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Nutrition Reviews Mar 2021Vegetarian and vegan diets are increasing in popularity. Although they provide beneficial health effects, they may also lead to nutritional deficiencies. Cognitive... (Meta-Analysis)
Meta-Analysis
CONTEXT
Vegetarian and vegan diets are increasing in popularity. Although they provide beneficial health effects, they may also lead to nutritional deficiencies. Cognitive impairment and mental health disorders have a high economic burden.
OBJECTIVE
A meta-analysis was conducted to examine the relationship between vegan or vegetarian diets and cognitive and mental health.
DATA SOURCES
PubMed, Scopus, ScienceDirect, and Proquest databases were examined from inception to July 2018.
STUDY SELECTION
Original observational or interventional human studies of vegan/vegetarian diets were selected independently by 2 authors.
DATA EXTRACTION
Raw means and standard deviations were used as continuous outcomes, while numbers of events were used as categorical outcomes.
RESULTS
Of 1249 publications identified, 13 were included, with 17 809 individuals in total. No significant association was found between diet and the continuous depression score, stress, well-being, or cognitive impairment. Vegans/vegetarians were at increased risk for depression (odds ratio = 2.142; 95%CI, 1.105-4.148) and had lower anxiety scores (mean difference = -0.847; 95%CI, -1.677 to -0.018). Heterogeneity was large, and thus subgroup analyses showed numerous differences.
CONCLUSIONS
Vegan or vegetarian diets were related to a higher risk of depression and lower anxiety scores, but no differences for other outcomes were found. Subgroup analyses of anxiety showed a higher risk of anxiety, mainly in participants under 26 years of age and in studies with a higher quality. More studies with better overall quality are needed to make clear positive or negative associations.
SYSTEMATIC REVIEW REGISTRATION
PROSPERO registration no. CRD42018097204.
Topics: Anxiety; Cognition; Depression; Diet, Vegan; Diet, Vegetarian; Humans; Mental Health; Vegans; Vegetarians
PubMed: 32483598
DOI: 10.1093/nutrit/nuaa030 -
Nutrition Reviews Jan 2019The numbers of vegans and vegetarians have increased in the last decades. However, the impact of these diets on bone health is still under debate. (Meta-Analysis)
Meta-Analysis
CONTEXT
The numbers of vegans and vegetarians have increased in the last decades. However, the impact of these diets on bone health is still under debate.
OBJECTIVE
This systematic review and meta-analysis sought to study the impact of vegetarian and vegan diets on bone mineral density (BMD) and fracture risk.
DATA SOURCES
A systematic search was conducted of PubMed, Scopus, and Science Direct, covering the period from the respective start date of each database to November 2017.
DATA EXTRACTION
Two investigators evaluated 275 studies against the inclusion criteria (original studies in humans, written in English or Spanish and including vegetarian or vegan diets and omnivorous diets as factors with BMD values for the whole body, lumbar spine, or femoral neck and/or the number of fractures as the outcome) and exclusion criteria (articles that did not include imaging or studies that included participants who had suffered a fracture before starting the vegetarian or vegan diet). The quality assessment tool for observational cohort and cross-sectional studies was used to assess the quality of the studies.
RESULTS
Twenty studies including 37 134 participants met the inclusion criteria. Compared with omnivores, vegetarians and vegans had lower BMD at the femoral neck and lumbar spine and vegans also had higher fracture rates.
CONCLUSIONS
Vegetarian and vegan diets should be planned to avoid negative consequences on bone health.
SYSTEMATIC REVIEW REGISTRATION
PROSPERO registration no. CRD42017055508.
