Table_1_Vitamin C intake potentially lowers total cholesterol to improve endothelial function in diabetic patients at increased risk of cardiovascular disease: A systematic review of randomized controlled trials.DOC

BackgroundVitamin C is one of the most consumed dietary compounds and contains abundant antioxidant properties that could be essential in improving metabolic function. Thus, the current systematic review analyzed evidence on the beneficial effects of vitamin C intake on cardiovascular disease (CVD)-related outcomes in patients with diabetes or metabolic syndrome.
MethodsTo identify relevant randomized control trials (RCTs), a systematic search was run using prominent search engines like PubMed and Google Scholar, from beginning up to March 2022. The modified Black and Downs checklist was used to assess the quality of evidence.
ResultsFindings summarized in the current review favor the beneficial effects of vitamin C intake on improving basic metabolic parameters and lowering total cholesterol levels to reduce CVD-risk in subjects with type 2 diabetes or related metabolic diseases. Moreover, vitamin C intake could also reduce the predominant markers of inflammation and oxidative stress like C-reactive protein, interleukin-6, and malondialdehyde. Importantly, these positive outcomes were consistent with improved endothelial function or increased blood flow in these subjects. Predominantly effective doses were 1,000 mg/daily for 4 weeks up to 12 months. The included RCTs presented with the high quality of evidence.
ConclusionClinical evidence on the beneficial effects of vitamin C intake or its impact on improving prominent markers of inflammation and oxidative stress in patients with diabetes is still limited. Thus, more RCTs are required to solidify these findings, which is essential to better manage diabetic patients at increased risk of developing CVD.

背景：维生素C是目前最常摄入的膳食化合物之一，其富含抗氧化特性，对于改善代谢功能至关重要。因此，本项系统综述分析了维生素C摄入对糖尿病或代谢综合征患者心血管疾病（Cardiovascular Disease, CVD）相关结局的有益影响相关证据。
方法：为筛选相关随机对照试验（randomized control trial, RCT），本研究通过PubMed、Google Scholar等主流搜索引擎开展系统性检索，检索时限为数据库建库起至2022年3月。研究采用改良版Black与Downs量表对证据质量进行评估。
结果：本综述汇总的研究结果显示，维生素C摄入可改善2型糖尿病或相关代谢疾病患者的基础代谢参数，降低总胆固醇水平，从而降低其心血管疾病风险。此外，维生素C摄入还可减轻炎症与氧化应激的核心标志物水平，如C反应蛋白、白细胞介素-6及丙二醛。值得注意的是，上述积极效应与患者内皮功能改善或血流量增加的表现相一致。该干预的最优有效剂量为每日1000mg，干预周期为4周至12个月不等。纳入本次综述的随机对照试验均具备较高的证据质量。
结论：目前关于维生素C摄入的有益效应，或其对糖尿病患者炎症与氧化应激核心标志物改善作用的临床证据仍较为有限。因此，仍需开展更多随机对照试验以巩固现有研究发现，这对于更好地管理心血管疾病风险升高的糖尿病患者至关重要。