Vegetarian, vegan diets and multiple health outcomes: a systematic review with meta-analysis of observational studies

DOI:10.1080/10408398.2016.1138447

Monica Dinu, Rosanna Abbate, Gian Franco Gensini, Alessandro Casini & Francesco Sofi.

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.

http://www.tandfonline.com/doi/full/10.1080/10408398.2016.1138447

Vegetarian Diets and the Incidence of Cancer in a Low-risk Population

Yessenia Tantamango-Bartley, Karen Jaceldo-Siegl , Jing Fan, and Gary Fraser

Abstract

Background: Cancer is the second leading cause of death in the United States. Dietary factors account for at least 30% of all cancers in Western countries. As people do not consume individual foods but rather combinations of them, the assessment of dietary patterns may offer valuable information when determining associations between diet and cancer risk.

Methods: We examined the association between dietary patterns (non-vegetarians, lacto, pesco, vegan, and semi-vegetarian) and the overall cancer incidence among 69,120 participants of the Adventist Health Study-2. Cancer cases were identified by matching to cancer registries. Cox proportional hazard regression analysis was conducted to estimate hazard ratios, with “attained age” as the time variable.

Results: A total of 2,939 incident cancer cases were identified. The multivariate HR of overall cancer risk among vegetarians compared with non-vegetarians was statistically significant [HR, 0.92; 95% confidence interval (CI), 0.85–0.99] for both genders combined. Also, a statistically significant association was found between vegetarian diet and cancers of the gastrointestinal tract (HR, 0.76; 95% CI, 0.63–0.90). When analyzing the association of specific vegetarian dietary patterns, vegan diets showed statistically significant protection for overall cancer incidence (HR, 0.84; 95% CI, 0.72–0.99) in both genders combined and for female-specific cancers (HR, 0.66; 95% CI, 0.47–0.92). Lacto-ovo-vegetarians appeared to be associated with decreased risk of cancers of the gastrointestinal system (HR, 0.75; 95% CI, 0.60–0.92).

Conclusion: Vegetarian diets seem to confer protection against cancer.

Impact: Vegan diet seems to confer lower risk for overall and female-specific cancer than other dietary patterns. The lacto-ovo-vegetarian diets seem to confer protection from cancers of the gastrointestinal tract.

This article is featured in Highlights of This Issue, p. 179

Nutr Neurosci. 2014 Nov 21.

Vegans report less stress and anxiety than omnivores.

Beezhold B, Radnitz C, Rinne A, DiMatteo J.

Abstract

Objective Studies investigating mood in vegetarian diets have yielded conflicting results, either demonstrating risk for mental disorders or mood protection. Our objective was to investigate mood, as well as factors that potentially impact mood in vegans (VG), vegetarians (VEG), and omnivores (OMN). Methods We surveyed mood, diet, and lifestyle factors in a broad geographic online sample of adult VG (n = 283), VEG (n = 109), and OMN (n = 228) who were recruited via diet-related social networks. Mood was measured with the Depression Anxiety Stress Scale-21 (DASS-21).

Results The sample was mostly female (78.5%), and age was inversely correlated with all DASS scores (P < 0.05). Mean DASS-A (anxiety) and DASS-S (stress) scores differed by group (F(2616) = 4.73, P = 0.009, η2 = 0.015, and F(2, 615) = 8.23, P < 0.001, η2 = 0.026, respectively), with VG scores lower than OMN scores, indicating less mood disturbance.
Analyses of covariance were conducted by gender, adjusting for age. Anxiety scores were different in males only (F(2128) = 5.39, P = 0.006, ηp2 = 0.078) and lower anxiety in males was related to a vegan diet and daily fruit and vegetable intake. Mean stress scores were different in females only (F(2476) = 3.82, P = 0.023, ηp2 = 0.016) and lower stress in females was related to a vegan diet and lower daily intake of sweets.

Discussion: A strict plant-based diet does not appear to negatively impact mood, in fact reduction of animal food intake may have mood benefits. The improved mood domains were not consistent with those found in other studies, which may be due to methodological differences.

http://www.ncbi.nlm.nih.gov/pubmed/25415255