TABLE 1.
Characteristics of observational studies examining the association of participants following vegetarian-based or non-vegetarian dietary patterns and common biomarkers of inflammation and immune function1
| Study (ref.) | Design/level of evidence | Population/gender | Comorbidities | Country | Age, y (mean or range) | Years on vegetarian diet | Biomarker investigated | Study quality/7 | Matched (NS different at baseline) | Difference in biomarker (significance P < 0.05) |
|---|---|---|---|---|---|---|---|---|---|---|
| Acosta-Navarro et al. (42) | Cross-sectional | V = 44 | Nil | Brazil | V3 = 45.5 | >4 | hs-CRP | 5 | Age | ● hs-CRP (NS)4 |
| Navarro et al.2 (48) | NV = 44 | NV = 46.8 | Leukocytes | Gender | ● Leukocytes significantly ↓ in V group | |||||
| M | Neutrophils | Smoking status | ● Neutrophils significantly ↓ in V group | |||||||
| hx of disease | ||||||||||
| Ambroszkiewicz et al. (43) | Cross-sectional | LOV = 43 | Nil | Poland | 4.5–9.0 | >4.5 | CRP | 4 | Age | ● CRP (NS) |
| NV = 46 | BMI | |||||||||
| M and F | ||||||||||
| Chen et al. (45) | Cross-sectional | V = 99 | Nil | Taiwan | V = 51.24 | >1 | Leukocytes | 4 | Age | ● CRP significantly ↑ in NV group |
| NV = 99 | NV = 49.38 | hs-CRP | BMI | |||||||
| M and F | ||||||||||
| Chen et al. (44) | Cross-sectional | LOV = 173 | Nil | Taiwan | LOV = 54.00 | >1 | hs-CRP | 5 | BMI | ● hs-CRP (NS) |
| NV = 190 | NV = 49.94 | Leukocytes | ● Leukocytes (NS) | |||||||
| F | Thrombocytes | ● Thrombocytes (NS) | ||||||||
| Chuang et al. (46) | Matched cohort/cross-sectional | V = 686 | Nil | Taipei and Taiwan | V = 45.2 | Long-term | CRP | 5 | Age | ● CRP significantly ↑ in NV group |
| NV = 3423 | O = 45.1 | Location | ||||||||
| M and F | Sex | |||||||||
| Dong and Scott (47) | Cross-sectional | Ve = 13 | Nil | USA | Ve: M = 57; F = 40 | >1 | Leukocytes | 1 | Nil | ● Significance not reported |
| LV = 28 | LV: M = 45; F = 42 | |||||||||
| LOV = 15 | LOV: M = 43; F = 35 | |||||||||
| NV = 4 | NV: M = 31; F = 55 | |||||||||
| M and F | ||||||||||
| Famodu et al. (49) | Cross-sectional | Ve = 8 | Nil | Nigeria | Ve = 47.1 | Long-term | Fibrinogen | 3 | Age BMI | ● Fibrinogen significantly ↑ in NV group compared with LOV and Ve group |
| LOV = 28 | LOV = 49.0 | ● Fibrinogen significantly ↑ in LOV group compared with Ve group | ||||||||
| NV = 40 | NV = 48.7 | |||||||||
| M and F | ||||||||||
| Fontana et al. (50) | Matched cohort/cross-sectional | Ve = 21 | Nil | USA | Ve = 53.1 | >2 | hs-CRP | 2 | Age | ● CRP significantly ↑ in NV group |
| NV = 21 | NV = 53.1 | |||||||||
| M and F | ||||||||||
| Fontana et al. (51) | Matched cohort/cross-sectional | Ve = 18 | Nil | USA | 54.2 | 1.5–10 (range) | hs-CRP | 2 | Age | ● hs-CRP significantly ↑ in NV group |
| NV = 18 | Sex | |||||||||
| M and F | SES | |||||||||
| Franco-de-Moraes (52) | Cross-sectional | Ve = 66 | Nil | Brazil | Ve = 49.6 | >1 | TNF-α | 3 | Age | ● TNF-α (NS) |
| LOV = 102 | LOV = 49.6 | CRP | Sex | ● hs-CRP significantly ↑ in NV group | ||||||
| NV = 100 | NV = 49.1 | IL-10 | ● IL-10 (NS) | |||||||
| Gorczyca et al. (53) | Cross-sectional | V = 22 | Nil | Poland | V = 4 | >1 | IgA | 3 | Age | ● IgA (NS) |
