Abstract

Objective and Aims: This study aims to conduct a systematic review and meta-analysis for prospective studies to investigate the improvement effects of natto on bone mineral density (BMD) in perimenopausal women.

Methods: PubMed, EMBASE and Cochrane database searched upto February 2019. This study was carried out according to the PRISMA guidelines10 for systematic reviews. The protocol of the review was registered in the PROSPERO registry (CRD42019133183).

Results: The review identified 3 unique prospective studies comprising 1658 non-overlapping participants. Meta-analysis showed that natto could significantly improve lumbar bone mineral density (BMD) (P=0.002, WMD=0.26; 95% CI:0.09-0.43) in cohort studies. However, the randomized controlled study showed no statistical difference between the two (P=0.31, WMD=0.05; 95% CI:- 0.05-0.15). In addition, natto significantly improved the BMD of the femoral neck in a cohort study and randomized control study (P=0.03, WMD=0.42). 95% CI:0.05-0.79, I2= 72%); (P < 0.0001, WMD=0.16; 95% CI:0.08-0.24), respectively. However, all studies demonstrated that natto has no improvement effects on a hip joint (BMD). In that, the cohort study showed no statistical significance between the natto intake group and the control group (P=0.21, WMD=0.10). 95% CI:-0.06-0.25, I2= 18%) and the randomized controlled study also showed no statistical significance between the natto intake group and the control group (P=0.09, WMD=-0.06). 95% CI:-0.13- 0.01).

Conclusion: Through our current systematic review and meta-analyize of these prosepctive studies of natto's anti-osteoporostic effecs on BMD, we found that the dietary intake of natto demonstrated a improving effects on the BMD of the femoral neck, but has no effects on the hip joint. Such interesting results may be related to the differences between anatomical structure between various tissues. Besides that, the results of the RCT study and cohort study on the lumbar spine were not the same, which may be related to the fact that participants in the RCT study were Caucasian and participants in the cohort study were Asian. Therefore, more large-sample and high-quality RCT studies are needed to further clarify the improvement effect of natto on osteoporosis.

Keywords: Natto, osteoporosis, Bone Mineral Density (BMD), Perimenopause, Randomised Control Trials (RCTs), osteoporotic fractures.