Dietary and Herbal Products

Approved by the Cancer.Net Editorial Board, 03/2015

Listen to the Cancer.Net Podcast: Dietary and Herbal Supplements, adapted from this content.

Key Messages:

  • Be an informed consumer before taking dietary and herbal products to reduce the treatment side effects of cancer and improve overall health.
  • Talk with your doctor to learn about the safety of any products, including any interactions with current cancer treatments and other side effects.

People living with cancer may consider taking dietary and herbal products, also called supplements. Many hope that these products boost health, improve nutrition, or reduce treatment side effects. It’s important to discuss the possible benefits and risks of specific products with your doctor before taking them. There are two different types of products:

  • Dietary products have one or more dietary ingredients, such as vitamins, minerals, herbs, enzymes, amino acids, and hormones. People do not need a prescription to purchase these in pharmacies, grocery stores, health food stores, and over the Internet. These products come in many forms, such as pills, capsules, tablets, liquids, creams, or powders.
  • Herbal and botanicals products contain plants or ingredients from plants. These also come in several forms, such as tablets, capsules, powders, liquids, and tea bags.

Dietary and herbal products as complementary therapy

Standard medicine is scientifically tested to make sure it is safe and works well. Standard treatments are approved by the U.S. Food and Drug Administration (FDA). But, dietary and herbal products do not usually undergo thorough testing or require the same type of FDA approval before being sold to consumers.

Patients may consider using dietary and herbal products as a complementary therapy. A complementary therapy is one that is combined with standard medicine. Complementary medicine is also commonly called integrative medicine. Alternative medicine, on the other hand, are therapies that some people promote instead of standard therapy.

For example, taking ginger to help reduce nausea during chemotherapy is a complementary therapy. Some products are safe when patients use them for a specific purpose with a doctor's guidance.  

However, taking ginger to cure cancer instead receiving chemotherapy would be an alternative therapy. Despite claims, there is no dietary or herbal product that cures or treats cancer. In fact, many products interfere with cancer treatment and can be harmful.

Evaluating the safety of products

It can be difficult to know how safe and effective dietary products are. Information about dietary products is often based on people's personal stories, instead of scientific studies. People commonly believe that herbs and other products are safe because they are "natural" or because people have used them for a long time. However, safety varies depending on the dietary product’s ingredients, dose, preparation, and effect on each person.

People receiving cancer treatment must be very cautious about the safety of dietary products because some can interfere with surgery, chemotherapy, and radiation therapy. For example, the herb kava can interfere with anesthesia for surgery. Other herbs interfere with blood clotting, and many interfere with chemotherapy. Consider the following safety issues of dietary and herbal products:

  • Some products can cause serious side effects even when taken at the recommended dose. These can include high blood pressure, nausea, diarrhea, constipation, fainting, headaches, seizures, heart attack, or stroke. Contact your doctor right away if you experience any harmful side effects.
  • Ingredients in some products can interfere with prescription and over-the-counter medications you may already be taking. In addition, as stated above, some can interact with cancer treatments.
  • Certain dietary products may be unsafe if you have specific health problems, including high blood pressure, diabetes, mental health conditions, or heart disease.

How the FDA regulates products

The FDA regulates dietary products differently than prescription or over-the-counter medications. The FDA does not approve dietary products as safe and effective before people can buy them. The FDA can only claim that a product is unsafe after consumers have reported problems with it. Thus, the degree of quality control depends on the manufacturer, the supplier, and others in the product's production process.

The claims made on product labels are often confusing. The FDA allows dietary product labels to include one of three types of claims:

  • A health claim, which describes an FDA-approved link between a food, food component, or dietary product and a disease or health-related condition
  • A nutrient content claim, which describes the level of a nutrient or dietary substance contained in the product
  • A structural or functional claim, which describes how a dietary ingredient affects the body. Product labels with this type of claim must also include a disclaimer that reads, "This statement has not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease." In other words, the claim may not be true because researchers have not tested it.

Recommendations if you decide to use supplements

  • Purchase only single-ingredient products approved by your doctor that clearly show how much each dose contains. Also, use brands from companies you or your doctor know are reputable. Most products contain more than one ingredient. Many are contaminated with other unlabeled herbs, pesticides, prescription drugs, heavy metals, or other substances.
  • Look for a certification mark or seal from an independent, third-party organization, such as U.S. Pharmacopeial Convention, the Good Housekeeping Research Institute, or Although tests differ, such labels indicate that the product has met certain manufacturing standards.
    • Check the label to find out if researchers have scientifically tested the product. Contact the manufacturer for the test results, and ask your doctor to explain anything that isn't clear.
    • Be skeptical of claims on the labels of products, particularly those that claim to cure cancer. No single remedy or treatment can successfully treat all cancers, and no dietary or herbal product can cure cancer.

Talking with your doctor about products

Deciding whether, when, and how to use a dietary product to complement cancer treatment is complicated. It's important to be an informed consumer. Discuss the choice with a member of your health care team, and use one of the scientific websites listed below to address the following considerations:

  • Possible benefits and risks, depending, in part, on personal medical history

  • Possible interactions with current cancer treatments

  • Possible side effects

  • Dosage levels and length of treatment

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

More Information

Side Effects

Vitamins and Minerals

Additional Resources

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: Background Information

FDA: Tips For Dietary Supplement Users