Table 2.
Information extracted from studies looking at flexitarianism in relation to diet quality and aspects of health.
| Reference; country | Subjects | Study design and methods | Findings |
|---|---|---|---|
| Body weight | |||
| Kim and Bae (12); Korea | Postmenopausal SV F (n = 54). Mean age 61.4 years | Cross-sectional. Anthropometric and blood biomarkers compared between the two groups | SV had sig. lower body weight (P < 0.01), BMI (P < 0.001), and percentage of body fat (P < 0.001) than the NV |
| Moore et al. (21); US | n = 15 SV/PVs | 6-month RCT. New DIETs study—randomization to one of four plant-based diets (vegan, vegetarian, PV, SV) or an omnivore diet | At 6 months, non-adherent vegan and vegetarian participants had a sig. decrease in cholesterol intake than non-adherent PV/SV (P = 0.02) or omnivore participants (P = 0.04) |
| Turner-McGrievy et al. (22); US | n = 13 SV (18–65 years) | 6-month RCT. Overweight and obese adults randomized to different diets for 6 months | At 6 months, the weight loss in the vegan group (−7.5%) was higher than the omnivorous (−3.1%; P = 0.03), SV (−3.2%; P = 0.03), and PV (−3.2%; P = 0.03) groups |
| Rizzo et al. (18); US and Canada | n = 4,042. Mean age 33.3 years. 67% F) | Cross-sectional. Data analyzed from Adventist Health Study-2. 204-item FFQ used to compare nutrient profiles | NV had the highest mean BMI values (28.7) and highest proportion of obese subjects (33.3%) when compared to any other dietary pattern |
| Tonstad et al. (15); US | n = 3,386 SV. Mean age 57.7 years. 65.7% F | Cross-sectional. Analysis of different types of vegetarian diet from the Adventist Health Study-2. Anthropometric data collected from a self-administered questionnaire | Mean BMI was lowest in vegans (23.6 kg/m2) and incrementally higher in LOV (25.7 kg/m2), PV (26.3 kg/m2), SV (27.3 kg/m2), and NV (28.8 kg/m2) |
| Baines et al. (13); Australia | n = 827 SV F (22–27 years) | Cross-sectional. Data analyzed from the Australian Longitudinal Study on Women’s Health | SV had a lower BMI (mean 23 kg/m2 than NVs (23.7 kg/m2) and tended to exercise more |
| Cancer | |||
| Tantamango-Bartley et al. (25); US | n = 26,346 M | Prospective cohort study. Data analyzed from Adventist Health Study-2 | Vegan diets showed a statistically sig. protective association with prostate cancer risk (HR: 0.65; 95% CI: 0.49, 0.85) |
| Penniecook-Sawyers et al. (24); US | n = 2,930 SV F | 7.8-year Prospective cohort. Data analyzed from Adventist Health Study-2. FFQ used to group diets and BC incidence measured | There was no evidence that vegetarians as a group had lower risk of BC than NVs either in pre- or postmenopausal, or in Black or White, women |
| Orlich et al. (20); US | n = 4,271. 67.8% F. 58.6 years | 7.3-year Prospective cohort. Data analyzed from Adventist Health Study-2. FFQ used to group diets and cases of colorectal cancer identified | Adjusted HR in vegans was 0.84; in LOV, 0.82; in PV, 0.57; and in SV 0.92 compared with NV. Mean fiber intake in SV was 30.4 g/day and calcium intakes 821 mg/day |
| Tantamango-Bartley et al. (26); US | n = 3,881 69% F | 4.1-year Prospective cohort. Data analyzed from Adventist Health Study-2 | Vegan diets showed statistically sig. protection for overall cancer incidence (HR = 0.84) in both genders combined and for female-specific cancers (HR = 0.66). LOV were associated with decreased risk of cancers of the GI system |
| Diabetes and metabolic health | |||
| Kim and Bae (12); Korea | Postmenopausal SV F (n = 54). Mean age 61.4 years | Cross-sectional. Blood biomarkers compared between the two groups | SV had sig. lower body weight (P < 0.01), BMI (P < 0.001), % of body fat (P < 0.001), and serum levels of leptin (P < 0.05), glucose (P < 0.001), and insulin (P < 0.01), than the NV |
| Agrawal et al. (14); India | n = 8,140 SV, n = 4,675 F (20–49 years) | Cross-sectional. Data from India’s third National Family Health Survey (2005–2006) | Consumption of a lacto- (OR: 0.67, P < 0.01), LOV (OR: P = 0.03), and SV (OR: P = 0.03) diet was associated with a lower likelihood of diabetes than an NV diet in the adjusted analyses |
