Popular Diets and Dietary Supplements

What about Dietary Supplements?

Dietary Supplements (vitamins, minerals, herbs, etc.)

Many companies claim their dietary supplements cure cancer or help slow its growth. Many patients going through cancer treatment want to use these supplements, think this will help them fight cancer and avoid side effects like fatigue.

While many of these products are "natural," that does not mean they are all safe. Many of them can actually interfere with chemotherapy treatments, making these treatments less effective at fighting cancer.

Current research does not support the use of supplemental vitamins, minerals, or herbs during cancer treatment.

It is true that a healthful diet can help protect against cancer and help fight cancer. However, vitamin supplements do not help protect against cancer or help fight cancer. Most experts agree that, for now, the best way to get nutrients if from foods, not supplements.

Instead of trying to use supplements to fill gaps in your diet, focus on eating healthfully. Plan your meals and snacks, and make regular shopping trips. A well-balanced diet that includes all food groups will often have all the nutrients essential to a cancer-fighting diet.


Many supplements can interact with medications and treatments, or make blood work worse. Supplements are not recommended during treatment. If you decide to take dietary supplements, be sure to discuss your plans with your medical team BEFORE treatment begins.

Research continues to explore the use of herbs, antioxidants, vitamins, and minerals during cancer treatment. Research currently suggests that taking supplements does not help prevent or reverse cancer.

Megadoses (very large doses) can be toxic or harmful in some instances. For example, high doses of vitamin C can increase the risk of kidney stones. Vitamin B6, even in moderate dosages, can result in nerve damage. Vitamin A toxicity can lead to changes in bone development, an enlarged liver, anemia, and loss of hair. If you want to take a dietary supplement, talk to you cancer doctor or pharmacist about whether a safe dose exists.

How to Get What You Need from Your Diet

The best way to eat all the nutrients you need is through a healthy diet. The nutrients needed to help your body fight cancer are found in a well-balanced diet emphasizing plant-based foods.

The New American Plate (pictured below) was developed by the American Institute for Cancer Research. This picture shows what a healthy meal can look like. When planning your meals, aim to cover most of each plate (at least 2/3) with plant foods like fruits, vegetables, beans, and whole grains. The rest of the plate (1/3) can include animal foods like chicken, fish, eggs, cheese, and yogurt.

The New American Plate

Included below is a list of "superfoods." According to the American Institute for Cancer Research, these foods have some cancer-fighting properties. A healthy diet including superfoods should not replace cancer treatments. Instead, use diet to help you fight cancer as you go through cancer treatment.

For a complete list of foods that fight cancer visit the AICR's section on Foods that Fight Cancer.

  • Apples
  • Blueberries
  • Cherries
  • Cranberries
  • Cruciferous Vegetables (broccoli, cauliflower, Brussels sprouts, cabbage, bok choy, kale, etc.)
  • Dark Leafy Greens (spinach, kale, collard greens, turnip greens, etc.)
  • Flaxseed (ground or milled)
  • Garlic
  • Grapes
  • Green Tea
  • Beans and Peas
  • Winter squash (butternut, acorn, pumpkins, etc.)
  • Soy (tofu, edamame, tempeh, miso)
  • Tomatoes
  • Whole Grains (oats, whole wheat, quinoa, millet, brown rice, wild rice, wheat berries, etc.)

Regulatory Issues

Dietary supplements are not required to meet the same safety standards as drugs. Companies that sell supplements don't even have to prove the supplement is effective before selling it to the public. You will notice that every supplement has a disclaimer on it.

Manufacturers are not required to have FDA approval prior to selling and marketing their products. This means that when using dietary supplements, you are relying solely on the manufacturer to make sure the product is safe, not the FDA. Only after there is a documented problem will the FDA take action.

More Resources

For more information on dietary supplements and specific food components and cancer risk, clic on the links below:

American Institute or Cancer Research, Diet Section - Provides current information regarding nutrition and cancer, and a full list of foods that fight cancer and glossary of nutrition and cancer terms.

Food, Nutrition, Physical Activity and the Prevention of Cancer - A report published by the World Cancer Research Fund and the American Institute for Cancer Research that reviews available research on cancer prevention by cancer type and specific dietary component.

Oregon State University Linus Pauling Center for Micronutrient Research - Summarizes function and current research regarding vitamins, minerals and popular dietary supplements.

NCI Office of Cancer Complementary and Alternative Medicine - Arm of the National Cancer Institute focused on research of complementary and alternative medicine techniques in the treatment of cancer.

National Cancer Institute, Nutrition in Cancer Care - Section of the NCI website devoted to maintaining adequate nutrition during cancer care.

Medline Plus - Trusted health information provided as a service from the U.S. National Library of Medicine, National Institutes of Health, contains information about specific dietary nutrients and food sources of those nutrients.

Natural Medicines Comprehensive Database - Database of natural medicines that evaluates current research findings for safety, efficacy, drug/nutrient interactions and common uses.

MedWatch - The FDA Safety Information and Adverse Event Reporting Program.

Note: We strongly encourage you to talk with your health care professional about your specific medical condition and treatments. The information contained in this website is meant to be helpful and educational, but is not a substitute for medical advice.

Key Points:

  • Don't take dietary supplements (vitamins, minerals, herbals, etc.)
  • If you choose to take dietary supplements during your cancer treatment, tell your doctor and cancer team before treatment begins.
  • Rely on foods, not supplements, to help fight cancer.
    • Choose a variety of foods from all food groups to make sure you are getting all the nutrients you need to fight cancer.
    • Include "superfoods" in your diet for additional anti-cancer benefits.

Due to variation in specific illness and treatment plans, eating practices of individuals diagnosed with cancer should be assessed throughout the continuum of care. Request an appointment with a registered dietitian at your treatment facility for a comprehensive nutrition assessment and tailored nutrition therapy plan to reflect your personal treatment goals.

If you are a patient at Taussig Cancer Institute at Cleveland Clinic, you can call (216) 444-6833 to schedule an appointment with the dietitian.

If you are a patient at Radiation Oncology at Cleveland Clinic, you can call (216) 444-5571 to schedule an appointment with a dietitian.

If you are not a Cleveland Clinic patient, you can call 216.444.3046 to schedule an appointment with a Cleveland Clinic dietitian.

If you are interested in corresponding with a Cleveland Clinic dietitian, but are unable to have an in-person appointment, we have two options for online, distance nutrition consultation services.

  • To schedule a MyConsult with a Cleveland Clinic dietitian, please to go http://www.eclevelandclinic.org/nutrition
  • To schedule a virtual nutrition consultation via the online platform ExpressCare Online, please call 216.444.3046.

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