Over 40% of cancer patients take supplements like vitamins and herbs during treatment, but according to Gram Research analysis, these products can dangerously interfere with cancer medications and reduce treatment effectiveness. Doctors and patients rarely discuss supplements, creating serious safety risks. Doctors should actively ask patients about all supplements they’re taking and work together to make safe choices that protect both the cancer treatment and the patient’s health.
More than 4 out of 10 cancer patients take supplements like vitamins, herbs, and minerals while receiving cancer treatment, often hoping to feel better or reduce side effects. However, according to Gram Research analysis, these supplements can interfere with cancer medications in dangerous ways. Doctors and patients often don’t talk enough about these products, which creates safety risks. A new review shows that doctors should ask patients directly about supplements and work together to make safe choices that protect both the cancer treatment’s effectiveness and the patient’s overall health.
Key Statistics
A 2026 review in the Nederlands tijdschrift voor geneeskunde found that over 40% of cancer patients use supplements such as herbs, vitamins, and minerals while undergoing anticancer treatment.
Research shows that supplements can cause pharmacokinetic or pharmacodynamic interactions with anticancer drugs, potentially reducing treatment effectiveness or causing additional harm to cancer patients.
According to the 2026 review, communication between clinicians and patients about supplements is often limited, creating a significant gap in cancer care safety.
The research indicates that cancer patients take supplements primarily because they believe these products improve overall health, reduce side effects, or correct nutritional deficiencies during treatment.
The Quick Take
- What they studied: Whether supplements like vitamins, herbs, and minerals are safe to take while getting cancer treatment, and how they might interact with cancer drugs
- Who participated: This was a review of existing research, not a study with human participants. It looked at information about cancer patients who use supplements during treatment
- Key finding: Over 40% of cancer patients use supplements during treatment, but these products can interfere with cancer medications in ways that reduce treatment effectiveness or cause harm
- What it means for you: If you have cancer and take any supplements, vitamins, or herbal products, tell your doctor immediately. Don’t stop taking them without asking first, but don’t assume they’re safe just because they’re natural. Work with your medical team to decide what’s best for your specific situation
The Research Details
This research is a review article, which means doctors looked at what we already know about supplements and cancer treatment interactions. Instead of doing a new experiment, they gathered information from existing studies and medical knowledge to create a guide for other doctors. The researchers focused on finding common supplements that cancer patients use and explaining how these products might interact with cancer drugs like chemotherapy. They looked at two main types of problems: pharmacokinetic interactions (when supplements change how the body absorbs or processes cancer drugs) and pharmacodynamic interactions (when supplements change how cancer drugs work in the body).
This type of research is important because it helps doctors understand real-world problems. Many cancer patients secretly take supplements without telling their doctors, which can be dangerous. By reviewing all available information, researchers can warn doctors about specific supplement-drug combinations to avoid. This helps doctors have better conversations with patients about what’s safe and what isn’t.
This is a review article published in a medical journal, which means it went through expert review before publication. However, because it’s not a new experiment with patients, it relies on other studies being accurate. The strength of the recommendations depends on how much research exists for each supplement. Some supplements have lots of studies showing interactions, while others have very little research. Readers should know that the authors are calling for better communication between doctors and patients, which suggests this is currently a weak point in cancer care.
What the Results Show
The research found that over 40% of cancer patients use supplements during treatment. This is a surprisingly high number that shows many patients are taking these products without necessarily telling their doctors. The main reason patients use supplements is because they believe these products will improve their overall health, reduce uncomfortable side effects from cancer treatment, or fix nutritional deficiencies. However, the review identified serious risks: supplements can interfere with how cancer drugs work in the body, potentially making the cancer treatment less effective. Some supplements can also increase side effects or cause new health problems when combined with cancer medications.
The researchers found that communication between doctors and patients about supplements is often very limited or doesn’t happen at all. Many patients don’t mention their supplements because they think natural products are automatically safe, or they’re embarrassed to tell their doctor. Many doctors don’t ask about supplements because they’re focused on cancer treatment and may not realize how common supplement use is. This communication gap creates a dangerous situation where patients might be taking supplements that directly interfere with their cancer treatment without anyone knowing.
The review emphasizes that patients have real needs and expectations that drive them to use supplements. Some patients feel they need to do something active to help themselves heal. Others are trying to manage side effects like nausea, fatigue, or pain. Some are worried about nutritional deficiencies from cancer treatment. These are legitimate concerns that doctors should address directly. The research suggests that when doctors understand why patients want supplements, they can have better conversations about safer alternatives or approved supplements that won’t interfere with treatment.
