January 19, 2023 – Cancer dietitian Lisa Cianciotta often finds herself sitting across from a patient who suddenly pulls a bottle of antioxidant supplements out of her bag and says: “My friend told me it works great,” or “I read on the internet that it’s supposed to be really good for cancer.”
Although taking an antioxidant pill seems harmless, Cianciotta, a clinical dietitian who works with cancer patients at NewYork-Presbyterian Hospital in New York, is well aware that this popular dietary supplement can interfere with a patient’s radiation therapy or chemotherapy. .
But many cancer patients believe that these over-the-counter vitamins, minerals, or herbal remedies will help them, and most use at least one dietary supplement alongside their cancer treatment.
And that leaves Cianciotta with an awkward conversation ahead of her.
Drug-supplement interactions are complex, often varying by the type of supplement, cancer, and treatment, and can do more harm than good. Popular dietary supplements can, for example, reverse the effects of cancer treatment, making it less effective, or increase serious side effects, such as liver toxicity. But in other cases, supplementation, such as vitamin D for patients who are deficient, may be beneficial, Cianciotta says.
These drug-supplement interactions can be difficult to identify, given that more than two-thirds of physicians are unaware that their patients are using supplements.
Here’s what patients need to know about the potential risks of using supplements during treatment and how oncologists can address this thorny and often misunderstood topic with patients.
The complex landscape of drug supplements
The list of food supplements and how they can interact with different treatments and types of cancer is long and nuanced.
But some supplements seem to affect cancer treatments independently of other things and should be avoided. Any supplement that strongly alters body levels of the cytochrome P450 protein is an example of this. This group of enzymes plays a key role in drug metabolism, including chemotherapy and immunotherapy agents.
Some supplements — including St. John’s wort extract — can decrease or increase cytochrome P450 activity, which can then affect blood levels of cancer drugs, says William Figg, PharmD, associate director of the Center for Cancer Research at the National Cancer Institute in Bethesda, MD. Studies show, for example, that this common herbal supplement can increase cytochrome P450 activity, resulting in lower levels anti-cancer drugs.
Aside from drug metabolism, patients with hormone-related cancers, such as breast and prostate cancer, should avoid dietary supplements that may alter testosterone or estrogen levels, Figg says. The evergreen ashwagandha shrub, for example, is marketed to reduce stress and fatigue, but may also increase testosterone levels – a potential problem for people with prostate cancer receiving androgen deprivation therapy, which lowers testosterone levels.
Many oncologists advise patients against using dietary supplements with antioxidants – especially turmeric and green tea extract – while receiving radiotherapy and certain chemotherapy. These therapies work by creating an abundance of highly reactive molecules called free radicals in tumor cells, which increase stress within those cells, ultimately killing them. Antioxidants, in theory, can neutralize this effect, says Skyler Johnson, MD, radiation oncologist at the Huntsman Cancer Institute at the University of Utah in Salt Lake City. Some studies suggest that antioxidant supplements may lessen the effects of radiation therapy and chemotherapy, although the evidence is mixed.
Certain dietary supplements, including high-dose green tea extract and vitamin A, can cause kidney or liver toxicity, and “many cancer patients already have compromised kidney or liver function,” says Jun J. Mao, MD, chief of integrative medicine at Memorial. Sloan Kettering Cancer Center in New York. Even herbs that don’t interfere with the effectiveness of a cancer drug, such as stevia, can increase treatment-related side effects, such as nausea and vomiting.
Another potential problem with dietary supplements: it’s almost impossible to know exactly what they contain. For example, last year the FDA sent nearly 50 warning letters to companies marketing dietary supplements. The problem is that federal regulations governing production are less stringent for supplements than for drugs. Therefore, some supplements contain ingredients that are not listed on the label.
One historical example was the PC-SPES supplement, a blend of eight herbs, marketed for men with prostate cancer. The supplement was recalled in 2002 after some lots contained traces of prescription drugs, including diethylstilbestrol, ethinyl estradiol, warfarin and alprazolam.
