Nonprescription Nutritional Supplements for Patients With Cancer

In the United States, cancer is responsible for more than half a million deaths annually and is the second-leading cause of death, after cardiovascular disease, according to the CDC.¹ Pharmacists can be helpful in educating patients regarding the safe use and proper selection of nutritional supplements, and they also play a key role in identifying possible drug—micronutrient interactions and contraindications. Pharmacists can be a vital resource in guiding patients with cancer who ask about the use of nutritional supplements, especially those undergoing chemotherapy and radiation treatments. Pharmacy shelves are lined with an abundance of nutritional supplements formulated as single-entity, combination, multivitamin/mineral, or all-natural supplements, and for some patients, the selection of these supplements may be overwhelming, especially for those with medical conditions or who are taking other medications. Although the use of nutritional supplements is generally safe when they are taken properly, many patients are unaware of the potential for drug–nutrient interactions or contraindications, and they sometimes take more than the recommended daily amounts (RDA) of these nutrients. Patients with cancer frequently experience symptoms related to the disease itself, as well as adverse effects linked to chemotherapy and radiation therapy.² Adverse effects may include loss of appetite, nausea, and vomiting. These factors may unfavorably affect overall quality of life, which may lead some patients with cancer to inquire about the use of nutritional supplements to boost energy and appetite, ensure adequate intake of essential nutrients, and/or enhance their immune systems.²

Over the years, there has been a continuing debate about the use of nutritional supplements for patients with cancer. Some health care advocates have expressed concern about the use of nutritional supplements, especially when used in conjunction with nonprescription and prescription medications, because of the potential for interactions that may cause toxicity or decrease therapeutic efficacy.^3,4 There are a growing number of studies demonstrating the number of interactions between herbs and supplements with chemotherapy and radiation therapy, according to the National Cancer Institute.⁵

The results of recent studies have shown that more than 80% of patients with cancer use supplements, including complementary and alternative medicine. Of that group, 75% use supplements without informing their oncologists.⁶ The results of a study published in the Journal of the Academy of Nutrition and Dietetics reported that adults were 2.5 times more likely to take a nutritional supplement in conjunction with a prescription medication than adults without a diagnosed medical condition.^4,7 Moreover, many patients are motivated to initiate nutritional supplements after receiving a cancer diagnosis, with cancer survivors commonly continuing to use dietary supplements for numerous reasons.^4,8 Results from a survey published in the Journal of Clinical Oncology showed that between 14% and 32% of individuals started using nutritional supplements after receiving a cancer diagnosis, and many elect to use these supplements, including herbal products, to boost their health, improve their nutrition, or reduce adverse effects associated with cancer treatment.^9,10 An estimated 56.2% of patients with cancer surveyed said that they use nutritional supplements because taking them was something they could do to help themselves.⁷ The results of some studies have also suggested that patients receiving chemotherapy, either because their cancer was more advanced or because they were under greater stress, were more likely to use nutritional supplements to relieve stress.^11-15

Additionally, results from a 2014 survey showed that less than 50% of oncologists discuss the risks and benefits of supplement use with their patients.¹⁶ It is also worth noting that of those patients with cancer using supplements, just 23% of supplements were reported to be used upon the recommendation of a physician or other health care provider.^4,8 Many patients also use natural or alternative supplements without consulting their primary health care providers.^4,8 Results from a recent study similarly reported that more than 50% of patients with chronic diseases or cancer may use nutritional supplements, and because these individuals are likely to take multiple medications, there is an increased risk for drug—supplement interactions.¹⁷ A drug—supplement interaction is considered to be clinically significant if it alters a pharmacotherapeutic response or compromises a patient’s nutritional status.¹⁸

Expert guidelines from the American Cancer Society, the American Institute for Cancer Research, and the World Cancer Research Fund advise against the use of supplements in patients with cancer and advocate obtaining nutrients from foods whenever possible. However, this is not always a feasible option.^19-21 Despite this recommendation, the self-use of nutritional supplements is extensive among patients with cancer, and it is not uncommon for some clinicians to recommend them when warranted and appropriate. Data collected between 2003 and 2010 in the Intergroup Phase III Breast Cancer Chemotherapy trial showed that an estimated 48% of patients were taking multivitamins; 20% were taking supplements containing vitamins C and D and n-3 oils; 15% were taking vitamins E, B₆, and folic acid; and 34% were taking calcium.^19,22 Clinicians also advised 33% to start taking a supplement during treatment, 10% advised discontinuing the use of one, 7% advised stopping all except a multivitamin, and 51% received no advice.^19,22

