Isoflavones dietary intake

The mean dietary intake of soy isoflavones in Asian populations consuming soy-based diets ranges from 20-40 mg isoflavones/day, with upper percentile consumer intakes of 70 mg/day (corresponding to around 1 mg/kg body weight). In the six month intervention studies in Western postmenopausal women, the effective dose for improved BMD was around 80-90 mg/day, while in the one year, randomized, double-blind, placebo controlled clinical trial, the effective dose was 54 mg/day. Overall, the dietary recommendation is to consume 50 mg isoflavones/day in combination with standard nutritional requirements for calcium and vitamin D. 

Y (1999) Dietary intake and sources of isoflavones among Japanese. iVnlr Cancer. 33 (2) 139 5. 

Aral, Y. et al.. Dietary intakes of flavonols, flavones and isoflavones by Japanese women and the inverse correlation between quercetin intake and plasma LDL cholesterol concentration, J. Nutr., 130, 2243, 2000. 

Setchell KDR, Brown NM, Deal PB et al. Bioavailability, disposition and dose-response effects of soy isoflavones when consumed by healthy women at physiologically typical dietary intakes. J. Nutr. 133, 1027-1035,2003. 

Sagara M, Kanda T, Njelekera M et al. Effects of dietary intake of soy protein and isoflavones on cardiovascular disease risk factors in high risk, middle-aged men in Scotland. J. Am. Coll Nutr. 23, 85-91, 2004. 

Arai Y, Uehara M, Sato Y, Kimira M, Eboshida A, Adlercreutz H, Watanabe S. 2000. Comparison of isoflavones among dietary intake, plasma concentration and urinary excretion for accurate estimation of phytoestrogen intake. J Epidemiol 10 127-135. 

Isoflavonoids also have been reported to have physiological activity in animal and human studies. Besides acting as an estro n mimic, it was reported that the isoflavones found in soybean seeds possess antihemolytic, antifungal, tumorsuppressing, and serum cholesterol-lowering effects. In addition, both epidemiological and dietary-intervention studies indicate that when isoflavones in soybean seeds and in subsequent protein products prepared from the seeds are part of the human dietary intake, those products provide many significant health benefits. - ... 

Wakai, K., Egami, I., Kato, K., Kawamura, T., Tamakoshi, A., Lin, Y., Nakayama, T., Wada, M., and Ohno, Y. 1999. Dietary intake and sources of isoflavones among Japanese. Nutr Cancer... 

Significant relationships (P <. 02) between both urinary and serum concentrations of isoflavones and dietary intakes spot urine correlated strongly with that in serum... 

Japanese women and women of Japanese origin living in Hawaii but who consume a diet similar to the traditional Japanese diet (rich in soy products) have a low breast cancer incidence and mortality. Women in the Far East who have low rates of breast cancer are thought to consume approximately 30-50 times more soy products than women in the United States. A case-control study in Singapore found that premenopausal women who consumed 55 g of soy per day had a 50% reduced risk of breast cancer compared to women who infrequently consumed soy foods. A high intake of miso soup has been associated with a reduced risk of breast cancer in Japanese women. In prospective trials, a trend toward an inverse association between intake of tofu and subsequent risk of breast cancer and an inverse association between intake of miso soup and development of breast cancer have been found. However, a large prospective study in Japan did not show any effect of soy consumption on breast cancer risk, although this may be because dietary intake was studied in adult women rather than in children or adolescents. A number of studies in rodents have indicated that a protective effect of a soy isoflavone-rich diet may... 

It has been shown that in postmenopausal women habitually high intakes of dietary isoflavones are associated with higher bone mineral density (BMD) values at both the spine and hip region (Mei et al, 2001). It is conceivable that an isoflavone-rich diet may help to reverse the state of secondary hyperparathyroidism associated with estrogen withdrawal and hence lower the rate of bone turnover in postmenopausal women, thus reducing the risk of osteoporosis (Valtuena et al, 2003). Phytoestrogens could be used as natural SERMs (Brzezinski and Debi, 1999) and some studies (Setchell, 2001 and refs therein) support such an idea since the molecular targets of... 

YAMAMOTO S, SOBUE T, SASAKI S, KOBAYASHI M, ARAI Y, UEHARA M, ADLERCREUTZ H, WATANABE S, TAKAHASHi T, iiTOi Y, IWASE Y, AKABANE M and TSUGANE s (2001) Vahdity and reproducibihty of a self-administered food-frequency questionnaire to assess isoflavone intake in a Japanese population in comparison with dietary records and blood and urine isoflavones. JNutr. 131 (10) 2741-7. 

---