Dietary and Herbal Products

Approved by the Cancer.Net Editorial Board, 05/2019

People with cancer often consider taking dietary and herbal products. These are also called supplements. Many hope that these products improve health, provide nutrition, boost the immune system, or reduce side effects. However, supplements may or may not be safe or effective. Make sure you discuss the benefits and risks of specific products with your health care team before taking them.

There are 2 different types of supplements:

  • Dietary products. These have 1 or more ingredients, such as vitamins, minerals, herbs, enzymes, amino acids, and hormones. People do not need a prescription to purchase these. They can be bought in pharmacies, grocery stores, health food stores, and online. They may come as pills, capsules, tablets, liquids, creams, or powders.
  • Herbal, botanical, and other natural products. These contain plants or parts of plants. Other natural products might contain extracts from animals, such as toad or snake venom. These products may come in tablets, capsules, powders, liquids, and tea bags.

Evaluating the safety of dietary and natural products

Standard medicines go through many scientific tests to make sure they are safe and effective. Then, in the United States, the Food and Drug Administration (FDA) approves these tested standard treatments. However, the FDA does not test or approve dietary or natural products before people can buy them. So information about their safety and effectiveness often comes from:

  • Promotions or other marketing

  • People who believe that they are safe because they are “natural”

  • Personal stories of people who have used these products for a long time and assume they are useful and safe

  • Naturopaths, traditional medicine doctors, and others who recommend them as part of their practice

However, the safety and effectiveness of these products depends on the ingredients, dose, and preparation. The supplement’s manufacturer and supplier are responsible for these factors. Without any regulation, these products may contain harmful ingredients or excess amounts of some ingredients.

It is important to read a product’s label before taking it. The FDA allows dietary product labels to include 1 of 3 types of claims:

  • Health claim. Describes an FDA-approved link between a food, ingredient, or dietary product and a disease or other health condition.

  • Nutrient content claim. Describes the level of a nutrient or dietary substance in the product.

  • Structural or functional claim. Describes how a dietary ingredient affects the body. These products must also include the disclaimer, "This statement has not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease." This means the claim may not be true because researchers have not tested it.

Once a dietary or natural product is available, the FDA can only claim that it is unsafe after consumers report problems with it.

Dietary and natural products for people with cancer

Some people receiving cancer treatment may choose to use dietary and natural products in 1 of these ways:

  • Complementary therapy. This is when people with cancer use dietary and natural products in addition to their standard medicine. For example, taking ginger supplements to reduce nausea during chemotherapy. Some products are safe when people use them for a specific purpose with a doctor's guidance. However, there can be concerns about interactions between drugs and herbs that have not been well researched.

  • Alternative therapy. This is when patients use these products in place of standard therapies. For example, taking ginger to cure cancer instead of receiving chemotherapy. No dietary or natural product can cure or treat cancer. Many products may even interfere with cancer treatment or be harmful.

People receiving cancer treatment must be very cautious about using dietary and natural products. Some of these products can:

  • Interfere with surgery, chemotherapy, and radiation therapy.

  • Cause serious side effects. These can include:

    • High blood pressure

    • Nausea

    • Diarrhea

    • Constipation

    • Fainting

    • Headaches

    • Seizures

    • Heart attack

    • Stroke

Contact your doctor right away if you experience any harmful side effects.

  • Interfere with prescription and over-the-counter medications you are already taking.

  • Be unsafe if you have specific health problems. These include high blood pressure, diabetes, mental health conditions, heart disease, or blood clotting problems.

Recommendations if you decide to use supplements

  • Buy only single-ingredient products approved by your doctor. Some products contain other unlabeled herbs, pesticides, prescription drugs, heavy metals, or other substances. Also, make sure the bottle clearly shows how much each dose contains.

  • Use brands from companies you or your doctor know are trustworthy.

  • Look for a certification mark or seal from an independent, third-party organization. These include:

These marks or seals usually indicate that the product has met certain manufacturing standards.

  • Check the label to see if researchers have tested the product. Contact the manufacturer for the test results. And ask your doctor to explain anything that is not clear.
  • Be skeptical of claims on labels, particularly those that say the product will cure cancer. No single remedy or treatment can successfully treat all cancers. And no dietary or natural product can cure cancer.

Talking with your health care team about products

Deciding if, when, and how to use a dietary or natural product during cancer treatment is difficult. Take the following steps to be an informed consumer:

  • Discuss your choice with a member of your health care team. Make sure they understand the reason you want to use the dietary product.

  • Ask your doctor about safer standard treatments for your issue that have been proven to be effective. For example, yoga or meditation are safer than a supplement for sleep problems and have been found effective.

  • Use the scientific websites listed under “More Information” below to address:   

    • Possible benefits and risks, depending on personal medical history

    • Possible interactions with cancer treatments

    • Possible side effects

    • Dosage and treatment length

    • New information about the supplement, preferably from clinical trials, rather than personal stories

Related Resources

Side Effects

Types of Complementary Therapies

Evaluating Complementary and Alternative Therapies

5 Things You Should Know About Herbs and Supplements

More Information

Federal Trade Commission: Cancer Treatment Scams

Memorial Sloan Kettering Cancer Center: About Herbs, Botanicals & Other Products

National Center for Complementary and Integrative Health: Using Dietary Supplements Wisely

National Institutes of Health’s Office of Dietary Supplements: Dietary Supplements

FDA: Tips For Dietary Supplement Users

Natural Medicines Comprehensive Database