According to Dr. Mark Messina, Ph.D., Soy foods contributed from 6.5%8 to 12.8%7 of total protein intake in older adult in Japan.(b)
The approval of cardiovascular benefit of soy by FDA in 1999 accompanied with the discovery of health benefits in clinical studies over past decade, prompted the promotion and advertisement of soy's health benefits in every aspect in Western society. Evidences can be seen by walking through the supermarkets and drug stores. Soy supplements and products such as tofu, soy milk, soy-based infant formula, and meatless “texturized vegetable protein” burgers are widely available. According to the United Soybean Board’s 2004–2005, 25% of Americans consume soy foods or beverages at least once per week, and 74% view soy products as healthy.
Today, the promotion of soy are no longer existed, it may be results of discovery of adverse effect in single ingredient and animal studies, as intake of soy is associated to induce risk certain mammary cancers and infertility. The publication of the result have drawn many criticisms. According to Thomas Badger, director and senior investigator at the Arkansas Children’s Nutrition Center in Little Rock, these effects are seen only under certain experimental conditions that are not likely to occur in humans—and therein lies the crux of the debate(a). Equol (4',7-isoflavandiol), an isoflavandiol metabolized from daidzein may be the causes, as 90% of Eastern population are equol producers but only 30% in the West.
The explanation of the positive effect of soy isoflavones in reduced risk of mammary cancers by University of Goettingen may be interesting, as researchers said" Most importantly, there is dispute as to whether isoflavones derived from soy or red clover have negative, positive or any effect at all on the mammary gland or endometrium. It is beyond any doubt that soy products may have cancer preventing properties in a variety of organs including the mammary gland. However, these properties may only be exerted if the developing organ was under the influence of isoflavones during childhood and puberty.
Soybean is genus Glycine, the family Fabaceae, one of the legumes that contains twice as much protein per acre as any other major vegetable or grain crop, native to Southeast Asia. Now, it is grown worldwide with suitable climate for commercial profits.
Nutrients
1. Carbohydrates
2. Dietary fiber
3. Fat
4. Protein
5. Essential amino acid
6. Vitamin A
7. Vitamin B6
8. Vitamin B12
9. Vitamin C
10. Vitamin K
11. Calcium
12. Iron
13. Magnesium
14. Phosphorus
15. Potassium
16. Sodium
17. Zinc
18. Etc.
Phytochemicals
1. Isoflavones
2. Genistein
3. Saponins
4. Beta-sitosterol
5. Daidzein
I. Soy in Eastern population
A. The Japanese population
Japan, an island nation in the Pacific Ocean, lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south(1). According to Moriyama, Japanese women and men live longer and healthier than everyone else on Earth, it may be result of healthier Japanese diet and lifestyle. According to the World Health Organization, the Japanese have an average of 75 years healthy living with disability-free, it may be due to average soy intake 10 to 70 times higher than in Western people(1a)(1b)
A.1. Soy and the risk of cerebral infarction (CI) and myocardial infarction (MI) in Japan population
The searching of the Keywords in PubMed, soy and heart diseases and stroke in Japan found 3 studies, all showed the positive effect of soy in reduced risk heart disease and stroke.
Cerebral infarction (CI) is defined as a type of ischemic stroke due to blockage in the blood vessels supplying blood to the brain.
Myocardial infarction (MI) is also known as heart attack. It is defined as a condition of blood stop flowing properly to part of the heart as a result of not receiving enough oxygen.
According to National Cardiovascular Center, Japan, the studied 40,462 Japanese (40 to 59 years old, without cardiovascular disease or cancer at baseline), yields interest results.
People who consume more soy are less likely to be current smokers but more likely to be hypertensive, with men are more likely to have diabetes mellitus. The frequency of soy intake was positively related to daily intake of rice, vegetables, fruits, fish, potassium, calcium, carbohydrate, polyunsaturated fatty acid, saturated fatty acid, fiber, and isoflavones for both sexes.
The study started in the 1990 with food-frequency questionnaire included 44 foods with 3 questions to assess soy, bean, and miso consumption. The 1995 follow-up questionnaire covered 147 foods with 8 questions on soy products.
The result is astonishing, during a follow-up period that averaged 12.5 years, 1230 strokes were documented, of which 1137 were confirmed through imaging or autopsy, even high isoflavone intake was associated with reduced risk of CI and MI in middle-aged Japanese subjects, but not in men and dietary isoflavones and may be beneficial to postmenopausal women for the prevention of ischemic CVD(2). Intake of miso soup although showed to reduce risk of hypertension but did not contributed to ischemic CVD mortality in either men or women.