There is a lack of proven clinical evidence regarding the benefits or risks of taking nutritional supplements for patients with cancer, possibly accounting for the inconsistent or lack of advice from many clinicians regarding supplement use.¹⁹ Many clinicians recommend that patients use multivitamin and mineral supplements that contain only the RDA. However, an estimated 33% of the US population and an estimated 50% of patients with cancer use supplements that contain larger amounts than the RDA.^19,23 The results of other recent studies show that more than 80% of patients with cancer use nutritional supplements with herbs and vitamins as the most popular choices and that 75% of these patients never disclose this information to their oncologists.^11,24

What the Clinical Studies Say

Various clinical studies have investigated the use of nutritional supplements. The results of clinical studies related to antioxidants have shown that they may have varied effects on chemotherapy toxicity, but unfortunately, there are no clinical data on the outcome.¹⁹ Vitamin D deficiency is quite common among patients with cancer, and continuing phase III trials are exploring the effect of vitamin D on outcome as well as ideal vitamin D and calcium intakes for bone health.¹⁹ The use of antioxidants has been studied in patients with cancer, primarily to measure their protective effects against cancer to improve patient outcomes and then to decrease oxidative damage from chemotherapy and radiotherapy and the dose-limiting toxicities of therapies.¹⁹ Moreover, results from large-scale, randomized cancer prevention trials have been inclusive, and some have reported noteworthy adverse as well as beneficial effects.¹⁹ Even after more than 2 decades of research investigating the use of dietary antioxidant supplementation during conventional chemotherapy and radiation therapy, there is still debate regarding the efficacy and safety of supplementation.^25,26 Several randomized clinical trials have demonstrated that the concurrent administration of antioxidants with chemotherapy or radiation therapy diminishes treatment-related adverse effects.²⁶ Some data indicate that antioxidants may protect tumor cells as well as healthy cells from oxidative damage generated by radiation therapy and some chemotherapeutic agents.²⁶ However, other data suggest that antioxidants can protect normal tissues from chemotherapy or radiation-induced damage without diminishing tumor control.²⁶

Results of studies have also shown that supplements such as St John’s wort, garlic extract, and echinacea are examples of those supplements that are believed to pharmacokinetically interact with chemotherapy agents (Table 1), according to the National Cancer Institute.^29-31 Additionally, supplements containing Panax ginseng and green tea have all been found to have toxicities and to interact with various medications, including chemotherapy agents.²⁹ One study of patients with cancer estimated that 28% were at risk of nutrient interactions, and an estimated 46% of these at-risk patients were being treated with curative intent.^29,31 A more recent study of patients with ovarian cancer estimated that 40% were at risk of an interaction between a supplement and their chemotherapy (Table 2).^29,32

On the other hand, research from clinical trials shows that nutritional supplements may aid in managing certain adverse effects related to chemotherapy.³² For example, American ginseng and astragalus root, which are often used in traditional Chinese medicine, may aid in lessening some of the adverse effects associated with chemotherapy such as fatigue.³² Additionally, supplements such as glutamine, vitamin B₆, vitamin E, and omega-3 have been evaluated as potential treatments for peripheral neuropathy when appropriate. However, more research is needed.³² Patients should be advised to discuss the use of these supplements with their oncologists.

Role of the Pharmacist

Although obtaining essential nutrients via dietary means is the optimal approach, it is not always a feasible option for some patients, and as a result, some patients elect to use nutritional supplements. Pharmacists can be an essential resource for those battling cancer and should be ready to answer patients’ questions. Prior to recommending the use of any supplements, pharmacists should always advise patients with cancer to seek counsel from their oncologists to ascertain appropriateness. For example, some dietary supplements can cause skin sensitivity and severe skin reactions when taken during radiation treatment, and patients may not be aware of this issue.³² Patients should be encouraged to have an open discussion concerning the use of nutritional supplements, especially during chemotherapy and radiation, with their oncologists. Patients with cancer are being told to take only the recommended daily doses of supplements because evidence from human clinical studies that confirm their safety and benefits is limited.

During counseling, it is also critical that pharmacists remind patients of potential drug—nutrient interactions, contraindications, and adverse effects, as well as the significance of notifying their oncologists about all the supplements that they are taking, including those labeled as natural or alternative and complementary products. Patients with cancer who elect to use nutritional supplements should be reminded that these should be used only under the supervision of an oncologist and to always discuss the use of these supplements before taking them, especially during chemotherapy and radiation (Table 3).

Yvette C. Terrie, BSPharm, RPh, is a clinical pharmacist and a medical writer based in Haymarket, Virginia.

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