Our Members Asked:
Do any supplements reduce the side effects of chemotherapy? Should any be avoided?
As discussed below, certain supplements have been shown to reduce side effects associated with chemotherapy, but the evidence is far from conclusive. Furthermore, be aware that some cancer experts suggest avoiding all dietary supplements until cancer treatment is completed. If you are undergoing treatment for cancer, consult your physician before taking any supplement.
Supplements that may have benefit
There is mixed evidence as to whether ginger helps during chemotherapy treatment. Some studies have shown it can reduce nausea and vomiting in women undergoing chemotherapy but may increase these symptoms in men.
One study suggests that taking the probiotic Lactobacillus rhamnosus GG may reduce the risk of chemotherapy-induced diarrhea.
Supplementing with whey protein may help to maintain muscle during chemotherapy.
Some, but not all studies, have found that drinking a suspension containing the amino acid glutamine can reduce oral mucositis (painful mouth irritation) and/or skin rash in people undergoing chemoradiotherapy for head and neck cancer. Glutamine may also help reduce the need for antidiarrheal medication in people undergoing chemotherapy, although the evidence is mixed (Sun, Asia Pac J Clin Nutr 2012). While there is some concern that glutamine may promote the growth of tumors, avoiding glutamine in food and supplements is unlikely to help slow cancer growth (see below).
A study in children suggests that milk thistle may reduce liver toxicity associated with chemotherapy, although the benefit was seen only after chemotherapy treatment was complete.
Low blood levels of magnesium (hypomagnesemia) are common among people being treated for cancer with certain chemotherapy drugs, including cisplatin (Platinol), carboplatin (Paraplatin), doxorubicin (Doxil), and others. Other medications given during chemotherapy (e.g., certain antibiotics and diuretics) can contribute to this. Oral magnesium supplements may be effective for boosting magnesium levels in chemotherapy patients with mild hypomagnesemia who do not have symptoms. In severe cases or among people displaying symptoms of hypomagnesemia, magnesium supplements are considered ineffective and magnesium is given intravenously (Workeneh, Kidney360 2021; Saif, J Support Oncol 2008).
Although higher magnesium intake has been linked with a lower risk of nerve damage after oxaliplatin chemotherapy (Wesselink, Nutrients 2018), there does not appear to be any evidence that magnesium supplements prevent chemotherapy-induced nerve damage and some experts advise against the use of intravenous magnesium along with calcium to prevent this condition (Loprinzi, J Clin Oncol 2020).
More details about each of these findings can be found using the links above to the respective reports on ConsumerLab.com.
Supplements that may interact with chemotherapy or increase risks
As discussed below in more detail, experts advise discontinuing use of certain supplements — including supplements with antioxidant effects, vitamin B-12 and iron (unless taken to treat deficiency or used as part of chemotherapy protocol), Miracle Mineral Solution, amygdalin, soy or other ingredients with estrogenic potential, and supplements with potential for increasing the risk of bleeding or nerve damage — during chemotherapy due to possible toxicity of the supplement, potential for interacting with chemotherapy, and potential for increasing cancer growth (D'Andre, Support Care Cancer 2022).
Fish oil supplements have been shown to help to prevent weight loss during chemotherapy, however, they may also interfere with chemotherapy treatment. Therefore, fish oil supplements should not be taken within 48 hours of chemotherapy (from the day before chemotherapy until the day after).
Soy isoflavones may not be safe for women with estrogen receptor-positive breast cancer.
Men with prostate cancer and/or undergoing treatment for prostate cancer should not take high doses of selenium, as this may increase the risk of death from prostate cancer.
Although some research suggests certain antioxidants may help reduce chemotherapy side effects, there is also concern that they may decrease the effectiveness of chemotherapy (Block, Integr Cancer Ther 2004). For example, a study among women with breast cancer in Germany found that those who supplemented with antioxidants during chemotherapy or radiation therapy were 64% more likely to die over a median follow-up period of six years than women who did not use antioxidants during therapy. The chance of surviving without a recurrence was also much lower among the supplemented group. The results suggest that antioxidant supplements should be avoided or used with caution during chemotherapy or radiation therapy. In this study, vitamins A, C, and E, zinc, and selenium, as well as multivitamins were grouped as antioxidants. It is speculated that antioxidants may interfere with cancer-killing properties of anticancer therapies by reducing the effects of reactive oxygen species those therapies intentionally produce (Jung, Am J Clin Nutr 2019). Furthermore, a study in the U.S. among 1,340 women with breast cancer who were receiving chemotherapy (cyclophosphamide, doxorubicin or paclitaxel) found that use of vitamins A, C, or E, carotenoids (beta-carotene, lutein, etc.), or CoQ10 was associated with increased risks of cancer recurrence (41% increase) and cancer death (40% increase). Although not antioxidants, B-12 supplementation was associated with much poorer rates of disease-free and overall survival and iron was associated with a 91% higher risk of cancer recurrence. Multivitamin use, however, was not associated with increases in any cancer risks (Ambrosone, J Clin Oncol 2020).
St. John's wort should be avoided during chemotherapy because it can interfere with certain chemotherapy drugs. Vitamin B-12, vitamin E and alpha-lipoic acid have shown no benefit for chemotherapy-related nerve damage, and experts recommend against using these supplements for preventing this condition in people treated with neurotoxic agents (e.g., taxanes, oxaliplatin, vincristine). Furthermore, vitamin B-12 has been linked with poorer disease-free survival and overall survival rate among breast cancer patients.
Among breast cancer patients, use of iron supplements before or during chemotherapy has been linked with a higher risk of recurrence.
Acetyl-L-carnitine may worsen chemotherapy-related nerve damage.
Miracle Mineral Solution is promoted by some distributers as a remedy for cancer, but experts advise avoiding this supplement for cancer treatment or any other condition due to its lack of evidence of benefit and potential toxicity when consumed.
Amygdalin is sometimes promoted for the treatment of cancer, but this ingredient can be toxic. Amygdalin (also called Laetrile, mandelonitrile, or "B17") is a compound derived from bitter apricot kernels. When ingested by humans, this compound can release cyanide. Consuming low or moderate amounts of cyanide can have serious adverse effects, and higher amounts can be fatal.
Research has found that cancer cells need glutamine to grow and spread (Nguyen, Cancer Drug Resist 2018). Consequently, some experts recommend avoiding glutamine supplements during chemotherapy to avoid promoting the growth of cancer (D'Andre, Support Care Cancer 2022). However, laboratory studies have shown that various types of tumors have developed adaptations to survive and grow even in environments with limited glutamine (Zhang, EMBO J 2017), suggesting that restricting intake of glutamine from supplements or the diet may not be beneficial.