| Tonstad et al. (16); US | n = 2,404, 65.7% F | 2-year Prospective cohort. Analysis of different types of vegetarian diet and lifestyle data from the Adventist Health Study-2 | In non-Blacks vegan, lacto ovo and SV diets were protective against diabetes (OR 0.429, OR 0.684, OR 0.501) |
| Rizzo et al. (17); US | n = 773 subjects; 16% SV (mean age 60 years) | Cross-sectional. Data analyzed from Adventist Health Study-2. Fasting blood samples taken and WC measured | MetS was highest in NV (39.7%), intermediate in SV (37.6%), and lowest in vegetarians (25.2%) |
| Rodenas et al. (27); Spain | n = 14 SV F | Cross-sectional. Blood pressure of postmenopausal F measured | Omnivores had sig. higher systolic (P < 0.01) and diastolic (P < 0.05) pressures than SVs |
| Tonstad et al. (15); US | n = 3,386 SV. Mean age 57.7 years. 65.7% F | Cross-sectional. Analysis of different types of vegetarian diet from the Adventist Health Study-2. Blood samples provided by a sub-sample | Prevalence of T2D increased from 2.9% in vegans to 7.6% in NV; the prevalence was intermediate in participants consuming LOV (3.2%), pesco (4.8%), or SV (6.1%) diets |
| Diet quality | |||
| Turner-McGrievy et al. (22); US | n = 13 SV | 6-month RCT. Overweight and obese adults randomized to five different plant-based diets. | Vegan, vegetarian, and PV subjects had sig. improvements in the dietary inflammation index score compared with SV participants at 2 months (P < 0.05) with no differences at 6 months |
| Clarys et al. (23); Belgium | n = 498 SV (20–69 years) | Cross-sectional. Online 52-item FFQ completed | SVs had some of the highest calcium intakes (1,470 mg/day) and had one of the strongest nutrient densities |
| Rizzo et al. (18); US and Canada | n = 4,042 SV. 67.3% F. Mean age 33.3 years. | Cross-sectional study. Data from the Adventist Health Study-2. 204-item validated semi-quantitative FFQ | SV had an intake of 1,713 kcal/day and the lowest energy intakes |
| Rodenas et al. (27); Spain | n = 14 SV F | Cross-sectional. 14-day weighing of foods to identify mineral intakes | The omnivorous diet contained a significantly higher mineral content than the SV one |
| Kornsteiner et al. (28); Austria | n = 13 SV | Observational study. Amount and composition of ingested fat were calculated from 24-h recalls | The unbalanced n-6/n-3 ratio and the limited dietary sources of EPA and DHA in vegans and vegetarians led to reductions in C20:5n-3, C22:5n-3, C22:6n-3, and total n-3 fatty acids compared with omnivores and semi-omnivores |
| Baines et al. (13); Australia | 9,113 F (22–27 years) | Cross-sectional. Data analyzed from the Australian Longitudinal Study on Women’s Health | The BMI and levels of physical activity of SV women suggest they were healthier than NV. There were greater reports of menstrual problems and the poorer mental health which could be of clinical significance |
| Other health outcomes | |||
| Chiba et al. (30); Japan | n = 22 adults patients with CD | Clinical Trial. Initiated a high-fiber SV diet containing 32.4 g fiber per 2,000 kcal among patients in remission with CD | High-fiber SV diets may have a role to play in the treatment of CD |
| Chiba et al. (29); Japan | n = 22 adults patients with CD | Prospective, single center, 2-year clinical trial was conducted. Patients in clinical remission were advised to continue with an SVD and avoid known high-risk foods for IBD | The concentration of C-reactive protein was normal at the final visit in more than half of the patients in remission who were on the SV diet. There was no untoward effect of SV diet |
| Orlich et al. (19); US | n = 4,031 SV | 5.9-year Prospective cohort. Data analyzed from Adventist Health Study-2 | The adjusted HR for all-cause mortality in vegans was 0.85; in LOVs, 0.91; in PV 0.81; and in SV, 0.92 compared with NV |
BC, breast cancer; BMI, body mass index; CD, Crohn’s disease; CI, confidence interval; DHA, docosahexaenoic acid; EPA, eicosapentaenoic acid; F, female; FFQ, food frequency questionnaire; HR, hazard ratio; IBD, inflammatory bowel disease; LOV, lacto-ovo-vegetarian; M, Male; MetS, metabolic syndrome; NV, non-vegetarian; OR, odds ratio; PV, pesco-vegetarian; RCT, randomized controlled trial; sig, significantly; SV, semi-vegetarian; SVD, semi-vegetarian diet; T2D, type 2 diabetes; WC, waist circumference.