Table 2.
Summary table of cohort studies included in the analysis.
| First author, year [ref] | Cohort name (country) | Participants | N baseline/ analysed | Baseline mean age(SD) or age range (y) | Exposure assessment | Mean protein intakea | Follow-up (y) | Relevant outcomes | Effect sizesb |
|---|---|---|---|---|---|---|---|---|---|
| Beasley, 2014 [23] | Women's Health Initiative (US) | Post- menopausal women | 161,808/ 144,580 (whole sample) | 55–79; subgroups: 65 & 75 | FFQ + calibrated with biomarkers | 0.52, 0.75, 0.92, 1.11, 1.50 (quantiles, whole sample) | 6 | TB BMD | Per 20% increase in protein intake: 65 y: mean 0.003 (0.001, 0.005) ns 75 y: mean 0.003 (0.001, 0.007) ns |
| Hip BMD | 65 y: mean 0.003 (0.001, 0.005) ns 75 y: mean 0.004 (0.001, 0.007) ns | ||||||||
| Any fracture | 65 y: HR 0.99 (0.96, 1.01) ns 75 y: HR 0.96 (0.91, 1.02) ns | ||||||||
| Hip fracture | 65 y: HR 0.91 (0.82, 0.99) ns 75 y: HR 0.92 (0.83, 1.02) ns |
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| Cauley, 2016 [24] | Osteoporotic Fractures in Men Study (US) | Men >65 y | 5994/5876 | No fracture: 73.5(5.8); fracture: 77.8(6.1) | Block semi-quantitative FFQ | No fracture: 16.1%; fracture: 15.3% of EI | 8.6 | Hip fracture | Per SD increase in protein intake (2.9% of EI): HR 0.82 (0.69, 0.97) p<0.05 |
| Chan, 2011 [25] | - (China) | Men and women ≥65 y | 2944/2217 (1225 men, 992 women) | Men: 71.6(4.6); women: 72.0(5.1) | FFQ | Men 88.8, women 65.7 g/d. Men 1.42; women 1.19 g/kg bw/d (estimated values) |
4 | Per unit increase in energy-adjusted protein intake: | |
| Hip BMD | Men: B -0.007 SE 0.005 p 0.147 Women: B 0.003 SE 0.009 p 0.744 |
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| FN BMD | Men: B -0.013 SE 0.008 p 0.088 Women: B 0.010 SE 0.013 p 0.416 |
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| Dawson-Hughes, 2002 [26] | - (US) | Men and women ≥65 y | 389/342 | Supplemented group: 70(5), 71(4), 70(4); placebo group: 71(5), 71(5), 71(5) (tertiles) | Willett semi-quantitative FFQ | 9.6–15.5, 15.5–18.2, 18.2–29.1% of EI (tertiles). Supplemented: 0.96, 1.07, 1.17; placebo: 0.90, 1.08, 1.20 g/kg bw/d (estimated values) | 3 | Supplemented group protein T3 vs T1: | |
| TB BMD | NR, less loss/gain p 0.042 | ||||||||
| FN BMD | NR, less loss/gain p 0.011 | ||||||||
| Spine BMD | NR, no difference ns | ||||||||
| Osteocalcin | NR, no difference ns | ||||||||
| N-telopeptide | NR, no difference ns | ||||||||
| Devine, 2005 [27] | - (Australia) | Women >70 y | 1077 | 75(3) | ACCV semi-quantitative FFQ | <0.84, 0.84–1.6, >1.6 (tertiles) | 1 | Hip BMD | Protein T3 vs T1: NR, higher p<0.05 |
| FN BMD | NR, higher p<0.05 | ||||||||
| Fung, 2017 [21] | Nurses' Health Study & Health Professionals Follow-Up Study (US) | Men ≥50 y and post-menopausal women | 74,443 women; 35,439 men | Whole sample ≥50 y; stratification: <65, 65–75, ≥75 |
