Study of diet, biomarkers and cancer risk in the United States, China and Costa Rica

One striking paradox in epidemiologic research is the strong association be tween diet and cancer in ecologic studies compared with the weaker associat ions reported in many within-country case-control and cohort studies. Howev er, most ecologic studies have relied on indirect measures of dietary intak e, such as food disappearance data. The objectives of our study were to ass ess the feasibility of collecting dietary and biomarker data from individua ls living in countries having markedly different dietary patterns and cultu res and to examine the magnitude of the between-country variation in their measurement. Adults surveyed in Shanghai (China), Costa pica and King Count y (Washington, USA) completed a 24-hr dietary recall, a cancer risk factor survey, and provided a blood sample. We analyzed a subset of the blood spec imens for vitamins C, E, carotenoids and phospholipid fatty acids. We obser ved substantial differences in nutrient intakes and in mean plasma concentr ations of dietary biomarkers across the study populations. For example, Kin g County participants had the highest daily intake of vitamin C (mean 78.3 +/- 12.2 mg compared with 42.6 +/- 38.3 mg in Shanghai and 34.8 2/3 43.8 mg in Costa Rica), The mean plasma vitamin C level in King County was also th e highest of the 3 study sites: 927.9 +/- 43.9 mu g/dl in King County, 585. 7 +/- 35.9 mu g/dl in Shanghai and 46 1.1 +/- 33.1 mu g/dl in Costa pica, P lasma trans fatty acids (a biomarker of a diet high in hydrogenated fats) w ere highest in King County and lowest in Shanghai. (C) 1999 Wiley-Liss, Inc .