Antioxidants and prevention of gastrointestinal cancers

Purpose of review Gastrointestinal cancers account for 20% of all incident cancers in the United States. Much work has been done to understand the role dietary factors play in the prevention of gastrointestinal cancers, yet evidence regarding the potential preventive effect of antioxidants is conflicting. This review highlights the recent studies investigating the associations between dietary antioxidants and cancers of the gastrointestinal tract. Recent findings In-vitro and in-vivo studies in animals continue to support the hypothesis that antioxidants reduce the risk of gastrointestinal cancers. Results in human populations are not as supportive. Antioxidant nutrients and fruits and vegetables do not seem to confer protection against colorectal cancer, and certain antioxidants were found to increase the risk of distal colon cancer. Individual antioxidants also do not help prevent pancreatic cancer. Total antioxidant intake and plant-based foods seem promising for stomach cancer prevention, while vitamin C lowers the risk of esophageal cancer. Preventive effects for stomach and esophageal cancers were often limited to or stronger in smokers. Evidence is scarce regarding antioxidants and liver cancer. Summary Antioxidants do not aid in the prevention of gastrointestinal cancers in the general population; however, they may act as chemopreventive agents for stomach and esophageal cancers, especially in high-risk populations.