A team of researchers from several Italian research institutes found that giving cancer mice a high dose of vitamin C (ascorbic acid) enhances immunotherapy to slow or block tumor growth. As early as the 1970s, medical researchers suspected that giving cancer patients high doses of vitamin C or helping to reduce tumor growth, but subsequent studies did not find a positive effect and the researchers gave up.
In recent years, researchers have also analyzed the effects of vitamin C in treating cancer and found that because the human gut does not absorb large amounts of vitamin C, this means that early patients do not receive high enough doses of vitamin C to have an effect.
So a new study by a team of Italian research institutes injected vitamin C directly into the veins of laboratory mice as part of an immunotherapy regimen and then monitored tumor growth.
The researchers found that adding high doses of vitamin C without immunotherapy slowed the growth of tumors in experimental mice. But when it was used as part of an immunotherapy regime in mice, the researchers found that they could slow or even stop the growth of melanoma, colorectal cancer, pancreatic and breast cancer.
In addition, the researchers found that this was done by supporting T cells, and found that vitamin C improved the effectiveness of PD-1 and CTLA-4 immune checkpoint antibodies. In some cases, adding vitamin C to an immunotherapy regimen may even cause some breast cancer tumors to disappear completely.
The researchers say the main obstacle to the use of vitamin C in treating human cancer patients is the possible side effects. Because the dose of vitamin C added to the mice in a few days of the experiment was equivalent to eating 2,000 oranges a day.