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Vegetarian, vegan diets and multiple health outcomes: A systematic review with meta-analysis of observational studies.
Dinu, M, Abbate, R, Gensini, GF, Casini, A, Sofi, F
Critical reviews in food science and nutrition. 2017;57(17):3640-3649
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Plain language summary
Vegetarian diet is experiencing a considerable popularity in the general population. The aim of this study was to obtain an estimate of the association between vegetarian, vegan diets, and multiple health outcomes, including risk factors for chronic diseases, risk of all-cause mortality, incidence and mortality from cardio-cerebrovascular diseases, total cancer and specific types of cancer. This study is a comprehensive systematic review with meta-analysis of all cross-sectional and cohort studies. A total of 108 articles were included in the meta-analysis with a total population of over 130,000 vegetarians and 15,000 vegans. Results indicate that: - vegetarians and vegans show significantly lower levels of the most relevant risk factor for chronic disease such as body mass index, lipid variables and fasting glucose, when compared to non-vegetarians and nonvegans. - a significant protection versus ischemic heart disease and cancer is present in vegetarian subjects, however this protection is not significant for overall mortality, cardio and cerebrovascular diseases. - vegan diet seems to be associated with a lower rate of cancer incidence (interpreted with caution due to the small sample size of the study). Authors conclude that their findings may be useful for helping to give correct information to subjects who want to adopt vegetarian or vegan dietary patterns.
Abstract
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.