Semi-quantitative FFQ | Women 14.3, 18.6, 24.4% of EI; men 14.2, 18.3, 23.4% of EI (whole sample). Women 0.88, 1.12, 1.41; men 0.87, 1.12, 1.40 g/kg bw/d (estimated values) |
32 | Hip fracture | Protein Q5 vs Q1: Women 65–75 y: RR 0.92 (0.71, 1.18) Women 75+ y: RR 0.91 (0.69, 1.20) Men 65–75 y: RR 0.59 (0.33, 1.07) Men 75+ y: RR 0.77 (0.51, 1.15) |
| Hannan, 2000 [28] | Framingham Osteoporosis Study (US) | Men and women | 855/615 | 75(4.4), 68–91 | Willett semi-quantitative FFQ | 0.21–0.71; 0.72–0.96; 0.97–1.23; 1.24–2.78 (quartiles) | 4 | FN BMD | Protein Q4 vs Q1: Mean − 2.32(0.74)% vs −4.61(0.70)% p<0.001 |
| LS BMD | Mean − 1.11(1.10)% vs −3.72(0.97)% p<0.05 | ||||||||
| Isanejad, 2017 [29] | Osteoporosis Risk Factor and Fracture Prevention Study (Finland) | Women ≥65 y | 750/544 | 68.1(1.9), 65–72 | 3 d food records | 0.79, 0.90, 0.96, 1.18 (quartiles) | 3 | TB BMC | Per unit increase in energy-adjusted protein intake: B -0.16 SE 30.04 p 0.159 |
| TB BMD | B 0.04 SE 0.01 p 0.507 | ||||||||
| FN BMD | B -0.01 SE 0.01 p 0.918 | ||||||||
| LS BMD | B -0.31 SE 0.01 p 0.001 | ||||||||
| Langsetmo, 2017 [30] | Osteoporotic Fractures in Men Study (US) | Men ≥65 y | 5994/5875 | 73.6(5.9) | Modified Block FFQ | 0.67, 0.75, 0.83, 0.93 (quartiles) | 10.5–11.2 | Hip BMD | Per SD increase in protein intake (2.9% of EI): B 0.06 SE 0.01 p<0.001 |
| Spine fracture | HR 1.06 (0.92, 1.22) p 0.45 | ||||||||
| Hip fracture | HR 0.84 (0.73, 0.95) p 0.01 | ||||||||
| Meng, 2009 [31] | - (Australia) | Women 70–85 y | 1500/862 | 74.9(2.6) | ACCV quantitative FFQ | <0.84, 0.84–1.6, >1.6 (tertiles) | 5 | TB BMC | Protein T3 vs T1: 5.3% higher p<0.05 |
| Misra, 2011 [22] | Framingham Osteoporosis Study (US) | Men and women ≥68 y | 976/946 | No fracture: 75(5.0); fracture: 76(5.2) | Willett semi-quantitative FFQ | 46.5, 59.6, 67.7, 82.7 g/d (quartiles); 0.69, 0.88, 1.00, 1.22 g/kg bw/d (estimated values) |
11.6 (median) | Hip fracture | Protein Q2–4 vs Q1: HR 0.63 (0.37, 1.09) p 0.04 |
| Rapuri, 2003 [32] | Sites Testing Osteoporosis Prevention/ Intervention (US) | Women 65–77 y | 489/92 | 71.3(0.8), 72.2(0.8), 70.1(0.8), 69.9(0.8) (quartiles) | 7 d food diaries | 0.95, 0.94, 0.98, 0.99 g/kg bw/d; 13.3, 15.2, 16.7, 19.5% of EI (quartiles) |
3 | TB BMD | Protein Q4 vs Q1: NR, no difference ns |
| Hip BMD | NR, no difference ns | ||||||||
| FN BMD | NR, no difference ns | ||||||||
| Spine BMD | NR, no difference ns | ||||||||
| Osteocalcin | Mean − 6.5(7.6)% vs −5.8(7.6)% p 0.042 | ||||||||
| N-telopeptide | Mean 12.1(11.2)% vs 10.4(11.0)% p 0.226 |
Note. BMC = bone mineral content; BMD = bone mineral density; EI = energy intake; FFQ = Food Frequency Questionnaire; FN = femoral neck; HR = hazard ratio; TB = total body; LS = lumbar spine; NR = not reported; ns = not significant; RR = risk ratio; SD = standard deviation; SE = standard error; US = United States.
a
Unit is g/kg bw/d, unless stated otherwise. Values presented as mean or range.
b
Values presented as mean(SE), mean (95% CI) or RR/HR (95% CI). BMD in g/cm2.