Questions and Answers About High-Dose Vitamin C Benefits
1. What is high-dose vitamin C?
Vitamin C (also called L-ascorbic acid or ascorbate) is a nutrient that humans must get from food or dietary supplements since it cannot be made in the body. Vitamin C is an antioxidant and helps prevent oxidative stress. It also works with enzymes to play a key role in making collagen.
When taken by intravenous (IV) infusion, vitamin C can reach much higher levels in the blood than when it is taken by mouth. A severe deficiency (lack) of vitamin C in the diet causes scurvy, a disease with symptoms of extreme weakness, lethargy, easy bruising, and bleeding. The lack of vitamin C in patients with scurvy makes collagen thinner in texture; when vitamin C is given, collagen becomes thicker again.
High-dose vitamin C has been studied as a treatment for patients with cancer since the 1970s. A Scottish surgeon named Ewan Cameron worked with Nobel Prize-winning chemist Linus Pauling to study the possible benefits of vitamin C therapy in clinical trials of cancer patients in the late 1970s and early 1980’s.
Surveys of healthcare practitioners at United States CAM conferences in recent years have shown that high-dose IV vitamin C is frequently given to patients as a treatment for infections, fatigue, and cancers, including breast cancer.
3. What is the theory behind the claim that high-dose vitamin C is useful in treating cancer?
More than fifty years ago, a study suggested that cancer was a disease of changes in connective tissue caused by a lack of vitamin C. In the 1970’s, it was proposed that high-dose ascorbic acid could help build resistance to disease or infection and possibly treat cancer.
Later studies showed that the levels of vitamin C that collect in the bloodstream depend on how it is taken.
4. How is high-dose vitamin C administered?
Vitamin C may be given by intravenous (IV) infusion or taken by mouth
Laboratory studies have shown 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
Ascorbic acid with arsenic trioxide may be more effective in ovarian cancer cells.
Ascorbic acid with gemcitabine may be more effective in pancreatic cancer cells.
Ascorbic acid with gemcitabine and epigallocatechin-3-gallate (EGCG) may be more effective in malignant mesothelioma cells.
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.
A study in a mouse model of ovarian cancer showed that combining intravenous high-dose vitamin C with the anticancer drugs carboplatin and paclitaxel made them more effective in treating ovarian cancer.
Studies of vitamin C combined with other drugs
Have any side effects or risks been reported from high-dose vitamin C?
Intravenous high-dose ascorbic acid has caused very few side effects in clinical trials. However, high-dose vitamin C may be harmful in patients with certain risk factors. In patients with a history of kidney disorders, kidney failure has been reported after ascorbic acid treatment. Patients with a tendency to develop kidney stones should not be treated with high-dose vitamin C. Since vitamin C may make iron more easily absorbed and used by the body, high doses of the vitamin are not recommended for patients with hemochromatosis (a condition in which the body takes up and stores more iron than it needs).
Have any drug interactions been reported from combining high-dose vitamin C with anticancer drugs?
Combining vitamin C with an anticancer drug called bortezomib has been studied in cell cultures and in animal models. Bortezomib is a targeted therapy that blocks several molecular pathways in a cell, causing cancer cells to die. Several studies showed that vitamin C given by mouth made bortezomib less effective, including in multiple myeloma cells. A study in mice transplanted with human prostate cancer cells, however, did not show that giving the mice different doses of vitamin C by mouth made bortezomib therapy less effective.
An oxidized form of vitamin C called dehydroascorbic acid has been studied in cell cultures and in animals with tumors. Several studies have found that high doses of dehydroascorbic acid can interfere with the anticancer effects of several chemotherapy drugs. Dehydroascorbic acid is found in only small amounts in dietary supplements and in fresh foods.