14 December 1999
Bad Vitamins for Cancer Treatment?
by Kate Melville
Here is an interesting dilemma; normally doctors and scientists agree that patients can and should take vitamins A and E, as they seem to boost the human immune system. However in cancer patients this seems to be quite the opposite, in fact they seem to keep cancer cells from dying via the natural protective process called apoptosis.
This somewhat controversial research result is the result of a study by scientists at the University of North Carolina (Chapel Hill). So now giving patients these particular vitamins may actually prevent cancer cells from self-destructing and work against the cancer therapy. Dr. Rudolph Salganik, research professor of nutrition said, "We believe this work is important because it may make cancer treatments more effective. It suggests that cancer patients, especially those undergoing chemotherapy or radiation therapy, may do better on an antioxidant-depleted diet."
The research team studied reactive oxygen species (ROS), that seems to play a pivotal role in the series of signals that allow cells to kill bacteria and viruses, destroy toxins and trigger the apototic "suicide" of defective cells (like cancer cells).
Antioxidants, such as vitamins A and E, normally protect cells from the ROS damage, but apparently prevent the targeted apoptotic death of cancer cells that threaten humans. The UNC-CH experiment involved using mice that were predisposed to developing brain tumors when placed on modified diets that were either supplemented with standard amounts of antioxidants or were antioxidant deficient for four months. The rodents health was then carefully monitored and their brain tumors, if any, to see how they fared on the different diets. Mice receiving extra vitamins A and E showed no benefit in either the size or incidence of brain tumors - but they also had relatively short lives. In mice getting low levels of vitamins A and E, no negative effects were seen in normal cells, but about 19 percent of tumor cells showed evidence of apoptosis. In those ingesting normal quantities of antioxidant vitamins, only about 3 percent of tumor cells were apototic.
These findings may also help to explain two previous studies that showed heavy smokers whose diets was high in beta-carotene antioxidants had much higher rates of lung cancer.
So for those who use vitamins an essential dietary supplements, as part of combination therapies, may need to rethink their approach.