The global population is aging. The global incidence of postmenopausal osteoporosis is also increasing [1,2]. Postmenopausal osteoporosis is characterized by increased low-grade inflammation that contributes to low bone mass and degradation of bone mineral content, resulting in postmenopausal bone loss [3-5]. Elevated levels of proinflammatory cytokines (eg, interleukin [IL]–6, tumor necrosis factor [TNF]-α, IL-1, and receptor activator of nuclear factor kappa-Β ligand produced by activated T cells) induce osteoclast formation and activity during senescence [2,6]. Meanwhile, it is well recognized that conventional estrogen therapy in the form of hormone replacement therapy (HRT), such as estradiol implants, increases bone density by increasing the activity of osteoblasts, reducing bone resorption, and reducing inflammation [7-9]. However, the long-term use of HRT as an anabolic treatment and high doses of estrogen may not reduce the incidence of bone fracture [7] and are associated with long-term side effects. Therefore, nutritional interventions are safe and reliable for improving bone health status.

Studies have reported that changes in the gut microbiome can affect distant organs, including the bone and subsequently the development of osteoporosis [10]. Recent studies in rats and mice have suggested that the gut microbiome modulates immune status [11] as well as calcium absorption and molecular control of bone resorption [12-14]. Although studies have been conducted in animals, there are few studies in humans that have investigated the effects of pre- and probiotics on the gut microbiome and postmenopausal osteoporosis. Moreover, human gut microbiota is different from that of rodents, which is why many studies have faced limited success in their attempt to humanize the murine microbiota [15].

Osteoporosis is “characterized by low bone mass and microarchitectural deterioration of bone tissues, consequently increasing bone fragility and breakage” [16]. The term osteoporosis (osteoun) refers to bone and pór (os) to passage+osis [17]. The widely accepted clinical diagnostic criteria and intervention threshold are defined as bone mineral density (BMD) ≥2.5 SDs (T score ≤−2.5) below the mean value of a young reference at the lumbar spine, femur neck, or total hip bone in older men and postmenopausal women [18].

The vast burden of osteoporosis constitutes an increase in morbidity and mortality [19], loss of quality-adjusted life-years (QALYs) [20], and a continuous rise in the cost of health care services, such as clinics, nursing homes, and hospitals [21,22]. It is a growing global health concern, with the lifetime risk of sustaining any fracture at approximately 50% for women and 20% for men in individuals aged >50 years living in Western countries [23]. It has also been predicted to become an issue in developing countries as the aging population rises. The risk of fracture becomes higher as people age, especially in postmenopausal women [24].

In 2011, osteoporosis-related QALYs were found to be 11,249, with a projection of 13,205 and 15,176 for 2013 and 2020, respectively, because of fractures. The results also suggest that there are more QALYs for women (6028) than men (5221) [22].

As a global epidemic situation, the International Osteoporosis Foundation suggests that 33% of middle-aged women and 20% of men (aged >50 years) will have an osteoporotic fracture [25]. The disease constitutes an economic burden, particularly because of the high cost of treatment. Over US $300 million per annum is estimated to be spent on treating fractures, whereas the total cost is estimated at US $1.15 billion per annum in health costs, posing a heavy burden on health care service providers in New Zealand [20].

Physical activity is defined by the World Health Organization as any “bodily movement of the skeletal muscle, which requires energy expenditure” [26]. Physical activity enhances the composition and function of the human skeletal system. However, skeletal muscle performance also deteriorates with age [27], and a lack of exercise and physical activity has been linked to bone loss and ultimately osteoporosis [28]. Osteoporosis may cause falls that result in osteoporotic fractures in older women.

Previous studies, including Cochrane reviews, have reported the effects of physical activity on bone strength across the life spans [29] of children and adolescents [30] as well as women, especially postmenopausal women [31-33]. A study from Italy reported progressive resistance strength training of the lower limbs to be most effective for the neck of the femur BMD in patients with osteoporosis. In contrast, a multicomponent training program was suggested for a spine BMD intervention [34].

