How many studies for a comprehensive meta analysis review

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.Р”В¬ONCLUSIONS: 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%). No significant association was evidenced when specific types of cancer were analyzed. 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. 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. RESULTS: Eighty-six cross-sectional and 10 cohort prospective studies were included. METHODS: A comprehensive search of Medline, EMBASE, Scopus, The Cochrane Library and Google Scholar was conducted. 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.

BACKGROUND: Beneficial effects of vegetarian and vegan diets on health outcomes have been supposed in previous studies.

How many studies for a comprehensive meta analysis review