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Evidence of a vegan diet for health benefits and risks–an umbrella
review of meta-analyses of observational and clinical studies
Selinger, E., Neuenschwander, M., Koller, A., Gojda, J., Kühn, T., Schwingshackl, L., Barbaresko, J., &
Schlesinger, S. (2022). Evidence of a vegan diet for health benefits and risks–an umbrella review of meta-
analyses of observational and clinical studies. Critical Reviews in Food Science and Nutrition.
https://doi.org/10.1080/10408398.2022.2075311
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Critical Reviews in Food Science and Nutrition
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/bfsn20
Evidence of a vegan diet for health benefits and
risks – an umbrella review of meta-analyses of
observational and clinical studies
Eliška Selinger, Manuela Neuenschwander, Alina Koller, Jan Gojda, Tilman
Kühn, Lukas Schwingshackl, Janett Barbaresko & Sabrina Schlesinger
To cite this article: Eliška Selinger, Manuela Neuenschwander, Alina Koller, Jan Gojda, Tilman
Kühn, Lukas Schwingshackl, Janett Barbaresko & Sabrina Schlesinger (2022): Evidence of a vegan
diet for health benefits and risks – an umbrella review of meta-analyses of observational and clinical
studies, Critical Reviews in Food Science and Nutrition, DOI: 10.1080/10408398.2022.2075311
To link to this article: https://doi.org/10.1080/10408398.2022.2075311
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CritiCal reviews in Food sCienCe and nutrition
https://doi.org/10.1080/10408398.2022.2075311
Review
Evidence of a vegan diet for health benefits and risks – an umbrella review
of meta-analyses of observational and clinical studies
a,b,c# d,e# f,g a,c
eliška Selinger , Manuela Neuenschwander , Alina Koller , Jan Gojda ,
g,h,i j d d,e
Tilman Kühn , Lukas Schwingshackl , Janett Barbaresko and Sabrina Schlesinger
a b
third Faculty of Medicine, Charles university, Prague, Czech republic; Centre for Public Health Promotion, national institute of Public
c
Health, Prague, Czech republic; department of internal Medicine, Královské vinohrady university Hospital, Prague, Czech republic;
dinstitute for Biometrics and epidemiology, German diabetes Center, leibniz Center for diabetes research at Heinrich Heine university
e f
düsseldorf, düsseldorf, Germany; German Center for diabetes research (dZd), Partner, düsseldorf, Germany; Faculty of Medicine,
g
university of Zurich, Zurich, switzerland; division of Cancer epidemiology, German Cancer research Center (dKFZ), Heidelberg, Germany;
h i
Faculty of Medicine and university Hospital, Heidelberg institute of Global Health (HiGH), Heidelberg, Germany; institute for Global Food
j
security (iGFs), Queen’s university, Belfast, uK; institute for evidence in Medicine, Medical Center, Faculty of Medicine, university of
Freiburg, Freiburg, Germany
ABSTRACT KEYWORDS
To summarize and evaluate the evidence on the health impact of a vegan diet, we conducted an Health;
umbrella review of systematic reviews and meta-analyses. PubMed, Cochrane Library, web of meta-analysis;
Science and epistemonikos were searched up to September 2021. Meta-analyses were recalculated plant-based;
by using a random effects model. The certainty of evidence (Coe) was evaluated by the GRADe systematic review;
approach. For the general healthy population, a vegan diet was effective for reducing body weight umbrella review;
[MD (95% Ci): −2.52 kg (−3.06, −1.98), n = 8 RCTs; moderate Coe] and was associated with further vegan diet
health benefits (with low Coe), including a lower risk of cancer incidence [SRR (95% Ci): 0.84 (0.75,
0.95), n = 2] and a trend for lower risk of all-cause mortality [SRR (95% Ci): 0.87 (0.75, 1.01), n = 2],
as well as lower ApoB levels [MD (95% Ci): −0.19 µmol/L (−0.23, −0.15), n = 7 RCTs). The findings
suggested adverse associations for a vegan diet with risk of fractures [SRR (95% Ci): 1.46 (1.03,
2.07), n = 3; low Coe]. For persons with diabetes or at high CvD risk, a vegan diet reduced measures
of adiposity, total cholesterol, LDL and improved glycemic control (Coe moderate to low). A vegan
diet may have the potential for the prevention of cardiometabolic health, but it may also impair
bone health. More well-conducted primary studies are warranted.
