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Table 2 Baseline characteristics of participants across tertiles of dietary and circulating linoleic acid

From: Associations of linoleic acid with markers of glucose metabolism and liver function in South African adults

  Dietary linoleic acid (en%)   Circulating linoleic acid (% total FA)  
T1
(n = 211)
T2
(n = 211)
T3
(n = 211)
P-trenda T1
(n = 211)
T2
(n = 211)
T3
(n = 211)
P-trenda
Median (range) 3.9 (0.4–5.3) 6.7 (5.4–8.0) 9.6 (8.0–18.4)   12.5 (6.0–14.4) 16.0 (14.4–17.7) 19.5 (17.7–25.7)  
Age (y) 52.4 ± 9.0 52.8 ± 11.3 53.8 ± 10.6 0.18 53.8 ± 9.4 54.2 ± 11.2 50.9 ± 10.1 0.004
Men 91 (43.1) 80 (37.9) 69 (32.7) 0.09 76 (36.0) 82 (38.9) 82 (38.9) 0.78
Body mass index (kg/m2) 23.8 ± 6.5 25.0 ± 7.5 25.9 ± 6.7 0.002 24.4 ± 7.1 25.2 ± 7.4 25.0 ± 6.3 0.36
 Obesity 40 (19.0) 47 (22.3) 56 (26.5) 0.17 40 (19.0) 52 (24.6) 51 (24.2) 0.30
Waist circumference (cm) 79.6 ± 12.3 80.2 ± 14.3 81.3 ± 12.1 0.20 80.8 ± 13.4 80.6 ± 13.5 79.6 ± 11.9 0.36
Locality (urban) 71 (33.6) 123 (58.3) 131 (62.1) < 0.001 107 (50.7) 113 (53.6) 105 (50.0) 0.72
Education levelb     0.12     < 0.001
 No school or primary 94 (45.6) 76 (36.4) 77 (37.9)   108 (51.9) 78 (38.2) 61 (29.6)  
 Secondary or higher 112 (54.4) 133 (63.6) 126 (62.1)   100 (48.1) 126 (61.8) 145 (70.4)  
Smoking statusb     0.008     0.010
 Non-smoker 84 (40.0) 87 (41.2) 113 (53.6)   81 (38.4) 92 (43.6) 111 (52.9)  
 Past or current smoker 126 (60.0) 124 (58.8) 98 (46.4)   130 (61.6) 119 (56.4) 99 (47.1)  
Physical activityb     < 0.001     0.006
 Low 1 (0.5) 3 (1.5) 1 (0.5)   1 (0.5) 2 (1.0) 2 (1.0)  
 Moderate 66 (32.4) 100 (49.0) 99 (48.8)   107 (52.4) 87 (42.4) 71 (35.2)  
 High 137 (67.2) 101 (49.5) 103 (50.7)   96 (47.1) 116 (56.6) 129 (63.9)  
Serum lipids (mmol/L)         
 Total cholesterol 5.10 ± 1.33 5.18 ± 1.31 5.28 ± 1.30 0.16 5.13 ± 1.31 5.34 ± 1.37 5.10 ± 1.25 0.81
 LDL-C 2.92 ± 1.16 3.01 ± 1.14 3.15 ± 1.08 0.047 2.87 ± 1.08 3.15 ± 1.18 3.06 ± 1.11 0.09
 HDL-C 1.60 ± 0.71 1.61 ± 0.60 1.55 ± 0.59 0.42 1.65 ± 0.72 1.60 ± 0.61 1.49 ± 0.56 0.012
 Triglycerides 1.06 (0.85–1.62) 1.07 (0.82–1.69) 1.20 (0.86–1.78) 0.09 1.17 (0.86–1.85) 1.15 (0.85–1.65) 1.04 (0.80–1.53) < 0.001
High sensitivity C-reactive protein (mg/L) 3.9 (1.3–10.0) 3.2 (1.0–9.5) 3.8 (1.2–11.4) 0.67 4.1 (1.4–14.0) 3.6 (1.5–9.2) 3.5 (0.9–8.8) 0.014
Interleukin-6 (pg/mL) 3.04 (1.58–7.29) 3.00 (0.75–4.91) 2.94 (0.75–5.54) 0.13 4.50 (1.98–8.83) 2.86 (0.76–5.12) 2.09 (0.75–4.16) 0.002
