The prevalence of dietary supplement use, such as vitamins, minerals, or fish oil, has increased among children in Japan; however, whether children are using dietary supplements appropriately remains unclear. This study aimed to determine dietary supplement use among children. In August 2017, a nationwide internet preliminary survey of 265,629 mothers aged from 25 to 59 years old was undertaken. Of these, 19,041 mothers of children attending either elementary school, junior high school, or high school were selected. Among them, 16.4% were currently providing their children with dietary supplements and 5.2% had previously given dietary supplements to their children. The prevalence of dietary supplement use was higher in boys than in girls, and the prevalence increased according to their grade. A total of 2439 participants were eligible to undertake a targeted survey on dietary supplement use. Dietary supplements were being taken to maintain health, supplement nutrients, and enhance growth in both boys and girls, and many children (37.5%) were provided with vitamin and mineral supplements. Mothers mainly obtained information concerning dietary supplements via the internet, and supplements were purchased in drug stores or via the internet. The prevalence of dietary supplement use in mothers was 65.4% and may be associated with the prevalence rates in children. Some mothers reported adverse events (3.6%) in their children, such as stomachache, diarrhea, nausea and vomiting, and constipation. The cause-and-effect relationships for adverse events were not clear, but some children were given products for adults. Children are more influenced by dietary supplements compared to adults. To prevent adverse events due to inappropriate use, parental education concerning dietary supplements is essential.

The introduction of mandatory fortification of grains with folate in 1998 in the United States resulted in 767 fewer spina bifida cases annually and a cost saving of $603 million per year. However, far more significant medical cost savings result from preventing common diseases, including myocardial infarction, stroke, dementia and osteoporosis. A cost‐effectiveness analysis showed a gain of 266 649 quality‐adjusted life‐years and $3.6 billion saved annually, mainly due to the reduction of cardiac infarction. The recommended folate intake in Japan is 240 μg/day whereas it is 400 μg/day internationally. Our Sakado Folate Project targeted individuals with genetic polymorphism of methylenetetrahydrofolate reductase or with hyperhomocysteinemia. Using, for example, folate‐fortified rice, resulted in an increase in serum folate and a decrease in serum homocysteine in the participants, and reduced medical costs were achieved by decreasing myocardial infarction, stroke, dementia and fracture. Due to the small population of Sakado City (approximately 101 000) and small number of births (693) in 2015, a decrease in spina bifida could not be confirmed but there was a significant decrease in the number of very low birthweight infants. The genome notification of subjects was effective in motivating intake of folate, but the increase in serum folate (from 17.4 to 22.5 nmol/L, 129%) was less than that observed following compulsory folic acid fortification of cereals in the USA (from 12.1 to 30.2 nmol/L, 149.6%). Mandatory folic acid fortification is cheap in decreasing medical costs and is thus recommended in Japan.

Lifestyle changes during the coronavirus disease (COVID-19) lockdown have been previously examined, but there is limited understanding about changes after such restrictions were lifted. This study examines changes in lifestyle habits and body weight among the Japanese population with regard to the length of at-home hours both during (April to May) and after (September) the nationwide stay-at-home request compared to those before the COVID-19 pandemic (January 2020). An online survey was conducted in September 2020 involving 10,000 Japanese survey monitors, selected according to population distribution. During the stay-at-home request, 34% participants extended their at-home hours. More respondents in the group with extended at-home hours experienced an increase or decrease in total physical activity, snacking, food intake, alcohol drinking, and body weight than those in the group with nonextended at-home hours. Some of these changes had a trend according to age. The prevalence of most of these changes decreased when at-home hours returned to normal after the stay-at-home request period; however, increased alcohol consumption and increased or decreased body weight persisted. Our findings suggest that close monitoring for further health outcomes and age-appropriate measures to encourage favorable health behaviors is needed.