TABLE 1.
Baseline characteristics of the Insulin Resistance Atherosclerosis Study participants (n = 659) overall and across quintiles of total dairy intake from the food-frequency questionnaire1
| Total dairy intake, servings/wk2 |
|||||||
| Characteristic | All | Q1 (0–2.07) | Q2 (2.10–4.10) | Q3 (4.13–6.65) | Q4 (6.69–9.73) | Q5 (9.80–31.08) | P value3 |
| Participants, n (%) | 659 | 132 (20.03) | 131 (19.88) | 133 (20.18) | 132 (20.03) | 131 (19.88) | |
| Age, y | 54.68 ± 8.56 | 54.74 ± 8.84 | 55.52 ± 8.27 | 53.69 ± 7.96 | 55.99 ± 9.24 | 53.50 ± 8.27 | 0.07 |
| Sex, n (%) | 0.16 | ||||||
| Male | 297 (45.07) | 61 (46.21) | 59 (45.04) | 60 (45.11) | 69 (52.27) | 48 (36.64) | |
| Female | 362 (54.93) | 71 (53.79) | 72 (54.96) | 73 (54.89) | 63 (47.73) | 83 (93.36) | |
| Ethnicity, n (%) | <0.0001 | ||||||
| Non-Hispanic white | 277 (42.03) | 36 (27.27) | 50 (38.17) | 56 (42.11) | 66 (50.00) | 69 (52.67) | |
| African American | 152 (23.07) | 55 (41.67) | 32 (24.43) | 28 (21.05) | 16 (12.12) | 21 (16.03) | |
| Hispanic | 230 (34.90) | 41 (31.06) | 49 (37.40) | 49 (36.84) | 50 (37.88) | 41 (31.30) | |
| Glucose tolerance status, n (%) | 0.04 | ||||||
| Normal glucose tolerance | 447 (67.83) | 81 (61.36) | 93 (70.99) | 103 (77.44) | 85 (64.39) | 85 (64.89) | |
| Impaired glucose tolerance | 212 (32.17) | 51 (38.64) | 38 (29.01) | 30 (22.56) | 47 (35.61) | 46 (35.11) | |
| Smoking status, n (%) | 0.0009 | ||||||
| Never | 306 (46.43) | 48 (36.36) | 59 (45.04) | 65 (48.87) | 53 (40.15) | 81 (61.83) | |
| Past | 259 (39.30) | 55 (41.67) | 53 (40.46) | 56 (42.11) | 58 (43.94) | 37 (28.24) | |
| Current | 94 (14.26) | 29 (21.97) | 19 (14.50) | 12 (9.02) | 21 (15.91) | 13 (9.92) | |
| Alcohol intake category, g ethanol/wk | 3.52 (0–39.54) | 2.24 (0–34.35) | 7.26 (0–57.82) | 0 (0–15.47) | 8.86 (0–63.92) | 3.52 (0–25.92) | 0.007 |
| Highest educational level completed, n (%) | 0.48 | ||||||
| <12 y | 87 (13.20) | 21 (15.91) | 16 (12.21) | 12 (9.02) | 20 (15.15) | 18 (13.74) | |
| ≥12 y | 572 (86.80) | 111 (84.09) | 115 (87.79) | 121 (90.98) | 112 (84.85) | 113 (86.26) | |
| BMI, kg/m2 | 27.24 (24.83–27.24) | 27.24 (24.81–29.99) | 26.58 (24.10–29.33) | 28.09 (25.56–30.80) | 27.20 (24.77–29.55) | 27.71 (24.75–33.07) | 0.04 |
| Waist circumference, cm | 90.28 ± 12.52 | 90.53 ± 12.74 | 87.87 ± 11.79 | 89.92 ± 11.06 | 91.53 ± 11.57 | 91.59 ± 14.92 | 0.10 |
| Total estimated energy expenditure, kcal/kg per wk | 272.28 (250.88–305.33) | 272.03 (247.84–304.72) | 270.05 (251.20–303.87) | 267.22 (249.16–295.37) | 284.22 (255.35–320.87) | 272.96 (251.64–309.56) | 0.05 |
| Insulin sensitivity, ×10−4 min−1 (μU/mL)−1 | 1.71 (0.95–3.01) | 1.73 (0.98–2.80) | 1.92 (1.00–3.25) | 1.73 (1.00–3.11) | 1.53 (0.92–2.50) | 1.65 (0.85–3.16) | 0.47 |