Topics: Bone Density; Diet, Vegetarian; Fractures, Bone; Humans; Risk Factors
PubMed: 30376075
DOI: 10.1093/nutrit/nuy045 -
International Journal of Sport... Jun 2016Humans consuming vegetarian-based diets are observed to have reduced relative risk for many chronic diseases. Similarly, regular physical activity has also been shown to... (Comparative Study)
Comparative Study Review
Humans consuming vegetarian-based diets are observed to have reduced relative risk for many chronic diseases. Similarly, regular physical activity has also been shown to assist in preventing, and reducing the severity of these conditions. Many people, including athletes, acknowledge these findings and are adopting a vegetarian-based diet to improve their health status. Furthermore, athletes are incorporating this approach with the specific aim of optimizing physical performance. To examine the evidence for the relationship between consuming a predominately vegetarian-based diet and improved physical performance, a systematic literature review was performed using the SCOPUS database. No date parameters were set. The keywords vegetarian OR vegan AND sport OR athlete OR training OR performance OR endurance were used to identify relevant literature. Included studies (i) directly compared a vegetarian-based diet to an omnivorous/mixed diet, (ii) directly assessed physical performance, not biomarkers of physical performance, and (iii) did not use supplementation emulating a vegetarian diet. Reference lists were hand searched for additional studies. Seven randomized controlled trials and one cross-sectional study met the inclusion criteria. No distinguished differences between vegetarian-based diets and omnivorous mixed diets were identified when physical performance was compared. Consuming a predominately vegetarian-based diet did not improve nor hinder performance in athletes. However, with only 8 studies identified, with substantial variability among the studies' experimental designs, aims and outcomes, further research is warranted.
Topics: Athletes; Athletic Performance; Diet; Diet, Vegetarian; Exercise; Humans; Muscle Strength; Muscle, Skeletal; Nutritional Status; Randomized Controlled Trials as Topic; Sports
PubMed: 26568522
DOI: 10.1123/ijsnem.2015-0231 -
The American Journal of Clinical... Mar 2013There is evidence that reducing blood glucose concentrations, inducing weight loss, and improving the lipid profile reduces cardiovascular risk in people with type 2... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
There is evidence that reducing blood glucose concentrations, inducing weight loss, and improving the lipid profile reduces cardiovascular risk in people with type 2 diabetes.
OBJECTIVE
We assessed the effect of various diets on glycemic control, lipids, and weight loss.
DESIGN
We conducted searches of PubMed, Embase, and Google Scholar to August 2011. We included randomized controlled trials (RCTs) with interventions that lasted ≥6 mo that compared low-carbohydrate, vegetarian, vegan, low-glycemic index (GI), high-fiber, Mediterranean, and high-protein diets with control diets including low-fat, high-GI, American Diabetes Association, European Association for the Study of Diabetes, and low-protein diets.
RESULTS
A total of 20 RCTs were included (n = 3073 included in final analyses across 3460 randomly assigned individuals). The low-carbohydrate, low-GI, Mediterranean, and high-protein diets all led to a greater improvement in glycemic control [glycated hemoglobin reductions of -0.12% (P = 0.04), -0.14% (P = 0.008), -0.47% (P < 0.00001), and -0.28% (P < 0.00001), respectively] compared with their respective control diets, with the largest effect size seen in the Mediterranean diet. Low-carbohydrate and Mediterranean diets led to greater weight loss [-0.69 kg (P = 0.21) and -1.84 kg (P < 0.00001), respectively], with an increase in HDL seen in all diets except the high-protein diet.
CONCLUSION
Low-carbohydrate, low-GI, Mediterranean, and high-protein diets are effective in improving various markers of cardiovascular risk in people with diabetes and should be considered in the overall strategy of diabetes management.
