Table 2.
Caffeine–placebo change scores for serum caffeine, paraxanthine and the paraxanthine:caffeine ratio, 30 and ~ 120-min post-supplementation
| ADORA2A | CYP1A2 | |||||||
|---|---|---|---|---|---|---|---|---|
| 30 min | 120 min | 30 min | 120 min | |||||
| ‘High’ | ‘Low’ | ‘High’ | ‘Low’ | ‘Fast’ | ‘Slow’ | ‘Fast’ | ‘Slow’ | |
| Δserum caffeine (μg mL−1) | + 1.65 ± 0.95 | + 2.12 ± 0.33 | + 1.95 ± 0.26 | + 1.79 ± 0.20 | + 1.95 ± 0.84 | + 1.67 ± 0.80 | + 1.97 ± 0.28 | + 1.80 ± 0.16 |
| Δserum paraxanthine (μg mL−1) | + 0.13 ± 0.10 | + 0.21 ± 0.12 | + 0.32 ± 0.10 | + 0.36 ± 0.20 | + 0.18 ± 0.13 | + 0.15 ± 0.08 | + 0.31 ± 0.12 | + 0.37 ± 0.15 |
| Δserum paraxanthine:caffeine ratio | + 0.17 ± 0.18 | − 0.04 ± 0.18 | + 0.19 ± 0.05 | − 0.05 ± 0.57 | + 0.08 ± 0.26 | + 0.11 ± 0.14 | + 0.01 ± 0.44 | + 0.23 ± 0.06 |
Participants are categorised according to ADORA2A (‘high’ or ‘low’ sensitivity) and CYP1A2 genotypes (‘fast’ or ‘slow’ metaboliser)
Data are mean ± SD. P > 0.05, ‘high’ vs. ‘low’ sensitivity and ‘fast’ vs. ‘slow’ metaboliser