Japan dataset (NHNS)

The NHNS is a national nutrition survey conducted annually since 1945 by public health centers under the supervision of the Ministry of Health, Labour and Welfare, and in accordance with the Health Promotion Law. The present cross-sectional analysis used data from the 2012 NHNS, with permission. The 2012 survey was selected because it had a larger sample size than more recently available surveys. The NHNS has been detailed elsewhere [20,21]. Briefly, on the basis of the population census, 475 of the approximately one million census units were sampled randomly as survey areas. All non-institutionalized Japanese aged ≥1 y living in a survey area (approximately n = 61,000) were asked to participate, excluding individuals holding foreign citizenship, those whose diet was not self-selected, and those following a special diet (mainly due to disease). The survey was conducted between 25 October and 7 December 2012.

A total of 12,750 of 24,555 eligible households (52%) participated in NHNS 2012. The number of participants aged ≥20 y was 30,639. Of these, the number with missing information on dietary intake, anthropometric measurements, and lifestyle variables was 3913, 8593, and 473, respectively (some had more than one missing variable), resulting in 20,099 participants with complete information. After further excluding 246 lactating and 136 pregnant women, the final sample in this analysis comprised 19,717 male participants and non-lactating and non-pregnant female participants aged ≥20 y (S1 Fig). These participants differed somewhat from those excluded from the analysis, who were more likely to be male, younger, a current smoker, and to have lower mean energy intake and BMI (all P <0.0001).

This survey was conducted according to the guidelines laid down in the Declaration of Helsinki, and verbal informed consent was obtained from all individual participants. Under the Statistics Act, the Ministry of Health, Labour and Welfare anonymized individual-level data collected from the NHNS, and provided the first author with the datasets for this study. In accordance with the Ethical Guidelines of Epidemiological Research established by the Ministry of Education, Culture, Sports, Science and Technology and the Ministry of Health, Labour and Welfare, institutional review board approval was not required for this analysis.