B Vitamins and Tumors A six-year randomized, double-blind, placebo-controlled nutritional intervention study conducted by the Chinese Academy of Medical Sciences and the National Cancer Institute in Linxian County, Henan Province, China, showed that long-term, high intake of fermented and moldy foods and chronic deficiencies of vitamins B2, A, C, E, beta-carotene, and the trace elements zinc and molybdenum were important dietary factors leading to esophageal and pancreatic cancers. It has been reported that deficiencies of vitamins A, C, E and trace element selenium can enhance chemical carcinogenesis. Another survey by researchers found that one of the common dietary characteristics in areas with high rates of esophageal cancer (including Linxian County, China, South Africa, and Iran) was a severe deficiency in the intake of B vitamins (especially vitamin B2 and niacin). Surveys have also shown that at least 90% of the residents of Linxian County, Henan Province, China, have a severe deficiency in vitamin B2 intake. Researchers have found through animal testing that vitamin B2 deficiency can lead to altered metabolism of nitrosamines and promote esophageal epithelial hyperplasia. Folic acid and tumors Studies have found a significant negative correlation between dietary folic acid intake and breast cancer incidence. The U.S. Nurses’ Health Study also showed that drinking women who consumed high levels of folic acid had a 25% lower risk of breast cancer than women in the low-level folic acid group. 2001 U.S. National Health and Nutrition Examination Survey (NHANESI) results showed that adult men with low levels of dietary folic acid intake were at increased risk of colon cancer, and supplementation with folic acid reduced men’s risk of colon cancer by about 60%. Vitamin C and Tumors Some epidemiological data suggest that increased intake of vitamin C via the dietary route (vegetables and fruits, etc.) may reduce the incidence of oral and gastric cancers. The possible mechanism is that vitamin C prevents the synthesis of nitrosamines in the stomach, thereby reducing the risk of GI malignancies. Some prospective studies have found that men with low serum vitamin C have a significantly higher overall mortality rate from malignant tumors. Meta-analyses have also shown that high dietary vitamin C intake reduces the risk of breast cancer by approximately 20%.