Strong evidence of epidemiological studies from the East and West has shown that hyperlipidemia is a major risk factor in contribution to heart diseases, notably on intermediate end points(3)(4). Soy foods intake has been known to contain lowering cholesterol and blood pressure effect. According to the Veterans Affairs Medical Center, daily soy protein showed a significantly decreased serum concentrations of total cholesterol, LDL cholesterol, and triglycerides without significantly affecting serum HDL cholesterol concentrations.(4). But the study suggested that the mechanism of reduced risk of cerebral infarction (CI) and myocardial infarction (MI) for postmenopausal Japanese women may not be through reduction of lipid profile but through exposure to a large quantity of isoflavones, which act as estrogen agonist because estrogen receptors are not occupied with plasma estradiol in postmenopausal women.
In case of hypertension in the subject of study, although the disease have been shown to contribute to the early risk factor for the progression heat disease and stroke(6)(7)(8)(9). Consumption of soy has no effect in reduce risk of the development of cerebral infarction (CI) and myocardial infarction for people with histories of hypertension and diabetes mellitus and medication use for hypercholesterolemia, even soy has shown effectively in reduced high blood pressure(12)
In support to the above, the dietary intervention study targeting female students by using cake containing soybean protein and isoflavone at the Mukogawa Women's University, 4 weeks dietary intake of soy protein found to reduce CHD risk among Japanese female students with a high plasma cholesterol level(10) and Dr. Nagata C. at the Gifu University School of Medicine, Gifu, Japan, in the study of association between soy product intake and mortality from cancer and heart disease in Japan, suggested that soy foods intake showed a preventive role in against stomach cancer and heart disease death(11).
Dr. Yoshihiro Kokubo and the research team also acknowledged the limitation of the study such as ethic group, measurement errors with nutrient intake or due to it self report, but insisted that nationwide annual health screenings may ease the self report concern.
They also clarified that the result of the study of dietary intake of isoflavones, are not relevant to the association of isoflavone supplement use with ischemic CVD.
In deed, the effectives of soy isoflavone in reduced risk of cerebral infarction (CI) and myocardial infarction in this case, yield some questions due to it ethnicity.
a. If soy is found to effective in reduce risk of hypertension and hyperlipidemia, why it does not contribute to the reduce risk of cerebral infarction (CI) and myocardial infarction in men with histories of hypertension and diabetes mellitus and medication use for hypercholesterolemia.
Would the medication is the cause? As epidemiological study insisted the lowering effect of blood pressure and cholesterol are associated to reduce risk heart disease and stroke.
b. Although soy isoflavone showed an effectiveness in reduce risk of cerebral infarction (CI) and myocardial infarction and mortality, would dietary with high in fruit and vegetable also best known for the reduce risk of heart disease and stroke be also taken into account?
c. The effectiveness of the study may only be true for equol producers population as 90% of subjects' study are equol producers?
b. Would the "Japanese Phenomenon" interfere with the study, as administration of isoflavone "inexperienced" women at the time of menopause, the phytoestrogens appear to share the same effects as estrogen used in classical preparations for hormone replacement therapy?
