Supplements During Cancer Immunotherapy: What Helps, What Harms, and What to Tell Your Oncologist

An evidence-informed guide to vitamins, antioxidants, herbal products, probiotics, and nutritional support during cancer treatment.

Last reviewed: October 22, 2026

Many people receiving cancer immunotherapy take supplements in the hope of strengthening their immune systems, reducing treatment side effects, or improving their chances of responding to treatment. Others use vitamins because cancer, poor appetite, surgery, or previous treatments have left them with nutritional deficiencies.

These are different situations, and they deserve different answers.

Some supplements may be appropriate when a deficiency has been identified. Others have promising but preliminary research. Some can interact with medicines, cause liver injury or bleeding, complicate the assessment of treatment-related symptoms, or create uncertainty about treatment safety.

The challenge is that a supplement that sounds beneficial for immunity is not necessarily beneficial during cancer immunotherapy.

This guide explains what the evidence shows, what remains uncertain, and how patients and caregivers can make supplement use part of a coordinated cancer care plan.

The essential message

• Tell your oncology team about every vitamin, mineral, herb, powder, probiotic, traditional remedy, and high-dose supplement you use.
• Correct documented deficiencies when clinically indicated, using an appropriate dose and monitoring plan.
• Do not assume that high-dose antioxidants, immune-boosting herbs, probiotics, or intravenous vitamin infusions improve immunotherapy outcomes.
• Do not stop prescribed cancer treatment or delay assessment of new symptoms in favor of a supplement.

The National Cancer Institute provides a useful reference on interactions between cancer therapies, foods, and dietary supplements.

1. What Does Cancer Immunotherapy Do?

Immunotherapy is a broad category of treatments that help the immune system recognize, attack, or otherwise control cancer. Different immunotherapies work in different ways, so supplement recommendations cannot be generalized across every treatment.

One widely used category is immune checkpoint inhibition. These medicines interfere with signals that tumors use to suppress immune responses.

Examples include:

• PD-1 inhibitors: pembrolizumab (Keytruda) and nivolumab (Opdivo).
• PD-L1 inhibitors: atezolizumab (Tecentriq) and durvalumab (Imfinzi).
• CTLA-4 inhibitors: ipilimumab (Yervoy).

Some patients receive immunotherapy alone. Others receive combinations with chemotherapy, targeted medicines, radiation, or additional immunotherapy drugs.

Other treatments, including CAR-T cell therapy and certain cellular or immune-based treatments, have different safety considerations. A supplement reviewed for one treatment should not automatically be assumed safe with another.

Why can supplements matter?

A supplement may affect treatment or patient safety through several mechanisms:

• Drug interactions: Certain herbs and concentrated extracts can alter the absorption, metabolism, or elimination of particular medicines.
• Liver or kidney toxicity: Supplement-related injury may complicate treatment or resemble an adverse effect attributed to cancer therapy.
• Immune effects: Products marketed as immune stimulants may have unpredictable biological effects.
• Gut microbiome changes: Diet and microbial composition may influence the response to some immunotherapies, but this does not establish that commercial probiotics improve outcomes.
• Diagnostic confusion: New symptoms or abnormal laboratory results may have multiple possible causes, including a supplement, cancer, infection, or treatment-related toxicity.

Many checkpoint inhibitor antibodies are not metabolized in the same way as conventional oral medicines through the liver's CYP enzyme system. However, patients often take multiple medicines alongside immunotherapy, and supplement interactions remain relevant to the overall treatment plan.

For more detail, consult the National Cancer Institute's health professional review of cancer therapy interactions.

2. Evidence Grades: How Strong Is the Case for a Supplement?

Before discussing individual products, it is useful to distinguish evidence about correcting a deficiency from evidence that a supplement directly improves cancer outcomes.

Evidence category	Meaning	How to apply it
A — Established supportive care	Recognized clinical indication, such as treating a confirmed nutritional deficiency.	Use when indicated, with an appropriate dose and follow-up.
B — Promising clinical evidence	Human studies suggest a possible association or benefit, but important uncertainties remain.	Consider the population, study design, and treatment-specific evidence.
C — Early or indirect evidence	Laboratory findings, animal research, small clinical studies, or uncertain mechanisms.	Do not interpret biological plausibility as proof of clinical benefit.
D — Benefit unproven	No convincing evidence establishes that the product improves cancer outcomes in the proposed use.	Avoid relying on it as an anticancer treatment.