Neilson et al [35] have defined activity energy expenditure (AEE) as “a modifiable component of total energy expenditure (TEE) derived from both volitional and non-volitional activities.“ Total energy expenditure comprises multiple components, including physical activity energy expenditure, resting energy expenditure, and the thermic effect of food [36]. The impact of physical activity has been used to alleviate several obesity-related diseases and the overall burden of diseases in men and women alike [37].

The G*Power statistical software, version 3.1.9.7, developed in Heinrich Heine University Düsseldorf, was used to calculate the sample size using the bone biomarker CTx-I; a recommended number of 36 women would be required for the study. However, 40 women aged >60 years will be recruited for each of the 4 groups to allow for a possible dropout rate of 10%. The test groups will receive the synbiotic food supplementation and exercise program (10,000 steps brisk walking per day required), whereas the control group will receive a placebo and no exercise; however, dietary intake and exercise will be monitored by a 3-day diet diary and the International Physical Activity Questionnaire. All study participants will read the information sheet, and signed and written consent forms will be obtained from them.

The inclusion criteria include a confirmed menopause diagnosis (by an initial blood test—baseline screening—that includes checking the levels of follicle-stimulating hormone [≥30 mIU/mL] and estrogen) of at least five years based on no menstruation and the BMI of all participants will be between 17 and 35 kg/m².

The following criteria are to be confirmed by medical history or measurements:

The following criteria are to be confirmed by the baseline questionnaire:

The study design is a randomized controlled trial (RCT). All the volunteer participants in the trial will undergo the following.

G*Power statistical software version 3.1.9.7 developed in Heinrich Heine University Düsseldorf was used to calculate the sample size to ensure 95% CI with an α value of .05. We require 36 participants for each group. The within-subject SD for the primary outcome variables CTx-I and P1NP with a correlation of 0.5 was used. The number of volunteers was increased to 40 to allow for a dropout rate of 10%.

The results will be presented as either percentages or mean differences. Normality tests will be assessed through Shapiro-Wilk tests carried out on each parameter before analysis. The conventional analysis of variance (ANOVA) for RCT analysis will be used, and ANOVA for repeated measures will be applied to study treatment differences, period effect, and the interaction between treatment and period (carryover effect). IBM SPSS version 25 and Minitab statistical software version 19 (Minitab LLC) will be used for statistical analyses. Comparing groups' pretest with Mann–Whitney U test and then comparing pre- and postintervention results with Wilcoxon is one option and transforming data into ranks and performing an analysis of covariance (or ANOVA) is another option. All analyses will be considered statistically significant at P≤.05.

Ethical approval for this study has been received from the Health and Disability Ethics Committee of New Zealand. The recruitment and collection of data will begin in September 2021. We aim to complete data collection by June 2022. Statistical analyses, report writing, and dissemination of results are expected to be completed by February 2023. Funding is being sought for the study.

The anticipated outcomes of this study are a reduction in bone turnover as measured using CTx-I as a marker, as well as a reduction in inflammation (reduced or changed levels of specific cytokines such as hs-CRP, IL-6, and TNF-α).

With menopause and the loss of estrogen, bone turnover (formation and resorption) increases significantly. Over time, because of increased levels of IL-6 and inflammation, bone resorption (breakdown) overtakes bone formation, and this increase in bone resorption can be measured using the marker CTx-I. Several studies over the past 20 years have shown that a reduction in CTx-I is associated with long-term changes in bone density and a reduction in fractures. CTx-I most sensitively reflects the change in bone resorption after mineral supplementation or increased absorption of calcium and can predict the rate of bone loss and fracture risk in postmenopausal women. CTx-I may reflect parameters of bone strength unrelated to BMD, such as microarchitectural deterioration of bone tissue resulting in microcracks that act as stress risers or trabecular perforation.

