The prevailing evidence against synthetic estrogens must be understood alongside evidence about the effects of plant estrogens (phytoestrogens). Foods such as whole grains, dried beans, peas, fruits, broccoli, cauliflower and especially soy products are rich in phytoestrogens. Although scientific evidence suggests that plant-based estrogens offer nutritional benefits and are associated with healthy diets (Cederroth, 2009), the data are conflicting as to whether soy-based diets are beneficial, harmful or neutral in their effects on breast cancer risk (Andres, 2011; Rice, 2006) Some of the disparity in the literature may be related to type of soy products or other phytoestrogen-containing vegetables consumed by individuals. For example, although two natural phytoestrogens found in soy — genistein and its metabolite genistin (both referred to as isoflavones because of their chemical structure) — have been shown to increase breast tumor growth in a number of different models, highly processed soy flour that does not contain isoflavones has no effect. Purified soy protein isolates are often processed to contain different concentrations of isoflavones, and their influence on mammary tumors is related to the amount of isoflavone, not the total amount of soy protein consumed (Helfrich, 2008).
Several epidemiological studies have shown that regular consumption of soy-based products, or other vegetables high in phytoestrogens, as part of a normal balanced diet can exert a protective influence against later development of breast cancer. This effect has been studied extensively in China, where soy intake is a regular part of the cultural diet. There, substantial evidence indicates that higher soy intake in adulthood or in adolescence is associated with a decreased risk of pre-menopausal breast cancer (Lee, 2009). Other studies have found protective effects of soy intake for both pre- and post-menopausal cancer, independent of the tumors’ receptor profile (estrogen-receptor and progesterone-receptor positive or negative) (Zhang, 2009). On the other hand, in a prospective study of women aged 43 to 55 years who had never been diagnosed with breast cancer but were considered to be at high risk, six months of dietary isoflavone (PTIG-2535, containing 150 mg genistein, 74 mg daidzein, and 11 mg glycitein) intake was associated with increased proliferation of breast cells. The effect was most pronounced in pre-menopausal women (Khan, 2012a).
For Chinese women who were previously diagnosed with breast cancer, consumption of soy in its many forms found regularly in a woman’s diet was correlated with decreased recurrence of cancer and longer survival (Shu, 2009). Complicating the picture further is a study of Korean women who had previously been diagnosed and treated for breast cancer. Dietary soy intake was associated with a decreased rate of recurrence in women whose cancers were HER-2 negative, and an increased rate of recurrence of cancer in women whose original tumors were HER-2 positive (Woo, 2012).
A study of Asian-American women living in California and Hawaii found that soy intake during childhood, adolescence and adulthood was associated in all three cases with decreased later risk of breast cancer (Korde, 2009). The protective effect of regular dietary soy intake during childhood was the strongest, and it was not mitigated when other variables such as site of birth (Asian countries or United States), degree of continuing Asian lifestyle and cultural practices, reproductive factors, or family history of breast cancer were factored into the analysis. A recent meta-analysis that combined data from six studies found that regular dietary intake of soy during adolescence decreased the incidence of all later breast cancers and was particularly effective in decreasing cancer incidence in pre-menopausal women. There was no reported difference in the effects of dietary intakes of soy during adolescence between Asian and American/European women (Zhao, 2012). In general, protective effects of dietary soy intake have been found to be strongest in association with childhood and early adolescent intake (Aldercruz 2003). One possible explanation for this association is that exposures to genistein and other phytoestrogens around the time of puberty may mimic the protective changes in breast development that are usually observed during the first pregnancy (Messina, 2009; Warri, 2008).