References
(a) The Science of Soy: What Do We Really Know? by Julia R. Barrett
(b) Guideline for healthy soy intake(the Unite Soybean board)
(1) Japan, Wikipedia
(1a) Erdman JW Jr. AHA Science Advisory: soy protein and cardiovascular disease: a statement for healthcare professionals from the Nutrition Committee of the AHA. Circulation. 2000; 102: 2555–2559
(Soy protein and cardiovascular disease)
(1b) van der Schouw YT, Kreijkamp-Kaspers S, Peeters PH, Keinan-Boker L, Rimm EB, Grobbee DE. Prospective study on usual dietary phytoestrogen intake and cardiovascular disease risk in Western women. Circulation. 2005; 111: 465–471(Cardiovascular diseases in women)
(5) Soy intake and breast cancer risk: an evaluation based on a systematic review of epidemiologic evidence among the Japanese population by Nagata C1, Mizoue T, Tanaka K, Tsuji I, Tamakoshi A, Matsuo K, Wakai K, Inoue M, Tsugane S, Sasazuki S; Research Group for the Development and Evaluation of Cancer Prevention Strategies in Japan.(PubMed)
(6) Probiotic Beverage with Soy Isoflavone Consumption for Breast Cancer Prevention: A Case-control Study by Toi M1, Hirota S, Tomotaki A, Sato N, Hozumi Y, Anan K, Nagashima T, Tokuda Y, Masuda N, Ohsumi S, Ohno S, Takahashi M, Hayashi H, Yamamoto S, Ohashi Y.(PubMed)
(7) Associations of intakes of fat, dietary fiber, soy isoflavones, and alcohol with levels of sex hormones and prolactin in premenopausal Japanese women by Tsuji M1, Tamai Y, Wada K, Nakamura K, Hayashi M, Takeda N, Yasuda K, Nagata C.(PubMed)
(8) Plasma isoflavone level and subsequent risk of breast cancer among Japanese women: a nested case-control study from the Japan Public Health Center-based prospective study group by Iwasaki M1, Inoue M, Otani T, Sasazuki S, Kurahashi N, Miura T, Yamamoto S, Tsugane S; Japan Public Health Center-based prospective study group.(PubMed)
(9) Isoflavones--safe food additives or dangerous drugs? by Wuttke W1, Jarry H, Seidlová-Wuttke D.(PubMed)
(10) Effect of a soybean product on serum lipid levels in female university students by Takahashi K1, Kamada Y, Hiraoka-Yamamoto J, Mori M, Nagata R, Hashimoto K, Aizawa T, Matsuda K, Kometani T, Ikeda K, Yamori Y.(PubMed)
(11) Ecological study of the association between soy product intake and mortality from cancer and heart disease in Japan by Nagata C.(PubMed)
(12) Association of blood pressure with intake of soy products and other food groups in Japanese men and women by Nagata C1, Shimizu H, Takami R, Hayashi M, Takeda N, Yasuda K.(PubMed)
(14) Effects of dietary intake of soy protein and isoflavones on cardiovascular disease risk factors in high risk, middle-aged men in Scotland by Sagara M1, Kanda T, NJelekera M, Teramoto T, Armitage L, Birt N, Birt C, Yamori Y.(PubMed)
A.2. Soy and Breast cancer in Japanese women
Breast cancer (malignant breast neoplasm) is a cancer that starts in the tissues of the breast either from the inner lining of milk ducts (Ductal carcinoma) or the lobules (Lobular carcinoma) that supply the ducts with milk. there is also rare cases that breast cancer starts in other areas of the breast. In 2010, over 250,000 new cases of breast cancer were expected to be diagnosed in women in the U.S. alone and the risk of getting invasive breast cancer during life time of a women is 1/8.
The searching of keyword in PubMed with keywords, soy and breast cancer in Japanese women, found 15 related studies.
Epidemiologic evidence suggesting high intake of soy in Japanese population is associated to reduce risk of breast cancer(1) and regular consumption of probiotic beverage and isoflavones since adolescence was inversely associated with the incidence of breast cancer in Japanese women(2)(2a).
The study in the testing of oral administration of IF-rich tablet (20 and 40 mg/day) on climacteric women, showed the product not only reduced risk of breast cancer but also showed an improvement of bone density, hypertension and climacteric symptoms, cardiovascular diseases, gynecological problems and possible immune potentiation(3)
Japanese women show lower incidence of and mortality from breast cancer, compared to Caucasians, it may be result of large amount intake soy protein and isoflavones, as high dietary intake of phytoestrogens, mainly in the form of soy products, can produce circulating levels of phytoestrogens that are known experimentally to have oestrogenic effects(4).
According to the Loma Linda University, Asian population consumes as much as 25 g of soy protein or 100 mg of isoflavones per day(5).
Epidemiological Western studies have link levels of Genistein and daidzein in stimulating breast tumor growth and antagonize the effects of tamoxifen have been inclusive. Some researchers suggested that women with current or past breast cancer should be aware of the risks of potential tumor growth when taking soy products(6).
In Japanese population, serum of isoflavones and insulin levels were not associated with breast cancer risk, in a case-control study of 63 histologically confirmed breast cancer patients and 76 controls, of serum isoflavone, insulin and adiponectin levels with breast cancer risk(7).
The review of Soy for breast cancer survivors, also rejected the above claim of adult consumption of soy affects the risk of developing breast cancer or that soy consumption affects the survival of breast cancer patients(8). In deed, in Japanese study in testing the serum concentrations of genistein and daidzein, showed urinary excretion in 10 women and 9 men who consumed a typical low-fat diet with much rice and soy products, fish, and vegetables, in a rural village south of Kyoto, Japan, indicated a co-related to isoflavonoids intake and serum concentrations of genistein and daidzein and suggested that these may be a result of low mortality in breast and prostate cancer of Japanese women and men, respectively(9). In fact, tofu is found to be associated with the serum concentrations of genistein and daidzein but fermented product, such as miso showed a slight association with serum concentrations of these phytoestrogens with serum concentrations of equol showed associated with dietary intake of tofu and miso soup(10).
