Table 1 Characteristics of studies and salt intake estimates based on 24-h and overnight/spot urine samples
First author, Year, Country | Mean age or range | Female (%) | Type of diet | Length of follow-up and type of sample | Equations used | SALT INTAKE ESTIMATES | ||||
|---|---|---|---|---|---|---|---|---|---|---|
Data point | 24-h urine | Overnight/spot urine | ||||||||
N | Mean salt intake, g/day | N | Mean salt intake, g/day | |||||||
Studies that collected 24-h urine and overnight urine samples | ||||||||||
Watson,1970 [25] United States | 21–23 years | 100 | Usual diet | 1 year; Matched sample | None; rate reported per hour | 1 (B)a | 25 | 5.96 ± 2.06 | 25 | 4.10 ± 1.64 |
2 (Y1) | 25 | 6.89 ± 2.46 | 25 | 5.58 ± 3.63 | ||||||
Luft, 1982 [26] United States | 19–54 years | 40 | Controlled diet; meals in a clinical research center | 15 days; Matched sample | None; rate reported per 8 h | 1 (B) | 43 | 7.89 ± 1.53 | 43 | 5.26 ± 2.30 |
2 (D15) | 43 | 8.12 ± 1.15 | 43 | 4.91 ± 1.15 | ||||||
Luft, 1982 [15] United States | 19–32 years | 0 | Controlled diet; meals in a clinical research center | 7 days; Matched sample | None; rate reported per 8 h | 1 (B) | 24 | 9.81 ± 6.30 | 24 | 5.24 ± 3.52 |
2 (D2) | 24 | 9.58 ± 4.01 | 24 | 5.59 ± 3.09 | ||||||
3 (D3) | 24 | 10.40 ± 2.58 | 24 | 5.61 ± 3.01 | ||||||
4 (D4) | 24 | 10.92 ± 2.58 | 24 | 5.43 ± 2.15 | ||||||
5 (D5) | 24 | 10.69 ± 2.86 | 24 | 5.63 ± 2.23 | ||||||
6 (D6) | 24 | 10.22 ± 2.86 | 24 | 5.19 ± 2.32 | ||||||
7 (D7) | 24 | 9.70 ± 2.58 | 24 | 5.26 ± 2.66 | ||||||
Liu, 1986 [16] China | 30–50 years | 0 | Usual diet | 3 months; Matched sample | None; rate reported per 12 h | 1 (B) | 49 | 13.51 ± 5.25 | 19 | 12.28 ± 7.12 |
2 (NS) | 49 | 14.58 ± 5.44 | 19 | 12.86 ± 7.24 | ||||||
3 (NS) | 49 | 15.34 ± 5.65 | 19 | 12.43 ± 5.34 | ||||||
4 (NS) | 49 | 13.82 ± 5.70 | 19 | 10.97 ± 5.11 | ||||||
5 (NS) | 49 | 14.81 ± 6.22 | 19 | 12.56 ± 7.08 | ||||||
6 (M3) | 49 | 13.81 ± 5.59 | 19 | 11.72 ± 6.20 | ||||||
Liu, 1987 [17] China | 27–50 years Mean: 35 | 0 | Usual diet | 10 days; Matched sample | None; rate reported per 12 h | 1 (B) | 50 | 13.75 ± 5.71 | 50 | 13.27 ± 5.94 |
2 (NS) | 50 | 15.14 ± 5.71 | 50 | 13.82 ± 5.54 | ||||||
3 (NS) | 50 | 15.14 ± 6.48 | 50 | 14.27 ± 6.24 | ||||||
4 (NS) | 50 | 14.28 ± 5.19 | 50 | 12.76 ± 5.92 | ||||||
5 (NS) | 50 | 15.18 ± 6.48 | 50 | 13.81 ± 6.38 | ||||||
6 (D10) | 50 | 14.97 ± 4.91 | 50 | 13.80 ± 5.75 | ||||||
He, 1993 [18] China | 19–55 years Mean: 37 | 0 | Usual diet | 3 days; Matched sample | None; rate reported per 8 h | 1 (B) | 63 | 8.58 ± 4.14 | 63 | 6.68 ± 4.01 |
2 (D2) | 63 | 9.08 ± 4.91 | 63 | 7.24 ± 4.89 | ||||||