This research adds to growing evidence that supplement use during cancer treatment is common but risky. Previous studies have shown specific interactions between popular supplements and cancer drugs, but this review brings that information together in one place for doctors. It also highlights that the problem isn’t just about the supplements themselves, it’s about the lack of communication between doctors and patients. This is a newer focus that recognizes the human side of the problem, not just the chemical side.
This is a review article, not a new study, so it can only tell us what other research has already found. Some supplements may not have much research available, so the review might not cover all possible interactions. The review doesn’t include specific numbers about how often interactions actually happen in real patients. It also doesn’t provide a complete list of which supplements are safe and which are dangerous: that would require more detailed research for each specific supplement and cancer drug combination. Finally, the review was published in a Dutch medical journal, so some of the research it discusses may be from European sources and might not apply equally to all populations.
The Bottom Line
If you’re being treated for cancer: (1) Tell your doctor about every supplement, vitamin, herb, and mineral you take or want to take, don’t assume anything is safe just because it’s natural. (2) Don’t stop taking supplements without asking your doctor first, as some may be important for your health. (3) Work with your doctor to decide which supplements are safe for your specific cancer treatment. (4) Ask your doctor about non-supplement ways to manage side effects, reduce fatigue, or address nutritional concerns. These recommendations have strong support from medical evidence.
Cancer patients and their families should care about this research. Doctors and nurses treating cancer patients should use this information to start conversations about supplements. People considering supplements while undergoing any medical treatment should also pay attention. This is less relevant for people not currently in cancer treatment, though it’s good general knowledge. If you’re a caregiver for someone with cancer, you should know about this so you can help them communicate with their medical team.
The risks from supplement-drug interactions can happen immediately or develop over time. Some interactions might reduce how well your cancer treatment works right away, while others might cause problems after weeks of use. The benefits of stopping a dangerous supplement can also vary, some side effects might improve within days, while others take longer. This is why it’s important to talk to your doctor as soon as possible rather than waiting.
Frequently Asked Questions
Can I take vitamins and supplements while getting cancer treatment?
Some supplements may be safe, but many can interfere with cancer drugs and reduce treatment effectiveness. Over 40% of cancer patients use supplements, but doctors and patients rarely discuss this. Always tell your doctor about every supplement before taking it, don’t assume natural products are automatically safe during cancer treatment.
What supplements interact with cancer medications?
Many supplements can interfere with cancer drugs, but the specific interactions depend on your particular cancer treatment. Common concerns include herbs like St. John’s Wort, high-dose vitamins, and certain mineral supplements. Your doctor can review your specific medications and supplements to identify potential problems.
Why do cancer patients take supplements if they’re risky?
Cancer patients take supplements hoping to improve health, reduce side effects like nausea and fatigue, or fix nutritional deficiencies. These are legitimate concerns. The problem is that patients and doctors don’t communicate about supplements, so risky interactions happen without anyone knowing. Talk to your doctor about safer ways to address these needs.
Should I stop taking my supplements during cancer treatment?
Don’t stop supplements without asking your doctor first, some may be important for your health. Instead, tell your doctor about every supplement you take. Together you can decide which ones are safe to continue, which to stop, and which safer alternatives might help with your concerns.
How can I talk to my doctor about supplements?
Make a list of every supplement, vitamin, and herb you take, including doses and how often you take them. Bring this list to your next appointment and ask your doctor directly if each one is safe with your cancer treatment. Be honest about why you want to take supplements, your doctor can then suggest safer alternatives.
Want to Apply This Research?
- Create a daily log of all supplements, vitamins, and herbs taken, including the name, dose, and time of day. Track any side effects or changes in how you feel. Share this log with your doctor at each appointment to identify any potential interactions with your cancer treatment.
- Before taking any new supplement, use the app to send a message to your healthcare team asking if it’s safe with your current cancer treatment. Set up a reminder to discuss all supplements at your next doctor’s appointment. Keep a running list in the app of supplements you want to ask about.
- Review your supplement list with your doctor every month during cancer treatment. Update the app whenever your cancer treatment changes, since new medications might interact with supplements differently. Track how you feel on your current treatment plan and note any changes that might be related to supplements.
This article is for educational purposes and should not replace professional medical advice. Cancer patients should never start, stop, or change supplements without consulting their oncology team. All supplements can potentially interact with cancer medications in serious ways. If you’re undergoing cancer treatment, discuss every supplement, vitamin, herb, and mineral with your doctor before use. This research provides general information about supplement use during cancer treatment but does not constitute personalized medical advice for your specific situation.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.