Topics: Blood Glucose; Cardiovascular Diseases; Diabetes Mellitus, Type 2; Diet, Carbohydrate-Restricted; Diet, Fat-Restricted; Diet, Mediterranean; Diet, Protein-Restricted; Diet, Vegetarian; Dietary Carbohydrates; Dietary Fats; Dietary Fiber; Dietary Proteins; Energy Intake; Glycemic Index; Humans; Lipids; Randomized Controlled Trials as Topic; Risk Factors; Weight Loss
PubMed: 23364002
DOI: 10.3945/ajcn.112.042457 -
The British Journal of Nutrition Mar 2024Plant-based diets have emerged as athletic performance enhancers for various types of exercise. Therefore, the present study evaluated the effectiveness of plant-based... (Meta-Analysis)
Meta-Analysis Review
Plant-based diets have emerged as athletic performance enhancers for various types of exercise. Therefore, the present study evaluated the effectiveness of plant-based diets on aerobic and strength/power performances, as well as on BMI of physically active individuals. This systematic review and meta-analysis was conducted and reported according to the guidelines outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement. A systematic search of electronic databases, including PubMed, Web of Science and SPORTDiscus, was performed. On the basis of the search and inclusion criteria, four and six studies evaluating the effects of plant-based diets on aerobic and strength/power performances in humans were, respectively, included in the systematic review and meta-analysis. Plant-based diets had a moderate but positive effect on aerobic performance (0·55; 95 % CI 0·29, 0·81) and no effect on strength/power performance (-0·30; 95 % CI -0·67, 0·07). The altogether analyses of both aerobic and strength/power exercises revealed that athletic performance was unchanged (0·01; 95 % CI -0·21, 0·22) in athletes who adopted plant-based diets. However, a small negative effect on BMI (-0·27; 95 % CI -0·40, -0·15) was induced by these diets. The results indicate that plant-based diets have the potential to exclusively assist aerobic performance. On the other hand, these diets do not jeopardise strength/power performance. Overall, the predicted effects of plant-based diets on physical performance are impactless, even though the BMI of their adherents is reduced.
Topics: Humans; Diet, Plant-Based; Athletic Performance; Diet; Exercise; Exercise Therapy; Muscle Strength
PubMed: 37869973
DOI: 10.1017/S0007114523002258 -
Translational Psychiatry Sep 2019Western societies notice an increasing interest in plant-based eating patterns such as vegetarian and vegan, yet potential effects on the body and brain are a matter of...
Western societies notice an increasing interest in plant-based eating patterns such as vegetarian and vegan, yet potential effects on the body and brain are a matter of debate. Therefore, we systematically reviewed existing human interventional studies on putative effects of a plant-based diet on the metabolism and cognition, and what is known about the underlying mechanisms. Using the search terms "plant-based OR vegan OR vegetarian AND diet AND intervention" in PubMed filtered for clinical trials in humans retrieved 205 studies out of which 27, plus an additional search extending the selection to another five studies, were eligible for inclusion based on three independent ratings. We found robust evidence for short- to moderate-term beneficial effects of plant-based diets versus conventional diets (duration ≤ 24 months) on weight status, energy metabolism and systemic inflammation in healthy participants, obese and type-2 diabetes patients. Initial experimental studies proposed novel microbiome-related pathways, by which plant-based diets modulate the gut microbiome towards a favorable diversity of bacteria species, yet a functional "bottom up" signaling of plant-based diet-induced microbial changes remains highly speculative. In addition, little is known, based on interventional studies about cognitive effects linked to plant-based diets. Thus, a causal impact of plant-based diets on cognitive functions, mental and neurological health and respective underlying mechanisms has yet to be demonstrated. In sum, the increasing interest for plant-based diets raises the opportunity for developing novel preventive and therapeutic strategies against obesity, eating disorders and related comorbidities. Still, putative effects of plant-based diets on brain health and cognitive functions as well as the underlying mechanisms remain largely unexplored and new studies need to address these questions.
Topics: Brain; Cognition; Diet, Vegan; Diet, Vegetarian; Humans
PubMed: 31515473
DOI: 10.1038/s41398-019-0552-0 -
Nutrition Reviews Jul 2023The popularity of plant-based diets, characterized by a partial or complete exclusion of animal products, has increased significantly over the last 10 years. The... (Meta-Analysis)
Meta-Analysis
CONTEXT
The popularity of plant-based diets, characterized by a partial or complete exclusion of animal products, has increased significantly over the last 10 years. The exclusion of animal products removes the most common sources of vitamin B12, which can lead to vitamin B12 deficiency and result in irreversible damage, such as growth stunting.
