Background: Olfactory stimulation with hinoki cypress essential oil reportedly reduces stress hormones and enhances parasympathetic activity, which may in turn increase salivary secretion and facilitate swallowing. However, its effects on swallowing in older adults with dysphagia remain unclear.

Methods: In this placebo-controlled, single-blind, randomized crossover study, older adults with dysphagia (Food Intake Level Scale ≤9) underwent 5-minute olfactory stimulation with hinoki cypress essential oil or rice oil (placebo) in two sessions one week apart. Repetitive saliva swallowing test (RSST), 3 mL modified water swallowing test (MWST), 30 mL water swallowing test (WST), saliva secretion for 5 minutes, blood pressure, and heart rate were measured before and after each stimulation. Changes from pre- to post-stimulation were compared within each condition and between conditions using Wilcoxon’s signed-rank test.

Results: Thirty-four participants (47% women; 80 ± 10 years) were included. Hinoki cypress essential oil significantly improved RSST (median difference 0.5, 95% CI 0.0–1.0; p = 0.004), MWST (0.5, 95% CI 0.0–1.0; p = 0.003), and saliva secretion (1.0 mL, 95% CI 0.5–2.0; p = 0.002), whereas placebo produced no significant change (all p > 0.05). Improvements in swallowing function were greater with hinoki than with placebo. The increase in saliva secretion following hinoki stimulation was not associated with changes in RSST or MWST scores.

Conclusions: Brief olfactory stimulation with hinoki cypress essential oil improved swallowing function and increased saliva secretion in older adults with dysphagia compared with placebo in a randomized crossover design. Hinoki cypress essential oil inhalation may represent a simple, noninvasive adjunctive strategy for dysphagia management, warranting confirmation in larger and longer trials.

Trial registration: This study was registered in the UMIN Clinical Trials Registry (UMIN-CTR) under registration number UMIN000053271.

Background: Per- and polyfluoroalkyl substances (PFAS) have raised significant health concerns. In 2019, drinking water source was changed due to PFAS contamination in the Tama region, Tokyo, Japan. This study aims to determine the PFAS exposure levels after reduction in drinking water contamination, and to estimate the half-lives of linear isomers of perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), and perfluorooctanoic acid (PFOA) in serum samples from residents.

Methods: 17 participants in 2020 and 2023 from Tama region, Tokyo, Japan (all females, age 53–83 years) were examined. PFAS concentrations in serum in 2023 were measured using gas chromatography-mass spectrometry. Biological half-lives were estimated using first-order kinetics model.

Results: The investigated population was exposed to six PFAS at levels associated with potential health risks, with 95% of them having total PFAS concentrations exceeding 20 ng/mL in 2023. Serum PFOS, PFHxS and PFOA levels decreased from 2000 to 2023 (p < 0.05 by paired t-test). The estimated half-lives for PFOS, PFHxS, and PFOA were 3.9 years (95% CI: 3.4–4.6), 5.7 years (95% CI: 4.6–7.5), and 8.0 years (95% CI: 6.0–10.0), respectively. After subtraction of background values in Japan, the estimated half-lives were 2.7 years (95% CI: 2.3–3.4) for PFOS, 5.6 years (95% CI: 4.5–7.4) for PFHxS, and 5.1 years (95% CI: 4.1–6.8) for PFOA.

Conclusions: This study demonstrates participants had still higher serum PFAS levels and these PFAS elimination half-lives in the investigated Japanese population are at years order.

Background: Optimizing nutrient intake is crucial for the health and development of preschool children. While previous studies assessed the risks and benefits of selenium (Se) from fish and seafood, few have examined its intake from common foods and its association with children’s growth.

Objective: In this study, we evaluated optimal foods for achieving a dietary Se surplus and the implications for the growth performance of preschool children.

Methods: Mercury (Hg) and Se concentrations were analyzed in 108 commercially available foods to conduct a dietary risk-benefit assessment of Se intake. Hg exposure was evaluated using hair samples from 349 preschool children enrolled between August 2017 and July 2022. Information on food consumption frequencies and nutrient compositions was obtained through dietary surveys.

