The Effects of Seaweed and Microalgae Supplementation on Exercise Performance and Recovery: A Systematic Review and Meta-Analysis

Objective: Seaweed and microalgae provide antioxidants, polyunsaturated fatty acids, and bioactive compounds that may enhance exercise performance and accelerate recovery. However, evidence remains inconsistent. This systematic review and meta-analysis aimed to evaluate the effects of algae-derived supplementation on exercise performance and physiological recovery outcomes in healthy and athletic adults. Methods: This review was registered in PROSPERO (CRD420251166723) and conducted in accordance with PRISMA 2020 guidelines. PubMed, Web of Science, Embase, Cochrane Library, EBSCO, and CNKI were systematically searched for randomized controlled trials (RCTs) evaluating algae supplementation in exercise contexts. Inclusion and exclusion criteria were defined based on the PICOS framework. Primary outcomes included VO2max, Time to exhaustion (TTE), maximal power output (WRmax), Time-Trial (TT) performance, and creatine kinase (CK). Standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated using a random-effects model. Subgroup, sensitivity, and publication bias analyses were performed. Results: Twenty-two RCTs (n = 822) investigating Spirulina, Chlorella, brown-algal polysaccharides, or astaxanthin met inclusion criteria. Algae supplementation showed a suggestive improvement in VO2max (SMD = 0.88, 95% CI: 0.00–1.75) and significantly improved in TTE (SMD = 1.06, 95% CI: 0.16–1.96), with smaller effects on WRmax (SMD = 0.29, 95% CI: 0.03–0.55), and no significant benefit for TT performance (SMD = −0.27, 95% CI: −0.74 to 0.21). Regarding recovery, CK concentrations were significantly reduced (SMD = −0.78, 95% CI: −1.28 to −0.28). Subgroup analysis suggested greater effects for Chlorella supplementation, higher dosages, and aerobic training contexts; reductions in muscle-damage markers were more evident following resistance exercise. Sensitivity analyses supported the robustness of the main findings with minimal evidence of publication bias. Conclusions: Algae-derived supplements—particularly Spirulina and Chlorella—may modestly enhance aerobic exercise performance and attenuate exercise-induced muscle damage under certain conditions. Effects appear to depend on algae species, dosing strategies, intervention duration, and training modality. High-quality, multi-center RCTs incorporating mechanistic endpoints are needed to clarify optimal application and to develop athlete-specific recommendations.