It's possible, but many questions remain, write Mark Levine, MD, and colleagues in Proceedings of the National Academy of Sciences.
"This is not ready for patients yet," Levine tells WebMD. He is the chief and senior staff physician at the Molecular and Clinical Nutrition Section of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), a branch of the National Institutes of Health.
"What this does is provide plausibility that we should be reinvestigating ascorbic acid in cancer treatment. It's not ready for patients. Patients shouldn't get the wrong idea. We don't want to provide false hope," says Levine.
"If it were to work, even in a couple of cancers, that would be wonderful for patients. So the message is that there may be new hope coming, but it's certainly not here," he says.
About the Study
Levine's team studied vitamin C (also called ascorbate or ascorbic acid) and cancer cells in lab tests. Vitamin C appeared to boost production of hydrogen peroxide, which killed cancer cells and left healthy cells unharmed.
The levels of vitamin C were so high that they could only be achieved through IV infusions.
"These findings give plausibility to IV ascorbic acid in cancer treatment, and have unexpected implications for treatment of infections where hydrogen peroxide may be beneficial," write the researchers.
Vitamin C's Role
Vitamin C didn't directly tackle cancer. Instead, it may set the stage for hydrogen peroxide production, says Levine.
"One would never want to give intravenous hydrogen peroxide," says Levine.
"If hydrogen peroxide formed in the blood or were given directly, either blood will destroy it or if enough hydrogen peroxide is given, hydrogen peroxide will break the red cells and cause havoc to the kidneys," he says.
When vitamin C is injected, it appears to diffuse outside of the bloodstream, allowing reactions to generate hydrogen peroxide.
"You don't want hydrogen peroxide in the blood itself," says Levine. "But if hydrogen peroxide is present outside the blood, there is the potential that it could work as a drug."
Vitamin C Safety Trial Under Way
Vitamin C was only tested on human cells -- not people -- in this study. But vitamin C is being tested in people in a new project.
"Because IV ascorbate is easily available to people who seek it, a phase 1 safety trial in patients with advanced cancer is justified and underway," write Levine and colleagues.
That trial will see if intravenous vitamin C is safe for people, Levine explains. Tests on animals will be done to see if it truly fights cancer.
"If there is something useful, that will be absolutely wonderful for patients. If it turns out that the mechanisms do not hold up in animals in vivo, then maybe we will say that there is no point to do IV ascorbate," says Levine.
He notes that some complementary and alternative medicine practitioners worldwide use intravenous vitamin C for cancer treatment.
New Twist on an Old Theory
The idea that vitamin C might protect against cancer is more than half a century old and has been "colorful and emotionally charged," says Levine.
The theory was discarded 20 years ago by many scientists when other researchers found no benefit in giving vitamin C to patients with advanced cancer. In that study, vitamin C was given orally, not intravenously, notes Levine.
Scientists may not have considered that injected vitamin C might work differently than oral vitamin C, Levine explains.
Levine's team didn't start by studying vitamin C and cancer. Instead, they were probing nutrition and vitamin recommendations in healthy people.
Normally, the body tightly controls vitamin C taken by mouth. It quickly gets rid of too much vitamin C. Injected vitamin C bypasses those controls, says Levine.
"I realized that concentrations given intravenously at higher doses could be much higher than could ever be achieved by mouth," he says. "This is not nutrition use of ascorbic acid. This is potential use of ascorbic acid as a drug, and it must be said, it's not ready for prime time."
Science has a lot to sort out about vitamin C and cancer. Meanwhile, Levine recommends eating your fruits and vegetables. These include orange and grapefruit juice and fruits, raw red peppers, strawberries, and broccoli.
"Independent of this work, our recommendations are to consume vitamin C through foods and eat at least five varied fruits and vegetables a day," he says.