OBJECTIVE
This aim of this systematic review and meta-analysis was to qualitatively evaluate all studies on this subject and to quantify the potential difference in vitamin B12 levels in healthy children and adolescents aged 5 to 18 years.
DATA SOURCES
PubMed and Embase databases were searched for relevant studies investigating vitamin B12 levels in healthy children and adolescents aged 5 to 18 years on plant-based diets.
DATA EXTRACTION
Studies were assessed qualitatively with the AXIS tool and quantitatively with Stata 16.0 software.
DATA ANALYSIS
Overall, children and adolescents on plant-based diets had a significantly lower vitamin B12 level than omnivorous children and adolescents (-97 pmol/L; 95%CI, -187 to -7; I2 = 98.5%), a difference that remained statistically significant after adjusting for methodological confounders. After subgroup analyses, this effect was not statistically significant for children and adolescents on vegetarian diets but remained significant in children and adolescents on vegan or macrobiotic diets. Moreover, total vitamin B12 intake nullified the mean difference in vitamin B12 levels.
CONCLUSION
Despite high heterogeneity across studies, these results indicate that children and adolescents on plant-based diets, especially those on vegan and macrobiotic diets, may be at risk of developing vitamin B12 deficiency.
Topics: Child; Humans; Diet; Diet, Vegetarian; Nutritional Status; Vitamin B 12; Vitamin B 12 Deficiency
PubMed: 36413044
DOI: 10.1093/nutrit/nuac096 -
Nutrients Oct 2023Health authorities increasingly recommend sustainable and healthy diets rich in plant foods and with moderate amounts of animal foods. However, there are concerns about... (Review)
Review
Health authorities increasingly recommend sustainable and healthy diets rich in plant foods and with moderate amounts of animal foods. However, there are concerns about whether such diets can meet all nutrient requirements, especially in children and adolescents, who have relatively high nutrient needs for growth and development. Therefore, we aimed to evaluate the nutrient intake and status of children and adolescents (2-18 y) consuming plant-based (i.e., vegetarian and vegan) diets compared to those of meat-eating children following a systematic literature review of studies published between 2000 and 2022. Mean intake and status data of nutrients were calculated across studies and benchmarked to dietary reference values and cut-off values for nutrient deficiencies. A total of 30 studies were included (15 in children 2-5 y, 24 in children 6-12 y, and 11 in adolescents 13-18 y). In all diets, there were risks of inadequate intakes of vitamin D and calcium. Children consuming meat had a risk of inadequate folate and vitamin E intake; and mean fiber, SAFA, and PUFA intakes were not in line with the recommendations. Children consuming plant-based diets risked inadequate vitamin B12, iron, and zinc intakes. In contrast to vegans, vegetarian children may not meet the recommended intakes of fiber, SAFA, and possibly PUFA, but their mean intakes were more favorable than in meat-eating children. Although the data are limited and need further validation, our findings indicate that there are risks of nutritional inadequacies in all diet groups. Therefore, increasing consumption of a variety of plant-based foods, in combination with food fortification and supplementation where needed, is recommended for children and adolescents to have sustainable and nutritionally adequate diets.
Topics: Animals; Humans; Child; Adolescent; Diet; Energy Intake; Meat; Eating; Diet, Vegan; Diet, Vegetarian
PubMed: 37892416
DOI: 10.3390/nu15204341 -
Critical Reviews in Food Science and... 2021To examine the relation between the consumption or avoidance of meat and psychological health and well-being. A systematic search of online databases (PubMed, PsycINFO,...
