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The aim of this report is to describe INTERMAP standardized procedures for assessing dietary intake of 4680 individuals from 17 population samples in China, Japan, UK and USA: Based on a common Protocol and Manuals of Operations, standardized collection by centrally trained certified staff of four 24 h dietary recalls, two timed 24-h urines, two 7-day histories of daily alcohol intake per participant; tape recording of all dietary interviews, and use of multiple methods for ongoing quality control of dietary data collection and processing (local, national, and international); one central laboratory for urine analyses; review, update, expansion of available databases for four countries to produce comparable data on 76 nutrients for all reported foods; use of these databases at international coordinating centres to compute nutrient composition. Chinese participants reported 2257 foods; Japanese, 2931; and UK, 3963. In US, use was made of 17 000 food items in the online automated Nutrition Data System. Average time/ recall ranged from 22 min for China to 31 min for UK. Among indicators of dietary data quality, coding error rates (from recoding 10% random samples of recalls) were 2.3% for China, 1.4% for Japan, and UK; an analogous US procedure (re-entry of recalls into computer from tape recordings) also yielded low discrepancy rates. Average scores on assessment of taped dietary interviews were high, 40.4 (Japan) to 45.3 (China) (highest possible score: 48); correlations between urinary and dietary nutrient valuesFsimilar for men and womenF were, for all 4680 participants, 0.51 for total protein, range across countries 0.40-0.52; 0.55 for potassium, range 0.30-0.58; 0.42 for sodium, range 0.33-0.46. The updated dietary databases are valuable international resources. Dietary quality control procedures yielded data generally indicative of high quality performance in the four countries. These procedures were time consuming. Ongoing recoding of random samples of recalls is deemed essential. Use of tape recorded dietary interviews contributed to quality control, despite feasibility problems, deemed remediable by protocol modification. For quality assessment, use of correlation data on dietary and urinary nutrient values yielded meaningful findings, including evidence of special difficulties in assessing sodium intake by dietary methods.

Abstract-Findings from short-term randomized trials indicate that dietary supplements of omega-3 polyunsaturated fatty acids (PFA) lower blood pressure of hypertensive persons, but effect size in nonhypertensive individuals is small and nonsignificant. Data are lacking on food omega-3 PFA and blood pressure in general populations. Key Words: blood pressure Ⅲ nutrition Ⅲ food Ⅲ omega-3 polyunsaturated fatty acids Ⅲ population study U nclarity persists concerning efficacy of omega-3 (-3) polyunsaturated fatty acid (PFA) intake for prevention and control of the cardiovascular diseases (CVD) and their major risk factors. This is particularly the case for populationwide -3 PFA from foods. As to -3 PFA supplements for secondary prevention of CVD, recent reviews/meta-analyses come to diverse conclusions. 1,2 Inconsistencies also prevail on influences of supplemental -3 PFA on blood pressure (BP). Meta-analyses of randomized clinical trials (RCTs) on -3 PFA supplements reported significant BP reduction overall and in hypertensive participants; significant heterogeneity in systolic BP (SBP) outcomes across trials; only small nonsignificant systolic and diastolic BP (DBP) lowering in nonhypertensive individuals. [3][4][5][6][7][8] Almost no population-based observational data exist on relation of food -3 PFA of individuals to their BP. 9 Possible reasons for the heterogeneous RCT findings on -3 PFA supplements and BP are: actual effect size is small, particularly in nonhypertensive individuals, hence falsenegative findings are probable unless sample sizes are large, and BP is measured repeatedly by high-quality techniques.In observational studies, data on nutrient intakes and other variables must be extensive and high-quality, enabling characterization of -3 PFA intake by individuals and control for