Vitamin C in Cancer Therapy

Introduction

Vitamin C or Ascorbic Acid (AA) was first implicated as an anti-cancer agent through the research of nobel Prize Winner Dr. Linus Pauling PhD and Dr. Ewan Cameron MD.  Their first clinical trial began in 1971 and the results of this and other research was published in the book “Cancer and Vitamin C” in 1979.  In their clinical trial they found a four-fold increase in survival time by those individuals treated with 10,000 mg of AA intravenously.  A later trial done by the Mayo clinic could not repeat these findings leading to a dismissal of AA potential role in Oncology. Dr. Pauling’s subsequent work in this field led to him being widely criticized as a “quack”.   Due to his ongoing research and years of anecdotal evidence from naturopathic and medical doctors alike there is a renewed interest and research into high doses of AA.

Why Intravenous Versus Oral Dosing of Ascorbic Acid?

Oral AA is absorbed through the intestinal lumen in an energy and dose dependant process.  It rapidly peaks so that at doses over 2g orally less than 20% is actually absorbed.  The result is a large quantity of Ascorbic Acid in the intestinal tract which brings water with it leading to gastrointestinal discomfort and diarrhea.  Recent research has shown that high doses of vitamin C have significant cyto-toxic effects.  These doses can only be achieved in humans by high dose intravenous administration.

The Mechanism of Action of Vitamin C in Cancer

Vitamin C is an important extracellular anti-oxidant and plays a role in a host of biochemical reactions in the body.  Vitamin C has been validated as supportive therapy in Case studies, Preclinical trials and cancer cell research.  The results of these studies show that vitamin C acts in the following ways:

1. Selective Cytotoxicity (cancer cell killing) Effect – vitamin c in high doses leads to the production of large amounts of hydrogen peroxide in the connective tissue of the body.  Hydrogen peroxide is an important oxidative molecule involved in many immune reactions in the body.  In healthy cells the hydrogen peroxide is absorbed and then quenched with intra-cellular anti-oxidants, but in cancer cells they often lack sufficient levels of anti-oxidants so hydrogen peroxide will build up.  As levels of hydrogen peroxide rise in cancer cells they eventually go through apoptosis (programmed cell death).
2. Inhibition of Tumor Growth and Metastasis – most tumors require the activity of various enzymes in order to invade and metastasize.  Ascorbic Acid inhibits the activity of these enzymes and promotes the production of collagen which may play a role in stabilizing the tumor and preventing local tissue invasion.
3. Chemosensitization – Ascorbic Acid has been tested in tissue cultures and animal models in combination with many different chemotherapeutics to evaluate a combined effect on tumors.   Most well designed trials have shown a generally positive enhancement of chemotherapeutic success in studies where chemotherapy is combined with Ascorbic Acid.  There are only a few select studies that show a negative interaction and we avoid concomitant therapy in those cases.