7 Natural Supplements Cancer Patients Should Avoid

By Administrator

Dietary supplements are incredibly popular among cancer patients. In one study of more than 200 patients receiving treatment at a former Cancer Treatment Centers of America (CTCA) center, now City of Hope, 73 percent had used some form of supplement during the past 30 days.

The majority of them (53 percent) had not discussed their use with a healthcare professional, perhaps believing it unnecessary to do so. However, even though dietary supplements are natural and perceived as safe, some may interfere with cancer treatment.

In the surveyed patients, for instance, 25 percent of those who were receiving chemotherapy were also using dietary supplements suspected to have adverse interactions with the treatment.

Potential Issues

While some dietary and botanicals have clinical evidence of being effective for specific disease states, there are limitations. Dietary supplements are not generally reviewed by the FDA before they are sold to consumers. They do not require pre-clinical or clinicals trials of safety or effectiveness before they are sold. The companies that sell these products are responsible for ensuring their products are safe and accurately labeled. In fact, in many cases, companies can produce and sell dietary supplements without even notifying the FDA.

Further, you shouldn’t expect your oncologist to bring up the topic of dietary supplements. Research published in the Journal of Clinical Oncology found that fewer than half of oncologists initiated discussions with patients about supplement use, largely because they felt they didn’t have enough information to answer patients’ questions on the subject.

Importance of Consulting Healthcare Professionals

If you’re receiving cancer treatment, you should speak with a clinical pharmacist or another health care provider who is knowledgeable about both natural supplements and cancer patients to be sure any you’re taking are going to be helpful and not harmful. It is essential for patients to always consult with their oncologists before taking any supplements, as some may interact with anti-cancer treatments like chemotherapy. This is highly recommended instead of just Googling the cancer diagnosis yourself.

The following six supplements, for example, may be harmful for cancer patients and should generally be avoided:

  1. St. John’s wort: Increases the production of the enzymes responsible for metabolizing drugs, including chemotherapy. Depending on the drug, this can lead to toxicities if the drug is rapidly metabolized to the active form and the drug accumulates, or render the drug to be ineffective if it is rapidly metabolized to its inactive form. 
  2. Grapefruit or grapefruit juice: Decreases the production of the enzymes responsible for metabolizing drugs, including chemotherapy. Depending on the drug, this can lead to toxicities if the drug is not metabolized to its inactive form and the drug accumulates, or render the drug to be ineffective if it is supposed to be metabolized to its active form. 
  3. Acai berry: Its antioxidant properties may interfere with the effectiveness of some chemotherapy and radiation treatments
  4. B17: “Vitamin” B17 is often derived from apricot kernel and promoted as a cancer fighter. However, scientific evidence has found it to be clinically ineffective in treating cancer. Furthermore, apricot kernel contains amygdalin, which converts to cyanide in the body and can cause cyanide poisoning. 
  5. Graviola or soursop: Soursop fruit and graviola leaves are traditionally used in the Caribbean, Mexico and Central and South America. Although they’re claimed to also have anti-cancer properties, these supplements have been largely called out by the Federal Trade Commission (FTC) and it has been found to be associated with increased odds of developing movement disorders that resemble Parkinson’s disease. 
  6. Green tea extract: This may interfere with the drug bortezomib, which is often used to treat multiple myeloma.

Additional Supplements to Be Aware of That May Potentially Affect Cancer Care

Vitamin D3 and Other Supplementation in Prostate Cancer

Vitamin D3 may benefit men on active surveillance for prostate cancer. In a Gateway-funded study of 68 patients, they found patients that had higher initial vitamin D blood levels were twice as likely to have a statistically significant downward trend in prostate specific antigen (PSA). Although the patients were given multiple interventions at the same time – dietary change, omega-3 supplementation, vitamin D supplementation, curcumin supplementation – so it is not possible to determine which intervention was responsible for the change in PSA levels. However, it was evident that there was an overall benefit from the dietary change and supplementation.

