Table 2.
Age-Adjusted Characteristics of Participants According to Baseline (1991) Total Protein Intake Among 92,088 Women in Nurses’ Health Study II, 1991–2009
| Characteristic | Quintile of Protein Intake |
|||||
|---|---|---|---|---|---|---|
| 1 (n = 18,417) (15.3% of Energy)a |
3 (n = 18,466) (18.8% of Energy) |
5 (n = 18,417) (22.6% of Energy) |
||||
| % | Mean | % | Mean | % | Mean | |
| Demographic and lifestyle factors | ||||||
| Age, yearsb | 35.9 | 36.0 | 36.4 | |||
| White race/ethnicity | 95.6 | 96.8 | 96.1 | |||
| Body mass indexc | 23.8 | 24.5 | 25.5 | |||
| Body mass index ≥25 | 31.0 | 36.1 | 44.6 | |||
| Physical activity, MET-hours/week | 20.7 | 20.3 | 22.4 | |||
| Current smoker | 14.6 | 11.8 | 11.7 | |||
| Hypertension | 5.8 | 5.9 | 7.3 | |||
| High cholesterol | 13.7 | 13.8 | 16.4 | |||
| Family history of diabetesd | 32.4 | 34.3 | 36.5 | |||
| Postmenopausal hormone use | 4.3 | 4.4 | 5.0 | |||
| Oral contraceptive use | 12.0 | 10.4 | 10.1 | |||
| Multivitamin use | 42.7 | 43.9 | 44.5 | |||
| Alcohol, g/day | 4.0 | 3.1 | 2.3 | |||
| Dietary intake | ||||||
| Total energy, kcal/day | 1,901 | 1,815 | 1,626 | |||
| Carbohydrate, % of energy intake | 55.8 | 49.4 | 44.6 | |||
| Total fat, % of energy intake | 30.4 | 32.1 | 31.5 | |||
| Saturated fat, % of energy intake | 10.7 | 11.4 | 11.2 | |||
| Monounsaturated fat, % of energy intake | 11.7 | 12.2 | 11.7 | |||
| Polyunsaturated fat, % of energy intake | 5.6 | 5.7 | 5.6 | |||
| Trans- fat, % of energy intake | 1.8 | 1.7 | 1.4 | |||
| Dietary cholesterol, mg/day | 187.1 | 241.7 | 297.6 | |||
| Daily dietary glycemic loade | 139.1 | 120.3 | 106.4 | |||
| Daily dietary glycemic indexf | 55.3 | 53.9 | 52.4 | |||
| Total dietary fiber, g/day | 17.7 | 18.3 | 18.6 | |||
| Cereal fiber, g/day | 5.6 | 5.7 | 5.4 | |||
| Magnesium, mg/day | 285.2 | 314.9 | 345.2 | |||
| Heme iron, mg/day | 0.75 | 1.1 | 1.5 | |||
| Potassium, mg/day | 2,649 | 2,944 | 3,189 | |||
| Calcium, mg/day | 857.7 | 1,028 | 1,145 | |||
| Vitamin C, mg/day | 264.5 | 246.5 | 268.3 | |||
| Vitamin E, mg/day | 47.1 | 41.2 | 48.6 | |||
| Whole grains, servings/day | 1.3 | 1.4 | 1.3 | |||
| Fruit, servings/day | 1.2 | 1.2 | 1.2 | |||
| Vegetables, servings/day | 3.0 | 3.3 | 3.6 | |||
| Red meat, servings/day | 0.57 | 0.77 | 0.75 | |||
| Processed meat, servings/day | 0.25 | 0.24 | 0.17 | |||
| Fish, servings/day | 0.18 | 0.27 | 0.42 | |||
| Chicken, servings/day | 0.39 | 0.66 | 1.1 | |||
| Eggs, servings/day | 0.17 | 0.19 | 0.17 | |||
| Dairy foods, servings/day | 2.2 | 2.5 | 2.4 | |||
| Legumes, servings/day | 0.35 | 0.38 | 0.40 | |||
| Nuts, servings/day | 0.29 | 0.26 | 0.18 | |||
| Peanuts, servings/day | 0.05 | 0.04 | 0.02 | |||
| Peanut butter, servings/day | 0.20 | 0.20 | 0.14 | |||
| Potatoes, servings/day | 0.39 | 0.39 | 0.31 | |||
| Coffee, servings/day | 1.5 | 1.6 | 1.5 | |||
| Sugar-sweetened beverages, servings/day | 1.1 | 0.36 | 0.13 | |||
Abbreviations: GI, glycemic index; MET, metabolic equivalent.
a Median percentage of energy intake in the quintile.
b Not adjusted for age.
c Weight (kg)/height (m)2.
d First-degree relatives.
e Average glycemic load was calculated by multiplying the amount of carbohydrates in the diet by the average glycemic index. For 1 serving of a food, a glycemic load of ≥20 is considered high, 11–19 is considered medium, and ≤10 is considered low. Among these 92,088 women from Nurses’ Health Study II, the mean glycemic load was 119.0 (range, 47.8–222.4).
f Average dietary glycemic index (GI) was calculated by summing the products of 1) the carbohydrate content of each food item per serving, 2) the average daily number of servings of that food, and 3) the food's GI value (derived from available databases and publications) and dividing by total daily carbohydrate content. Foods with a GI value of ≤55 are considered to have a low GI, foods with a value of 56–69 are considered to have a medium GI, and foods with a value of ≥70 are considered to have a high GI. Among these 92,088 women from Nurses’ Health Study II, the mean GI was 52.9 (range, 37.0–64.8).