Supplementation with a synbiotic will modify the gut microbiota and improve calcium and magnesium absorption. Prebiotic supplementation promotes bacterial growth that induces nondigestible carbohydrate fermentation, increases short-chain fatty acids (SCFAs), and reduces the pH of the gut, thereby increasing calcium absorption. The reduction in pH promotes the growth of bacteria that are less likely to cause inflammation, and SCFAs stimulate the effects of anti-inflammatory cytokines. Probiotic supplementation by Lactobacillus and Bacillus species may promote an immunoprotective response in the gut mucosa by reducing the levels of systemic inflammatory cytokines and preventing the reduction in bone density.

Degeneration of bone health in the form of osteoporosis, osteoporotic fractures, and osteoarthritis are major health care issues leading to a significant increase in morbidity and mortality in New Zealand and all over the world. Similarly, the growing number of patients with osteoporosis or osteoarthritis results in huge health care costs. The aim is to measure the effect of synbiotics, weight-bearing exercises (10,000 brisk walking steps per day), or a combination of both on gut microbiota, inflammation status, and bone health. This study is important for several reasons. This study is directed toward postmenopausal women who have experienced a rapid phase of bone loss 5 years postmenopause. The use of a synbiotic (a combination of probiotic and prebiotic) supplement is particularly novel in the modulation of the immune system, gut microbiota, and anti-inflammatory response. Studies are needed to measure the effects of synbiotic supplementation and weight-bearing exercise on gut microbiota, inflammatory status, and bone health. Randomization by exercise history will help eliminate the effects of the previous exercise regime for the study. There is a critical need for measures of bone turnover and not BMD only as a primary outcome.

The effects of probiotic or synbiotic supplementation on markers of inflammation have also been reported. A reduction in proinflammatory cytokines (eg, IL-1β, TNF-α, IL-6, and IL-8) and an increase in anti-inflammatory cytokines (IL-10 and IL-4) [44] were observed in response to these interventions. Similarly, studies have indicated the protective factors of probiotic supplementation [45] and exercise in bone metabolism and health [34]. Long-term participation in a relevant and targeted exercise regime is known to improve bone mechanical properties over time [46].

Prebiotic supplementation promotes bacterial growth that induces nondigestible carbohydrate fermentation, increases SCFAs, and reduces the pH of the gut contents, thereby increasing calcium absorption. The reduction in pH promotes the growth of bacteria that are less likely to cause inflammation, and SCFAs stimulate the effects of anti-inflammatory cytokines. In addition, probiotic supplementation with Lactobacillus and Bacillus species promotes immunoprotective response or effects in the gut, reducing inflammatory cytokines and preventing the reduction in bone density [47].

Prediction of bone loss and risk of fractures is conducted using biomarkers of bone turnover independent of bone density in women. The occurrence of menopause results in a period of bone loss, where the rate of bone resorption exceeds that of formation (approximately 5 years). A bone remodeling cycle of formation and resorption takes place between 4 and 6 months, replenishing approximately 5%-15% of the total bone mass in a year [46]. These data provide the rationale for the length of time and a comprehensive investigation of body composition and bone turnover status in the study described here.

The strength of the RCT will account for exercise history and the sample size and duration to ensure an adequately powered sample needed to detect clinically and statistically significant results.

This study was designed as an RCT to account for exercise history, and the sample size and duration have been selected to ensure an adequately powered sample needed to detect clinically and statistically significant results. In this study, investigating the effects of both prebiotics and probiotics with and without weight-bearing exercise provides strong evidence for an RCT. The limitation of the study lies in the inability to extend the duration in terms of further follow-up.

Our research study aims to decrease the possibility of osteoporotic fractures resulting because of the incidence of inflammation and loss of bone mass by improving body composition (lean and fat mass) among postmenopausal women after ≥5 years. This study compares the effectiveness of synbiotic supplementation and weight-bearing exercise intervention, both of which may be used as a therapy for bone health maintenance in postmenopausal women. To the best of our knowledge, this will be the first RCT to analyze the effects of both a synbiotic supplement and an exercise intervention in postmenopausal women. On the basis of the results obtained, a combination of synbiotic supplementation and exercise might serve as a noninvasive approach to manage and/or improve body composition and bone health in postmenopausal women.