Telephone screens were performed on 197 women. Of 82 subjects enrolled in the study after the run-in period, 22 (25%) dropped out. Reasons for dropouts included flatulence and bloating (3), constipation (1), teeth problems (1), intolerable hot flashes off HRT or soy (4), did not want to be off soy in control arm (1), family death or ill family member (3), work conflict (2), vacation conflict (2), pregnancy (1), entered raloxifene study (1), weight gain (1), started statin drug (1), and lost job and moved (1).
Of the 60 who finished, 39 women had hot flashes. Because initial hot flash frequency may affect the response to soy,18
the women were separated into two groups based on average number of daily hot flashes in the control diet arm, a high hot flash group (>4.5 hot flashes/day) and a low hot flash group (≤4.5 hot flashes/day). shows the baseline characteristics by hot flash frequency. Women with > 4.5 hot flashes/day had a significantly lower body mass index (BMI) than women with ≤ 4.5 hot flashes/day; otherwise, there were no significant differences.
Baseline characteristics by hot flash status
Urinary isoflavone levels were measured to assess compliance and were significantly higher on the soy arm compared with the control arm for daidzein, genistein, equol, and glycitein (). Levels of enterolactone, a lignan phytoestrogen found in fruits and vegetables,26
were similar in the control and soy arms, a finding suggesting that fruit and vegetable intake was similar on soy and control arms.
Isoflavone concentrations in control vs. soy diet arms by hot flash status
Diet composition (other than the soy nuts) did not significantly differ on the control vs. the soy arm for either hot flash group except for total fat in the low hot flash group (). Compliance was achieved with < 200 mg cholesterol/day on each diet arm and close to goal (7%) for saturated fat.
Dietary intake in control vs. soy diet arms by hot flash status
The average number of hot flashes during the first week in the control diet was 22.3 ± 24.9 compared with 23.3 ± 23.5 during the last week of the control diet. Therefore, hot flashes did not decrease in the control group. Compared with the control diet arm, soy nut ingestion was associated with a 45% decrease in hot flashes in women with >4.5 hot flashes/day at baseline (7.5 ± 3.6 vs. 4.1 ± 2.6, respectively, p < 0.001) and a 41% decrease in those with ≤4.5 hot flashes/day (2.2 ± 1.2 vs. 1.3 ± 1.1, respectively, p < 0.001) (). Both equol producers and nonproducers had similar reductions in hot flashes with soy nuts compared with the control diet (44%, p < 0.017 for both groups). The reduction in hot flashes was apparent at 2 weeks of treatment in both groups (53% and 54%, respectively) (). There appeared to be some attenuation in the benefit of soy nuts over time in the low hot flash group. A longer duration study with soy nuts would be necessary to confirm this.
FIG. 1 Average number of hot flashes/day during each 8-week diet—TLC plus soy (Soy) and TLC without soy (Control)—in women divided into two groups based on the average number of daily hot flashes in the control (baseline) diet arm: > (more ...)
Percent reduction from baseline in hot flashes at 2, 4, and 8 weeks of treatment in soy diet arm compared with control arm in women with < 4.5 hot flashes/day (top) and > 4.5 hot flashes/day (bottom).
Compared to the control arm, soy nut ingestion was associated with significant improvement in scores on the menopausal symptom quality of life questionnaire: 19% decrease in vasomotor score (p = 0.004), 12.9% reduction in psychosocial score (p = 0.01), and 9.7% decrease in physical score (p = 0.045) after 8 weeks of ingestion. There was a trend toward improvement in the sexual score, with a 17.7% reduction in symptoms (p = 0.129).
The reduction in hot flashes with soy nuts was compared by quintiles of exercise based on average minutes of exercise per week to test the hypothesis that those who exercised more may have greater reductions in hot flashes. No significant differences in baseline characteristics were observed among the five exercise groups (). As shown in , those in the lowest exercise group (0–30 minutes/week) had a similar reduction in hot flashes with soy (56%) compared with those in the highest quintile (>276 minutes/week) (57%). Therefore, amount of exercise did not appear to affect hot flash reductions with soy.
Baseline characteristics stratified by minutes of exercise per week
Percent reduction in hot flashes stratified by minutes of exercise per week