An animal study published in the American Journal of Clinical Nutrition (1991;54:1256S–60S) demonstrated that vitamin C inhibited kidney tumors induced by estrogen. Research appearing in the Journal of the National Cancer Institute (1990;82:561–569) reported an inverse association between vitamin C intake and breast cancer risk.
In many circles, there has long been interest in vitamin C as an adjunctive therapy for cancer. At a symposium held by the National Cancer Institute in December 1990, 40 papers were presented demonstrating potential benefits of vitamin C for cancer patients. A number of additional animal studies have also shown an inhibitory effect of vitamin C on tumor growth. Intravenous vitamin C has been reported to shrink tumors in patients with adenocarcinoma and is used extensively for cancer patients in Germany.
Vitamin C protects cells by acting as an antioxidant. Research published in Biological Chemistry (May 10, 2002;277(19):16895–16899) demonstrated that vitamin C prevented mutations in cells exposed to oxidative stressors. Another study, appearing in FEBS Letters (1998;363:363–367), showed that vitamin C plays a role in DNA repair. Vitamin C has also been shown to enhance natural killer cell activity—cells that play an important role in immune surveillance and cancer defense—according to research published in Nutrition Research (1993;13:753–764).
In another animal study published in Carcinogenesis (2009;30(7)), researchers found that vitamin C may protect against estrogen-induced breast tumors. The study was conducted in rats bred to readily develop breast cancer. Among animals given estradiol alone, 82% developed breast tumors. Rats given a combination of estradiol and vitamin C developed 29% fewer tumors over the 240-day course of the study.
Granted, many of these studies are small, involve animals, or were conducted in vitro. Nonetheless, the findings are encouraging. Vitamin C is also inexpensive and generally well tolerated. Given that vitamin C is used as part of cancer therapy in other countries, it may warrant further investigation.