Important: These grades describe the strength of evidence for the particular use discussed here, not the overall quality of a supplement or its usefulness for every medical condition. They are not a validated clinical grading system.

3. Supplements That May Be Appropriate During Immunotherapy

Vitamin D: Correct Deficiency, but Do Not Assume It Enhances Treatment

Vitamin D is involved in bone health, calcium regulation, and immune function. A person with vitamin D deficiency may need treatment regardless of whether they have cancer.

A systematic review and meta-analysis published in 2025 evaluated 13 studies involving 2,592 cancer patients receiving immunotherapy. Higher vitamin D concentrations were associated with better survival and treatment-response outcomes. The analysis also reported an association between vitamin D supplementation and longer overall survival.

However, these findings do not establish that supplementation causes a better cancer response. The included studies covered different populations and treatments, and many of the associations came from observational evidence. Vitamin D concentration may also reflect other aspects of health.

Evidence assessment: A for correcting a confirmed deficiency when clinically indicated; B/C for a possible relationship with immunotherapy outcomes.

Practical approach:

• Ask whether testing is appropriate given your clinical situation and nutritional risks.
• If deficient, discuss a replacement dose and whether follow-up testing is needed.
• Avoid taking very high doses solely to increase immune activity or improve tumor response.
• Tell your team about calcium and vitamin D products, especially if you have kidney disease, a history of kidney stones, or abnormal calcium levels.

Research source: Yang et al., 2025 — systematic review and meta-analysis of vitamin D and cancer immunotherapy.

Vitamin B12, Iron, Folate, and Other Nutrients

Cancer and its treatment can contribute to nutritional deficiencies through poor intake, gastrointestinal problems, bleeding, malabsorption, or previous surgery. Fatigue, weakness, and anemia may have several causes, including the cancer itself, treatment effects, infection, or a deficiency.

Correcting a genuine deficiency can be appropriate supportive care. That does not mean the same nutrient will benefit someone whose nutritional status is already adequate.

Iron supplementation deserves particular care. Iron deficiency and anemia should be evaluated rather than assuming that fatigue means more iron is needed. Unnecessary iron can cause adverse effects and may be inappropriate in some clinical circumstances.

Likewise, folate and vitamin B12 should be used according to the underlying indication. Laboratory testing and the patient's treatment regimen can help guide decisions.

Evidence assessment: A for treatment of appropriately diagnosed deficiencies; D for claims that extra doses directly improve immunotherapy efficacy in otherwise replete patients.

Multivitamins: Is a Standard-Dose Product Reasonable?

A standard-dose multivitamin may sometimes be considered when a person cannot maintain a varied diet or has particular nutritional risks. It is not automatically necessary for every cancer patient.

Choose a product based on nutritional needs, not a marketing claim about activating immunity. Avoid automatically combining a multivitamin with multiple additional products containing the same vitamins and minerals.

The total dose matters. A conventional nutritional dose and a high-dose intervention are not equivalent, and the ingredients should be reviewed against the treatment plan.

Evidence assessment: A/B for meeting nutritional needs in selected patients; D for use as a proven cancer treatment.

Protein and Overall Nutrition

Maintaining adequate energy and protein intake can help support strength, daily function, and recovery. Cancer-related appetite loss, weight loss, swallowing difficulties, nausea, and digestive symptoms can make this challenging.

Food-first nutrition is generally a sensible starting point, with oral nutrition supplements or individualized dietary support when clinically appropriate.

Protein powders are not inherently unsafe, but their full ingredient lists should be reviewed. Some products combine protein with herbs, stimulants, concentrated plant extracts, or large doses of vitamins and minerals.

Evidence assessment: Established supportive nutrition, but not proof that a particular protein supplement makes immunotherapy more effective.

4. Antioxidants During Immunotherapy: Vitamin C, Vitamin E, Selenium, and Glutathione

Antioxidants are often promoted as a way to protect healthy cells from treatment-related damage. Common examples include:

• High-dose vitamin C.
• Vitamin E.
• Beta-carotene and other concentrated carotenoids.
• Selenium supplements.
• N-acetylcysteine (NAC).
• Glutathione.
• Coenzyme Q10 (CoQ10).

