Best Practices for Conducting Observational Research to Assess the Relation between Nutrition and Bone: An International Working Group Summary

Diet is a modifiable factor that can affect bone strength and integrity, and the risk of fractures. Currently, a hierarchy of scientific evidence contributes to our understanding of the role of diet on bone health and fracture risk. The strength of evidence is generally based on the type of study conducted, the quality of the methodology employed, the rigor and integrity of the data collected and analysis plan, and the transparency and completeness of the results. Randomized controlled trials (RCTs) are considered to be the gold standard from a clinical research paradigm, but there is a dearth of high-quality diet-related intervention trials with bone as the primary outcome, forcing the use of observational research to inform research and clinical practices. However, for observational research to be of the most utility, standardization and optimization of the study design, accurate and reliable measurement of key variables, and appropriate data analysis and data reporting are paramount. Although there have been recommendations made in relation to RCTs in the field of nutrition, no clear rubric exists for best practices in conducting observational research with regard to nutrition and bone health. Therefore, the purpose of this paper is to describe the best practices and considerations for designing, conducting, analyzing, interpreting, and reporting observational research specifically for understanding the role of nutrition in bone health, amassed by a global panel of scientific experts with strengths in bone, nutrition epidemiology, physical activity, public health, clinical and translational trials, and observational study methods. The global panel of scientific experts represents the leadership and selected participants from the 10th annual International Symposium for the Nutritional Aspects of Osteoporosis. The topics selected and best practices presented reflect expert opinion and areas of scientific expertise of the authors rather than a systematic or comprehensive literature review or professional reporting guidelines

A two-cohort study on the association between the gut microbiota and bone density, microarchitecture, and strength

The gut microbiome affects the inflammatory environment through effects on T-cells, which influence the production of immune mediators and inflammatory cytokines that stimulate osteoclastogenesis and bone loss in mice. However, there are few large human studies of the gut microbiome and skeletal health. We investigated the association between the human gut microbiome and high resolution peripheral quantitative computed tomography (HR-pQCT) scans of the radius and tibia in two large cohorts; Framingham Heart Study (FHS [n=1227, age range: 32 – 89]), and the Osteoporosis in Men Study (MrOS [n=836, age range: 78 – 98]). Stool samples from study participants underwent amplification and sequencing of the V4 hypervariable region of the 16S rRNA gene. The resulting 16S rRNA sequencing data were processed separately for each cohort, with the DADA2 pipeline incorporated in the16S bioBakery workflow. Resulting amplicon sequence variants were assigned taxonomies using the SILVA reference database. Controlling for multiple covariates, we tested for associations between microbial taxa abundances and HR-pQCT measures using general linear models as implemented in microbiome multivariable association with linear model (MaAslin2). Abundance of 37 microbial genera in FHS, and 4 genera in MrOS, were associated with various skeletal measures (false discovery rate [FDR] ≤ 0.1) including the association of DTU089 with bone measures, which was independently replicated in the two cohorts. A meta-analysis of the taxa-bone associations further revealed (FDR ≤ 0.25) that greater abundances of the genera; Akkermansia and DTU089, were associated with lower radius total vBMD, and tibia cortical vBMD respectively. Conversely, higher abundances of the genera; Lachnospiraceae NK4A136 group, and Faecalibacterium were associated with greater tibia cortical vBMD. We also investigated functional capabilities of microbial taxa by testing for associations between predicted (based on 16S rRNA amplicon sequence data) metabolic pathways abundance and bone phenotypes in each cohort. While there were no concordant functional associations observed in both cohorts, a meta-analysis revealed 8 pathways including the super-pathway of histidine, purine, and pyrimidine biosynthesis, associated with bone measures of the tibia cortical compartment. In conclusion, our findings suggest that there is a link between the gut microbiome and skeletal metabolism

Dairy Food Intake Is Not Associated with Measures of Bone Microarchitecture in Men and Women: The Framingham Osteoporosis Study

Previous studies reported that dairy foods are associated with higher areal bone mineral density (BMD) in older adults. However, data on bone strength and bone microarchitecture are lacking. We determined the association of dairy food intake (milk, yogurt, cheese, milk + yogurt, and milk + yogurt + cheese, servings/week) with high resolution peripheral quantitative computed tomography (HR-pQCT) measures of bone (failure load, cortical BMD, cortical thickness, trabecular BMD, and trabecular number). This cross-sectional study included participants with diet from a food frequency questionnaire (in 2005–2008 and/or 1998–2001) and measurements of cortical and trabecular BMD and microarchitecture at the distal tibia and radius (from HR-pQCT in 2012–2015). Sex-specific multivariable linear regression estimated the association of dairy food intake (energy adjusted) with each bone measure adjusting for covariates. Mean age was 64 (SD 8) years and total milk + yogurt + cheese intake was 10.0 (SD 6.6) and 10.6 (6.4) servings/week in men and women, respectively. No significant associations were observed for any of the dairy foods and bone microarchitecture measures except for cheese intake, which was inversely associated with cortical BMD at the radius (p = 0.001) and tibia (p = 0.002) in women alone. In this cohort of primarily healthy older men and women, dairy intake was not associated with bone microarchitecture. The findings related to cheese intake and bone microarchitecture in women warrant further investigation