Introduction (The Vegan Society 2021). And though the motivations
A transition toward healthy and environmentally sustain- for following a vegan diet are diverse, including animal
able food is among major global challenges. Replacing ani- welfare, religious aspects, and environmental sustainabil-
mal sources, namely red meat and milk, with plant-based ity, one important reason is health benefits (Norman and
sources has the potential to impact on cutting greenhouse Klaus 2020).
gas emissions (Springmann et al. 2018). That is a reason With an increasing number of persons reducing or elim-
for the growing popularity of diets eliminating or reducing inating animal-based sources of food, there is an unmet
meat, milk, dairy, and eggs, especially in wealthy devel- need for evidence-based guidance on the health effects as
oped countries. A vegan diet, strictly excluding all kinds well as safety issues and its management at the population
of animal-derived foods, has gained popularity and is of level that could be translated into public health as well as
immense public health interest (Medawar et al. 2019). primary health care sectors. Emerging scientific interest has
Surveys and online polls indicate that the prevalence of yielded several systematic reviews and meta-analyses on this
veganism has risen worldwide in the last few years (The topic in the past decades. Observational studies suggest that
Vegan Society 2021). According to these sources, 6% of a vegan diet might be associated with decreased risk of
the US population follows a strict plant-based. i.e. vegan death, cancer, and other health conditions, such as diabetes
diet, compared to up to 4% in Europe and 13% in Asia (Dinu et al. 2017). In addition, evidence from meta-analyses
CONTACT sabrina schlesinger sabrina.schlesinger@ddz.de
#these authors contributed equally to this work.
supplemental data for this article can be accessed online at https://doi.org/10.1080/10408398.2022.2075311.
© 2022 the author(s). Published with license by taylor & Francis Group, llC.
this is an open access article distributed under the terms of the Creative Commons attribution-nonCommercial-noderivatives license (http://creativecommons.org/licenses/
by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed,
or built upon in any way.
2 e. SeLiNGeR eT AL.
of randomized controlled trials (RCT) pointed to beneficial Materials and methods
effects of a vegan diet regarding cardiometabolic parame- All analytical steps were carried out following the Preferred
ters, including reduced total cholesterol and LDL-cholesterol, Reporting Items for Systematic Reviews and Meta-Analyses
glycemic control, and reductions in body weight and other (PRISMA-2020) statement (Page et al. 2021). The umbrella
anthropometric measures among generally healthy individ- review was a priori registered in the International
uals or persons with underlying chronic diseases (e.g. dia- Prospective Register of Systematic Reviews (PROSPERO:
betes) or at high cardiovascular diseases (CVD) risk (Lopez CRD42020173424).
et al. 2019; Yokoyama, Levin, and Barnard 2017; Huang
et al. 2016; Rees et al., 2021). On the other hand, several
safety issues have emerged from epidemiological evidence, Literature search
such as the association of veganism with lower bone density
and increased risk of fractures (Rees et al., 2021). Finally, The systematic literature search was conducted in PubMed,
cross-sectional studies on the quality of nutrient intake in Web of Science, the Cochrane Library, and Epistemonikos
vegans and non-vegans showed both beneficial and critical th
up to September 20 , 2021 without using any filters. The
aspects of the nutritional quality in vegans. For example, full search strategy can be found in the supplemental mate-
persons following a vegan diet were observed to have a rial (Table S1). Two researchers independently conducted
lower intake of total fat but a higher intake of polyunsatu- all steps of the systematic review process. First, titles and
rated fatty acids, dietary fiber, and several micronutrients, abstracts of the retrieved articles were screened for eligibility.