3 (D3) | 63 | 9.65 ± 3.91 | 63 | 7.62 ± 4.36 | ||||||
Yasutake, 2015 [31], Japan | Mean: 22 | 55 | Controlled diet | 15 days; Matched sample | None; self-monitoring device used | 1 (B) | 10 | 8.60 ± 1.20 | 20 | 8.29 ± 0.98 |
2 (D15) | 12 | 4.40 ± 1.30 | 20 | 6.63 ± 1.44 | ||||||
Yasutake, 2016 [19], Japan | 20–70 years Mean: 40 | 80 | Usual diet | Varies: 2 weekdays and 1 holiday; Matched sample | None; self-monitoring device used | 1 (B) | 44 | 8.00 ± 1.80 | 50 | 8.00 ± 1.70 |
2 (NS) | 44 | 8.50 ± 2.60 | 50 | 8.10 ± 1.80 | ||||||
3 (NS) | 39 | 8.30 ± 3.30 | 50 | 8.30 ± 2.00 | ||||||
Kramers, 2019 [21], Netherlands | 18–70 years Mean: 46 | 52 | Usual diet | 6 weeks; Matched sample | None; rate reported per 8 h | 1 (B) | 27 | 9.29 ± 3.27 | 27 | 8.41 ± 3.79 |
2 (W3) | 27 | 8.70 ± 3.10 | 27 | 8.55 ± 3.51 | ||||||
3 (W6) | 27 | 8.88 ± 3.91 | 27 | 7.57 ± 4.49 | ||||||
Studies that collected 24-h urine and spot urine samples | ||||||||||
Do, 2016 [22] Viet Nam | 25–64 years Mean: 45 | 53 | Usual diet before and after an intervention | 1 year; Unmatched sample | 5 equations used; Intersalt treated as the main analysis | 1 (B) | 88 | 9.43 ± 3.69 | 509 | 8.48 ± 2.13 |
2 (Y1) | 73 | 7.44 ± 4.09 | 511 | 8.05 ± 2.11 | ||||||
Petersen, 2016 [11], Australia | 18 years and up | 56 | Usual diet | 3 years; Unmatched sample (with some matched) | 6 equations used; Kawasaki provided the closest estimate of the change | 1 (B) | 1000 | 8.37 ± 3.43 | 1000 | 11.69 ± 3.45 |
2 (Y3) | 1012 | 7.89 ± 3.66 | 1012 | 11.27 ± 3.52 | ||||||
Huang, 2018 [23] China | 60 years and up Mean: 66 | 50 | Usual diet before and after an intervention | Varies: up to 24 months Unmatched sample (with some matched) | 8 equations used; using individual volume spot provided the closest estimate of the change | 1 (B) | 532 | 10.92 ± 4.57 | 532 | 12.19 ± 7.37 |
2 (Y2) | 2864 | 9.91 ± 4.32 | 2864 | 10.67 ± 6.60 | ||||||
Dong, 2018 [24] China | 10–15 years Mean: 12 | 48 | Usual diet | 2–3 weeks; Matched sample | 8 equations used; Whitton provided the closest estimate of the change | 1 (B) | 284 | 6.56 ± 2.69 | 284 | 9.92 ± 2.50 |
2 (W3) | 284 | 7.26 ± 2.91 | 284 | 10.17 ± 2.48 | ||||||
Kim, 2018 [20] South Korea | 19–75 years Mean: 50 | 49 | Usual diet | 16 weeks; Matched sample with two treatment groups | 5 equations used; Intersalt provided the closest estimate of the change for both groups consistently | 1 (B) | 228 | 9.00 ± 4.07 | 228 | 7.41 ± 2.21 |
2 (M2) | 228 | 9.15 ± 4.12 | 228 | 7.61 ± 2.35 | ||||||
3A (M4) | 118 | 8.48 ± 3.51 | 118 | 7.62 ± 2.16 | ||||||
3B (M4) | 111 | 7.12 ± 3.48 | 111 | 7.03 ± 2.19 | ||||||