HIV-positive 2 (1.0) 0 (0) 3 (1.4) 0.38 2 (1.0) 0 (0) 3 (1.4) 0.30
Dietary variablesc
 Total energy intake (kJ/d) 7413 ± 3265 7338 ± 2979 7319 ± 2846 0.75 7699 ± 3263 7282 ± 2920 7088 ± 2875 0.038
 Carbohydrate 62.7 ± 10.7 59.3 ± 7.4 54.3 ± 7.2 < 0.001 57.8 ± 9.5 59.4 ± 9.2 59.1 ± 9.0 0.15
 Protein 11.4 ± 2.3 12.8 ± 2.1 13.1 ± 2.1 < 0.001 12.0 ± 2.4 12.7 ± 2.2 12.7 ± 2.3 0.001
 Total fat 16.4 ± 6.1 24.6 ± 5.3 31.7 ± 6.9 < 0.001 22.6 ± 9.0 24.0 ± 8.6 26.0 ± 8.3 < 0.001
 Saturated FA 3.9 ± 2.4 6.2 ± 2.5 7.6 ± 2.9 < 0.001 5.4 ± 2.8 5.9 ± 3.0 6.5 ± 3.1 < 0.001
 Monounsaturated FA 3.8 ± 2.0 6.6 ± 2.4 8.9 ± 3.1 < 0.001 5.8 ± 3.1 6.5 ± 3.4 7.0 ± 3.3 < 0.001
 Polyunsaturated FA 4.3 ± 2.6 7.2 ± 1.1 10.6 ± 2.1 < 0.001 7.1 ± 3.7 7.1 ± 3.0 7.9 ± 3.0 0.013
 n-3 fatty acids (mg/d) 221.1 (145.5–362.4) 325.3 (209.8–497.2) 391.5 (253.5–543.7) < 0.001 296.0 (182.2–452.5) 319.6 (207.5–487.2) 319.9 (192.6–476.2) 0.37
 Trans-FA (g/d) 0.09 (0.03–0.25) 0.20 (0.08–0.48) 0.33 (0.12–0.68) < 0.001 0.18 (0.07–0.43) 0.17 (0.06–0.48) 0.19 (0.07–0.53) 0.71
 Total fiber (g/d) 20.4 ± 9.0 21.1 ± 9.3 19.9 ± 9.1 0.55 20.3 ± 9.0 20.4 ± 8.6 20.6 ± 9.9 0.75
 Dietary cholesterol (mg/d) 90 (48–159) 159 (99–268) 204 (129–307) < 0.001 151 (78–248) 148 (90–246) 143 (81–254) 0.56
 Alcohol use: yesd 118 (55.9) 84 (39.8) 69 (32.7) < 0.001 117 (55.4) 88 (41.7) 66 (31.3) < 0.001
 (g/d) 4.6 (0–36.2) 0 (0–11.6) 0 (0–4.3) < 0.001 2.9 (0–27.0) 0 (0–8.6) 0 (0–5.8) < 0.001
Fatty acid composition
 Arachidonic acid (20:4n-6), % 13.5 ± 2.7 13.4 ± 2.5 13.7 ± 2.3 0.43 12.9 ± 2.9 14.1 ± 2.4 13.6 ± 2.0 0.011
 Estimated D6D activity (20:3n-6/18:2n-6) 0.200 ± 0.061 0.192 ± 0.055 0.187 ± 0.058 0.016 0.234 ± 0.053 0.196 ± 0.047 0.150 ± 0.040 < 0.001
  1. Values are mean ± SD, median (Q1-Q3), or n (%) unless otherwise stated;
  2. D6D Delta-6-desaturase, FA Fatty acids, HIV Human immunodeficiency virus
  3. aP-values for trend for continuous variables were obtained by assigning median value of dietary or circulating linoleic acid and this value was modelled as continuous; for categorical variables p-values from (exact) Chi-squared tests were displayed;
  4. b Missing values for 15 participants for education level, 1 participant for smoking status, 22 participants for physical activity level, 1 participant for HIV status, 1 participant for dietary n-3 fatty acids and 62 participants for interleukin-6;
  5. c Dietary variables are expressed as percentage of energy unless otherwise stated;
  6. d Alcohol use: ‘No’: alcohol intake = 0 g/d, ‘Yes’ alcohol intake > 0 g/d;