The safety question is more complicated than whether oxidation is good or bad. Cancer therapies can have different mechanisms, and the effects of a supplement may depend on the specific treatment, dose, timing, and patient.

Research involving chemotherapy and radiation has raised concerns that some antioxidant supplements may interfere with particular treatments or be associated with worse outcomes. Those findings cannot automatically be applied to every immune checkpoint inhibitor, but they provide a reason not to assume that high-dose antioxidant supplementation is harmless during cancer treatment.

There is insufficient clinical evidence to recommend high-dose antioxidant supplements as a general method of improving checkpoint inhibitor effectiveness.

Clinical distinction: Eating ordinary portions of fruits and vegetables is not the same as taking concentrated antioxidant extracts or high-dose vitamin pills. Do not eliminate nutritious foods simply because they contain antioxidants.

What About Intravenous Vitamin C?

Intravenous vitamin C produces blood concentrations that differ substantially from those achieved through ordinary food intake or oral supplements. It should not be treated as equivalent to eating vitamin C-rich foods.

High-dose intravenous vitamin C is not established as a standard method for enhancing cancer immunotherapy. It also requires medical consideration of kidney function, the risk of oxalate-related kidney injury, glucose-6-phosphate dehydrogenase (G6PD) deficiency, and other patient-specific issues.

Discuss any proposed infusion with the treating oncologist before proceeding. Do not assume that a product is safe because it is administered at a wellness clinic rather than taken as a pill.

Evidence assessment: C/D for claims of improved immunotherapy outcomes; clinical review is necessary before use.

Sources:

• National Cancer Institute: Cancer Therapy Interactions With Foods and Dietary Supplements
• National Center for Complementary and Integrative Health: Antioxidant Supplements

5. Probiotics, Prebiotics, and the Gut Microbiome

The gut microbiome has become an important area of cancer immunotherapy research. Intestinal microorganisms may influence immune signaling, inflammation, and the response to some immune checkpoint inhibitors.

However, the fact that the microbiome matters does not establish that taking a commercial probiotic capsule will improve cancer outcomes.

What Does the Research Show?

A study published in Science in 2021 examined dietary fiber, probiotic use, and immunotherapy outcomes in patients with melanoma. Higher dietary fiber intake was associated with better progression-free survival in the patient cohort. In experimental mouse models, some probiotic interventions were associated with impaired anti-PD-1 treatment responses.

These findings are important but require careful interpretation. The human findings were observational and cannot prove that probiotics caused poorer outcomes or that fiber alone caused better responses.

More recent research has added complexity. A 2026 systematic review and meta-analysis of 22 studies involving 3,274 patients reported associations between microbiome-modulating interventions, including probiotics and fecal microbiota transplantation, and improved immunotherapy outcomes. The studies varied in design and intervention, and the findings do not establish that an off-the-shelf probiotic is effective for a particular patient.

The emerging literature is therefore promising, but it is not a basis for recommending every probiotic product during immunotherapy.

Should Patients Take Probiotics?

Do not start a probiotic specifically to enhance cancer treatment without discussing it with the oncology team.

Consider the following:

• Different probiotic strains and formulations can have different effects.
• Research involving a defined clinical intervention cannot automatically be applied to a commercial supplement with different organisms or doses.
• Patients who are severely immunocompromised or have particular medical devices or other risk factors may need additional precautions against infection from live microorganisms.
• Probiotics are not an established substitute for managing diarrhea, infection, or immune-related colitis.

What About Dietary Fiber?

When medically appropriate and tolerated, a varied diet containing vegetables, fruit, legumes, whole grains, nuts, and seeds can provide fiber without requiring a supplement.

Increase fiber gradually and maintain adequate hydration, subject to any fluid restrictions or other medical advice. People with bowel obstruction, significant strictures, certain postoperative conditions, or active severe gastrointestinal symptoms may require a different approach.

If fiber intake is poor or a fiber supplement is being considered, ask an oncology dietitian or clinician how to proceed.

Evidence assessment:

• Dietary fiber: B for an observational association in melanoma immunotherapy; not proof of universal benefit.
• Commercial probiotics: C/B for an emerging and heterogeneous research area; insufficient for routine use as a proven immunotherapy booster.
• Microbiome treatments such as fecal microbiota transplantation: Investigational in this context and not equivalent to taking an ordinary probiotic supplement.

