TABLE 2.
Summary of study characteristics of studies included in the meta-analysis of whether higher-protein intakes affect kidney function in healthy people1
| Study characteristic | Study references | Notes |
|---|---|---|
| Study design | ||
| Parallel group | (43–56) | |
| Crossover | (29–42) | |
| Includes washout | (29–36) | |
| No washout | (37–42) | |
| Type 2 diabetes | (31, 47, 50, 54) | |
| Sex | ||
| Men | (30, 37, 39, 41, 49, 56) | |
| Women | (32, 34, 42, 48, 52) | |
| Both | (29, 31, 33, 35, 36, 40, 43–47, 50, 51, 53–55) | |
| Diet | ||
| Isocaloric | ||
| Modified CHO | (33–35, 40, 42, 44, 47, 48, 50, 52, 56) | |
| Modified fat | (36, 49, 51) | |
| Modified both | (29, 30, 32, 41, 43, 45, 46, 54) | |
| Ad libitum | ||
| Modified CHO | (31, 53, 55) | |
| Food provided | ||
| All | (29, 32–36, 39–42, 46, 49) | |
| Some | (37, 38) | Protein powder provided to HP group |
| (48, 51, 52, 54) | 30–60% of total energy provided | |
| (56) | 60% provided during weeks 1–12 | |
| Dietary advice only | (30, 31, 43–45, 47, 50, 55) | Includes counselling, detailed menus, diet tools (i.e., food scales) |
| Major sources of protein provided | ||
| Yes | (29–35, 37–44, 46–49, 51–56) | |
| (45, 50) | For HP only | |
| No | (36) | |
| Type of protein | ||
| Animal + vegetable | (29–39, 41–56) | |
| Non-animal | (40) | |
| Energy status | ||
| Energy balance | (29–42, 50, 55) | |
| Energy restriction | (43, 45, 46, 48, 49, 52–54, 56) | |
| Both | (44, 47, 51) | |
| Diet adherence measured | ||
| Yes | (30–40, 43, 44, 46–53, 55, 56) | Includes participant diet logs and urinary output measures |
| No | (29, 32, 41, 42, 45) | |
| Study completion rates | ||
| All completed | (29, 32, 37, 39, 41, 49, 53, 54) | |
| Dropouts reported | (30, 31, 33, 35, 36, 38, 42–48, 50–52, 55, 56) | Drop-out rates similar between groups |
| Text implies all completed | (34, 40) | |
| GFR measurement type | ||
| Isotope clearance | (31, 36, 53) | 125I-Iothalamate, 99mtechnetium-DTPA, 51chromium-EDTA |
| Creatinine clearance | (32, 39–42, 44–46, 51, 52, 56) | |
| Inulin/sinistrin clearance | (29, 30, 55) | |
| eGFR | (33–35, 37, 38, 43, 47–50, 54) | |
1CHO, carbohydrate; DTPA, diethylenetriaminepentacetate; eGFR, estimated glomerular filtration rate; GFR, glomerular filtration rate; HP, high-protein.