To examine the relation between the consumption or avoidance of meat and psychological health and well-being. A systematic search of online databases (PubMed, PsycINFO, CINAHL Plus, Medline, and Cochrane Library) was conducted for primary research examining psychological health in meat-consumers and meat-abstainers. Inclusion criteria were the provision of a clear distinction between meat-consumers and meat-abstainers, and data on factors related to psychological health. Studies examining meat consumption as a continuous or multi-level variable were excluded. Summary data were compiled, and qualitative analyses of methodologic rigor were conducted. The main outcome was the disparity in the prevalence of depression, anxiety, and related conditions in meat-consumers versus meat-abstainers. Secondary outcomes included mood and self-harm behaviors. Eighteen studies met the inclusion/exclusion criteria; representing 160,257 participants (85,843 females and 73,232 males) with 149,559 meat-consumers and 8584 meat-abstainers (11 to 96 years) from multiple geographic regions. Analysis of methodologic rigor revealed that the studies ranged from low to severe risk of bias with high to very low confidence in results. Eleven of the 18 studies demonstrated that meat-abstention was associated with poorer psychological health, four studies were equivocal, and three showed that meat-abstainers had better outcomes. The most rigorous studies demonstrated that the prevalence or risk of depression and/or anxiety were significantly greater in participants who avoided meat consumption. Studies examining the relation between the consumption or avoidance of meat and psychological health varied substantially in methodologic rigor, validity of interpretation, and confidence in results. The majority of studies, and especially the higher quality studies, showed that those who avoided meat consumption had significantly higher rates or risk of depression, anxiety, and/or self-harm behaviors. There was mixed evidence for temporal relations, but study designs and a lack of rigor precluded inferences of causal relations. Our study does not support meat avoidance as a strategy to benefit psychological health.
Topics: Anxiety; Depression; Diet, Vegetarian; Female; Humans; Male; Meat; Mental Health
PubMed: 32308009
DOI: 10.1080/10408398.2020.1741505 -
Critical Reviews in Food Science and... May 2018Vegetarian diets exclude meat, seafood, and products containing these foods. Although the vegetarian lifestyle could lead to a better health status in adults, it may... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Vegetarian diets exclude meat, seafood, and products containing these foods. Although the vegetarian lifestyle could lead to a better health status in adults, it may also bear risks for certain nutritional deficiencies. Cross-sectional studies and narrative reviews have shown that the iron status of vegetarians is compromised by the absence of highly bioavailable haem-iron in meatless diets and the inhibiting effect of certain components present in plant foods on non-haem iron bioavailability.
METHODS
The databases Pubmed, Scopus, Embase, and Cochrane CentralRegister of Controlled Trials were searched for studies comparing serum ferritin, as the major laboratory parameter for iron status of adult vegetarians with non-vegetarian control groups. A qualitative review was conducted as well as an inverse-variance random-effects meta-analysis to pool available data. In addition the effect of vegetarian diets according to gender was investigated with a subgroup analysis. The results were validated using a sensitivity analysis.
RESULTS
A total of 27 cross-sectional studies and three interventional studies were selected for the systematic review. The meta-analysis which combined data of 24 cross-sectional studies showed that adult vegetarians have significantly lower serum ferritin levels than their non-vegetarian controls (-29.71 µg/L, 95% CI [-39.69, -19.73], p < 0.01). Inclusion of semi-vegetarian diets did not change the results considerably (-23.27 µg/L, 95% CI [-29.77, -16.76], p < 0.01). The effects were more pronounced in men (-61.88 µg/L, 95% CI [-85.59, -38.17], p < 0.01) than in both premenopausal women (-17.70 μg/L, 95% CI [-29.80, -5.60], p < 0.01) and all women (-13.50 μg/L, 95% CI [-22.96, -4.04], p < 0.01), respectively.
CONCLUSIONS
In conclusion our results showed that vegetarians are more likely to have lower iron stores compared with non-vegetarians. However, since high iron stores are also a risk factor for certain non-communicable diseases, such as type 2 diabetes, it is recommended that not only vegetarians but also non-vegetarians should regularly control their iron status and improve their diet regarding the content and bioavailability of iron by consuming more plants and less meat.
Topics: Adult; Diet, Vegetarian; Ferritins; Humans; Iron; Risk Factors
PubMed: 27880062
DOI: 10.1080/10408398.2016.1259210