Vitamin C is an essential nutrient required by humans. It is a cofactor (a helper molecule) that allows enzymes in the body to do their thing. Vitamin C is also an antioxidant, which means that it helps to neutralize free radicals (highly reactive molecules that can damage cells and DNA). DNA damage is thought to be a factor in the development of cancer. Many animals produce Vitamin C internally, but humans do not. At some point, humans lost the last phase in a series of reactions that converts glucose into Vitamin C. That's why humans have to take Vitamin C from their diet.
A scientific report (read it here) looked at 21 studies involving 8938 lung cancer cases. The report found that:
"The highest Vitamin C intake level versus the lowest level was significantly associated with the risk of lung cancer, especially in the United States and in prospective studies. A linear dose-response relationship was found, with the risk of lung cancer decreasing by 7% for every 100 mg/day increase in the intake of Vitamin C."
Vitamin C has also been shown to be helpful in stress regulation. A German study (link) found that Vitamin C curbed levels of Cortisol (a stress hormone) in stressed-out test subjects. Cortisol is responsible for triggering the fight or flight response in humans, which gets the body ready to deal with stress. Prolonged Cortisol exposure is linked to chronic inflammation (link), which is indicated in cancer development (link).
The National Institutes of Health has stated that high doses of Vitamin C have been shown to slow cancer cell growth and spread, to improve the effectiveness of chemotherapy, and to reduce the side-effects of chemotherapy. High dose Vitamin C has shown few side effects (link).
Air and heat destroy Vitamin C, so avoid these factors when preparing foods rich in this nutrient. Vitamin C is also water soluble, which means that it will leak into cooking water.
