Vitamin D Status in Japanese Adults: Relationship of Serum 25-Hydroxyvitamin D with Simultaneously Measured Dietary Vitamin D Intake and Ultraviolet Ray Exposure

Abstract

Vitamin D insufficiency/deficiency is prevalent worldwide. We investigated the effect of vitamin D intake and ultraviolet ray (UV) exposure on serum vitamin D concentration in Japan. A total of 107 healthy adult participants were recruited from Hokkaido (43 • N) and Kumamoto (33 • N) prefectures. All participants undertook surveys in both summer and winter. Serum 25-hydroxyvitamin D (25(OH)D 3 ) was examined, and vitamin D intake was assessed with a diet history questionnaire. UV exposure was measured with a wearable UV dosimeter. Regression analysis was performed to investigate the relationship between these factors, with covariates such as sun avoidance behavior. The prevalence of vitamin D insufficiency (serum 25(OH)D 3 ; 12 ng/mL (30 nmol/L) ≤ and <20 ng/mL (50 nmol/L))/deficiency (<12 ng/mL) was 47.7% in summer and 82.2% in winter. UV exposure time was short in Kumamoto (the urban area), at 11.6 min in summer and 14.9 min in winter. In Hokkaido (the rural area), UV exposure time was 58.3 min in summer and 22.5 min in winter. Vitamin D intake was significantly associated with serum 25(OH)D 3 , and a 1 µg/1000 kcal increase in intake was necessary to increase 25(OH)D 3 by 0.88 ng/mL in summer and by 1.7 ng/mL in winter. UV exposure time was significantly associated with serum 25(OH)D 3 in summer, and a 10 min increase in UV exposure time was necessary to increase 25(OH)D 3 by 0.47 ng/mL. Although consideration of personal occupation and lifestyle is necessary, most Japanese may need to increase both vitamin D intake and UV exposure.

Impact of the vitamin D deficiency on COVID-19 infection and mortality in Asian countries

“…A total of 24 countries, satisfying the inclusion/exclusion criteria were selected for the analysis ( Table 1 ) [ [28] , [29] , [30] , [31] , [32] , [33] , [34] , [35] , [36] , [37] , [38] , [39] , [40] , [41] , [42] , [43] , [44] , [45] , [46] , [47] , [48] , [49] , [50] , [51] ]. Study population size varied extensively, from 107 (Japan) to 142,131 (Lebanon).…”

Incidence rate of vitamin D deficiency and FGF23 levels in 12- to 13-year-old adolescents in Japan

“…The Third National Health and Nutrition Examination Survey showed that the dietary intake of vitamin D from food was reported to be lower for female teenagers compared with male teenagers [42]. Furthermore, women tended to avoid tanning, use of sunscreen and sunshade clothing, and this might have caused lower UV exposure energy in women, particularly in summer [10]. In the current study, we speculate that the reasons for the sex differences was boys engaged in greater outdoor physical activity than in girls and girls tended to use sunscreen more than boys.…”

“…There are several reports of the incidence rate of vitamin D deficiency in Japan. The majority of these reports focus on infants, toddlers [8,9] or adults [10][11][12][13]. There was only one report on adolescent (12-18 years old) vitamin D deficiency in Japan [14].…”

Vitamin D and Sarcopenia: Potential of Vitamin D Supplementation in Sarcopenia Prevention and Treatment

“…The Dietary Reference Intake (2020) in Japan determines the Adequate Intake (AI) for vitamin D which was recently reviewed upwards from 5.5 µg/day (220 IU) to 8.5 µg/day (340 IU) ( Table 2 ) [ 69 ]. However, this value is still much lower than in other countries.…”