| NV = 18 | NV = 9 (range 2–18) | IgM | Body weight | ● IgM (NS) | ||||||
| M and F | IgG | Height | ● IgG (NS) | |||||||
| Haddad et al. (54) | Cross-sectional | Ve = 25 | Nil | USA | Ve = 36.0 | >1 | Leukocytes | 3 | AgePhysical activity level | ● Leukocytes significantly ↓ in Ve group |
| NV = 20 | O = 33.5 | Lymphocytes | Blood lipid concentrations | ● Lymphocytes significantly ↓ in Ve group | ||||||
| M and F | Neutrophils | ● Neutrophils (NS) | ||||||||
| Monocytes | ● Monocytes (NS) | |||||||||
| Eosinophils | ● Eosinophils (NS) | |||||||||
| Basophils | ● Basophils (NS) | |||||||||
| Thrombocytes | ● Thrombocytes significantly ↓ in Ve group | |||||||||
| IgA | ● IgA (NS) | |||||||||
| IgG | ● IgG (NS) | |||||||||
| IgM | ● IgM (NS) | |||||||||
| CRP | ● CRP (NS) | |||||||||
| NK cell cytotoxic activity | ● NK cell cytotoxic activity (NS) | |||||||||
| Krajcovicova-Kudlackova and Blazicek (55) | Cross-sectional | LOV = 133 | Nil | Slovakia | LOV = 46.2 | >1 | hs-CRP | 2 | Age | ● hs-CRP significantly ↑ in NV group. |
| NV = 137 | NV = 47.2 | |||||||||
| M and F | ||||||||||
| Malter et al. (56) | Cross-sectional | V = 22 | Nil | Germany | V = 28–50 | >1 | Thrombocytes | 2 | Age | ● Thrombocytes (NS) |
| O = 22 | Leucocytes | Gender | ● Leucocytes (NS) | |||||||
| M | Lymphocytes | ● Lymphocytes (NS) | ||||||||
| Monocytes | ● Monocytes (NS) | |||||||||
| Basophilic granulocytes | ● Basophilic granulocytes (NS) | |||||||||
| Eosinophilic granulocytes | ● Eosinophilic granulocytes (NS) | |||||||||
| NK cell cytotoxic activity | ● NK cell activity of peripheral blood lymphocytes significantly ↑ in V group. | |||||||||
| Mezzano et al. (57) | Cross-sectional | V = 26 | Nil | Chile | V = 39 | >1 | Platelet count | 3 | Age | ● Thrombocytes significantly ↓ in NV group |
| NV = 26 | Fibrinogen | Sex | ● Fibrinogen significantly ↑ in NV group | |||||||
| M and F | CRP | SES | ● CRP (NS) | |||||||
| Montalcini et al. (58) | Cross-sectional | LOV = 26 | Nil | Italy | LOV = 32.6 | ≥3 | IL-2 | 5 | Age | ● IL-2 (NS) |
| NV = 26 | NV = 30.5 | IL-4 | BMI | ● IL-4 (NS) | ||||||
| M and F | IL-6 | Gender | ● IL-6 (NS) | |||||||
| IL-8 | ● IL-8 (NS) | |||||||||
| IL-10 | ● IL-10 (NS) | |||||||||
| TNF-α | ● TNF-α (NS) | |||||||||
| IL-1α | ● IL-1α (NS) | |||||||||
| IL-1β | ● Interleukin-β significantly ↑ in LOV group | |||||||||
| Ou et al. (59) | Case control/cross-sectional | V = 21 | Patients on dialysis therapy for >6 mo | Taiwan | V = 56.27 | ≥1.5 | hs-CRP | 2 | Age | ● hs-CRP (NS) |
| NV = 42 | O = 56.29 | Sex | ||||||||
| M and F | ||||||||||
| Paalani et al. (60) | Cross-sectional | V = 216 | Nil | USA | 68.8 | >1 | CRP | 4 | Not reported | ● CRP significantly ↑ in NV group |
| NV = 289 | IL-6 | |||||||||
| M and F | IL-10 | |||||||||
| TNF-α | ||||||||||
| Pinto et al. (61) | Matched cohort/cross-sectional | Ve = 23 | Nil | UK | Ve = 49 | >2 | IL-6 | 6 | Age | ● IL-6 (NS) |
| NV = 24 | NV = 54 | Sex | ||||||||
| F | BMI | |||||||||
| Pongstaporn et al. (62) | Cross-sectional | V = 179 | Nil | Thailand | V = 18+ | >1 | Leukocytes | 2 | Nil | ● Leukocytes significantly ↓ in Ve group |
| NV = 58 | Thrombocytes | ● Thrombocytes (NS) | ||||||||
