The role of dietary patterns, inflammatory status and gut microbiome in bone health maintenance of postmenopausal women : a cross-sectional study : a thesis presented in fulfilment of the requirements for the degree of Doctor of Philosophy in Nutritional Science, School of Health Sciences, Massey University, Palmerston North

Abstract

The incidence of postmenopausal osteoporosis (a disease in which bones become weak and brittle) is increasing in parallel with the ageing of the global population. Postmenopausal osteoporosis is characterized by increased low grade inflammation that contributes to low bone mass and degradation of bone mineral density (BMD) resulting in postmenopausal bone loss. Elevated levels of pro-inflammatory cytokines such as IL-6, TNF-α, IL-1β and RANKL are produced by activated T-cells inducing osteoclast formation and activity during senescence. The objective of the “Bugs’n’Bones” clinical study was to assess the relationship between dietary patterns, inflammatory status, gut microbiota and bone health status in New Zealand postmenopausal women. We hypothesised that lack of physical activity, increased intake of poor diets, low in fibre and nutrients, and high in fat, salt and/or sugar will increase chronic inflammation and reduce BMD. The results of this human study indicated that alongside improving physical activity status with increase in lean body mass, a nutrient pattern with high loadings of B-vitamins, calcium and phosphorus was related to an increase in BMD. In addition, dietary pattern with a high factor loading of milks and milk-rich beverages was associated with a high BMD and T-score. The results of this study also indicated that a high circulatory level of inflammatory cytokines was associated with lower BMD in postmenopausal women. The results of the gut microbiota analyses showed that microbial composition diversity (alpha diversity by Shannon index) was significantly lower amongst the osteopenic/osteoporotic groups than their healthy counterparts. The interferon gamma receptor 1 orthology group was significantly higher in abundance for the OP (osteopenic/osteoporotics) than the H (healthy) groups based on the hip and femoral neck osteoporosis status. Future longitudinal and intervention studies which aim to modulate the gut microbiota via dietary change is warranted. It is also important to conduct these interventions with prebiotics, probiotics and synbiotics in animal and human models.