By Kyle J. Norton
Soy foods, including tofu have been in traditional Chinese diet over thousands of year, according to Chinese literature. The reduced risk of chronic disease, including metabolic syndrome such as cardiovascular diseases, obesity and diabetes and lesser menopause symptoms in advanced age, may be aided by eating a lot of soy food accompanied with large portion of vegetables and fruits. Indeed, according to the study, only 10% of women in the East are experience symptoms of menopause in advanced age compared to over 70% of their Western counterparts.
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 could 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 were 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 the genus Glycine, belonging to 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.
2. Dietary fiber
5. Essential amino acid
6. Vitamin A
7. Vitamin B6
8. Vitamin B12
9. Vitamin C
10. Vitamin K
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(1c). 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).
A5. Soy and menopause symptom in Japan
Menopause is defined as a condition in which women have not had a menstrual period in a minimum of 12 months period as a result of the inactive ovaries, assuming the women are not pregnant and experience the ease of visible symptoms of menopause such as hot flashes and night sweats but not the invisible effects of menopause. During post menopause, any bleeding or spotting should be reported to your doctor immediately, it may be caused by tumors rarely but it is possible. Symptoms may include Bleeding or spotting, Vagina itching and dryness, Hot flash, Bone pain and fracture, Bladder infection, Skin wrinkle, Hypertension, Bone density loss, etc.
Eppidemiological studies, linking soy effect on menopause symptoms have been inconclusive(1)(2)(3)(4). In japanese women, phytochemicals in soy found effectively in reduced vasomotor symptoms of menopause. In a supplement containing equol on the menopausal symptoms of Japanese, researchers at the Tokyo Medical and Dental University, showed that The equol-ingesting grou, noy only significantly reduced severity and frequency of hot flashes as, the severity of neck or shoulder but also exhibit trends of improvement in sweating and irritability and a significant improvement in the somatic category symptoms(5). Administration of 10-mg natural S-(-)equol supplement consumed daily for 12 weeks also indicated an reduction of hot flushes and neck or shoulder muscle stiffness, in postmenopausal Japanese women(6). And fermented soy products hhave been also showed to alleviate the severity of hot flushes(14).
Some researchers suggested that the effectiveness of soy isoflavone in relieved symptoms of menopause may link to equol-producing status. In a 1-year double-blind, randomized trial in comparison of the effects of isoflavone (75 mg of isoflavone conjugates/day) with those of placebo on bone mineral density, fat mass, and serum isoflavone concentrations in early postmenopausal equol-producer phenotype.Japanese women, found that isoflavones exhibited the preventive effects of isoflavones on bone loss and fat accumulation in early postmenopausal women depend on an individual’s equol-producing capacity(7) and S-equol supplement improved mood-related symptoms in perimenopausal/postmenopausal even in equol nonproducers in Japan women, in total of 127 participants completed the trial(8).
Soy isoflavone extracts on testing on lumbar spine or hip BMD in menopausal women of controlled trials published in English, Japanese, or Chinese, showed a result of varying effects of isoflavones on spine BMD across trials associated with study characteristics of intervention duration (6 vs. 12 months), region of participant (Asian vs. Western), and basal BMD (normal bone mass vs. osteopenia or osteoporosis)(9). In ciompared the symptom of hot flash and chilliness in menopause women, Dr. Melby MK. suggested that Japanese women are experience important vasomotor symptom than hot flushes and sweats, it may be result of dietary high in soy(10).
In Osteoporosis, menaquinone-7, the major chemical compound found Japanese fermented soybeans, showed to prevent postmenopausal bone loss(11) and promotion of bone formation(13)(15) as well eleviating early postmenopausal women, such as in palpitation and backaches(15). Other study also suggested that intake of supplementation of isoflavones (ISO) regulary associated to risk reduction of osteoporosis in middle-aged Japanese menopausal Japanese women(12).
In fact, according to the study of cross-sectional relationships of dietary and other lifestyle variables to menopause by the Gifu University School of Medicine, such as smoking, calcium and soy product intakes, intakes of fat, cholesterol, and coffee were significantly associated with the onset menopause in Japanese women(16).