To complicate matters further, certain dietary supplements can be helpful. Most cancer patients “are malnourished and lack nutrients that they could get from food,” says Cianciotta.
Patients are regularly tested for vitamin deficiencies and given supplements as needed, she says. Vitamin D and folic acid are two of the most common deficiencies in this patient population. Vitamin D supplementation may improve outcomes in patients who have had stem cell transplants by facilitating the transplant and rebuilding the immune system, while folic acid supplementation may help increase red blood cell count and rate. of hemoglobin.
Although she rarely sees vitamin toxicity, Cianciotta stresses that more is not always better and that the use of supplements, even when it seems safe or warranted due to a deficiency, should be taken under supervision and carefully monitored by the patient’s care team.
Highlight the use of supplements
Too often, providers are unaware of a patient’s supplement use.
One main reason: Dietary supplements are often advertised as natural, which many patients equate with safety, says Samantha Heller, senior clinical nutritionist at New York University Langone Health in New York.
This means that patients may not be aware that a supplement may act as a drug and interfere with their cancer treatment, and therefore may not see the importance of telling their doctor.
Still, the promise of herbs, vitamins, and minerals can be alluring, and there are many reasons patients choose to participate. A major attraction: dietary supplements can help some patients feel independent.
“Cancer is a disease that takes a lot of control away from the individual. Taking supplements or herbs is a way to regain some sense of control,” Mao explains.
The phenomenon can also be cultural, he says. Some people grow up taking herbs and supplements to stay healthy or fight health issues.
Pressure or advice from family or friends who may feel they are helping a loved one with their dietary recommendations may also play a role. Friends and family “can’t prescribe chemo, but they can buy herbs and supplements,” Mao says.
Patients seeking greater control over their health or experiencing high levels of anxiety may be more likely to take suggestions from friends and family or more likely to believe false or misleading claims about efficacy or safety supplements, says medical oncologist William Dahut, MD, scientific director of the American Cancer Society.
Additionally, social media often amplifies and normalizes this misinformation, Johnson notes. In a study 2021 published in the Journal of the National Cancer Institutehe and his colleagues found that a third of the most popular cancer treatment articles posted on social media in 2018 and 2019 contained false, inaccurate or misleading information that was often harmful.
Some of the false claims centered on unproven and potentially dangerous herbal remedies, according to Johnson. These included “lung cancer can be cured with cannabis oil” and “golden berries cure and prevent cancer”.
Given the exaggerated “cure” claims, some patients may keep their use of supplements under the radar for fear of being judged or criticized.
“Clinicians should avoid making patients feel judged or telling people not to go online to do their own research,” Johnson said.
Instead, guiding patients to accurate sources of information online can be a way to help patients feel empowered, he says. Cancer.gov and Memorial Sloan Kettering Cancer Center About the Herbs Database provide accessible and accurate information about dietary supplements and cancer treatment to healthcare professionals and patients, he notes.
If a particular supplement is unsafe during treatment, providers should be able to explain why, Cianciotta says. In a recent study, 80% of health care providers surveyed thought herbal drug interactions could be problematic, but only 15% could explain why.
“Being able to explain why we’re discouraging a particular supplement right now tends to be much better received than just telling a patient not to take something, because it’s bad,” she says.
Another key is to listen carefully to patients to understand why they may be taking a particular supplement. Does the patient feel out of control? Is nausea a problem?
“Allowing patients to tell you why they use a particular supplement will often reveal unmet needs or psychosocial challenges,” Mao says. This information can allow providers to suggest an evidence-based alternative, such as mindfulness meditation or acupuncture to manage stress.
What if a patient received a dietary supplement from well-meaning family and friends?
“Just telling a patient that a given supplement is unnecessary or harmful could create family tension,” Mao says.
Instead, he recommends reframing the question.
“We want to get a better understanding of how patients are tolerating chemo or immunotherapy before throwing other things at it. Let them know that now may not be the right time to add a supplement to the mixture,” said Mao.
The bottom line: “Patients want to take an active role in their own care, and we want to help them do that in a safe way,” he says.