Soymilk, a flavor drink on breakfast in Asian diet, when conbined with combination with probiotic Lactobacillus casei Shirota (LcS) also showed to prevent the development of mammary tumors through suppressesion of tumor growth and might be a beneficial dietary style for breast cancer prevention(11). Intake of soy combined with seaweed in equol producers, showed seaweed favorably alters estrogen and phytoestrogen metabolism and these changes likely include modulation of colonic bacteria, in healthy postmenopausal women(12). In premenopausal Japanese women study with randomly assigned to receive either a soymilk-supplemented diet (n = 31) or a normal (control) diet (n = 29), involved three consecutive menstrual cycles showed the estrone and estradiol levels were decreased by 23% and 27%, respectively, in the soymilk-supplemented group but insisted that larger studies will be required to confirm the ability of soy products to reduce serum estrogen levels(12a). Other study in 50 healthy premenopausal Japanese women, also showed a similar result as blood samples drawn from each subject on Days 11 and 22 of her menstrual cycle, suggested that the consumption of soy products lowers the risk of developing breast cancer risk in modifying estrogen metabolism(12b).
In postmenopausal Japanese women, according to the study from the Takayama, with participants members aged 35 years or older in 1992 with follow-up was conducted from the time of the baseline study (September 1, 1992) to the end of March 2008, concluded that soy and isoflavone intakes may have a protective effect on postmenopausal breast cancer. Risks of breast cancer were decreased among women with a moderate intake of soy and isoflavone(13).
In a total of 678 breast cancer cases and 3,390 age- and menopausal status-matched noncancer controls, soy showed a protective effect against breast cancer risk differs by receptor status, including with ER-positive (ER+) and HER2-negative (HER2-)(14). Genistein a major component of soybean isoflavone, has been found to induce breast cancer in some Western study, also exert its anti breast cancer preventive effect in a breast cancer cell overexpressing HER-2, as genistein enhances necrotic-like cell death of the breast cancer cells through the inactivation of HER-2 receptor and Akt which plays a key role in multiple cellular processes in combined with chemotherapeutic agent (15).
Unfortunately, report on a Japan Collaborative Cohort (JACC) Study. From 1988 to 1990, 30,454 women aged 40-79 years, completed a questionnaire on diet and other lifestyle features, suggested that consumption of soy food has no protective effects against breast cancer, but insisted that further large-scale investigations eliciting genetic factors may clarify different roles of various soybean-ingredient foods on the risk of breast cancer(16).
According to DR. Nagata C. the protective risk against breast cancer only found in in Asian but not Western populations with intake of soy may be due to consume levels of soy typical in Asian diets. researchers should also take account of amount of soy isoflavones consumed, the form and food source of isoflavones, timing of isoflavone exposure, estrogen receptor status of tumors, and equol-producer status and hormonal profile of individuals. These factors might explain the heterogeneity of results from studies(17).
Conclusion
Dr, Rice S. Dr. Whitehead SA., in the differentiation of phytoestrogens and breast cancer--promoters or protectors? said "a paradox concerning the epidemiology of breast cancer and the dietary intake of phytoestrogens that bind weakly to oestrogen receptors and initiate oestrogen-dependent transcription. In Eastern countries, such as Japan, the incidence of breast cancer is approximately one-third that of Western countries whilst their high dietary intake of phytoestrogens, mainly in the form of soy products, can produce circulating levels of phytoestrogens that are known experimentally to have oestrogenic effects. The actions of phytoestrogens on oestrogen receptors and key enzymes that convert androgens to oestrogens in relation to the growth of breast cancer cells. In addition, it compares the experimental and epidemiological evidence pertinent to the potential beneficial or harmful effects of phytoestrogens in relation to the incidence/progression of breast cancer and their efficacy as natural alternatives to conventional HRT"(18).