Key references:

• Spencer et al., 2021. Dietary fiber and probiotics influence the gut microbiome and melanoma immunotherapy response. Science.
• National Cancer Institute. A high-fiber diet may improve the response of melanoma patients to immunotherapy.
• 2026 systematic review and meta-analysis. Modulating the gut microbiome to enhance cancer immunotherapy.

6. Herbal Supplements and Concentrated Plant Extracts

Herbal products are frequently marketed as immune boosters, anti-inflammatory agents, detoxification aids, or natural anticancer therapies. Their effects can vary considerably with the plant species, extraction method, dose, formulation, and manufacturing quality.

Some herbs may affect the liver or influence enzymes and transport proteins involved in the handling of particular medicines. Others have potential effects on bleeding, blood pressure, glucose levels, or the immune system.

The following table identifies products that deserve review. It does not mean that every product in a category is proven to interfere with every immunotherapy drug.

Product	Main concern	Recommended approach
St. John's wort	Can alter the metabolism or transport of numerous medicines and reduce exposure to some anticancer drugs.	Avoid self-prescribing; have all medicines reviewed, especially when oral anticancer drugs are also used.
Concentrated green tea extract	Some concentrated extracts can cause liver injury and may interact with certain medicines.	Review concentrated extracts separately from ordinary brewed tea.
Turmeric or curcumin extracts	Potential drug interactions, variable formulations, and reported liver injury with some turmeric products.	Disclose dose and formulation; do not assume an extract is equivalent to culinary turmeric.
Ashwagandha	Possible liver injury, thyroid effects, and interactions; cancer-specific benefit is unproven.	Discuss before use, especially with thyroid disease or abnormal liver tests.
Mushroom extracts	Products vary in composition and potency; reliable evidence of benefit alongside a particular immunotherapy may be lacking.	Identify the exact species, ingredients, extraction, and dose for review.
Ginkgo, garlic, ginseng, and other herbal blends	Potential medication interactions, variable biological effects, and possible bleeding or other adverse effects depending on the product.	Check the exact formulation against anticoagulants, other medicines, and the planned procedures.

Evidence of an interaction with a chemotherapy or targeted therapy drug does not automatically establish an interaction with a checkpoint inhibitor. Nevertheless, these medicines may be used together, and the potential risks should be evaluated for the complete treatment regimen.

Practical rule: Do not start concentrated herbal extracts or multi-ingredient traditional remedies during cancer treatment without a review by your treating clinician or oncology pharmacist.

Reference: Memorial Sloan Kettering Cancer Center's About Herbs, Botanicals & Other Products resource provides product-specific discussions of potential risks and interactions.

7. Other Supplements That Deserve Careful Review

Omega-3 Fish Oil

Omega-3 fatty acids may be useful for selected nutritional or medical indications, but they are not established as universal enhancers of immunotherapy.

High doses may be inappropriate for some patients, especially when other medicines affect bleeding or when a procedure is planned. Discuss the reason for use, dose, and other medications before starting or continuing a high-dose product.

Melatonin

Melatonin is used for sleep problems and has been investigated in cancer-related research. Findings from small studies or laboratory experiments do not establish that taking melatonin improves checkpoint inhibitor response or survival.

Review its use with your treatment team, particularly if you are taking sedating medications or other supplements, or if the product is being promoted as an anticancer therapy.

Curcumin, Resveratrol, Quercetin, and Other Polyphenols

These compounds have attracted attention because of laboratory findings involving inflammation, cell signaling, and cancer biology. Concentrated supplements can behave differently from the foods in which related compounds occur naturally.

There is insufficient evidence to recommend these products routinely for the purpose of improving immunotherapy outcomes. Potential interactions and product quality should be assessed individually.

CBD and Cannabis-Derived Products

Cannabidiol (CBD) and other cannabis-derived products may be used for symptoms or other reasons. Their composition and doses vary, and some can affect drug-metabolizing enzymes or cause adverse effects, including sedation or liver abnormalities.

Tell your oncology team about oils, extracts, gummies, and other cannabis-derived products, including those obtained without a prescription. Do not assume that taking a product separately from your cancer medicine eliminates the possibility of an interaction.

Traditional Chinese Medicines, Ayurvedic Products, and Multi-Ingredient Remedies

Traditional products may contain several active ingredients, and the English label may not fully communicate their composition. Products can also vary in quality and may occasionally contain undeclared pharmaceuticals, heavy metals, or other contaminants.

