Background: Beneficial effects of vegetarian and vegan diets on health outcomes have been supposed in previous studies. Objectives: Aim of this study was to clarify the association between vegetarian, vegan diets, risk factors for chronic diseases, risk of all-cause mortality, incidence, and mortality from cardio-cerebrovascular diseases, total cancer and specific type of cancer (colorectal, breast, prostate and lung), through meta-analysis. Methods: A comprehensive search of Medline, EMBASE, Scopus, The Cochrane Library, and Google Scholar was conducted. Results: Eighty-six cross-sectional and 10 cohort prospective studies were included. The overall analysis among cross-sectional studies reported significant reduced levels of body mass index, total cholesterol, LDL-cholesterol, and glucose levels in vegetarians and vegans versus omnivores. With regard to prospective cohort studies, the analysis showed a significant reduced risk of incidence and/or mortality from ischemic heart disease (RR 0.75; 95% CI, 0.68 to 0.82) and incidence of total cancer (RR 0.92; 95% CI 0.87 to 0.98) but not of total cardiovascular and cerebrovascular diseases, all-cause mortality and mortality from cancer. No significant association was evidenced when specific types of cancer were analyzed. The analysis conducted among vegans reported significant association with the risk of incidence from total cancer (RR 0.85; 95% CI, 0.75 to 0.95), despite obtained only in a limited number of studies. Conclusions: This comprehensive meta-analysis reports a significant protective effect of a vegetarian diet versus the incidence and/or mortality from ischemic heart disease (−25%) and incidence from total cancer (−8%). Vegan diet conferred a significant reduced risk (−15%) of incidence from total cancer.

背景：先前的研究已经假设素食和纯素食对健康结局具有有益作用。目的：本研究旨在阐明素食，纯素饮食，慢性疾病的危险因素，全因死亡率的风险，发病率以及心脑血管疾病的死亡率，总癌症和特定类型的癌症（结直肠癌，乳房，前列腺和肺），通过荟萃分析。方法：对Medline，EMBASE，Scopus，Cochrane图书馆和Google Scholar进行了全面搜索。结果：包括86个横断面和10个队列的前瞻性研究。横断面研究的整体分析表明，素食主义者和素食主义者与杂食者相比，体重指数，总胆固醇，低密度脂蛋白胆固醇和葡萄糖水平显着降低。关于前瞻性队列研究，分析显示缺血性心脏病的发生和/或死亡的风险显着降低（RR 0.75； 95％CI，0.68至0.82）和总癌症的发生率（RR 0.92； 95％CI 0.87至95）。 0.98），但不包括全部心脑血管疾病，全因死亡率和癌症死亡率。分析特定类型的癌症时，没有明显的关联性证据。在纯素食者中进行的分析报告说，其与总癌症发生率之间存在显着相关性（RR 0.85； 95％CI，0。结论：这项综合的荟萃分析报告说，素食相对于缺血性心脏病的发生率和/或死亡率（−25％）和总癌症的发生率（−8％）具有显着的保护作用。素食饮食使罹患总癌症的风险显着降低（−15％）。