1. Have any preclinical (laboratory or animal) studies been conducted using high-dose vitamin C?
Many laboratory studies have been done to find out how high-dose vitamin C may cause the death of cancer cells. The anticancer effect of vitamin C in different types of cancer cells involves achemical reaction that makes hydrogen peroxide, which may kill cancer cells.
Laboratory studies have shown the following:
However, not all laboratory studies combining vitamin C with anticancer therapies have shown benefit. Combining dehydroascorbic acid, a particular form of vitamin C, with chemotherapy made it less effective in killing some kinds of cancer cells.
Studies of high-dose vitamin C have been done in animal models (animals given a disease either the same as or like a disease in humans).
Some of the studies showed the vitamin C helped kill more cancer cells:
However, other animal studies have shown that vitamin C interferes with the anticancer action of certain drugs, including the following:
- Treatment with high-dose vitamin C slowed the growth and spread of prostate, pancreatic,liver, colon, malignant mesothelioma, neuroblastoma, and other types of cancer cells.
- Combining high-dose vitamin C with certain types of chemotherapy may be more effective than chemotherapy alone:
- Another laboratory study suggested that combining high-dose vitamin C with radiation therapykilled more glioblastoma multiforme cells than radiation therapy alone.
- High-dose vitamin C blocked tumor growth in animal models of pancreatic, liver, prostate, sarcoma, and ovarian cancers and malignant mesothelioma.
- High-dose vitamin C combined with chemotherapy in a mouse model of pancreatic cancer showed that the combination treatment shrank tumors more than chemotherapy treatment alone.
- Another study showed that vitamin C made a type of light therapy more effective when used to treat mice injected with breast cancer cells.
- Mouse models of human lymphoma and multiple myeloma treated with combinations of vitamin C and chemotherapy or the drug bortezomib had more tumor growth than mice treated with bortezomib alone
2. Have any clinical trials (research studies with people) of high-dose vitamin C been conducted?
Several studies of high-dose vitamin C in patients with cancer have been done in recent years, including the following:
Studies of vitamin C alone
Studies of vitamin C combined with other drugs
Studies of vitamin C combined with other drugs have shown mixed results:
- Intravenous (IV) vitamin C was studied in patients with breast cancer who were treated withadjuvant chemotherapy and radiation therapy. The study found that patients who received IV vitamin C had better quality of life and fewer side effects than those who did not.
- A study of IV vitamin C and high doses of vitamin C taken by mouth was done in patients with cancer that could not be cured. Vitamin C was shown to be a safe and effective therapy to improve quality of life in these patients, including physical, mental, and emotional functions, symptoms of fatigue, nausea and vomiting, pain, and appetite loss.
- Vitamin C has been shown to be safe when given to healthy volunteers and cancer patients at doses up to 1.5 g/kg, while screening out patients with certain risk factors who should avoid vitamin C. Studies have also shown that Vitamin C levels in the blood are higher when taken by IV than when taken by mouth, and last for more than 4 hours.
- In a small study of 14 patients with advanced pancreatic cancer, IV vitamin C was given along with chemotherapy and treatment with a targeted therapy. Patients had very few bad side effects from the vitamin C treatment. The nine patients who completed the treatment hadstable disease as shown by imaging studies.
- In another small study of 9 patients with advanced pancreatic cancer, patients were given chemotherapy in treatment cycles of once per week for 3 weeks along with IV vitamin C twice per week for 4 weeks. These patients had disease that did not progress for a period of months. The combined treatment was well tolerated and no serious side effects were reported.
- Patients with acute myeloid leukemia, refractory metastatic colorectal cancer, or metastaticmelanoma treated with vitamin C combined with other drugs had serious side effects and the disease got worse.
Find out more at National Cancer Institute - High doses of Vitamin C