Provide the original packaging, ingredient list, manufacturer, and dose whenever possible. A photograph of the label may help the oncology pharmacist identify the product.

8. Which Supplements Should Patients Avoid or Pause Pending Review?

There is no scientifically defensible universal list declaring every supplement unsafe for every immunotherapy patient. The appropriate decision depends on the specific treatment, other medicines, laboratory findings, and clinical circumstances.

However, the following categories should not be started casually during treatment:

• High-dose antioxidant regimens marketed as ways to protect cells or improve cancer-treatment effectiveness.
• Concentrated herbal extracts with uncertain dosing, liver effects, or potential interactions.
• Supplements containing multiple active ingredients whose combined effects are poorly characterized.
• Probiotic or microbiome products taken specifically to increase immunotherapy response without clinical guidance.
• Unsupervised intravenous vitamin infusions or other high-dose interventions promoted as cancer treatments.
• Products claiming to replace prescribed treatment or promising to cure cancer, reverse resistance, or guarantee an immunotherapy response.

If you already take one of these products, disclose it promptly. Do not assume that every product must automatically be stopped, but do not continue an unreviewed regimen on the assumption that natural products are harmless.

9. Supplements Can Complicate Immune-Related Adverse Events

Checkpoint inhibitors can trigger immune-related adverse events when the activated immune system affects normal tissues. Depending on the drug and patient, complications may involve the intestines, liver, lungs, skin, thyroid, adrenal glands, kidneys, heart, nervous system, or other organs.

Some supplement-related adverse effects can produce similar symptoms or abnormal laboratory results. For example:

• A supplement-related liver injury may complicate the assessment of abnormal liver enzymes.
• Severe diarrhea may be due to several causes, including infection, medication effects, or immune-related colitis.
• Fatigue may reflect cancer progression, anemia, dehydration, sleep problems, or an immune-related endocrine disorder.
• New breathing problems may indicate a serious condition such as pneumonitis, infection, a blood clot, or another medical emergency.

These symptoms should not be self-treated with supplements.

When to contact the oncology team urgently

During immunotherapy, promptly report new or worsening diarrhea, persistent abdominal pain, yellowing of the skin or eyes, dark urine, unusual weakness, new cough, shortness of breath, marked changes in thirst or urination, or other unexplained symptoms.

Seek emergency care for severe breathing difficulty, chest pain, confusion, collapse, severe abdominal symptoms, or other signs of a medical emergency.

Do not wait for your next scheduled infusion or appointment if serious symptoms develop. Follow the emergency instructions supplied by your cancer center.

10. How to Disclose Supplements to Your Oncologist

A useful supplement review is specific. Saying “I take some vitamins” does not give your clinician enough information to assess interactions or duplicate ingredients.

Prepare an inventory before your next oncology appointment or contact the team sooner if you are considering a new product.

Patient Supplement Disclosure Checklist

For every product, record:

• Product name and manufacturer.
• All active ingredients and the amount per serving.
• Number of capsules, tablets, scoops, or doses taken each day.
• Reason for taking it, such as a confirmed deficiency, a symptom, or a recommendation.
• Date started and any recent dose changes.
• Where it was obtained, including online marketplaces, traditional medicine practitioners, or infusion clinics.
• Any symptoms or laboratory abnormalities that appeared after starting it.

Also disclose:

• Vitamins, minerals, herbal teas, medicinal mushrooms, probiotics, protein powders, and meal replacements.
• Traditional medicines, cannabis-derived products, and nonprescription sleep or energy products.
• Intravenous nutrient infusions, injections, and products recommended by a wellness clinic.
• Prescribed medicines, over-the-counter medicines, and any recent antibiotic use.

Bring the product container or clear photographs of the front label, Supplement Facts or nutrition panel, ingredient list, and dosing instructions. This is especially helpful for blends with proprietary ingredient names.

Questions to Ask

1. Is this product compatible with my exact immunotherapy regimen and other medicines?
2. Is there evidence that it helps my particular nutritional problem or symptom?
3. Could it affect my liver, kidneys, bleeding risk, blood tests, or immune-related adverse events?
4. Is a laboratory test needed before using it?
5. Should I avoid it, continue it, or use a different dose?
6. How will we monitor for benefits or adverse effects?

