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Abstract
It is our working hypothesis that the high rate of the liver and gastric cancers in North and Northeast Thailand is associated with increased daily dietary intake of nitrate, nitrite, and nitrosodimethylamine (NDMA). Samples of fresh and preserved Thai foods were systematically collected and analyzed from 1988 to 1996 and from 1998 to 2005. Consumption frequencies of various food items were determined on the basis of a dietary questionnaire given to 467 adults (212 males and 255 females) from 1998 to 2005. Food consumption data for the preceding and current year were collected and intakes (day, week, and month) of nitrate, nitrite, and NDMA were calculated. The trends in liver and stomach cancer age-standardized incidence rates (ASR) in four regions of Thailand were compared with the dietary intake of nitrate, nitrite, and NDMA in those same geographic regions. Mean daily intakes of nitrate of 155.7 mg/kg, of nitrite of 7.1 mg/kg, and of NDMA of 1.08 μ g/kg per day were found. Significant differences in dietary nitrate, nitrite, and NDMA intakes were seen between various Thai regions (P < 0.0001), and these corresponded to the variations in liver and stomach cancer ASR values between the regions. Dietary factors are likely to play key roles in different stages of liver and stomach carcinogenesis in Thailand.
ACKNOWLEDGMENTS
The laboratory assays on analyses of food samples and on smoke yields of the tobacco products were carried out at the American Health Foundation and were supported by Grant CA-29580 from the US National Cancer Institute. In Thailand, we thank Dr. Songsak Srianujata (Institute of Nutrition at Mahidol University), Dr. Petcharin Srivatanakul (National Cancer Institute), Dr. Panata Migasena (Institute of Tropical Medicine at Mahidol University), Dr. Mathuros Ruchirawat and Dr. Jutamaad Satayavivad (Chulabhorn Research Institute), Dr. Vanchai Vatanasapt (Khon Kaen University), and Dr. Thira Limsila (Siriraj Hospital Mahidol University) for help given to Dr. Eugene J. Mitacek while he was visiting research professor at the Mahidol University, Chiang Mai University and Mahasarakham University in Thailand during the Summer semesters in 1995–2005.
Notes
a Abbreviation is as follows: ASR, age-standardized incidence rates.
b Average of ASR incidence in Chiang Mai and Lampang, rate per 100,000. Data from Refs. 1, 2, and 3.
a Abbreviation is as follows: ASR, age-standardized incidence rates.
b Average of ASR incidence in Chiang Mai and Lampang, rate per 100,000. Data from Refs. 1, 2, and 3.
a Abbreviation is as follow: NDMA, nitrosodimethylamine. Mean concentrations ± SD in mg/kg for nitrate and nitrite, and in μ g/kg for NDMA.
b Includes sausages, bacon, and cured meat only. ND = not detected (below detection limit).