplement containing turmeric extract may stabilize disease progression in some patients with treatment refractory colorectal cancer. However, curcumin can cause blood thinning, so caution should be used.
Glutamine powder, a conditionally essential amino acid, is another supplement that may help lessen cancer treatment side effects, such as mouth sores and diarrhea. Research shows it appears safe in doses up to 40 grams per day and appears to decrease the incidence, severity and duration of mouth pain in some patients undergoing chemotherapy or bone marrow transplant.
Many supplement interventions have not been studied in oncology patients, so additional research on safety and efficacy is critical. Research will likely continue to emerge on dietary supplements to help maximize the therapeutic effect while reducing toxicity of chemotherapy drugs.
Patients undergoing cancer treatment often take multiple drugs, which increases their risk of potential interactions. For safety, it's important to disclose all supplements to health care providers and not begin taking new supplements without clearance from an oncologist. In addition, use caution and avoid products that claim to be miracle cures, breakthroughs or new discoveries, as well as those that claim to have benefits but no side effects, or are based on a secret ingredient or method. The American Cancer Society advises, "If a supplement claims to do the same thing as a prescription drug, you are right to be doubtful."