11. A Practical Supplement Decision Framework

Use the following framework to organize a discussion with the oncology team. It is a decision aid, not a substitute for a clinical interaction check.

Question	If yes	If no or uncertain
Is there a recognized clinical indication or documented deficiency?	Discuss targeted treatment and follow-up.	Do not assume supplementation is needed.
Has the exact product and dose been reviewed?	Confirm the plan and monitoring.	Obtain a review before adding a new product.
Is the proposed benefit supported by human clinical evidence?	Check whether the evidence applies to your cancer and treatment.	Treat the claim as unproven, particularly when based only on laboratory studies.
Could the product cause toxicity or interact with medicines?	Use only under an agreed clinical plan, if appropriate.	Uncertainty does not establish safety; seek product-specific review.
Is the product being used instead of prescribed cancer treatment?	Stop and discuss the plan with the oncology team before changing treatment.	Continue appropriate evidence-based treatment and agreed supportive care.

12. What About Food, Green Tea, and Ordinary Dietary Antioxidants?

Patients sometimes worry that eating antioxidant-rich foods will interfere with immunotherapy. This is not the same question as whether concentrated supplements should be used.

A varied diet can provide fiber, protein, vitamins, minerals, and other nutrients. Unless a specific dietary restriction is medically necessary, the goal should generally be to maintain adequate nutrition rather than eliminate entire groups of nutritious foods.

Ordinary brewed green tea, for example, is not equivalent to a highly concentrated green tea extract. Nevertheless, dietary restrictions can depend on the specific cancer medicine, so ask about any known food-drug interactions.

For patients with poor intake, substantial weight loss, swallowing difficulties, persistent nausea, or gastrointestinal complications, an oncology dietitian may help adapt food choices to individual needs.

13. How to Evaluate Supplement Claims Online

Claims about supplements frequently rely on laboratory research, testimonials, mechanistic explanations, or selective reporting of small studies. These sources can be useful starting points for research, but they do not establish that a product improves survival or tumor response.

Before accepting a claim, ask:

• Was the research done in humans? A result in cancer cells or animals does not establish clinical effectiveness.
• Was immunotherapy actually studied? Evidence involving chemotherapy, radiation, or cancer prevention may not apply to checkpoint inhibitors.
• What outcome was measured? A change in a laboratory marker is not equivalent to a longer life, improved quality of life, or a durable tumor response.
• Was there a suitable comparison group? People who choose supplements may differ from those who do not in ways that affect outcomes.
• Was the exact product tested? An isolated compound or standardized research preparation is not necessarily equivalent to a commercial mixture.
• Were harms and interactions assessed? A study may be too small or too short to detect uncommon but serious adverse effects.
• Who funded the research? Funding does not automatically invalidate findings, but study design, transparent reporting, and independent replication matter.

Be cautious of products claiming to work for every cancer type, activate the immune system without risk, reverse resistance to immunotherapy, or replace standard cancer treatment.

14. Frequently Asked Questions

Can I take vitamin C during immunotherapy?

Vitamin C obtained through ordinary foods is different from high-dose oral supplements or intravenous infusions. There is insufficient evidence to recommend high-dose vitamin C as a general immunotherapy enhancer. Discuss supplements and infusions with your oncology team, particularly if you have kidney problems or other medical risks.

Is vitamin D safe during cancer immunotherapy?

Vitamin D may be appropriate when indicated, including for a documented deficiency. Research published in 2025 found associations between vitamin D status, supplementation, and better immunotherapy outcomes, but it did not establish that high-dose vitamin D improves cancer treatment response. Dose selection should account for clinical circumstances, kidney function, and calcium levels.

Should I stop all antioxidants?

There is no universal instruction to eliminate all antioxidants from food. The principal concern is unreviewed supplementation, particularly high-dose products during active cancer treatment. Discuss individual products with your treating team rather than avoiding nutritious foods.

Can probiotics make immunotherapy more effective?

The gut microbiome is an active research area, and clinical studies have produced promising but heterogeneous findings. They do not establish that a particular commercial probiotic is effective for every cancer or immunotherapy regimen. Do not start probiotics specifically to improve treatment response without discussing the risks and potential benefits with your oncology team.

Can I take turmeric or curcumin?

Food-level turmeric and concentrated curcumin extracts are different exposures. Concentrated products may have variable formulations and potential interactions or liver risks. Disclose the product, dose, and reason for use before continuing or starting it.

