Many people gobble big doses of vitamin C in hopes of boosting their immune system and warding off illness. But new research shows that in people with cancer, the vitamin may do more harm than good. Researchers at Memorial Sloan-Kettering Cancer Center in New York studied the effects of vitamin C on cancer cells. As it turns out, the vitamin seems to protect not just healthy cells, but cancer cells, too. The findings were published today in the journal Cancer Research. “The use of vitamin C supplements could have the potential to reduce the ability of patients to respond to therapy,” said Dr. Mark Heaney, an associate attending physician at the cancer center, in a press release. Dr. Heaney and his colleagues tested five different chemotherapy drugs on cancer cells in the laboratory. Some of the cells were first treated with vitamin C. In every case, including a test of the powerful new cancer drug Gleevec, chemotherapy did not work as well if cells had been exposed to vitamin C.
The chemotherapy agents killed 30 to 70 percent fewer cancer cells when the cells were treated with the vitamin. A second set of experiments implanted cancer cells in mice. They found that the tumors grew more rapidly in mice that were given cancer cells pretreated with vitamin C. The researchers found that just like healthy cells, cancer cells also benefit from vitamin C. The vitamin appeared to repair a cancer cell’s damaged mitochondria, the energy center of cells. When the mitochondria is injured, it sends signals that force the cell to die, but vitamin C interrupts that process. “Vitamin C appears to protect the mitochondria from extensive damage, thus saving the cell,” Dr. Heaney said. “And whether directly or not, all anticancer drugs work to disrupt the mitochondria to push cell death.” Dr. Heaney measured the buildup of vitamin C levels in cells and said that the levels of vitamin C used in the experiments were similar to those that would result if a patient took large doses of the vitamin in supplement form.
Earlier research at the cancer center showed that vitamin C seems to accumulate within cancer cells more than in normal cells. Patients should eat a healthy diet that includes foods rich in vitamin C, Dr. Heaney said, but it’s the large doses of vitamin C in tablet form that are worrisome. Also known as: Ascorbic acid.Potential uses: Vitamin C is used to prevent cardiovascular problems, such as heart attacks and strokes, the breakdown of joint cartilage (osteoarthritis), and eye problems such as cataracts and macular degeneration. Vitamin C may help ease the length or severity of colds in some people. It also may play a role in lowering the risk for certain cancers, such as lung cancer and cancers of the digestive and gastrointestinal tract.Usual dose: The recommended daily minimum intake of vitamin C is 75 milligrams per day for women and 90 milligrams per day for men. People who smoke should take 35 milligrams per day more than that. Between 250 milligrams per day and 1,000 milligrams per day is considered a reasonable dosage.
This can come from foods and/or vitamin C supplements.Are there any risks? Very high doses of vitamin C — more than 2,000 milligrams per day — can cause side effects such as diarrhea, gas, and stomach upset. Other risks include kidney damage and having too much iron in the blood. Vitamin C can interfere with blood thinners such as Coumadin (chemical name: warfarin). There are some concerns that large doses of vitamin C might reduce the effectiveness of certain cancer treatments, such as chemotherapy and radiation.What does the research show? Although selected studies have found that women who consume higher amounts of vitamin C have a lower risk of breast cancer, research in general has not shown a strong connection. A recent review of 38 studies on vitamin C and cancer in general concluded that vitamin C cannot treat or prevent cancer. However, some studies have shown a connection between eating foods rich in vitamin C, such as fruits and vegetables, and reduced risk of breast cancer and other forms of cancer.
Researchers are investigating whether vitamin C given intravenously, rather than orally, may be helpful in treating cancer. Stay informed about current research, online events, and more. Read our privacy policyNew research is underway which might shed much-needed light on a popular but highly controversial cancer treatment. Thousands of cancer patients worldwide are turning to high-dose infusions of vitamin C in the hopes of halting the cancers' spread. However to date there has been little to no hard scientific evidence the treatment can help with this. Now world-leading New Zealand vitamin C researcher Professor Margreet Vissers is launching a new study which it's hoped will help give a more definitive answer as to whether vitamin C holds genuine potential as a treatment. Her Otago University study will analyse the levels of vitamin C in breast tumours and compare health outcomes for patients with varying levels of the vitamin in those tumours. The NZ Breast Cancer Foundation and the Canterbury Medical Research Foundation have teamed up for the first time to fund the study which will be carried out analysing samples from the Christchurch Cancer Society tissue bank.
Professor Vissers has been studying how vitamin C works in tumour tissue for the past decade. Her previous ground-breaking study, published last year, examined bowel and endometrial tumor tissue and discovered that patients with higher levels of vitamin C in their tumours had extended disease-free survival. "The use of vitamin C by cancer patients is commonplace but highly controversial," Professor Vissers said. "Some patients claim to benefit but we've been short on clinical evidence. If vitamin C works, we need to know how it works and for which tumours. If this study shows that breast cancer responds in the same way as bowel cancer, we'll be able to include breast cancer patients in upcoming clinical studies." Auckland mother Rochell Adams has been battling stage four breast cancer since 2009. Despite surgery and chemotherapy the cancer returned in 2013 and spread to her lungs, spine, lymph nodes, and hips. I certainly walk out of the clinic feeling a million dollars and my skin is glowing.
It also helps with the pain" She was told she had two to four months left to live. She travelled to Germany for various treatments which shrank the tumours but didnt totally eradicate them. Her German doctors suggested she try vitamin C infusions on her return home. She now credits vitamin C, along with other natural therapies, for her ability to defy the odds so far. "It makes me feel good when I've had vitamin C. I dont know what effect its having but it makes me feel good," she said. "I certainly walk out of the clinic feeling a million dollars and my skin is glowing. It also helps with the pain." Northland policeman Anton Kuria is another cancer patient who credits vitamin C infusions, along with a vitamin-rich diet, for his continued good health. He too was told he had just months to live two years ago when he left Auckland hospital with stage four leukemia. Vitamin C infusions are currently offered in New Zealand by several doctors and health practitioners with a focus on complementary health.