A study from China shows that antioxidant pills caused mice with liver cancer or colon cancer to have their cancers spread rapidly though their bodies (Science Translational Medicine, Apr 13, 2016:8(334):334ra51). The study used saxagliptin, sitagliptin, and a-lipoic acid, three powerful antioxidant drugs used to treat diabetes. The antioxidants protected the cancer cells from harm, rather than protecting the mice from spread of their cancers. These antioxidants activated NRF2 antioxidant signaling pathway that protected the cancer cells instead of protecting the mice.
The authors then tested antioxidant pills on cells taken from patients with malignant cancers and grown in test tubes. The antioxidants caused the human cancer cells to grow faster and spread through the cultures. Overall, the conclusion from this and several other cancer studies is that antioxidants can help healthy cells to be protected from free radicals in the body, but they can cause already-developed cancer cells to grow and spread. The researchers cautioned that more studies are needed to evaluate the safety of antioxidant-containing medications for diabetic patients with cancer. They want to confirm their findings in human cancer patients before any definitive clinical recommendations can be made.
Radiation and chemotherapy, the most common cancer treatments used today, are both based on generating oxidants that help to keep cancer from spreading. Ionizing radiation kills cancer cells by generating oxidants. Chemotherapy drugs such as paclitaxel kill cancer cells by generating very powerful oxidants -- superoxide, hydrogen and hydrogen peroxide (Cancer Res, September 15, 2005;65(8455)).
What are Antioxidants? Every chemical reaction in your body works by transferring electrons from one molecule to another. During a chemical reaction, molecules and atoms called free radicals are formed and contain an unpaired electron that has an electrical charge that can destroy tissue and damage DNA. Antioxidants are molecules that donate an electron to the free radical, thus neutralizing the electrical charge and stabilizing it. Without antioxidants, the electrical charge of free radicals causes oxidative stress that is associated with aging, heart failure, cancer, Alzheimer’s, and just about every disease.
There are thousands of antioxidants, including vitamins A, C and E, minerals such as selenium and zinc, and enzymes that cause chemical reactions to proceed in your body. Foods containing antioxidants include fruits, vegetables, grains, tea, chocolate, red wine and many others, but no good studies have shown that antioxidants in foods are harmful. The many studies showing harm from antioxidants have used pills containing single antioxidants or combinations of antioxidants that have been removed from foods or manufactured in laboratories. We do not know why antioxidants in foods are different, but it may be be that antioxidants in foods are affected by other chemicals found in the same foods. For example, "chocolate has more than 20 antioxidant flavonoids. One is converted into a free radical and becomes reactive, but less reactive [than the first]. It then reacts with another, and that one is less reactive and so on and so forth, and all of them react with each other, decreasing the damage that would be happening to our lipids, or proteins or DNA" (Int J Mol Sci, 2012; 13(2): 2091–2109).
How Antioxidants Can Harm You After an antioxidant donates an electron to a free radical, it becomes charged and can damage your cells. Foods contain many different antioxidants, so an antioxidant in a food has many other antioxidants readily available to neutralize the charge it picks up. However, in a pill, the antioxidant stands alone or has only one or a few other antioxidants to protect it. Antioxidants taken in pills can carry and retain electrical charges that damage your cells, which can cause aging and diseases including cancer.
Your cells are supposed to protect you from free radicals by producing their own antioxidants. Since exercise produces huge amounts of oxidants, exercise causes a natural production of antioxidants by your own body, and therefore exercise helps to protect you from free radicals, aging, cancer and disease (Nutrition & Food Science, 2014;44(2):95-101). When you take antioxidant pills, you markedly reduce the amount of antioxidants that your own body produces. Antioxidant supplements also prevent growth of new mitochondria in exercisers (The Journal of Physiology, February 3, 2014) See my report on Antioxidant Pills May Reduce Gains from Exercise
Other Studies Showing That Antioxidant Pills May Cause Cancers to Spread This new study from China is just the latest of many studies showing that antioxidant pills may cause an existing cancer to spread. A study from Notre Dame showed that antioxidant pills may cause an existing breast cancer to spread through the body (Cancer Res, June 15, 2013;73(12);3704–15). Research from the University of Gothenburg in Sweden showed that people who take antioxidant vitamin pills suffer twice as much melanoma metastasis (Science Translational Medicine, Oct 7, 2015:7(308):308re8). Another study from Gothenburg's Sahlgrenska Academy showed that antioxidants accelerate lung cancer progression in mice (Science Translational Medicine, Jan 29, 2014:6(221):221ra15). The authors of this study state, "Our current research combined with information from large clinical trials with antioxidants suggests that people who have been recently diagnosed with cancer should avoid such supplements." They also note that skin lotions and suntan lotions often contain large amounts of antioxidants such as vitamin E and beta carotene.
Antioxidants Not Shown to Prevent Cancer or Heart Attacks One of the largest trials on antioxidants was halted because it showed that the antioxidant vitamin E offered no prevention of cancer and that it was associated with increased risk for prostate cancer (JAMA, October 12, 2011;306(14):1549-1556). A review of 68 controlled trials showed that antioxidant pills beta, carotene, vitamin A, and vitamin E are associated with an increased death rate (JAMA, 2007;297(8):842-857). Clinical trials also showed that antioxidants do not prevent heart attacks or strokes (British Medical Journal, June 17, 2014).
Antioxidant Pills are Everywhere Antioxidant supplements are widely available in stores and online, and they are often promoted with claims that they can help to prevent and cure cancer. A 2011 report from the National Center for Health Statistics estimated that 53 percent of American adults take supplements and spent $28 billion on them in 2010 alone. Research at Sahlgrenska Academy has shown that cancer patients are particularly prone to taking supplements containing antioxidants.
• There is no credible evidence that antioxidant pills, such as vitamins A, C, and E or minerals such as selenium, are effective in preventing cancer, heart attacks or diabetes.
• A multibillion dollar industry is based on the unproven concept that antioxidants promote health.
• There is evidence that antioxidant pills may spread existing cancers.
• Some data show that antioxidant pills may increase risk for cancer and reduce benefits of chemotherapy.
• Instead of taking antioxidant pills or any other supplements, I recommend that you eat a varied diet that contains plenty of plants.
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