Are medicinal mushrooms safe during immunotherapy?

Different mushroom species and extracts have different compositions. Evidence that a particular product improves outcomes with a specific checkpoint inhibitor is generally insufficient to support routine use. Product quality, possible adverse effects, and interactions need to be considered.

Can I take a multivitamin?

A standard-dose multivitamin may be reasonable for some people with inadequate dietary intake, but it is not necessary for everyone and is not a proven anticancer treatment. Check the ingredient amounts to avoid duplicating high doses across multiple products.

Should I stop a supplement before every immunotherapy infusion?

There is no universal pause interval for all supplements and immunotherapy drugs. Some products may require discontinuation, while others may be appropriate to continue. Ask your oncology team for product-specific instructions; simply separating a supplement and medicine by a few hours may not prevent an interaction.

What if my oncologist does not know much about a supplement?

Ask for a review by an oncology pharmacist, oncology dietitian, or another qualified clinician with access to reliable interaction resources. Provide the exact ingredient list and dose. If the evidence is inadequate, the safest conclusion may be to avoid a nonessential product during treatment.

Can supplements replace immunotherapy or reduce its dose?

No supplement should be used as a reason to replace prescribed cancer treatment or change its dose. Decisions about continuing, delaying, or modifying treatment should be made with the oncology team based on clinical findings, treatment response, and adverse effects.

15. Key Takeaways for Patients and Caregivers

• Disclose everything. Include vitamins, herbal preparations, probiotics, protein powders, traditional remedies, and intravenous products.
• Treat a deficiency, not a marketing promise. A supplement may be valuable for a specific nutritional indication without being an anticancer therapy.
• Be cautious with high doses. More is not necessarily better, especially when evidence of benefit is uncertain.
• Interpret microbiome research carefully. Emerging findings about fiber, probiotics, and immunotherapy are interesting, but they do not justify universal supplement recommendations.
• Separate food from concentrated extracts. A normal food ingredient and a high-dose capsule may have different risks.
• Report new symptoms promptly. Do not self-treat possible immune-related adverse events with supplements or delay medical evaluation.
• Keep standard cancer care central. Supportive nutrition and appropriate complementary approaches should be coordinated with, rather than substituted for, evidence-based oncology treatment.

References and Further Reading

1. National Cancer Institute. Cancer Therapy Interactions With Foods and Dietary Supplements (PDQ®) — Patient Version. Read the evidence summary.
2. National Cancer Institute. Cancer Therapy Interactions With Foods and Dietary Supplements (PDQ®) — Health Professional Version. Read the professional review.
3. National Cancer Institute. Popular Diets, Supplements, and Cancer. Read the patient resource.
4. National Center for Complementary and Integrative Health. Cancer and Complementary Health Approaches: What You Need to Know. Read the guidance.
5. National Center for Complementary and Integrative Health. Antioxidant Supplements: What You Need to Know. Review the evidence and safety information.
6. Yang Q, et al. Higher serum vitamin D concentration and supplementation were associated with improved survival outcomes and treatment response in cancer patients receiving immunotherapy: A systematic review and meta-analysis. Nutrition Research. 2025;141:82–95. https://doi.org/10.1016/j.nutres.2025.08.003.
7. Spencer CN, et al. Dietary fiber and probiotics influence the gut microbiome and melanoma immunotherapy response. Science. 2021;374(6575):1632–1640. https://doi.org/10.1126/science.aaz7015.
8. National Cancer Institute. A high-fiber diet may improve the response of melanoma patients to immunotherapy. Read the research summary.
9. Memorial Sloan Kettering Cancer Center. About Herbs, Botanicals & Other Products. Search product-specific information.
10. Modulating the gut microbiome to enhance cancer immunotherapy: A systematic review and meta-analysis of probiotics and fecal microbiota transplantation. 2026. Review the published abstract.

Medical Disclaimer

This article is for general educational purposes and is not a substitute for personalized medical advice, diagnosis, or treatment. Supplement safety depends on the specific cancer, immunotherapy regimen, other medicines, laboratory results, organ function, and individual risk factors. Evidence may change as new clinical trials are published. Always discuss supplements and complementary therapies with your treating oncology team before starting, stopping, or changing them.

Editorial principle: Complementary care should support patients, preserve informed choice, and work alongside appropriate standard cancer treatment—not promise cures or create avoidable risks.