References
(1) Soy intake and breast cancer risk: an evaluation based on a systematic review of epidemiologic evidence among the Japanese population(PubMed)
(2) Probiotic Beverage with Soy Isoflavone Consumption for Breast Cancer Prevention: A Case-control Study by Toi M1, Hirota S, Tomotaki A, Sato N, Hozumi Y, Anan K, Nagashima T, Tokuda Y, Masuda N, Ohsumi S, Ohno S, Takahashi M, Hayashi H, Yamamoto S, Ohashi Y.(PubMed)
(2a) Yamamoto S1, Sobue T, Kobayashi M, Sasaki S, Tsugane S; Japan Public Health Center-Based Prospective Study on Cancer Cardiovascular Diseases Group.(PubMed)
(3) Isoflavones for prevention of cancer, cardiovascular diseases, gynecological problems and possible immune potentiation by Watanabe S1, Uesugi S, Kikuchi Y.(PubMed)
(4) Phytoestrogens and breast cancer--promoters or protectors? by Rice S1, Whitehead SA.(PubMed)
(5) Estimated Asian adult soy protein and isoflavone intakes, by Messina M1, Nagata C, Wu AH.(PubMed).
(6) Effects of soy phytoestrogens genistein and daidzein on breast cancer growth by de Lemos ML.(PubMed)
(7) Minatoya M1, Kutomi G, Asakura S, Otokozawa S, Sugiyama Y, Ohnishi H, Akasaka H, Miura T, Mori M, Hirata K.(PubMed)
(8) Soy for breast cancer survivors: a critical review of the literature by Messina MJ1, Loprinzi CL.(PubMed)
(9) Association of serum phytoestrogen concentration and dietary habits in a sample set of the JACC Study by Ozasa K1, Nakao M, Watanabe Y, Hayashi K, Miki T, Mikami K, Mori M, Sakauchi F, Washio M, Ito Y, Suzuki K, Kubo T, Wakai K, Tamakoshi A; JACC Study Group.(PubMed)
(10) Urinary excretion of lignans and isoflavonoid phytoestrogens in Japanese men and women consuming a traditional Japanese diet by Adlercreutz H1, Honjo H, Higashi A, Fotsis T, Hämäläinen E, Hasegawa T, Okada H.(PubMed)
(11) Lactobacillus casei Shirota enhances the preventive efficacy of soymilk in chemically induced breast cancer by Kaga C1, Takagi A, Kano M, Kado S, Kato I, Sakai M, Miyazaki K, Nanno M, Ishikawa F, Ohashi Y, Toi M.(PubMed)
(12) Dietary seaweed modifies estrogen and phytoestrogen metabolism in healthy postmenopausal women by Teas J1, Hurley TG, Hebert JR, Franke AA, Sepkovic DW, Kurzer MS.(PubMed)
(12a) Effect of soymilk consumption on serum estrogen concentrations in premenopausal Japanese women by Nagata C1, Takatsuka N, Inaba S, Kawakami N, Shimizu H.(PubMed)
(12b) Decreased serum estradiol concentration associated with high dietary intake of soy products in premenopausal Japanese women by Nagata C1, Kabuto M, Kurisu Y, Shimizu H.(PubMed)
(13) Soy isoflavone intake and breast cancer risk in Japan: from the Takayama study by Wada K1, Nakamura K, Tamai Y, Tsuji M, Kawachi T, Hori A, Takeyama N, Tanabashi S, Matsushita S, Tokimitsu N, Nagata C.(PubMed)
(14) Effect of soybean on breast cancer according to receptor status: a case-control study in Japan by Suzuki T1, Matsuo K, Tsunoda N, Hirose K, Hiraki A, Kawase T, Yamashita T, Iwata H, Tanaka H, Tajima K.(PubMed)
(15) Genistein, a soy isoflavone, enhances necrotic-like cell death in a breast cancer cell treated with a chemotherapeutic agent by Satoh H1, Nishikawa K, Suzuki K, Asano R, Virgona N, Ichikawa T, Hagiwara K, Yano T.(PubMed)
(16) Consumption of soy foods and the risk of breast cancer: findings from the Japan Collaborative Cohort (JACC) Study by Nishio K1, Niwa Y, Toyoshima H, Tamakoshi K, Kondo T, Yatsuya H, Yamamoto A, Suzuki S, Tokudome S, Lin Y, Wakai K, Hamajima N, Tamakoshi A(PubMed)
(17) Factors to consider in the association between soy isoflavone intake and breast cancer risk.
PubMed)
(18) Phytoestrogens and breast cancer--promoters or protectors? by Rice S1, Whitehead SA.(PubMed)
A3. Soy and Prostate cancer in Japanese Men
Prostate cancer is defined as a condition in which the cells of prostate has become cancerous, causing abnormal cell growth with possibility of spreading to the distant parts of the body. Most prostate cancers are slow growing and enlarged prostate and prostate cancer may be detected during physical (rectum) exams.
