Effects of antioxidant-rich foods on altitude-induced oxidative stress and inflammation in elite endurance athletes: A randomized controlled trial

BackgroundVarious altitude training regimes, systematically used to improve oxygen carrying capacity and sports performance, have been associated with increased oxidative stress and inflammation. We investigated whether increased intake of common antioxidant-rich foods attenuates these processes.MethodsIn a randomized controlled trial, 31 elite endurance athletes (23 ± 5 years), ingested antioxidant-rich foods (n = 16), (> doubling their usual intake), or eucaloric control foods (n = 15) during a 3-week altitude training camp (2320 m). Fasting blood and urine samples were collected 7 days pre-altitude, after 5 and 18 days at altitude, and 7 days post-altitude. Change over time was compared between the groups using mixed models for antioxidant capacity [uric acid-free (ferric reducing ability of plasma (FRAP)], oxidative stress (8-epi-PGF2α) and inflammatory biomarkers (IFNγ, IL1α, IL1RA, IL1β, IL2, IL5, IL6, IL7, IL10, IL12p70, IL13, IL17, TNFα, MCP-1 and micro-CRP). The cytokine response to a stress-test (VO2max ramp test or 100 m swimming) was assessed at pre- and post-altitude.ResultsFRAP increased more in the antioxidant compared to the control group (p = 0.034). IL13 decreased in the antioxidant group, while increasing in the controls (p = 0.006). A similar trend was seen for IL6 (p = 0.062). A larger decrease in micro-CRP was detected in the antioxidant group compared to controls (β: -0.62, p = 0.02). We found no group differences for the remaining cytokines. 8-epi-PGF2α increased significantly in the whole population (p = 0.033), regardless group allocation. The stress response was significantly larger post-altitude compared with pre-altitude for IL1β, IL6, IL7, IL13, IL12p70 and TNFα, but we found no group differences.ConclusionsIncreased intake of antioxidant-rich foods elevated the antioxidant capacity and attenuated some of the altitude-induced systemic inflammatory biomarkers in elite athletes. The antioxidant intervention had no impact on the altitude-induced oxidative stress or changes in acute cytokine responses to exercise stress-tests.

研究背景：系统性应用于提升血氧携氧能力与运动表现的各类高原训练方案（altitude training regimes），已被证实与氧化应激及炎症反应加剧相关。本研究旨在探究增加日常富含抗氧化剂食物的摄入，是否能够缓解上述病理过程。
研究方法：本研究采用随机对照试验（randomized controlled trial）设计，纳入31名优秀耐力运动员（elite endurance athletes，年龄23±5岁），在为期3周、海拔2320米的高原训练营（altitude training camp）期间，让受试者分别摄入富含抗氧化剂的食物（摄入量为日常摄入量的2倍以上，n=16）或等热量对照食物（eucaloric control foods，n=15）。分别于高原暴露前7天、高原停留第5天和第18天，以及高原撤离后7天采集空腹血液与尿液样本（fasting blood and urine samples）。采用混合效应模型（mixed models），比较两组受试者在抗氧化能力[无尿酸血浆铁还原能力（ferric reducing ability of plasma, FRAP）]、氧化应激（oxidative stress）指标（8-表-前列腺素F2α，8-epi-PGF2α）及炎症生物标志物（inflammatory biomarkers，包括干扰素γ（IFNγ）、白细胞介素1α（IL1α）、白细胞介素1受体拮抗剂（IL1RA）、白细胞介素1β（IL1β）、白细胞介素2（IL2）、白细胞介素5（IL5）、白细胞介素6（IL6）、白细胞介素7（IL7）、白细胞介素10（IL10）、白细胞介素12p70（IL12p70）、白细胞介素13（IL13）、白细胞介素17（IL17）、肿瘤坏死因子α（TNFα）、单核细胞趋化蛋白1（MCP-1）及微量C反应蛋白（micro-CRP））方面的随时间变化情况。另在高原暴露前后，分别评估受试者对应激测试（stress-test，包括最大摄氧量递增测试（VO2max ramp test）或100米游泳（100 m swimming））的细胞因子（cytokine）应答水平。
研究结果：抗氧化组的FRAP水平较对照组提升更为显著（p=0.034）。抗氧化组的IL13水平呈下降趋势，而对照组则呈上升趋势（p=0.006）；IL6也呈现类似的变化趋势（p=0.062）。与对照组相比，抗氧化组的micro-CRP水平下降幅度更大（β=-0.62，p=0.02）。其余细胞因子未观察到组间显著差异。无论分组情况如何，全体受试者的8-epi-PGF2α水平均显著升高（p=0.033）。高原撤离后，受试者针对应激测试的IL1β、IL6、IL7、IL13、IL12p70及TNFα应答水平均显著高于高原暴露前，但未观察到组间差异。
研究结论：增加富含抗氧化剂食物的摄入，可提升优秀耐力运动员的抗氧化能力，并缓解部分高原暴露诱导的全身性炎症生物标志物变化。但本抗氧化干预并未对高原诱导的氧化应激，或运动应激测试下的急性细胞因子应答变化产生显著影响。