Badger T M, Ronis M J, Hakkak R
Arkansas Children's Nutrition Center and Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock 72202, USA.
Int J Toxicol. 2001 May-Jun;20(3):165-74. doi: 10.1080/109158101317097755.
Dietary factors other than the traditional nutrients are found in the so-called functional foods. They are becoming increasingly recognized as potentially important for maintaining good health. Soybeans are rich in such factors thought to help prevent certain chronic diseases. Soy protein isolate (SPI) is one of the three major proteins used in infant formulas sold in the United States, with casein (CAS) and whey (WPH) proteins being the others. We have been studying the health effects of these proteins. Safety concerns have developed over the consumption of soy-based infant formula, partly because of the high circulating levels of the total isoflavones (phytoestrogens) during "critical periods of infant development." There is a paucity of data on developmental, physiological, neurophysiological, behavioral, metabolic, or molecular effects of soy phytochemicals in humans, especially during pregnancy and infancy. We have studied the effects of CAS, SPI, and WPH in short-term, long-term, and multigenerational studies in rats. Aside from minor differences in body weight gain profiles, CAS-, SPI- or WPH-fed rats did not differ in development, organ weights, in vitro hepatic metabolism of testosterone (T), or reproductive performance. However, some endocrine-related functions differed between rats fed these proteins. We found that SPI accelerated puberty in female rats (p < .05) and WPH delayed puberty in males and females, as compared with CAS (p < .05). Gender differences were also found in gonadectomy-induced steroid responses. Male rats had normal serum T levels, but female rats fed SPI had reduced serum 17beta-estradiol concentrations and a blunted 17beta-estradiol response to ovariectomy, as compared to rats fed CAS or WHP (p < .05). Female rats fed SPI or WHP or treated with genistein had reduced incidence of chemically induced mammary cancers (p < .05) compared to CAS controls, with WHP reducing tumor incidence by as much as 50%, findings that replicate previous results from our laboratory. Together, these results suggest gender-specific differences in development and certain endocrine responses among rats fed diets composed of a single protein source such as those used in infant formulas. Whether similar developmental effects occur in human infants is unknown, but unlikely because (1) most infants do not consume such diets throughout life as these rats did, and (2) no such effects have been reported in millions of American infants fed infant formula containing these proteins. The long-term health consequence implications of early diet exposure to SPI and WPH, such as reduced breast cancer incidence, are likely to be very positive.
所谓的功能性食品中含有除传统营养素之外的膳食因素。它们越来越被认为对维持健康具有潜在的重要意义。大豆富含这类被认为有助于预防某些慢性疾病的因素。大豆分离蛋白（SPI）是美国销售的婴儿配方奶粉中使用的三种主要蛋白质之一，另外两种是酪蛋白（CAS）和乳清蛋白（WPH）。我们一直在研究这些蛋白质对健康的影响。人们对食用大豆基婴儿配方奶粉产生了安全担忧，部分原因是在“婴儿发育的关键时期”总异黄酮（植物雌激素）的循环水平较高。关于大豆植物化学物质对人类发育、生理、神经生理、行为、代谢或分子方面的影响，尤其是在怀孕和婴儿期的影响，数据很少。我们在大鼠的短期、长期和多代研究中研究了CAS、SPI和WPH的影响。除了体重增加情况存在细微差异外，喂食CAS、SPI或WPH的大鼠在发育、器官重量、睾酮（T）的体外肝脏代谢或生殖性能方面没有差异。然而，喂食这些蛋白质的大鼠之间某些与内分泌相关的功能有所不同。我们发现，与喂食CAS的大鼠相比，SPI使雌性大鼠青春期提前（p < 0.05），而WPH使雄性和雌性大鼠青春期延迟（p < 0.05）。在性腺切除诱导的类固醇反应中也发现了性别差异。雄性大鼠血清T水平正常，但与喂食CAS或WHP的大鼠相比，喂食SPI的雌性大鼠血清17β - 雌二醇浓度降低，对卵巢切除的17β - 雌二醇反应减弱（p < 0.05）。与CAS对照组相比，喂食SPI或WHP或用染料木黄酮处理的雌性大鼠化学诱导的乳腺癌发病率降低（p < 0.05），其中WHP使肿瘤发病率降低多达50%，这些发现重复了我们实验室之前的结果。总之，这些结果表明，在喂食由单一蛋白质来源组成的饮食（如婴儿配方奶粉中使用的那些）的大鼠中，发育和某些内分泌反应存在性别特异性差异。人类婴儿是否会出现类似的发育影响尚不清楚，但可能性不大，因为（1）大多数婴儿不像这些大鼠那样终生食用此类饮食，（2）数百万食用含有这些蛋白质的婴儿配方奶粉的美国婴儿中尚未报告有此类影响。早期饮食接触SPI和WPH对长期健康的影响，如降低乳腺癌发病率，可能是非常积极的。
