Vitamin C performs many functions that may offer protection against cancer, including acting as an antioxidant and protecting cellular structures (including DNA) from damage. Vitamin C also helps the body deal with environmental pollution and toxic chemicals, enhance immune function, and inhibit the formation of cancer-causing compounds in the body.
The epidemiological evidence of a protective effect of vitamin C against cancer is undeniable. A high vitamin C intake reduces the risk for virtually all forms of cancer, including cancers of the lung, colon, breast, cervix, esophagus, oral cavity, and pancreas.The bottom line from all of the research is once again that Americans need to increase the consumption of foods high in vitamin C and possibly supplement with vitamin C for added protection. While most of this evidence is based upon a high vitamin C intake from foods also rich in carotenes and other protective nutrients against cancer, a few of the studies also looked at supplementation. Let’s examine the evidence in some of these cancers in closer detail.
Lung Cancer
Of the 11 investigations into the role of vitamin C against lung cancer, 9 found reduced risk with high intake of Vitamin C. In five of these studies, the results were quite significant and in four of these five studies the protection offered by vitamin C was greater than that provided by beta-carotene in several of the studies. Gladys Block, one of America’s foremost authorities on the role of antioxidant intake and cancer risk, has stated that “Whereas a large body of evidence suggests an important effect for carotenoids in lung cancer prevention, the recent data suggests that there may be an independent protective effect of vitamin C intake.
Stomach, Esophageal, and Oral Cancers
Seven of eight oral cancer studies found low vitamin C intake to be a major risk factor. Persons with the lowest vitamin C intake had a twofold increase in oral cancer compared to persons with the highest vitamin C intake. Similar results were seen in esophageal cancer. In stomach cancer, all 16 investigations in stomach cancer showed a substantial reduction in risk with high vitamin C intake. Stomach cancer is linked to excessive formation of cancer-causing compounds known as nitrosamines within the stomach. Nitrosamines are formed most of the time by ingesting nitrates and nitrites used in the production of cured meats (e.g., bacon). Vitamin C significantly inhibits the formation of nitrosamines.