Lu L J, Anderson K E, Grady J J, Nagamani M
Departments of Preventive Medicine and Community Health, The University of Texas Medical Branch, Galveston, Texas 77555, USA.
J Clin Endocrinol Metab. 2001 Jul;86(7):3045-52. doi: 10.1210/jcem.86.7.7684.
Soy intakes have been associated with reduced rates of breast cancer in some Asian populations. The isoflavones daidzein and genistein and other components of soybeans may modulate endocrine function and lead to beneficial health effects. This study determined the effects of a soy diet containing minimum amounts of isoflavones on circulating levels of ovarian hormones and gonadotropins. Nine healthy, regularly cycling women consumed a constant soya-containing diet on a metabolic unit starting on day 2 of a menstrual cycle until day 2 of the next cycle. The soy diet was calculated to maintain constant body weight and included a 36-oz portion of soymilk that provided 334 kilocalories and less than 5 mg/day of total isoflavones. The energy distribution of the soy diet was 35.9% fat, 14.0% protein, and 49.8% carbohydrate whereas the home diets averaged 39% fat, 16.6% protein, and 42.5% carbohydrate. For the group, the soya diet provided more carbohydrate (P = 0.002) and less protein (P = 0.005) than the home diets. Daily consumption of the soya diet reduced daily circulating levels of 17beta-estradiol over the entire menstrual cycle by 20% (P < 0.01, paired t test, two-tailed) and progesterone by 33% (P < 0.0001) compared with levels during the home diet period, but had no effect on LH, FSH, or sex hormone-binding globulin. The decreases in follicular phase 17beta-estradiol during the soy diet can be accounted for by changes in energy intakes, nutrient density, and fiber intake, whereas changes in luteal phase 17beta-estradiol were most strongly associated with differences in fiber intake. Changes in progesterone levels were most strongly associated with changes in protein intake and much less with other nutrients. Isoflavones were not detectable in plasma and urine during either the soy or home diet periods. These results suggest that at least under the conditions of this study, a soy diet with low levels of isoflavones and low energy intake from protein can reduce circulating ovarian steroids without altering gonadotropins. Our results are consistent with previous studies showing decreased ovarian hormone levels and decreased risk of breast cancer in populations consuming soya diets and an inverse relationship between animal protein intake and breast cancer risk and, therefore, may have implications for breast cancer prevention.
在一些亚洲人群中，大豆摄入量与乳腺癌发病率降低有关。大豆中的异黄酮大豆苷元和染料木黄酮以及其他成分可能调节内分泌功能，并带来有益的健康影响。本研究确定了一种含最低量异黄酮的大豆饮食对卵巢激素和促性腺激素循环水平的影响。九名健康、月经周期规律的女性在代谢单元中从月经周期的第2天开始食用持续的含大豆饮食，直至下一个周期的第2天。计算得出该大豆饮食能维持恒定体重，其中包括一份36盎司的豆浆，提供334千卡热量，总异黄酮含量低于5毫克/天。大豆饮食的能量分布为脂肪35.9%、蛋白质14.0%、碳水化合物49.8%，而家庭饮食的平均值为脂肪39%、蛋白质16.6%、碳水化合物42.5%。对于该组而言，大豆饮食比家庭饮食提供了更多的碳水化合物（P = 0.002）和更少的蛋白质（P = 0.005）。与家庭饮食期间的水平相比，每日食用大豆饮食使整个月经周期中17β-雌二醇的每日循环水平降低了2０%（P < 0.01，配对t检验，双侧），孕酮降低了33%（P < 0.0001），但对促黄体生成素、促卵泡生成素或性激素结合球蛋白没有影响。大豆饮食期间卵泡期17β-雌二醇的降低可归因于能量摄入、营养密度和纤维摄入量的变化，而黄体期17β-雌二醇的变化与纤维摄入量的差异最为密切相关。孕酮水平的变化与蛋白质摄入量的变化最为密切相关，与其他营养素的关系则小得多。在大豆饮食期和家庭饮食期，血浆和尿液中均未检测到异黄酮。这些结果表明，至少在本研究的条件下，低异黄酮水平且蛋白质能量摄入低的大豆饮食可降低循环中的卵巢类固醇水平，而不改变促性腺激素。我们的结果与先前的研究一致，先前的研究表明食用大豆饮食的人群中卵巢激素水平降低且乳腺癌风险降低，以及动物蛋白摄入量与乳腺癌风险呈负相关，因此，可能对乳腺癌预防具有重要意义。