| M and F | Neutrophils | ● Neutrophils (NS) | ||||||||
| Lymphocytes | ● Lymphocytes (NS) | |||||||||
| Refsum et al. (63) | Cross-sectional | V = 78 | 100 CVD (42 of which DM) | India | V = 27–55 | Long-term | Thrombocytes | 3 | Nil | ● Thrombocytes (NS) |
| NV = 126 | 104 without CVD (41 DM) | |||||||||
| M and F | ||||||||||
| Sebekova et al. (64) | Cross-sectional | LOV = 90 | Nil | Slovakia | LOV = 37.7 | >2 | Hs-CRP | 2 | Age | ● Hs-CRP (NS) |
| NV = 46 | O = 37.1 | Leukocytes | Gender | ● Leukocytes (NS | ||||||
| M and F | BMI | |||||||||
| Sebekova et al. (65) | Cross-sectional | Ve = 19 | Nil | Slovakia | Ve = 39.6 | Ve = 7.2 | CRP | 2 | Age | ● CRP (NS) |
| LOV = 19 | LOV = 36.1 | LOV = 8.2 | ||||||||
| NV = 9 | NV = 30.5 | |||||||||
| M and F | ||||||||||
| Su et al. (66) | Cross-sectional | LOV = 49 | Nil | Taiwan | LOV = 58.6 ± 6.0 | 10.8 | hs-CRP | 3 | Age | ● hs-CRP (NS) |
| NV = 41 | O = 57.2 ± 5.4 | Gender | ||||||||
| F | ||||||||||
| Suwannuruks et al. (67) | Cross-sectional | LOV = 50 | Nil | Thailand | LOV 18–50 | >1 | Fibrinogen | 1 | Nil | ● Fibrinogen (NS) |
| NV = 30 | Leukocytes | ● Leukocytes (NS) | ||||||||
| M and F | Thrombocytes | ● Thrombocytes (NS) | ||||||||
| Szeto et al. (68) | Cross-sectional | LOV = 30 | Nil | Hong Kong | LOV = 44.2 | 5–55 (range) | hs-CRP | 2 | Age | ● CRP significantly ↑ in NV group |
| NV = 30 | NV = 44.0 | Sex | ||||||||
| M and F | ||||||||||
| Tungtrongchitr et al. (69) | Cross-sectional | LV = 132NV = 47M and F | Nil | Thailand | LV: M = 35.5; F = 33NV: M = 32.5; F = 32Median | >1 | Leukocytes | 2 | Age | ● Leukocytes (NS) |
| Neutrophils | Sex | ● Neutrophils (NS) | ||||||||
| Lymphocytes | SES | ● Lymphocytes significantly ↓ in LV group | ||||||||
| Monocytes | Ethnic origin | ● Monocytes (NS) | ||||||||
| Eosinophil | ● Eosinophils significantly ↓ in female LV group compared with male LV and NV group | |||||||||
| Basophil | ● Eosinophils significantly ↑ in male LV group compared with female LV group and NV group | |||||||||
| Thrombocytes | ● Basophils (NS) | |||||||||
| ● Thrombocytes (NS) | ||||||||||
| Wu et al. (70) | Cross-sectional | V = 19 | Patients receiving dialysis therapy >6 mo | Taiwan | V = 63.3 | Long before HD—note mean length of HD = 5.9 | hs-CRP | 4 | Age | ● hs-CRP significantly ↑ in NV group |
| NV = 299 | NV = 57.5 | Leukocytes | Sex | ● Leukocytes significantly ↓ in V group | ||||||
| M and F | Mean HD length | |||||||||
| Yang et al. (71) | Matched cohort/cross-sectional | V = 171 | Nil | China | V = 32.6 | > 1 | CRP | 4 | age | ● CRP (NS) |
| NV = 12 | NV = 34.2 | |||||||||
| M |
1
(hs-)CRP, (high-sensitivity) C-reactive protein; CVD, cardiovascular disease; DM, diabetes mellitus; F, female, HD, hemodialysis; Hx, History; LOV, lacto-ovo-vegetarian; LV, lacto-vegetarian; M, male, NR, not reported; NS, not significant; NV, non-vegetarian; SES, socioeconomic status; Ve, vegan.
2
Two separate papers identified reporting on same study participants, with different outcome markers; slight difference in Navaro et al.’s population: V = 43, NV = 41; age, V = 45.0 y; NV = 46.5 y; and study quality = 4 between studies.
3
V, participants followed combinations of Ve, LV, or LOV diets.
4
NS, P > 0.05.