Potential Risks & Side Effects

Supplements, including vitamins, minerals, botanicals, amino acids, and enzymes, can interact with cancer treatments in complex ways. These interactions may affect the metabolism of chemotherapy drugs and other medications, potentially impacting their efficacy or increasing their toxicity as described above with St. John’s wort and grapefruit juice. Some supplements could influence how the body interacts with the drug, which involve processes such as absorption, distribution, metabolism, and excretion of the drug. Therefore, it’s critical for patients to communicate with their healthcare providers about any supplements they are taking during their cancer treatment.

Bleeding Risk: What to Know

Many supplements and botanicals can increase the risk of bleeding and bruising in patients. These substances often have blood-thinning effects, which can be beneficial in preventing blood clots and improving circulation. However, they can also lead to undesired consequences, especially for individuals with a propensity to bleed, such as those with anemia or thrombocytopenia, or those taking blood-thinning medications like aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), platelet inhibitors, warfarin, and direct-acting oral anticoagulants (DOACs). These situations can result in unwanted bleeding and bruising. As a precaution, patients on these medications are often advised to stop using them at least 10 days before surgery to reduce the likelihood of perioperative bleeding and hemorrhage. This advice is particularly relevant for patients undergoing cancer treatment, as these complications could further impact their health.

Questions to Ask Your Doctor

It is important for patients to take the initiative and ask their healthcare providers questions about the use of supplements. Some questions that you can ask include: 

  • Are there any known interactions between the supplements I am taking and my cancer treatments?
  • How will the supplements affect my body’s ability to metabolize chemotherapy drugs?
  • Should I take the supplements at a specific time in relation to my cancer treatment schedule?
  • What is the recommended dosage if it is safe to take?
  • Are there any specific supplements that I should avoid while undergoing treatment?
  • What are the potential side effects of the supplements I am considering?
  • Can any supplements support my treatment plan?
  • Is there scientific evidence supporting the benefits of the supplements I am interested in?
  • Do you have any resources or literature that can provide more information on the supplements and their effects?

Key Takeaways

As we have explored, dietary supplements can have a complex relationship with cancer care. While some supplements may offer benefits, others can interact with treatments or have unintended side effects. The key takeaway is the importance of open communication and consultation with healthcare professionals. It’s crucial not to make assumptions about the safety or efficacy of supplements simply because they are “natural.” Research in this area is still evolving, and information may not always be readily available even to oncologists. Being proactive in seeking advice, asking questions, and staying informed can make a significant difference in the effective management of cancer care. Remember that the goal is to support your treatment and overall well-being, so making well-informed decisions is paramount.


Why should cancer patients be cautious about taking natural supplements?

Cancer patients should be cautious because certain natural supplements can interact with cancer treatments such as chemotherapy. These interactions may reduce the effectiveness of the treatments or cause harmful side effects.

Are all natural supplements harmful for cancer patients?

No, not all natural supplements are harmful for cancer patients. However, it is essential to consult a healthcare professional before taking any supplements, as some can have adverse interactions with cancer treatments.

Can natural supplements with antioxidant properties, like acai berry, affect cancer treatment?

Yes, supplements with antioxidant properties, such as acai berry, may interfere with the effectiveness of some chemotherapy and radiation treatments. Antioxidants can sometimes protect cancer cells from the damage intended by these treatments.

What should I do if I am already taking one of the listed supplements?

If you are already taking one of the supplements listed as potentially harmful for cancer patients, it’s important to talk to your healthcare provider as soon as possible. They can provide guidance on whether you should continue or stop taking the supplement.

Who should I talk to about the supplements I am considering taking during my cancer treatment?

You should speak with your medical oncologist or a clinical pharmacist who is knowledgeable about both natural supplements and cancer treatments. They can provide guidance on which supplements are safe to take and which ones should be avoided.

Is there any natural supplement that is considered safe and beneficial for cancer patients?

There may be supplements that can be beneficial for cancer patients, but it varies depending on the type of cancer and the treatment being received. It’s essential to consult with a healthcare professional who is knowledgeable about the specific circumstances.

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