Reviewed by Lise Alschuler, ND

What are antioxidants?

Antioxidants are substances that may protect cells against damage through interacting with and stabilizing free radicals. According to the National Cancer Institute, free radical damage may lead to cancer. Therefore, learning about the relationship between antioxidants and cancer is an important part of an integrative cancer care plan.

What are free radicals? What is oxidative stress? What is their relationship to cancer?

Free radicals are unstable molecules that play a role in illness. High levels of free radicals in the body develop from oxidative stress. Oxidation involves the loss of an electron from an atom or molecule. Since atoms and molecules want to have a full set of electrons, free radicals that form during oxidative stress search for and combine with other molecules to acquire electrons. In this process, free radicals can attack the mitochondria and damage DNA. Since pieces of DNA are genes telling cells how to work in the body, when to grow, and divide, free radicals can initiate cancer development and growth.

“Free radicals do not stop with DNA. They can also damage the endothelial cells that line blood vessels, making it easier for tumor cells to enter and exit the bloodstream—their highway to metastasis. Free radicals help tumors release metastatic cells, promote angiogenesis (growth of blood vessels that feed tumors), and damage the cancer cell’s internal communication network by increasing the level of signaling molecules responsible for out-of-control proliferation.”
-Keith Block, MD, Life Over Cancer

What causes oxidative stress?

A poor diet, pollution, toxins, medications, alcohol, smoking, lack of exercise, stress, trauma, aging, infections, radiation, cancer cells, conventional cancer treatments, and other factors contribute to oxidative stress.

What are the potential health benefits of antioxidants?

The potential benefits of antioxidants vary based on the specific type of antioxidant and dosage.

• Stabilizes free radicals  
• Reduces inflammation
• Aids detoxification
• Supports the mitochondria—the powerhouse of energy production in cells 
• Slows and possibly prevents the development of cancer
• Reduces toxicity from and enhances conventional cancer treatment efficacy^1-3

According to the National Cancer Institute, antioxidants protect cells against free radicals and therefore provide cancer protection. For people with cancer, the effects of antioxidants in the body vary based on the cancer cell type.

What are the potential risks of antioxidants? What is essential to know about antioxidants and cancer?

Controversy exists about potential contraindications between antioxidants, chemotherapy, and radiation. Some research results show both potential benefits and harm from antioxidants⁴. Previous research-related concerns about combining antioxidants with chemotherapy and/or radiation predominantly stem from the following mechanisms. Antioxidants fight oxidative stress and kill free radicals providing significant health benefits. Some chemotherapy agents and radiation create oxidative stress and high levels of free radicals producing anti-cancer activity and severe adverse effects in the process. Patients and providers must know that risks of interactions between chemotherapy and antioxidants depend on the type of chemotherapy since some chemotherapy agents do not rely on oxidative stress and free radicals for anti-cancer activity^5,6.

However, more recent research indicates that antioxidants increase oxidation and therefore increase benefits of chemotherapy. Studies suggest much less concerns about chemotherapy and antioxidants compared to radiation.

The benefits and risks of antioxidants, some chemotherapy agents, and radiation are also explained as follows.

“Many of the natural substances that show promise as adjuvant cancer treatments are powerful antioxidants, meaning they can prevent and reverse oxidative damage caused by free radicals. Total antioxidant status declines during cancer treatment, so shoring up antioxidant status naturally may help reduce side effects of conventional therapies. In addition, antioxidant decline is correlated with decreased quality of life and decreased longevity. However, despite compelling reasons to use antioxidants along with chemotherapy and radiation, there are also times when this is ill advised. Radiation therapy and some chemotherapy agents create free radicals and oxidation purposefully in order to damage the DNA of the cancer cells. Certain antioxidants, when present in high amounts, interfere with this tumor-killing effect, so it is inadvisable to use them while undergoing these conventional treatments.”
-Lise Alschuler, ND and Karolyn Gazella, Definitive Guide to Cancer, 3rd Edition: An Integrative Approach to Prevention, Treatment, and Healing

What specific recommendations regarding antioxidants exist for people receiving chemotherapy and/or radiation?

No broad consensus exists around recommendations for this issue and guidance is often contradictory. At the same time, studies provide information about specific chemotherapy agents that produce high oxidative stress creating a higher risk for increased interactions with antioxidant supplements⁶. Providers may or may not be informed about the studies and recommend that patients not use antioxidants in general or take antioxidants without any restrictions.

Dr. Alschuler also recommends using antioxidants with the following guidelines and considerations⁵.

Avoid high dose antioxidant supplementation during days of administration and 1/2 life of oxidative chemotherapy and radiation, unless the following factors are present.

• Specific antioxidant compound has been studied with the specific chemotherapeutic agent or radiation and has known quality of life and survival benefits
• Chemotherapy agent does not exert its effects through the oxidative mechanism
• Quality of life outweighs the survival benefit such as palliative chemotherapy
• Individual depletion of antioxidants may reduce the efficacy of chemotherapy

What are some specific antioxidants?

Many foods and supplements are rich in antioxidants. Cancer Fighting Foods provides information about many foods with antioxidants. Also read the article Glutathione and Cancer since glutathione is the master detoxifier and main antioxidant in the body, including information about foods and supplements that provide glutathione. A qualified integrative cancer care provider can optimally recommend specific supplements for each individual with the specific dosages and combinations.

For More Information

• The Definitive Guide to Cancer, 3rd Edition: An Integrative Approach to Prevention, Treatment, and Healing by Lise Alschuler, ND and Karolyn A. Gazella
• Integrative Oncology by Donald Abrams, MD and Andy Weil, MD
• Life Over Cancer by Keith Block, MD

References

1. Block KI, Koch AC, Mead MN, Tothy PK, Newman RA, Gyllenhaal C. Impact of antioxidant supplementation on chemotherapeutic toxicity: a systematic review of  the evidence from randomized controlled trials. Int J Cancer. 2008 Sep 15;123(6):1227-39. Review. PubMed PMID: 18623084.
2. Block KI, Koch AC, Mead MN, Tothy PK, Newman RA, Gyllenhaal C. Impact of antioxidant supplementation on chemotherapeutic toxicity: a systematic review of  the evidence from randomized controlled trials. Int J Cancer. 2008 Sep 15;123(6):1227-39. Review. PubMed PMID: 18623084.
3. Simone CB 2nd, Simone NL, Simone V, Simone CB. Antioxidants and other nutrients do not interfere with chemotherapy or radiation therapy and can increase kill and increase survival, part 1. Altern Ther Health Med. 2007 Jan-Feb;13(1):22-8. Review. PubMed PMID: 17283738.
4. Lawenda BD, Kelly KM, Ladas EJ, Sagar SM, Vickers A, Blumberg JB. Should supplemental antioxidant administration be avoided during chemotherapy and radiation therapy? J Natl Cancer Inst. 2008 Jun 4;100(11):773-83. Epub 2008 May 27. Review. PubMed PMID: 18505970.
5. Lise Alschuler, ND presentation at the 17th International Symposium on Functional Medicine, May 2010
6. Integrative Oncology by Donald Abrams, MD and Andy Weil, MD