| Acute insulin response, μU/mL | 51.5 (29.5–87.0) | 50.50 (30.00–92.25) | 51.0 (24.5–93.0) | 60.0 (36.0–84.0) | 49.5 (30.5–82.0) | 49.5 (25.0–81.5) | 0.49 |
| Disposition index | 85.68 (43.44–154.59) | 103.86 (43.10–151.16) | 89.70 (48.02–149.49) | 98.05 (57.38–179.41) | 66.28 (41.22–140.27) | 76.44 (36.25–153.00) | 0.07 |
| Dietary variables | |||||||
| Total energy intake, kcal/wk | 12,416.84 (8999.48–16,181.69) | 9559.99 (7181.22–13,685.13) | 11,457.43 (7858.01–13,914.89) | 12,257.03 (9288.20–15,780.76) | 13,505.43 (10,679.84–17,341.15) | 15,005.27 (11,425.64–19,989.34) | <0.0001 |
| % Energy from fat | 35.44 ± 8.44 | 34.68 ± 8.66 | 35.62 ± 9.51 | 35.64 ± 8.84 | 34.94 ± 7.91 | 36.29 ± 7.14 | 0.57 |
| % Energy from SFA | 12.05 ± 3.39 | 11.18 ± 3.42 | 11.74 ± 3.66 | 12.17 ± 3.31 | 12.25 ± 3.25 | 12.88 ± 3.08 | 0.001 |
| Dietary intake TFA, g/wk | 15.05 (7.56–25.90) | 11.69 (6.09–21.00) | 12.67(6.23–22.19) | 14.81 (9.57–22.54) | 16.59 (8.62–29.89) | 19.75 (11.83–33.32) | <0.0001 |
| Total dairy consumption, servings/wk | 5.53 (2.59–8.75) | 0.96 (0.35–1.54) | 3.05 (2.59–3.54) | 5.53 (4.80–6.13) | 8.05 (7.28–8.75) | 12.46 (11.06–15.23) | <0.0001 |
| Total cheese consumption, servings/wk | 1.51 (0.49–3.26) | 0.28 (0–0.58) | 0.98 (0.32–1.96) | 1.58 (0.77–3.01) | 2.24 (0.98–3.89) | 3.5 (1.96–7.00) | <0.0001 |
| Total milk consumption, servings/wk | 0.98 (0–3.50) | 0 (0-0.21) | 0.56 (0–0.98) | 0.98 (0.21–3.50) | 2.54 (0.56–4.66) | 3.71 (1.75–7.00) | <0.0001 |
| Total yogurt consumption, servings/wk | 0.210 (0–1.12) | 0 (0–0.21) | 0.11 (0–1.05) | 0.21 (0–1.12) | 0.56 (0–2.52) | 0.88 (0–3.82) | <0.0001 |
| Serum dairy fatty acid, mol% of total fatty acids | |||||||
| Pentadecanoic acid (15:0) | 0.25 ± 0.06 | 0.23 ± 0.05 | 0.24 ± 0.05 | 0.26 ± 0.05 | 0.25 ± 0.06 | 0.26 ± 0.07 | <0.0001 |
| Trans-palmitoleic acid (trans 16:1n−7) | 0.30 ± 0.10 | 0.30 ± 0.11 | 0.32 ± 0.10 | 0.32 ± 0.09 | 0.30 ± 0.10 | 0.29 ± 0.09 | 0.02 |
1
Total dairy intake was defined as sum of whole milk; 2% milk; skim milk, 1%, or buttermilk; cottage and ricotta cheese; cheese; flavored yogurt (2%, nonfat, or whole); low-fat flavored yogurt (2% or nonfat); ice cream; frozen yogurt, ice milk; milk in coffee or tea; and cream or half-and-half in coffee or tea. Continuous variables are presented as means ± SDs if normal or medians (IQRs) if distribution is nonnormal. Categorical variables are presented as n (%). Q, quintile; TFA, trans fatty acid.
2
Range of total dairy intake per quintile.
3
For continuous variables, P values are from ANOVA or Kruskal-Wallis comparison across quintiles for normal and skewed variables, respectively. For categorical variables, P values are from χ2 value for comparison across quintiles.