The widespread of prostate cancer, once considered a disease of aging male, now have become major concerns of governments and scientific community in South East Asian with tendency to effect even younger age population. Suggestions emerged of over consuming bad fats in any time in history accompanied with unhealthy diet and life style may be the possible causes of the disease, linking to the economic prosperity over 2 decades.
In fact, the incidence of prostate cancer is still lower if compared to their Western counterparts.
The study of the Research Center for Cancer Prevention and Screening, National Cancer Center. suggested that isoflavones and soy food are associated with a dose-dependent decrease in the risk of localized cancer, in a population-based prospective study in 43,509 Japanese men ages 45 to 74 years with participants responded to a validated questionnaire, which included 147 food items. During follow-up from 1995 through 2004, 307 men were newly diagnosed with prostate cancer, of which 74 cases were advanced, 220 cases were organ localized, and 13 cases were of an undetermined stage(5).
Environment, Diet, intestinal microbiota and Geography
The testing of North American Japanese and Japanese in Japan showed the environment factor may be involved in the development of prostate cancer regardless to genetic similar(7). The incidence of the disease increased vary both from country to country and according to the ethnic group, with the highest incidence reported for Afro-Americans and the lowest for Asian men(2).
The study of the associations between nutritional and other lifestyle factors and the prevalence of prostate cancer in a case-control study of Japanese men, showed that soy isoflavone significantly decreased the risk of prostate cancer regardless to the intake of other nutrients such as PUFA, (n-6) fatty acids or magnesium from other food sources(9).
Other suggested that legumes (not limited to soy products) and certain categories of vegetables may protect against prostate cancer(10).
DR. Akaza H. said "not having equol converting bacteria in the intestine (non-equol producers) can be a risk factor for prostate cancer and that one direction for future research will be to examine the possibility of improving the intestinal environment to enable equol production"(13).
Genes differentiation
1n gene differentiation, estrogen related genes may be the culprits for the development of prostate cancer. In an one hundred and eighty cases and 177 controls selected from three geographic areas of Japan study, though analysis by the multifactor dimensionality reduction method, soy isoflavones, showed to exhibit its anti prostate cancer, depending to differ between the genotypes of estrogen related genes(3).
According to Dr. Kimura T., the incidence of prostate cancer in Asia is much lower than that in African Americans and European Caucasians and soy food consumption, more popular in Asian populations, is associated with a 25% to 30% reduced risk of prostate cancer, it may be as a result of genetic mutation of approximately 30 genetic polymorphisms in populations of countries in the West.(1).
Serum of isoflavones
In a case-control study within the Japan Public Health Center-based Prospective of a total of 14,203 men aged 40 to 69 years who had returned the baseline questionnaire and provided blood samples observed from 1990 to 2005, showed that plazma genistein level is associated inversely to the risk of prostate cancer(4).
Other in the study of four isoflavonoids in plasma of 14 Japanese and 14 Finnish men, also showed that the mean plasma of total individual isoflavonoid levels of Japnaese are 7 to 110 times higher Japanese than in the Finnish men. Genistein, a tyrosine kinase inhibitor, occurred in the highest concentration(11).
In the experiment of Urinary excretion of lignans and isoflavonoid phytoestrogens in Japanese men and women consuming a traditional Japanese diet showed that the excretion of isoflavonoids correlated with soybean-product intake is associated to reduced mortality in breast and prostate cancer of Japanese women and men(12).
In view of above, the Loma Linda University, insisted that soy isoflavones should be tested against different populations of prostate cancer patients for its efficacy(6). Other suggested that the lower incidence of prostate cancer in Japanese men may be a result of traditional Japanese diet with a lot of soy foods and fishes(8). Together with Soy-derived food products and the metabolization of the isoflavones they contain by intestinal microbiota among Asian and European/North American populations(13).