Taken altogether, High soy food intakes are associated to reduce symptoms of menopause in Japanese women, chilliness. In take of supplement containing equol are effective in symptom reduction even in non equol producers in these population as well. According to the Royal Hospital for Women, highest soy consumption in Japan lowered the rates of diseases, such as breast, endometrial, colon and prostatic cancers atherosclerotic, etc. but induced extremely high urinary levels of phytoestrogen metabolites may be a result of isoflavones in exhibited bioactivity when intake of high concentrations.(17)
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(a) The Science of Soy: What Do We Really Know? by Julia R. Barrett
(b) Guideline for healthy soy intake(the Unite Soybean board)
(1c) 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)
(1) S-equol and the fermented soy product SE5-OH containing S-equol similarly decrease ovariectomy-induced increase in rat tail skin temperature in an animal model of hot flushes by Yoneda T1, Ueno T, Uchiyama S.(PubMed)
(2) A pilot study on the effects of S-equol compared to soy isoflavones on menopausal hot flash frequency by Jenks BH1, Iwashita S, Nakagawa Y, Ragland K, Lee J, Carson WH, Ueno T, Uchiyama S.(PubMed)
(3) Extracted or synthesized soybean isoflavones reduce menopausal hot flash frequency and severity: systematic review and meta-analysis of randomized controlled trials by Taku K1, Melby MK, Kronenberg F, Kurzer MS, Messina M.(PubMed)
(4) Treatment of vasomotor symptoms of menopause with black cohosh, multibotanicals, soy, hormone therapy, or placebo: a randomized trial by Newton KM1, Reed SD, LaCroix AZ, Grothaus LC, Ehrlich K, Guiltinan J.(PubMed)
(5) Equol improves menopausal symptoms in Japanese women by Aso T.(PubMed)
(6) A natural S-equol supplement alleviates hot flushes and other menopausal symptoms in equol nonproducing postmenopausal Japanese women by Aso T1, Uchiyama S, Matsumura Y, Taguchi M, Nozaki M, Takamatsu K, Ishizuka B, Kubota T, Mizunuma H, Ohta H.(PubMed)
(7) Possible role of equol status in the effects of isoflavone on bone and fat mass in postmenopausal Japanese women: a double-blind, randomized, controlled trial by Wu J1, Oka J, Ezaki J, Ohtomo T, Ueno T, Uchiyama S, Toda T, Uehara M, Ishimi Y.(PubMed)
(8) New equol supplement for relieving menopausal symptoms: randomized, placebo-controlled trial of Japanese women by Ishiwata N1, Melby MK, Mizuno S, Watanabe S.(PubMed)
(9) Effect of soy isoflavone extract supplements on bone mineral density in menopausal women: meta-analysis of randomized controlled trials by Taku K1, Melby MK, Takebayashi J, Mizuno S, Ishimi Y, Omori T, Watanabe S.(PubMed)
(10) Chilliness: a vasomotor symptom in Japan by Melby MK.(PubMed)
(11) Intake of fermented soybeans, natto, is associated with reduced bone loss in postmenopausal women: Japanese Population-Based Osteoporosis (JPOS) Study by Ikeda Y1, Iki M, Morita A, Kajita E, Kagamimori S, Kagawa Y, Yoneshima H.(PubMed)
(12) Soy isoflavone tablets reduce osteoporosis risk factors and obesity in middle-aged Japanese women by Mori M1, Aizawa T, Tokoro M, Miki T, Yamori Y.(PubMed)
(13) Promotion of bone formation by fermented soybean (Natto) intake in premenopausal women by Katsuyama H1, Ideguchi S, Fukunaga M, Fukunaga T, Saijoh K, Sunami S.(PubMed)
(14) Hot flushes and other menopausal symptoms in relation to soy product intake in Japanese women by Nagata C1, Shimizu H, Takami R, Hayashi M, Takeda N, Yasuda K.(PubMed)
(15) Soy intake related to menopausal symptoms, serum lipids, and bone mineral density in postmenopausal Japanese women by Somekawa Y1, Chiguchi M, Ishibashi T, Aso T.(PubMed)
(16) Association of diet and other lifestyle with onset of menopause in Japanese women by Nagata C1, Takatsuka N, Inaba S, Kawakami N, Shimizu H.(PubMed)
(17) Phytoestrogens and the menopause by Mackey R1, Eden J.(PubMed)