Vitamin C Reduces Chemo Effectiveness in Cancer Cells and Mice

Oncologists often recommend that patients on chemotherapy avoid antioxidant supplements including vitamin C.  Now basic research shows that vitamin C reduces the activity of several different chemotherapy drugs, both in cancer cell lines and in experimental mice.

Vitamin C appears to protect the cell against death during chemotherapy by restoring its mitochondria.  Mitochondria power cells, converting nutrients to energy.  When mitochondria are damaged they force the cell to die — the goal of chemotherapy.  By revitalizing damaged mitochondria, the vitamin reduced the effectiveness of all the chemo drugs tested, by as much as 70 percent for some.

Laboratory researchers at Memorial Sloan Kettering Cancer Center in New York pretreated cancer cells with dehydroascorbic acid (DHA), the form that ascorbic acid (vitamin C) takes to enter cells. They then exposed them to a variety of chemotherapy drugs.  When they compared the cells that had been treated with DHA to untreated cells, they found that more untreated cells died.

When the pretreated cells were injected into laboratory mice, the mice developed cancers that did not respond well to chemotherapy.   Chemo kept cancers from untreated cells in check longer, while tumors from cells treated with DHA grew faster.

The scientists believe that similar activity takes place in humans, although they say that clinical research is necessary to prove that idea.

Mark L. Heaney, MD, PhD, who led the research said,

The use of vitamin C supplements could have the potential to reduce the ability of patients to respond to therapy.

SOURCE: Heaney et al., Cancer Research, Volume 68, Issue 9, October 1, 2008.