Association between Sleep Duration, Insomnia Symptoms and Bone Mineral Density in Older Boston Puerto Rican Adults

Objective: To examine the association between sleep patterns (sleep duration and insomnia symptoms) and total and regional bone mineral density (BMD) among older Boston Puerto Rican adults. Materials/Methods We conducted a cross-sectional study including 750 Puerto Rican adults, aged 47–79 y living in Massachusetts. BMD at 3 hip sites and the lumbar spine were measured using dual-energy X-ray absorptiometry. Sleep duration (≤5 h, 6 h, 7 h, 8 h, or ≥9 h/d) and insomnia symptoms (difficulty initiating sleep, difficulty maintaining sleep, early-morning awaking, and non-restorative sleep) were assessed by a questionnaire. Multivariable regression was used to examine sex-specific associations between sleep duration, insomnia symptoms and BMD adjusting for standard confounders and covariates. Results: Men who slept ≥9h/d had significantly lower femoral neck BMD, relative to those reporting 8 h/d sleep, after adjusting for age, education level, smoking, physical activity, depressive symptomatology, comorbidity and serum vitamin D concentration. This association was attenuated and lost significance after further adjustment for urinary cortisol and serum inflammation biomarkers. In contrast, the association between sleep duration and BMD was not significant in women. Further, we did not find any significant associations between insomnia symptoms and BMD in men or women. Conclusions: Our study does not support the hypothesis that shorter sleep duration and insomnia symptoms are associated with lower BMD levels in older adults. However, our results should be interpreted with caution. Future studies with larger sample size, objective assessment of sleep pattern, and prospective design are needed before a conclusion regarding sleep and BMD can be reached

The Feasibility of Using Computrition Software for Nutrition Research—A Pilot Study

We evaluated the feasibility of using Computrition to design and implement a low vs. typical sodium meal plan intervention for older adults. Dietitians used Computrition to design a 7-day meal plan with three caloric levels (≤1750, 2000, ≥2250 kcals/day) and two sodium densities (low = 0.9 mg/kcal; n = 11 or typical = 2 mg/kcal; n = 9). Feasibility was determined by post-hoc definitions of effectiveness, sodium compliance, palatability of diet, sustainability, and safety. Given the low number of participants in one of the three calorie groups, the higher calorie groups were combined. Thus, comparisons are between low vs. typical meal plans at two calorie levels (≤1750 or ≥2000 kcals/day). Overall, regardless of the calorie group, the meal plans created with Computrition were effective in reaching the targeted sodium density and were safe for participants. Furthermore, individuals appeared to be equally compliant and reported similar palatability across meal plans. However, one of the three criteria for the sustainability definition was not met. In conclusion, we successfully used Computrition to design low and typical sodium meal plans that were effective, compliable, and safe. Future studies of older adults in similar settings should focus on improving the palatability of the meal plans and scaling this protocol to larger studies in older adults

Protective Effect of Total Carotenoid and Lycopene Intake on the Risk of Hip Fracture: A 17-Year Follow-Up From the Framingham Osteoporosis Study

In vitro and in vivo studies suggest that carotenoids may inhibit bone resorption, yet no previous study has examined individual carotenoid intake (other than β-carotene) and the risk of fracture. We evaluated associations of total and individual carotenoid intake (α-carotene, β-carotene, β-cryptoxanthin, lycopene, lutein + zeaxanthin) with incident hip fracture and nonvertebral osteoporotic fracture. Three hundred seventy men and 576 women (mean age, 75 ± 5 yr) from the Framingham Osteoporosis Study completed a food frequency questionnaire (FFQ) in 1988–1989 and were followed for hip fracture until 2005 and nonvertebral fracture until 2003. Tertiles of carotenoid intake were created from estimates obtained using the Willett FFQ adjusting for total energy (residual method). HRs were estimated using Cox-proportional hazards regression, adjusting for sex, age, body mass index, height, total energy, calcium and vitamin D intake, physical activity, alcohol, smoking, multivitamin use, and current estrogen use. A total of 100 hip fractures occurred over 17 yr of follow-up. Subjects in the highest tertile of total carotenoid intake had lower risk of hip fracture (p = 0.02). Subjects with higher lycopene intake had lower risk of hip fracture (p = 0.01) and nonvertebral fracture (p = 0.02). A weak protective trend was observed for total β-carotene for hip fracture alone, but associations did not reach statistical significance (p = 0.10). No significant associations were observed with α-carotene, β-cryptoxanthin, or lutein + zeaxanthin. These results suggest a protective role of several carotenoids for bone health in older adults