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References
(1) East meets West: ethnic differences in prostate cancer epidemiology between East Asians and Caucasians by Kimura T.(PubMed)
(2) Hereditary prostate cancer and other genetic predispositions to prostate cancer by Cussenot O1, Valeri A, Berthon P, Fournier G, Mangin P.(PubMed)
(3) Polymorphisms in estrogen related genes may modify the protective effect of isoflavones against prostate cancer risk in Japanese men by Sonoda T1, Suzuki H, Mori M, Tsukamoto T, Yokomizo A, Naito S, Fujimoto K, Hirao Y, Miyanaga N, Akaza H.(PubMed)
(4) Plasma isoflavones and subsequent risk of prostate cancer in a nested case-control study: the Japan Public Health Center by Kurahashi N1, Iwasaki M, Inoue M, Sasazuki S, Tsugane S.(PubMed)
(5) Soy product and isoflavone consumption in relation to prostate cancer in Japanese men by Kurahashi N1, Iwasaki M, Sasazuki S, Otani T, Inoue M, Tsugane S; Japan Public Health Center-Based Prospective Study Group.(PubMed)
(6) An overview of the health effects of isoflavones with an emphasis on prostate cancer risk and prostate-specific antigen levels by Messina M1, Kucuk O, Lampe JW.(PubMed)
(7) Prostate cancer in native Japanese and Japanese-American men: effects of dietary differences on prostatic tissue by Marks LS1, Kojima M, Demarzo A, Heber D, Bostwick DG, Qian J, Dorey FJ, Veltri RW, Mohler JL, Partin AW.(PubMed)
(8) A case-control study of diet and prostate cancer in Japan: possible protective effect of traditional Japanese diet by Sonoda T1, Nagata Y, Mori M, Miyanaga N, Takashima N, Okumura K, Goto K, Naito S, Fujimoto K, Hirao Y, Takahashi A, Tsukamoto T, Fujioka T, Akaza H.(PubMed)
(9) Nagata Y1, Sonoda T, Mori M, Miyanaga N, Okumura K, Goto K, Naito S, Fujimoto K, Hirao Y, Takahashi A, Tsukamoto T, Akaza H.(PubMed)
(10) Vegetables, fruits, legumes and prostate cancer: a multiethnic case-control study by Kolonel LN1, Hankin JH, Whittemore AS, Wu AH, Gallagher RP, Wilkens LR, John EM, Howe GR, Dreon DM, West DW, Paffenbarger RS Jr.(PubMed)
(11) Plasma concentrations of phyto-oestrogens in Japanese men by Adlercreutz H1, Markkanen H, Watanabe S.(PubMed)
(18) Phytoestrogens and breast cancer--promoters or protectors? by Rice S1, Whitehead SA.(PubMed)
A3. Soy and Prostate cancer in Japanese Men
Prostate cancer is defined as a condition in which the cells of prostate has become cancerous, causing abnormal cell growth with possibility of spreading to the distant parts of the body. Most prostate cancers are slow growing and enlarged prostate and prostate cancer may be detected during physical (rectum) exams.
The widespread of prostate cancer, once considered a disease of aging male, now have become major concerns of governments and scientific community in South East Asian with tendency to effect even younger age population. Suggestions emerged of over consuming bad fats in any time in history accompanied with unhealthy diet and life style may be the possible causes of the disease, linking to the economic prosperity over 2 decades.
In fact, the incidence of prostate cancer is still lower if compared to their Western counterparts.
The study of the Research Center for Cancer Prevention and Screening, National Cancer Center. suggested that isoflavones and soy food are associated with a dose-dependent decrease in the risk of localized cancer, in a population-based prospective study in 43,509 Japanese men ages 45 to 74 years with participants responded to a validated questionnaire, which included 147 food items. During follow-up from 1995 through 2004, 307 men were newly diagnosed with prostate cancer, of which 74 cases were advanced, 220 cases were organ localized, and 13 cases were of an undetermined stage(5).
Environment, Diet, intestinal microbiota and Geography
The testing of North American Japanese and Japanese in Japan showed the environment factor may be involved in the development of prostate cancer regardless to genetic similar(7). The incidence of the disease increased vary both from country to country and according to the ethnic group, with the highest incidence reported for Afro-Americans and the lowest for Asian men(2).
The study of the associations between nutritional and other lifestyle factors and the prevalence of prostate cancer in a case-control study of Japanese men, showed that soy isoflavone significantly decreased the risk of prostate cancer regardless to the intake of other nutrients such as PUFA, (n-6) fatty acids or magnesium from other food sources(9).
Other suggested that legumes (not limited to soy products) and certain categories of vegetables may protect against prostate cancer(10).
DR. Akaza H. said "not having equol converting bacteria in the intestine (non-equol producers) can be a risk factor for prostate cancer and that one direction for future research will be to examine the possibility of improving the intestinal environment to enable equol production"(13).
Genes differentiation
1n gene differentiation, estrogen related genes may be the culprits for the development of prostate cancer. In an one hundred and eighty cases and 177 controls selected from three geographic areas of Japan study, though analysis by the multifactor dimensionality reduction method, soy isoflavones, showed to exhibit its anti prostate cancer, depending to differ between the genotypes of estrogen related genes(3).
