Protecting Your Recovery: A Guide To Supplements To Avoid With Cancer

As part of their treatment regime, cancer patients often include supplements in their diet. A study published in 2005 by the journal Support Cancer Care found that 73% of 227 cancer patients had used some type of dietary supplement in the 30 days before they were surveyed.

While supplements might seem like a healthy option for cancer patients, they can lead to problems. In the Support Cancer Care study, 25% of the patients who’d had a chemotherapy treatment in the past 30 days had consumed at least one herbal supplement that’s been linked to negative reactions.

The nonprofit Gateway for Cancer Research advises that people undergoing cancer treatment consult a clinical pharmacist or another qualified health care provider who understands natural supplements and cancer care to ensure any supplements they use are beneficial rather than harmful.

“Supplements can be useful when taken under the guidance of a trained health care professional,” Daniel Kellman, director of naturopathic support and rehabilitation services at City of Hope Atlanta, is quoted as saying in a Gateway for Cancer Research article. “But what many people, especially cancer patients, may not know is that some herbal remedies can actually work against them.”

City of Hope Atlanta is a cancer research and treatment center.

So, if you’re a cancer patient, which dietary supplements should you avoid — particularly if you’re undergoing chemotherapy?

According to the American Cancer Society, many cancer experts advise avoiding dietary supplements altogether while undergoing cancer treatment. But if you want to take a supplement, check with your cancer care providers before doing so.

Supplements to avoid with cancer

Here are supplements you generally should stay away from if you have cancer, according to Gateway for Cancer Research and City of Hope.

1. St. John’s wort

St. John’s wort boosts production of enzymes responsible for metabolizing drugs, including chemotherapy. Depending on the drug, this can become a toxic situation if the drug is rapidly metabolized to its active form and the drug accumulates or can make the drug ineffective if it is rapidly metabolized to its inactive form.

2. Grapefruit

Grapefruit has the opposite effect of St. John’s wort. It decreases production of enzymes responsible for metabolizing drugs, including chemotherapy. Depending on the drug, this can become a toxic situation if the drug is not metabolized to its active form and the drug accumulates or can make the drug ineffective if it is supposed to be metabolized to its active form.

3. Echinacea, garlic, ginkgo, ginseng and kava

Like St. John’s wort and grapefruit, echinacea, garlic, ginkgo, ginseng and kava can harm the body’s ability to metabolize chemotherapy drugs.

5. Açai berry

Açai’s antioxidant features may decrease the effectiveness of some chemotherapy and radiation treatments.

6. B17

Often derived from apricot kernels, B17 is touted as a cancer-fighting supplement. However, scientific evidence has shown B17 isn’t effective in treating cancer. In addition, apricot kernels contain amygdalin, which transforms into cyanide in the body and can lead to cyanide poisoning.

7. Graviola or soursop

Graviola leaves and soursop fruit are commonly used in the Caribbean, Mexico, Central America and South America, and they’re touted as having anti-cancer properties. However, the Federal Trade Commission has debunked that claim. Graviola and soursop have been tied to greater odds of being diagnosed with movement disorders similar to Parkinson’s disease.

8. Green tea extract

Green tea extract can interfere with a drug called bortezomib, which is frequently prescribed to treat multiple myeloma.

Other supplement concerns for people with cancer

Aside from the previously listed supplements, polyphenols in many herbs and teas may affect enzymes that help process chemotherapy drugs. This might prompt resistance to chemotherapy drugs like anthracyclines, tamoxifen, taxanes, tyrosine kinase inhibitors, vinblastine and vincristine.

In addition, beta carotene, vitamin D and vitamin E may help the body attack cancer cells, but they also may limit the success of cancer treatments.

Further complicating matters, folic acid, probiotics and selenium are considered safe for cancer patients being treated with chemotherapy, but they might cause side effects. These side effects include diarrhea, nausea, vomiting and fatigue (selenium); neurological issues for people who have pernicious anemia, or difficulty absorbing vitamin B12 (folic acid); or harmful bacteria or fungi in the blood (probiotics).

Can dietary supplements help fight cancer?

The National Cancer Institute says some dietary supplements, such as vitamin C, oral glutamine and melatonin, may help combat side effects of cancer treatment.

City of Hope adds fish oil to the list, as research suggests it may help relieve cancer-related joint pain, muscle aches, neuropathy and depression. Additionally, the omega-3s in fish oil might aid recovery from cancer surgery.

“Before you buy a dietary supplement, it’s important to read the label carefully. Look at the claims, packaging, ingredients and directions for use,” the American Cancer Society says. “It can be easy to misread the claims that are being made about products.”

^†These statements have not been approved by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent disease.