Supplements in the Fight Against Cancer

Reviewed by Melinda Ratini, DO, MS on September 04, 2020

Many people take vitamins and supplements while they are being treated for cancer; some take them to prevent cancer. Here are tips to help you shop wisely.

Vitamins and Supplements to Fight Cancer

Cancer patients are increasingly turning to supplements to strengthen their immune systems and ease nausea from chemotherapy.

Vitamin D

Vitamin D is one of the most studied supplements for cancer prevention and treatment right now.


Vitamin A, vitamin C, vitamin E , and beta-carotene contain antioxidants once thought to help prevent cancer. However, more recent studies show that high levels of these, in supplement form, may increase cases of gastrointestinal cancers, such as stomach, colon, and esophageal, in some populations. However, eating foods that contain these vitamins reduces the risk of many kinds of cancer.

Fiber (Psyllium)

Dietary fiber helps ease constipation, which may be caused by some cancer medicines.

Folic Acid

Folic acid helps reduce the toxicity of the cancer drug methotrexate. However, in men, high levels of folic acid may raise the risk of prostate cancer.


Iron supplements can improve the fatigue caused by iron-deficiency anemia, which can result from chemotherapy and radiation.

Information About Vitamins and Supplements

Do you know how to evaluate vitamins and supplements? There are so many vitamins, supplements, and herbal extracts on the shelves. Use these tips to find out which ones may be right for you.

Safe Upper Limits for Vitamins and Minerals

When it comes to vitamins and minerals, how much should you take? Find out the safe upper limits for the vitamins you take, as well as the recommended daily allowance you may need.

Vitamin and Supplement Glossary: Common Definitions

This glossary provides simple definitions for common terms such as antioxidants, fat soluble, or phytochemicals. Find out what the lingo really means.

Show Sources


American Cancer Society: “What are the possible side effects of chemotherapy?” “Cancer-related fatigue and anemia;” “Dietary supplements: How to know what is safe;” and“Antioxidants and cancer: The jury’s still out.”

World Cancer Research Fund: “Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective.”

Memorial Sloan-Kettering Cancer Center: "About Herbs Database. 

"National Center for Complementary and Alternative Medicine: “Cancer and CAM.”

National Cancer Institute, Surveillance Epidemiology and End Results (SEER): “SEER Stat Fact Sheets.”American Society of Clinical Oncology 44th Annual Meeting, Chicago, May 30-June 2, 2008.

Natural Medicines Comprehensive Database.

Harvard Health Publications: "Online Medical Dictionary." "Vitamins and Minerals: What You Should Know."

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