American Journal of Physiology Regulatory, Integrative and Comparative Physiology · Jan 12, 2026

Limited effects of dietary nitrate supplementation with resistance training on skeletal muscle and vascular outcomes in middle-aged and older adults

By McIntosh MC, Mueller BJ, Tiede DR et al.

Increasing dietary nitrate (NO₃⁻) through beetroot juice (BRJ) supplementation elicits acute ergogenic benefits. However, it is unknown whether chronic NO₃⁻ supplementation can enhance resistance training (RT) adaptations in middle-aged and older individuals. Therefore, we sought to determine whether 12 wk of combined RT and NO₃⁻ supplementation enhanced hypertrophic, vascular, strength, and skeletal muscle angiogenesis adaptations in this population. Twenty-eight apparently healthy, untrained men (M) and women (W) (56 ± 7 yr old and 29.1 ± 5.3 kg/m² body mass index) completed 12 wk of supervised full-body RT (2×/wk) while ingesting either BRJ (140 mL daily, providing 800 mg NO₃⁻; n = 14 with 7 M/7 W) or NO₃⁻-depleted BRJ placebo (PLA; n = 14 with 7 M/7 W). Participants underwent a whole body dual-energy X-ray absorptiometry scan, right mid-thigh ultrasonography for muscle imaging, right leg popliteal artery flow-mediated dilation (FMD) assessments, a biopsy of the right mid-thigh vastus lateralis, and strength testing before and following the 12-wk intervention. Biopsy analyses included a NO₃⁻/nitrite (NOx) fluorometric assay, immunoblotting for proteins involved in angiogenesis, and immunohistochemistry to quantify fiber type-specific capillaries and cross-sectional areas. Muscle NOx values did not significantly change: +15.4% in BRJ (P = 0.073) and +7.8% (P = 0.514) in PLA. Both groups significantly improved measures related to muscle hypertrophy, strength, and FMD. However, no significant group × time interactions were observed for whole body lean mass, mid-thigh muscle cross-sectional area, popliteal artery FMD outcomes, or histological or molecular markers. In conclusion, these preliminary data on a limited number of participants indicate that BRJ supplementation does not enhance RT adaptations in middle-aged and older adults.NEW & NOTEWORTHY Results from this study suggest that 12 wk of dietary nitrate supplementation does not significantly alter skeletal muscle hypertrophic, strength, or vascular outcomes in previously untrained middle-aged and older adults who performed resistance training.

doi.org/10.1152/ajpregu.00195.2025 PubMed 41525148 Interventions