Results: Overall, 42.4% of children had hair Hg levels above the US Environmental Protection Agency’s reference dose of 1 µg/g, showing that Hg exposure among preschool children in Taiwan remains a significant issue. The risk-benefit assessment revealed that eggs and fish are superior sources of Se compared to other animal- and plant-based foods. Although marine fish contained higher Hg concentrations than eggs, their relatively high Se and ω-3 polyunsaturated fatty acid (PUFA) contents supported a favorable nutritional profile when consumed in moderation. The minor negative health benefit value of Se (HBV_Se) observed for fruit does not pose a health concern, as it is offset by other Se-rich foods in the diet. The cumulative HBV_Se across food groups indicated that the children’s overall dietary Se intake was positive and nutritionally advantageous. Dietary Se, mainly from fish and eggs, was positively associated with weight and height development, whereas excessive fruit consumption may slightly reduce Se intake and adversely affect growth.

Conclusions: Moderate consumption of fish and eggs should be encouraged to support optimal growth and neurodevelopment. Overall, dietary patterns of Taiwanese preschool children provide beneficial levels of Se and ω-3 fatty acids while maintaining low Hg-related risks, emphasizing the need for continued monitoring of Hg levels in locally consumed foods to ensure dietary safety.

Background: The creatinine (Cre) concentration in urine is used as an adjustment factor in chemical exposure and nutritional intake assessments. Because Cre excretion varies by sex, age, race, and anthropometric measurements such as height and weight, developing a method suitable for estimating one-day Cre excretion is necessary. Accordingly, this study aimed to develop a predictive equation for individual one-day Cre excretion in Japanese school children.

Methods: Urine samples were collected from 113 boys and 91 girls (aged 6–12 years) from the Aichi Prefecture, Japan, who were free from diseases affecting the renal, muscle, or nervous systems. Urinary concentrations and one-day excreted amounts of Cre were measured and compared with the values obtained using previously reported equations or a fixed value, totaling 11 methods. Subsequently, we developed a new equation using machine learning and multiple regression analyses. Additionally, the estimated one-day sodium excretion value calculated using this equation was compared with the measured value.

Results: Among the 11 methods to predict Cre excretion, 7 overestimated—5 of which showed a positive trend bias with larger differences at higher average concentrations—and 3 underestimated—2 of which showed a negative trend bias with larger differences at lower average concentrations. A new machine learning model using sex, age, and body surface area (calculated from height and weight) yielded the most accurate prediction. Multiple regression analysis, which demonstrated the most accurate prediction, used sex, age, and body surface area as independent variables with or without the first void Cre concentration divided by urination duration from the previous night’s urination to the first void. Moreover, the difference in one-day sodium excretion from first-void urine predicted using our newly developed Cre equation increased as the measured values increased.

Conclusions: Our study suggests that the estimation of one-day Cre excretion based on sex, age, and body surface area is most appropriate for Japanese schoolchildren, particularly in assessing their chemical exposure and dietary nutrient intake.

Trial registration: Trial registration is not applicable as this observational study did not involve any intervention or randomization requiring registration in a clinical trials registry.

Background: Difficulty in chewing has been shown to be associated with increased mortality, geriatric syndromes, and poor activities of daily living, indicating the need for intervention. Chewing difficulties are related to tooth loss, periodontitis, dry mouth, and a number of oral health conditions. Diabetes mellitus (DM) is one of the major causes of global burden of diseases, and has been associated with poor oral health. Prospective association between oral health status and the development of diabetes has also been reported. However, relationship between glycemic control and self-reported chewing difficulty remains less explored in working-age populations. The objective of this study is to cross-sectionally explore the association between fasting blood glucose (FBG) and self-reported chewing difficulty in adults working in a Japanese worksite.

Methods: Participants from the Aichi Workers’ Cohort Study who responded to the 2018 survey were included. Participants were categorized into five FBG groups (<100, 100–109, 110–125, 126–159, and ≥160 mg/dl). Multivariable odds ratios (ORs) and 95% confidence intervals (CIs) for chewing difficulty were estimated using logistic regression adjusted for age, sex, body mass index, smoking and alcohol consumption status, number of teeth, presence of periodontal disease and the number of anti-diabetic medication classes.

Results: A total of 164 participants (4.2%) reported difficulty with chewing, the prevalence of which tended to increase with increasing FBG level. FBG ≥160 mg/dl was significantly and strongly associated with difficulty with chewing in the final multivariable model (multivariable OR 3.84 [95% CI 1.13–13.0]).

Conclusions: A relationship between higher FBG levels and difficulty with chewing was observed, independent of potential confounding factors. However, prospective or interventional studies are needed to determine causality.