Table 1.
Characteristics of the included studies
| Study | Participants | Groups | Age, y | Phenolic Content/Nitrate Content/Betanin Content | Supplementation Period | Exercise Protocol to Induce Muscle Damage |
|---|---|---|---|---|---|---|
| Clifford et al 12 | Recreationally active males | 10 (BR HD) 10 (BR LD) 10 (PLA) |
22 ± 6 21 ± 3 21 ± 3 |
HD: ~803.44 mg pc ~500 mg nit ~388 mg betanin LD: ~401.72 mg pc ~250 mg nit ~194 mg betanin |
3 days (exercise on day 0) | 100 Drop jumps (60 cm) |
| Clifford et al 13 | Male collegiate team-sport players | 10 (BR) 10 (PLA) |
23 ± 3 21 ± 2 |
810 mg pc 286 mg nit 388 mg betanin |
4 days (exercise on days 0 and 3) | Repeated sprint test (20 maximal-effort 30-m sprints) |
| Montenegro et al 37 | Male and female competitive triathletes | 22 (BR) 22 (PLA) |
38.0 ± 11.3 COD |
— nit pc: NP 24 mg betanin |
6 days (exercise on day 7) | 40 min submaximal cycling + 10 km running TT |
| Clifford et al 11 | Male and female marathon runners | 17 (BR) 17 (PLA) |
42 ± 10 39 ± 12 |
1200 mg pc 630 mg nit 582 mg betanin |
2 + 1/3 days (exercise on day 0) | Marathon race |
| Clifford et al 15 | Recreationally active males | 10 (SN) 10 (BR) 10 (PLA) |
21.7 ± 2.8 22.6 ± 2.8 21.0 ± 1.4 |
SN: — pc ~420 mg nit — betanin BR: ~810 mg pc ~420 mg nit ~388 mg betanin |
3 days (exercise on day 0) | 100 Drop jumps (60 cm) |
| Carriker et al 8 | Well-trained male cyclists | 9 (BR) 9 (PLA) |
29 ± 7 COD |
pc: NP 793.6 mg nit betanin: NP |
One single dose 2.5 h before exercise | Incremental cycling test at 25%, 40%, 50%, 60%, and 70% wattages of the normobaric VO2max in hypobaric chamber |
| Clifford et al 14 | Male and female marathon runners | 7 (BR) 7 (PLA) |
45 ± 7 45 ± 10 |
803.5 mg pc 501.2 mg nit 389 mg betanin |
5 + 1/2 days (exercise on day 5) | Marathon race |
| Daab et al 16 | Semiprofessional male soccer players | 13 (BR) 13 (PLA) |
22.12 ± 0.56 COD |
115.5 mg pc 250 mg nit 48.9 mg betanin |
7 days (exercise on day 4) | Loughborough intermittent shuttle test |
| Kozłowska et al 30 | Elite fencers (men) | 20 (BR) 20 (PLA) |
27.2 ± 5.4 (men) 22.6 ± 5.3 (women) COD |
38.34 mg pc nit: NP 371.83 mg betanin |
4 weeks | Normal training |
BR, beetroot; COD, crossover design; HD, high dose; LD, low dose; nit, nitrate; NP, not provided; pc, phenolic content; PLA, placebo group; SN, sodium nitrate; TT, time trial.