High consumption of vitamin E either from diet or vitamin supplements may lower the risk of liver cancer, according to a study published July 17 in the Journal of the National Cancer Institute.
Vitamin E is a fat-soluble vitamin which is considered an antioxidant and numerous experimental studies have suggested that vitamin E may prevent DNA damage.
Liver cancer is the third most common cause of cancer mortality in the world, the fifth most common cancer found in men and the seventh most common in women. Approximately 85 percent of liver cancers occur in developing nations, with 54 percent in China alone.
To determine the relationship between vitamin E intake and liver cancer risk, Wei Zhang, M.D., MPH., Shanghai Cancer Institute, Renji Hospital, Shanghai Jiaotong University School of Medicine, and colleagues analyzed data from a total of 132,837 individuals in China who were enrolled in the Shanghai Women's Health Study (SWHS) from 1997-2000 or the Shanghai Men's Health Study (SMHS) from 2002-2006, two population-based cohort studies jointly conducted by the Shanghai Cancer Institute and Vanderbilt University.
Using validated food-frequency questionnaires, the researchers conducted in-person interviews to gather data on study participants' dietary habits. Participants were asked how often they ate some of the most commonly consumed foods in urban Shanghai and whether they took vitamin supplements.
The investigators then compared liver cancer risk among participants who had high intake of vitamin E with those who had low intake.
The analysis included 267 liver cancer patients (118 women and 149 men) who were diagnosed between two years after study enrollment and an average of 10.9 (SWHS) or 5.5 (SMHS) years of follow-up. Vitamin E intake from diet and vitamin E supplement use were both associated with a lower risk of liver cancer. This association was consistent among participants with and without self-reported liver disease or a family history of liver cancer.
"We found a clear, inverse dose-response relation between vitamin E intake and liver cancer risk," the authors write, noting a small difference between men and women in the risk estimate, which is likely attributable to fewer liver cancer cases having occurred among male participants due to the shorter follow-up period.
"Overall, the take home message is that high intake of vitamin E either from diet or supplements was related to lower risk of liver cancer in middle-aged or older people from China," said Xiao Ou Shu, M.D., Ph.D., professor of Medicine at the Vanderbilt Epidemiology Center.
Conversely, participants who had the highest vitamin C intake from supplements and who had a family history of liver cancer or self-reported liver disease were more likely to develop liver cancer. There was no link to liver cancer among participants who had the highest levels of vitamin C or other vitamins from food.
Other investigators involved with the study included Honglan Li, M.D., M.Ph., Jing Gao, M.D., Yong-Bing Xiang, M.D., M.Ph., and Yu-Tang Gao, M.D., Shanghai Cancer Institute; Gong Yang, M.D., MPH, Hui Cai, M.D., Ph.D., and Wei Zheng, M.D., Ph.D., Vanderbilt Epidemiology Center, Vanderbilt-Ingram Cancer Center; and Bu-Tian Ji, M.D., Dr.PH, National Cancer Institute.
Funding for the study was supported by grants from the National Cancer Institute, a division of the National Institutes of Health (R37 CA070867 and R01 CA082729), the State Key Project Specialized for Infectious Diseases of China (2008ZX10002-015 and 2012ZX10002008-002), and a training grant from the Fogarty International Center (D43 TW008313).