Daily Intake of a Functional Synbiotic Yogurt Increases Calcium Absorption in Young Adult Women

Foods containing both prebiotics and probiotics (synbiotics) might enhance calcium bioavailability.

We investigated the acute effect in young adult women on calcium absorption of consuming (185 mL) a synbiotic yogurt (SYN) containing inulin (4 g) and Lactobacillus rhamnosus GG (>1 × 107 CFU/mL) compared with a control yogurt (CON).

Adult normal-weight women (25.0 ± 3.5 y, n = 30) participated in a 3-wk crossover study testing daily consumption of SYN compared with CON. Habitual dietary intake, bone mineral density (BMD), calcium biomarkers, and serum 25-hydroxyvitamin D were measured at baseline. Calcium absorption was tested after each phase of the study using a 42Ca oral tracer. Cumulative tracer recovery was measured in 0-4-h,  0-24-h, and 0-36-h urine pools collected postdosing. The SYN/CON tracer ratio from the timed urine pools was the primary outcome. A beneficial response to SYN was defined as 0-36-h SYN/CON tracer ratio >1.

Net 42Ca recovered increased over time in each of the SYN and CON urine pools postdosing (Friedman, P < 0.001), with a trend for higher 42Ca recovery in the 0-36-h urine pool postdosing in the SYN (1.14%) compared with the CON (0.90%) study (Wilcoxon, P = 0.07). For CON, the majority of total tracer was recovered in the 0-24-h pool (86%), whereas for SYN only 50% of total tracer was recovered in the 0-24-h pool (Friedman, P = 0.001). The SYN/CON tracer ratio in the 0-36-h pool (1.24) was >1 (Wilcoxon, P = 0.015). About two-thirds (n = 19) of women studied responded to the SYN treatment. Responders had higher vegetable intake (P = 0.03), tended to have higher potassium and calcium intakes (P ≤ 0.08), and had higher total body BMD (P = 0.09), than nonresponders.

Short-term daily consumption of a synbiotic yogurt enhanced calcium absorption relative to a control yogurt in adult women. Given the observed time delays in tracer recovery, enhancement of calcium absorption likely occurred in the large intestine.The study was registered at clinicaltrials.gov (study registration ID: NCT03420716).