(P19-050-25) The Effect of Dairy-Derived Calcium and Fermentable Fiber Supplementation on the Fecal Microbiome of Postmenopausal Danish Women

Objectives: Osteoporosis is a global burden, particularly in postmenopausal women, due to reduced estrogen levels, which increase bone resorption. A recent study linked lower stool pH to higher bone mineral density in women, suggesting gut microbiome involvement in calcium absorption. Intake of fermentable fiber, such as inulin, is known to reduce fecal pH. However, the combined effects of calcium and fermentable fiber on gut microbiome function in postmenopausal women remain unclear. The objective of the current study was to determine the effect of long-term calcium and inulin supplementation on microbial taxonomy and function.

Methods: The RENEW study recruited 417 healthy postmenopausal women aged 45-69 years in Denmark. This 1-year randomized, double-blind, controlled trial included four groups: I) placebo, II) calcium carbonate (800 mg of Ca/day), III) milk-derived calcium permeate (800 mg of Ca/day), IV) milk-derived calcium permeate (800 mg of Ca/day) + inulin (12 g/day). Women with osteoporosis or using medications/supplements affecting bone metabolism were excluded. All received vitamin D (10 μg/day). A 7-day online dietary record estimated dietary fiber and calcium intake. Fecal metagenomic sequencing was performed using NovaSeqX, annotated for taxa and gene function. Treatments remain blinded as Groups A, B, C, D.

Results: The most abundant microbial genera that was also significantly modulated by treatment was Bifidobacterium, which was highest in Group C (p.adj = 0.013). Group C had marginally higher exo-inulinase genes than Groups A or D (p.adj = 0.052) and higher beta-galactosidase genes compared to the other 3 groups after 1-year treatment (p.adj < 0.0001).

Conclusions: Diets supplemented with dairy-derived calcium and/or inulin potentially (pending unblinding) modulate the gut microbiome and its inulin-degrading and/or lactose-degrading capacity.

Funding Sources: Innovation Fund Denmark, Arla Foods Ingredients Group P/S, Arla Foods amba