Comparative efficacy of different dietary interventions for cardiopulmonary fitness at high altitude: A systematic review and network meta-analysis

Chao Kang^1*Bin Wang²Yanle Xiong³Ning Lin¹Jiaojiao Shi¹Bo Zou²Xin Ma¹Kaihong Zeng⁴

• ¹Chinese People's Liberation Army Western Theater General Hospital, Chengdu, China
• ²Longgang Central Hospital of Shenzhen, Shenzhen, China
• ³The University of Hong Kong, Hong Kong, Hong Kong, SAR China
• ⁴Sichuan Academy of Medical Sciences and Sichuan People's Hospital, Chengdu, China

Background: A plateau hypoxic environment can increase the physiological burden on athletes. Although nutritional interventions have been recognised as a potential strategy to improve plateau acclimatisation, evidence in support of specific dietary patterns is still lacking. This study compared the effects of different dietary interventions on cardiopulmonary fitness during plateau exercise through systematic evaluation and network meta-analysis methods. Methods: This study systematically reviewed relevant literature up to June 2025 and included 20 randomized controlled trials conducted at altitudes above 1,500 meters involving healthy participants aged 16 years and above who engaged in physical activities. The primary outcomes included cardiopulmonary indicators [maximal oxygen uptake (VO2max), heart rate (HR)], blood biomarkers [peripheral oxygen saturation (SpO2), hematocrit (HCT)], and subjective perception indicators [rating of perceived exertion (RPE)]. Results: A total of 20 randomized controlled trials involving 329 participants were included, evaluating eight dietary interventions. Moderate-quality evidence indicated that carbohydrate supplementation significantly improved the percentage of maximal oxygen uptake (VO2max) compared to placebo (SMD = 1.13, 95% CrI: 0.25 to 2.05) and reduced RPE scores (MD = -0.77, 95% CrI: -1.83 to -0.09). Moderate-quality evidence indicated that carbohydrate supplementation combined with glutamine ranked highest in improving SpO2(SUCRA 84.54%) and RPE (SUCRA 69.37%), while iron supplementation showed the highest SUCRA rankings for HR (56.54%) and HCT (66.67%). However, these interventions did not demonstrate statistically significant advantages. Notably, the observed increase in VO2max exceeded the minimally clinically important difference (MCID) of 1.0 ml/kg/min reported in previous studies, suggesting that the effect of carbohydrate supplementation on VO2max may have clinical relevance. Conclusions: Differences exist in the effects of different dietary interventions on cardiopulmonary fitness during altitude exercise. The current network meta-analysis indicates that carbohydrate-based strategies show beneficial effects, with carbohydrate plus glutamine supplementation demonstrating greater advantages in SpO2 and RPE, while carbohydrate alone is more supported in improving VO2max. Therefore, carbohydrate-based strategies may serve as effective options to promote altitude acclimatisation, whereas iron supplementation may have potential benefits in improving HCT and HR.