Vitamin C has been investigated as a complementary cancer therapy for decades. Interest has focused particularly on high-dose intravenous (IV) vitamin C, which produces much higher concentrations of vitamin C in the bloodstream than can be achieved by taking vitamin C orally.
Laboratory research has found that very high concentrations of vitamin C can damage or kill certain cancer cells, and clinical researchers continue to investigate IV vitamin C alone and in combination with conventional cancer treatments. However, vitamin C has not been established as a stand-alone cure for cancer, and IV vitamin C is not FDA-approved as a cancer treatment.
The distinction between oral and intravenous vitamin C is important. The body tightly controls the amount of vitamin C that reaches the bloodstream after oral supplementation. Increasing an oral dose therefore does not produce the extremely high blood concentrations achievable through IV administration. ...
Vitamin C has been investigated as a complementary cancer therapy for decades. Interest has focused particularly on high-dose intravenous (IV) vitamin C, which produces much higher concentrations of vitamin C in the bloodstream than can be achieved by taking vitamin C orally.
Laboratory research has found that very high concentrations of vitamin C can damage or kill certain cancer cells, and clinical researchers continue to investigate IV vitamin C alone and in combination with conventional cancer treatments. However, vitamin C has not been established as a stand-alone cure for cancer, and IV vitamin C is not FDA-approved as a cancer treatment.
The distinction between oral and intravenous vitamin C is important. The body tightly controls the amount of vitamin C that reaches the bloodstream after oral supplementation. Increasing an oral dose therefore does not produce the extremely high blood concentrations achievable through IV administration.
When vitamin C is administered intravenously, the digestive system is bypassed and substantially higher concentrations can temporarily be achieved in the blood. These pharmacological concentrations are the focus of much of the modern research into vitamin C and cancer.
Early studies of high-dose vitamin C generated considerable interest, but later randomized trials using high-dose oral vitamin C did not demonstrate improved survival or other significant benefits.
Researchers subsequently discovered that oral and IV vitamin C produce dramatically different concentrations in the bloodstream. This led to renewed investigation of IV vitamin C.
More recent clinical studies have examined IV vitamin C in several cancers, both alone and in combination with chemotherapy and other standard treatments. Some trials have suggested potential benefits, while others have found little or no improvement in cancer outcomes.
Research is continuing to determine which cancers, if any, may benefit from pharmacological vitamin C and whether particular combinations with conventional treatment are useful.
IV vitamin C has been studied in combination with chemotherapy and other cancer treatments. Some small studies have found that these combinations were well tolerated, and some have reported reduced treatment-related side effects or improved quality of life.
Results should not be generalized to every cancer or chemotherapy regimen. Vitamin C can interact differently with different cancer drugs, so high-dose supplementation or IV treatment should be discussed with the treating oncology team.
Vitamin C from food is an essential nutrient, and adequate intake is important for normal health. Oral supplements can also correct or prevent vitamin C deficiency.
However, taking increasingly large amounts by mouth does not reproduce the pharmacological blood concentrations achieved with IV vitamin C. Clinical trials of high-dose oral vitamin C have not demonstrated that it cures cancer.
IV vitamin C has generally been well tolerated in appropriately screened patients in clinical studies, but it is not risk-free.
High-dose IV vitamin C may be particularly dangerous for people with certain conditions, including kidney disease and glucose-6-phosphate dehydrogenase (G6PD) deficiency. People with hemochromatosis or other problems involving excess iron also require caution.
High-dose IV vitamin C can additionally interfere with some laboratory tests, including certain glucose meters.
Whether antioxidants help or interfere with cancer treatment has been debated for many years. The answer may depend on the specific antioxidant, dose, route of administration, cancer type, and cancer treatment.
Laboratory research has raised concerns about interactions between vitamin C and certain cancer medications, while other studies have investigated vitamin C specifically as an addition to chemotherapy.
For this reason, people receiving chemotherapy, radiation, targeted therapy, or immunotherapy should tell their oncology team about high-dose vitamin C or other antioxidant supplements rather than assuming they are universally beneficial or harmful.
Earth Clinic readers have shared personal experiences using vitamin C as part of their cancer-support programs. These reports may include oral vitamin C, high-dose supplementation, or intravenous vitamin C.
These experiences are anecdotal and cannot establish that vitamin C caused a tumor response, remission, or other cancer outcome. Cancer type, stage, conventional treatment, other supplements, and the natural course of the disease can all influence an individual's outcome.
If you have used vitamin C during cancer treatment, we invite you to share your experience below. Reports are particularly useful when they include the type and stage of cancer, whether vitamin C was oral or intravenous, conventional treatments received, and medically documented outcomes.
