Table 2.
Weighted linear mixed models evaluating the association between daily protein intakes assessed up to 4 times per menstrual cycle (censtruation, midfollicular phase, expected ovulation, and midluteal phase) for 2 cyclesa and percent difference in log-transformed serum reproductive hormone concentrations measured up to 8 times per menstrual cycle for 2 cycles
| Unadjusted | Adjustedb | |||
|---|---|---|---|---|
| Tertile 1 vs Tertile 2 | Tertile 3 vs Tertile 2 | Tertile 1 vs Tertile 2 | Tertile 3 vs Tertile 2 | |
| % Difference (95% CI) | % Difference (95% CI) | % Difference (95% CI) | % Difference (95% CI) | |
| Total protein (% energy) | ||||
| Estradiol (pg/mL) | 0.4 (-4.5, 5.5) | 1.8 (-3.2, 7.0) | 0.4 (-4.5, 5.5) | 1.5 (-3.5, 6.8) |
| Progesterone (ng/mL)c | -6.0 (-20.5, 11.0) | 1.6 (-13.3, 18.9) | -4.9 (-19.3, 12.1) | -0.2 (-14.7, 16.7) |
| LH (ng/mL) | -0.8 (-5.9, 4.5) | -2.1 (-7.1, 3.3) | -1.0 (-6.2, 4.4) | -2.1 (-7.2, 3.4) |
| FSH (mIU/mL) | 0.4 (-3.0, 4.0) | -0.4 (-3.9, 3.2) | 0.4 (-3.1, 4.0) | -0.5 (-4.0, 3.2) |
| Testosterone (ng/dL) | 0.8 (-1.1, 2.6) | -1.5 (-3.3, 0.3) | 0.7 (-1.2, 2.6) | -1.4 (-3.3, 0.4) |
| SHBG (nmol/L) | -1.9 (-3.6, -0.1) | -1.3 (-3.1, 0.5) | -1.8 (-3.5, -0.1) | -1.2 (-3.0, 0.6) |
| Animal protein d (%energy) | ||||
| Estradiol (pg/mL) | -2.0 (-6.8, 3.0) | 1.1 (-3.8, 6.3) | -0.7 (-5.6, 4.5) | 1.5 (-3.5, 6.8) |
| Progesterone (ng/mL)c | -6.5 (-20.9, 10.4) | 0.7 (-14.2, 18.2) | -1.6 (-16.8, 16.4) | -0.3 (-15, 16.8) |
| LH (ng/mL) | 0.8 (-4.5, 6.4) | 1.8 (-3.5, 7.3) | 1.1 (-4.4, 6.8) | 1.9 (-3.5, 7.5) |
| FSH (mIU/mL) | 1.2 (-2.4, 4.8) | 2.4 (-1.2, 6.1) | 1.3 (-2.3, 5.0) | 2.3 (-1.3, 6.1) |
| Testosterone (ng/dL) | 0.6 (-1.3, 2.5) | -1.0 (-2.8, 0.8) | 0.6 (-1.3, 2.5) | -0.7 (-2.5, 1.2) |
| SHBG (nmol/L) | -0.4 (-2.1, 1.4) | 0.2 (-1.5, 2.0) | -0.4 (-2.2, 1.4) | 0.2 (-1.6, 2.0) |
| Vegetable protein e (%energy) | ||||
| Estradiol (pg/mL) | 0.7 (-4.2, 5.8) | -4.4 (-9.2, 0.7) | -0.6 (-5.5, 4.6) | -4.0 (-9.0, 1.3) |
| Progesterone (ng/mL)c | -15.5 (-28.2, -0.6) | -0.7 (-15.6, 16.9) | -18.0 (-30.2, -3.6) | 13.6 (-3.9, 34.3) |
| LH (ng/mL) | 3.3 (-2.1, 8.9) | 0.8 (-4.6, 6.4) | 3.0 (-2.4, 8.8) | 0.5 (-5.0, 6.4) |
| FSH (mIU/mL) | 3.8 (0.2, 7.5) | 1.1 (-2.6, 4.9) | 3.8 (0.2, 7.6) | 1.4 (-2.4, 5.4) |
| Testosterone (ng/dL) | -0.3 (-2.1, 1.6) | 1.0 (-1.0, 2.9) | -0.1 (-2.0, 1.7) | 0.6 (-1.3, 2.6) |
| SHBG (nmol/L) | -0.1 (-1.8, 1.7) | 0.0 (-1.8, 1.9) | -0.1 (-1.9, 1.6) | 0.0 (-1.8, 1.9) |
All models were adjusted for prior hormone levels using inverse probability weights.
Abbreviations: BMI, body mass index; CI, confidence interval; FSH, follicle-stimulating hormone; LH, luteinizing hormone; SHBG, sex hormone-binding globulin.
a Energy from total protein intake, tertile 1: 3.5%–13.2% of energy; tertile 2: 13.2%–17.4% of energy; tertile 3: 17.4%–41.7% of energy. Energy from animal protein intake, tertile 1: 0.0%–7.5% of energy; tertile 2, 7.5%–12.1% of energy; tertile 3, 12.1%–40.7% of energy. Energy from vegetable protein intake, tertile 1, 0.4%–4.3% of energy; tertile 2, 4.3%–5.9% of energy; tertile 3, 5.9%–19.8% of energy.
b Adjusted for age, race, BMI, physical activity, alcohol, blood cadmium, mercury, and lead concentrations, and fiber and total energy intakes.
c Includes only measurements of progesterone during the luteal phase.
d Derived from consumption of red meats (beef, veal, lamb, pork, game, and organ meats), poultry, processed meats (cured pork, cold cuts, and sausage), fish (fish and shellfish), and eggs.
e Derived from consumption of meat alternatives (veggie burgers, tofu, tempeh, textured vegetable protein, and soy nut), legumes (dried beans, mature lima beans, refried beans, and beans in sauce and recipe), nuts and seeds, and nut and seed butters.