Self-reported lactose intolerance is inversely associated with calcium intake and bone mineral density: a cross-sectional data analysis from the Iwaki Health Promotion Project

Self-reported lactose intolerance (LI) is associated with gastrointestinal symptoms after consuming lactose-containing foods and avoiding dairy products; however, few studies have investigated its prevalence and nutritional significance in Asian populations. Consequently, this study aimed to determine the relationship between self-reported LI and bone health in Japanese adults. A community-based nutritional survey, including self-reported LI and forearm bone mineral density (BMD) measurements, was conducted. In 843 healthy Japanese adults, as part of an annual medical checkup at the Iwaki Health Promotion Project 2023, self-reported LI prevalence was characterized based on the presence of subjective abdominal symptoms after consuming lactose-containing foods. Relationships among self-reported LI, dairy consumption, calcium intake, and BMD were analyzed. Participants with the self-reported LI (n = 191, 22.7% of the participants) had lower intakes of milk and calcium than those without self-reported LI (n = 652; 32.9 ± 83.8 vs. 63.4 ± 111.9 g/1000 kcal/d for milk and 243.7 ± 140.4 vs. 285.5 ± 162.3 mg/1000 kcal/d for calcium, respectively). The presence of self-reported LI was associated with the decreased BMD Z-score after adjustments with age, sex, body mass index, smoking, alcohol, vitamin D, and walking speed (β = –0.1615, P = 0.042), and comparison using propensity score matching revealed that self-reported LI was associated with a significant decrease in BMD parameters after the adjustments (β = − 0.2543, − 0.3903, and − 0.0148; P = 0.007, 0.010, and 0.023 for Z-score, T-score, and BMD itself, respectively). Self-reported LI is negatively associated with calcium intake and bone health in healthy Japanese adults. UMIN000040459 ( https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000046175 ). Registration date: May 20, 2020.