Studies examining non-soy phytoestrogen intake and breast cancer risk in non-Asian populations have found more mixed results (Wu, 2008). This may be related to the difference in both amounts and types of phytoestrogens typically eaten as part of the traditional diets found in the United States and in Europe (Mense, 2008). As examples, a French study found that consuming non-soy phytoestrogens as part of a woman’s daily diet had a protective effect against post-menopausal breast cancer (Touillaud, 2007), yet a British study found no such relationship
The prevailing evidence against synthetic estrogens must be understood alongside evidence about the effects of plant estrogens (phytoestrogens). Foods such as whole grains, dried beans, peas, fruits, broccoli, cauliflower and especially soy products are rich in phytoestrogens. Although scientific evidence suggests that plant-based estrogens offer nutritional benefits and are associated with healthy diets (Cederroth, 2009), the data are conflicting as to whether soy-based diets are beneficial, harmful or neutral in their effects on breast cancer risk (Andres, 2011; Rice, 2006) Some of the disparity in the literature may be related to type of soy products or other phytoestrogen-containing vegetables consumed by individuals. For example, although two natural phytoestrogens found in soy — genistein and its metabolite genistin (both referred to as isoflavones because of their chemical structure) — have been shown to increase breast tumor growth in a number of different models, highly processed soy flour that does not contain isoflavones has no effect. Purified soy protein isolates are often processed to contain different concentrations of isoflavones, and their influence on mammary tumors is related to the amount of isoflavone, not the total amount of soy protein consumed (Helfrich, 2008).Several epidemiological studies have shown that regular consumption of soy-based products, or other vegetables high in phytoestrogens, as part of a normal balanced diet can exert a protective influence against later development of breast cancer. This effect has been studied extensively in China, where soy intake is a regular part of the cultural diet. There, substantial evidence indicates that higher soy intake in adulthood or in adolescence is associated with a decreased risk of pre-menopausal breast cancer (Lee, 2009). Other studies have found protective effects of soy intake for both pre- and post-menopausal cancer, independent of the tumors’ receptor profile (estrogen-receptor and progesterone-receptor positive or negative) (Zhang, 2009). On the other hand, in a prospective study of women aged 43 to 55 years who had never been diagnosed with breast cancer but were considered to be at high risk, six months of dietary isoflavone (PTIG-2535, containing 150 mg genistein, 74 mg daidzein, and 11 mg glycitein) intake was associated with increased proliferation of breast cells. The effect was most pronounced in pre-menopausal women (Khan, 2012a).สำหรับผู้หญิงจีนที่ก่อนหน้านี้ถูกวินิจฉัยกับโรคมะเร็งเต้านม การใช้ถั่วเหลืองในรูปแบบต่าง ๆ ที่พบเป็นประจำในอาหารของผู้หญิงถูก correlated กับลดการเกิดซ้ำของมะเร็งและการอยู่รอดที่ยาว (ชู 2009) Complicating รูปภาพเพิ่มเติมคือ การศึกษาของผู้หญิงเกาหลีที่ก่อนหน้านี้ได้รับการวินิจฉัย และรับการรักษามะเร็งเต้านม ถั่วเหลืองอาหารบริโภคเกี่ยวข้องกับอัตราเกิดในมะเร็งมีค่าลบ HER 2 ผู้หญิงลดลง อัตราการเพิ่มขึ้นของการเกิดซ้ำของมะเร็งในสตรีที่มีเนื้องอกเดิมมี HER 2 บวก (เกี้ยวพาน 2012)A study of Asian-American women living in California and Hawaii found that soy intake during childhood, adolescence and adulthood was associated in all three cases with decreased later risk of breast cancer (Korde, 2009). The protective effect of regular dietary soy intake during childhood was the strongest, and it was not mitigated when other variables such as site of birth (Asian countries or United States), degree of continuing Asian lifestyle and cultural practices, reproductive factors, or family history of breast cancer were factored into the analysis. A recent meta-analysis that combined data from six studies found that regular dietary intake of soy during adolescence decreased the incidence of all later breast cancers and was particularly effective in decreasing cancer incidence in pre-menopausal women. There was no reported difference in the effects of dietary intakes of soy during adolescence between Asian and American/European women (Zhao, 2012). In general, protective effects of dietary soy intake have been found to be strongest in association with childhood and early adolescent intake (Aldercruz 2003). One possible explanation for this association is that exposures to genistein and other phytoestrogens around the time of puberty may mimic the protective changes in breast development that are usually observed during the first pregnancy (Messina, 2009; Warri, 2008).ศึกษาตรวจสอบสรรพคุณไม่ใช่ถั่วเหลืองเต้านมและการเสี่ยงมะเร็งในประชากรเอเชียไม่พบผลลัพธ์ขึ้นผสม (Wu, 2008) นี้อาจเกี่ยวข้องกับความแตกต่างของจำนวนและชนิดของ phytoestrogens กินโดยทั่วไปเป็นส่วนหนึ่งของอาหารแบบดั้งเดิมที่พบ ในสหรัฐอเมริกา และ ในยุโรป (Mense, 2008) เป็นตัวอย่าง การศึกษาฝรั่งเศสพบว่า บริโภค phytoestrogens มีถั่วเหลืองเป็นส่วนหนึ่งของอาหารประจำวันของผู้หญิงมีผลป้องกันกับมะเร็งเต้านมหลังหมดประจำเดือน (Touillaud, 2007), แต่ความสัมพันธ์ดังกล่าวไม่พบการศึกษาภาษาอังกฤษ
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