including vitamin C and magnesium, compared to omni- Full-texts of relevant studies were checked for inclusion and
vores (Clarys et al. 2014; Sobiecki et al. 2016). At the same any disagreements between the two researchers were dis-
time, a vegan diet was associated with nutritional deficien- cussed and resolved by consensus. No restrictions regarding
cies, especially deficits of vitamin B12, vitamin D, zinc, iron, language were applied. The reference lists from the eligible
and iodine as well as a lower protein quality (Clarys et al. systematic reviews and meta-analyses were checked to iden-
2014; Sobiecki et al. 2016; Elorinne et al. 2016). tify further relevant studies. To identify studies that were
To support evidence-based dietary recommendations and published after the last update, we conducted hand-searches
guidelines, a systematic and comprehensive overview to sum- and used the PubMed e-mail alert service.
marize and evaluate the existing evidence on a vegan diet
and health outcomes is warranted. A recently published
umbrella review summarized evidence from systematic Eligibility criteria
reviews and meta-analyses on vegetarian diets (defined as
lacto-vegetarians, ovo-vegetarians, lacto-ovo-vegetarians, veg- The detailed selection criteria are shown in Table 1. Briefly,
ans and Seventh-day Adventists) regarding different health the inclusion criteria for the studies were: (i) investigation
outcomes. This overview indicated that vegetarian diets were of the association between a vegan diet and any health
associated with beneficial blood lipid values and reduced risk outcome, nutritional status, or nutrient intakes; (ii) system-
of diabetes, ischemic heart disease, and cancer risk (Oussalah atic reviews including a meta-analysis of observational (e.g.
et al. 2020). However, this umbrella review is limited by cohort, case-control, cross-sectional) and intervention studies
exploring a combination of vegetarian and vegan diets. Given (randomized and non-randomized controlled trials); and
additional restrictions of a vegan diet compared to vegetar- (iii) reported effect estimates for the associations [including
ianism, and considering the increased popularity of a strict hazard ratios (HR), relative risks (RR), odds ratios (OR),
vegan diet, the evidence needs to be evaluated separately. or mean differences (MD) and mean values] with the 95%
Moreover, the study did not rate the certainty of evidence confidence interval (95% CIs) or standard deviation (SD).
(CoE) by using the recommended GRADE approach, that We included meta-analyses based on adults from the general
provides a systematic framework for making clinical practice healthy population, children, adolescents, pregnant women,
recommendations (Zhang, Akl, and Schunemann 2018). as well as persons with underlying chronic diseases or at
Therefore, the aim of the current study was to conduct high risk (e.g. persons with diabetes, hyperlipidemia, hyper-
an umbrella review i) to summarize the existing evidence tension, or persons at high risk of CVD as previously
derived from systematic reviews with meta-analyses on a defined (Rees et al., 2021)). Studies were excluded if: (i)
vegan diet regarding health outcomes, nutritional status, and they were primary studies, (ii) no summary estimate was
nutrient intakes, ii) to evaluate the CoE of the identified reported (e.g. systematic reviews without meta-analysis or
findings, and iii) to identify gaps in knowledge and future meta-analysis included only one study finding/risk estimate),
research perspectives. (iii) they were not systematic, e.g. pooled analyses of cohorts
Table 1. PiCos statement summarizing study rationale and study selection criteria.
Population adults from the general population, children, adolescents, pregnant women and patient groups (e.g. with diabetes, hypertension or
hyperlipidemia)
intervention vegan diet defined as a plant-based diet avoiding all animal foods such as meat, fish, shellfish, insects, dairy, and eggs
Comparison any other diet, mostly omnivore (e.g. diet allowing consumption of all foods of plant or animal origin)
outcome any health outcomes, nutritional status and dietary intake
study design systematic reviews with meta-analysis of observational (prospective, cross-sectional and retrospective) or interventional studies
(randomized and non-randomized trials)
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