According to Dr. Kimura T., the incidence of prostate cancer in Asia is much lower than that in African Americans and European Caucasians and soy food consumption, more popular in Asian populations, is associated with a 25% to 30% reduced risk of prostate cancer, it may be as a result of genetic mutation of approximately 30 genetic polymorphisms in populations of countries in the West.(1).
Serum of isoflavones
In a case-control study within the Japan Public Health Center-based Prospective of a total of 14,203 men aged 40 to 69 years who had returned the baseline questionnaire and provided blood samples observed from 1990 to 2005, showed that plazma genistein level is associated inversely to the risk of prostate cancer(4).
Other in the study of four isoflavonoids in plasma of 14 Japanese and 14 Finnish men, also showed that the mean plasma of total individual isoflavonoid levels of Japnaese are 7 to 110 times higher Japanese than in the Finnish men. Genistein, a tyrosine kinase inhibitor, occurred in the highest concentration(11).
In the experiment of Urinary excretion of lignans and isoflavonoid phytoestrogens in Japanese men and women consuming a traditional Japanese diet showed that the excretion of isoflavonoids correlated with soybean-product intake is associated to reduced mortality in breast and prostate cancer of Japanese women and men(12).
In view of above, the Loma Linda University, insisted that soy isoflavones should be tested against different populations of prostate cancer patients for its efficacy(6). Other suggested that the lower incidence of prostate cancer in Japanese men may be a result of traditional Japanese diet with a lot of soy foods and fishes(8). Together with Soy-derived food products and the metabolization of the isoflavones they contain by intestinal microbiota among Asian and European/North American populations(13).
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References
(1) East meets West: ethnic differences in prostate cancer epidemiology between East Asians and Caucasians by Kimura T.(PubMed)
(2) Hereditary prostate cancer and other genetic predispositions to prostate cancer by Cussenot O1, Valeri A, Berthon P, Fournier G, Mangin P.(PubMed)
(3) Polymorphisms in estrogen related genes may modify the protective effect of isoflavones against prostate cancer risk in Japanese men by Sonoda T1, Suzuki H, Mori M, Tsukamoto T, Yokomizo A, Naito S, Fujimoto K, Hirao Y, Miyanaga N, Akaza H.(PubMed)
(4) Plasma isoflavones and subsequent risk of prostate cancer in a nested case-control study: the Japan Public Health Center by Kurahashi N1, Iwasaki M, Inoue M, Sasazuki S, Tsugane S.(PubMed)
(5) Soy product and isoflavone consumption in relation to prostate cancer in Japanese men by Kurahashi N1, Iwasaki M, Sasazuki S, Otani T, Inoue M, Tsugane S; Japan Public Health Center-Based Prospective Study Group.(PubMed)
(6) An overview of the health effects of isoflavones with an emphasis on prostate cancer risk and prostate-specific antigen levels by Messina M1, Kucuk O, Lampe JW.(PubMed)
(7) Prostate cancer in native Japanese and Japanese-American men: effects of dietary differences on prostatic tissue by Marks LS1, Kojima M, Demarzo A, Heber D, Bostwick DG, Qian J, Dorey FJ, Veltri RW, Mohler JL, Partin AW.(PubMed)
(8) A case-control study of diet and prostate cancer in Japan: possible protective effect of traditional Japanese diet by Sonoda T1, Nagata Y, Mori M, Miyanaga N, Takashima N, Okumura K, Goto K, Naito S, Fujimoto K, Hirao Y, Takahashi A, Tsukamoto T, Fujioka T, Akaza H.(PubMed)
(9) Nagata Y1, Sonoda T, Mori M, Miyanaga N, Okumura K, Goto K, Naito S, Fujimoto K, Hirao Y, Takahashi A, Tsukamoto T, Akaza H.(PubMed)
(10) Vegetables, fruits, legumes and prostate cancer: a multiethnic case-control study by Kolonel LN1, Hankin JH, Whittemore AS, Wu AH, Gallagher RP, Wilkens LR, John EM, Howe GR, Dreon DM, West DW, Paffenbarger RS Jr.(PubMed)
(11) Plasma concentrations of phyto-oestrogens in Japanese men by Adlercreutz H1, Markkanen H, Watanabe S.(PubMed)
(13) Prostate cancer chemoprevention by soy isoflavones: role of intestinal bacteria as the "second human genome" by Akaza H.(PubMed)
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