Efficacy of Human Milk Oligosaccharide 6′-Sialyllactose Supplementation on Exercise Performance and Training Adaptations

Background/Objectives: The purpose of this proof-of-concept study was to examine the effects oligosaccharide 6′-sialyllactose (6′-SL) supplementation (900 mg/d) during training on exercise performance and training adaptations in recreationally active males. Methods: In a randomized, double-blind design, 19 healthy males (24.4 ± 6.0 yrs, 174.9 ± 5.9 cm, 82.0 ± 15.2 kg, 27.1 ± 4.7 kg/m2, 26.4 ± 6.9% body fat) ingested 3 × 300 mg/d of a placebo or 6′-SL for 12 weeks while partaking in a supervised resistance-training program while following their normal diet. Body composition (DXA), body water, submaximal lactate and substrate oxidation, 5RM dynamic muscular strength, ventilatory anaerobic threshold (VANT), peak aerobic capacity (VO2), blood lactate, cycling anaerobic sprint capacity, and fasting blood samples were obtained at week 0, 6, and 12 of training and supplementation. Data were analyzed using multivariate and univariate general linear models (GLM) with repeated measures, along with assessments of mean changes from baseline and corresponding 95% confidence intervals. Results: Both groups observed positive training adaptations with no significant differences observed between groups in body composition, 5RM dynamic strength, or anaerobic sprint capacity. Significant interaction effects were observed VANT (p = 0.032), VO2 at VANT (p = 0.028), and submaximal glucose and fat oxidation (p = 0.034) while time to reach peak VO2 (p = 0.083), absolute (p = 0.075) and relative (p = 0.057) peak VO2 approached significance. At Week 6, changes in time to peak effort (196 s −16, 409, p = 0.068), absolute (0.76 L/min −0.005, 1.53, p = 0.051) and relative (10.9 mL/kg/min 0.52, 21.5, p = 0.045), and fat oxidation (20.5% 3.1, 37.9, p = 0.023) were significantly greater in the 6′-SL group while VANT (−9.2% −18.3, −0.04, p = 0.049), VO2 at VANT (−4.8% −9.8, 0.2, p = 0.06) and submaximal glucose oxidation values (−20.5% −37.9, −3.1, p = 0.024) were lower with 6′-SL. After 12 weeks of training, VANT (−9.7% −17.7, −1.5, p = 0.023) and VO2 at VANT (−6.4% −11.8, −1.0, p = 0.024) values were significantly lower in the 6′-SL group. No significant differences were observed in resting, submaximal, or maximal exercise blood lactate while the ratios of LDL to HDL (−0.27 −0.53, −0.01, p = 0.042) and total cholesterol to HDL (−0.32 −0.60, −0.04, p = 0.028) decreased significantly from baseline after 6 weeks of training with 6′-SL. Conclusions: 6′-SL supplementation did not promote greater gains dynamic strength, fat free mass or changes in body composition. However, while there was some evidence that 6′-SL supplementation influenced training-induced changes in aerobic capacity during the first six weeks, fewer effects were observed after 12 weeks. Moreover, several differences only approached significance in this small proof-of-concept study, so results should be viewed as exploratory and hypothesis generating for additional research.