Ann M. Coulston and Carol J. Boushey
See book keywords and concepts |  Results of in vitro animal studies indicate that equol has a higher estrogenic effect than its precursor, daidzein [56]. Hence, equol has garnered much attention for its potential in the prevention and/or treatment of chronic diseases or conditions associated with estrogen levels (e.g., breast cancer, osteoporosis, and menopause) [57].
In humans, the conversion of soy isoflavones (genistein and daidzein) to the more potent metabolite (equol) appears to be dependent on intestinal microflora. Evidence for this conversion comes from animal and clinical studies. |
Thomson Healthcare, Inc.
See book keywords and concepts |  Of note is that a later analysis of the data indicated that participants who were equol-positive had significant improvements in plasma lipids; equol is a metabolite of daidzein produced by digestion of bacteria in the gut, and the ability to produce it may be linked to certain health benefits. More research on the potential role of equol in lowering lipid levels are merited (Meyer, 2004).
Soy isoflavones decreased lipid levels in a randomized, double-blind, placebo-controlled study of 80 healthy women aged 45 to 55 years. Subjects received isoflavones 100 mg (including genistein 69. |
Bill Sardi
See book keywords and concepts |  Among the soy plant estrogens (genistein, daidzen and equol) and the lignans from fiber-rich foods like rye and flax (enterodiol, enterolactone and matairesinol), only equol from soy and enterolactone from flax were associated with substantial risk reduction for breast cancer. [Lancet 350: 990-94, 1997]
BLACK COHOSH
Black cohosh is an herb widely used in Europe and marketed in the United Staes under the brand name Remifemin. |
Ann M. Coulston and Carol J. Boushey
See book keywords and concepts | | It is unclear which bacterial strain is involved in equol production [61, 62] and whether the ability to convert daidzein to equol can be induced in nonproducers [63].
V. METHODOLOGY FOR STUDYING INTESTINAL MICROFLORA
A. Conventional Methodology and Its Limitations
Our present knowledge of intestinal microflora is largely based on classical approaches of cultivation, direct microscopic observation, and biochemical analysis [64]. Results obtained using these conventional methodologies have improved our understanding of the intestinal microflora. | | In vitro incubation of human feces with daidzein and antibiotics suggests interindividual differences in the bacteria responsible for equol production. J. Nutr. 134, 596-599.
62. Atkinson, C, Frankenfeld, C. L., and Lampe, J. W. (2005). Gut bacterial metabolism of the soy isoflavone daidzein: Exploring the relevance to human health. Exp. Biol. Med. 230, 155-170.
63. Vedrine, N., Mathey, J., Morand, C, Brandolini, M., Davicco, M.-J., Guy, L., Remesy, C, Coxam, V., Manach, C. (2006). One-month exposure to soy isoflavones did not induce the ability to produce equol in postmenopausal women. |
Bill Sardi
See book keywords and concepts | | Among the soy plant estrogens (genistein, daidzen and equol) and the lignans from fiber-rich foods like rye and flax (enterodiol, enterolactone and matairesinol), only equol from soy and enterolactone from flax were associated with substantial risk reduction for breast cancer. [Lancet 350: 990-94, 1997]
BLACK COHOSH
Black cohosh is an herb widely used in Europe and marketed in the United Staes under the brand name Remifemin. |
Tori Hudson, N.D.
See book keywords and concepts |  A recent study demonstrated that plasma levels of equol and enterodiol, two isoflavonoids, were positively associated with a lower cervical dysplasia risk, and in addition found a nonsignificant positive association with enterolactone, a lignan. Consistent with these results, dietary sources of lignans, including garlic, onions, grapefruit, seeds, seaweed, and taro, were positively associated with lowered CIN risk.22
Indole-3-carbinol, found in cruciferous vegetables such as broccoli, cabbage, brussels sprouts, cauliflower, and kale, has the potential to prevent and treat several cancers. | | These compounds are similar in their chemical structure to estradiol, and to equol, a phytoestrogen metabolite, but they are not actually estrogens. Phytoestrogens are categorized into three main classes: isoflavones, lignans, and coumes-tans. Isoflavones contribute significantly to our dietary phytoestrogen intake. Isoflavones are found in legumes and are highest in soybeans. These isoflavones are associated with the protein part of the soybeans and are not found in soy oils or soy lecithin.
One potential dietary influence for a cholesterol-lowering strategy is to consume more soy protein. |
Ann M. Coulston and Carol J. Boushey
See book keywords and concepts | | One-month exposure to soy isoflavones did not induce the ability to produce equol in postmenopausal women. European J. Clin. Nutr. 60, 1039-1045.
64. O'Sullivan, D. (2000). Methods for analysis of the intestinal microflora. Curr. Issues Intest. Microbiol. 1, 39-50.
65. Franks, A. H., Harmsen, H. J. M., Raangs, G. C, Jansen, G. J., Schut, F., and Welling, G. W. (1998). Variations of bacterial populations in human feces measured by fluorescent in situ hybridization with group-specific 16S rRNA-targeted oligonucleotide probes. Appl. Environ. Microbiol. 64, 3336-3345.
66. Wilson, K. |
Thomson Healthcare, Inc.
See book keywords and concepts | | More research on the potential role of equol in lowering lipid levels are merited (Meyer, 2004).
Soy isoflavones decreased lipid levels in a randomized, double-blind, placebo-controlled study of 80 healthy women aged 45 to 55 years. Subjects received isoflavones 100 mg (including genistein 69.9 mg, daidzein 18.6 mg, and glycitein 11.4 mg) (n=40) or placebo (n=40) daily for 5 months. Total cholesterol (TC) and LDL cholesterol decreased significantly in the isoflavone group (TC=199; LDL=120) compared to placebo (TC=227; LDL=139) and baseline (TC=226; LDL=134) (p<0.001). |
Simon Mills and Kerry Bone
See book keywords and concepts |  However, equol appears to be produced to different degrees in different people. Table 2.5 illustrates that individuals can be grouped into high and low equol producers. The high equol producers are likely to experience significantly greater oestrogenic effects from the consumption of soya or red clover.
Figure 2.10 Major isoflavones and equol
Table 2. |
Bottom Line Health
See book keywords and concepts | | The phytoestrogens in soy are metabolized in the body into equol, an estrogen-like compound. Soy seems to be most effective for women who experience five or more hot flashes a day—it can reduce hot-flash frequency by up to 40%. Some menopausal women who eat soy also notice an improvement in vaginal dryness.
•Diabetic renal disease. One of the most serious complications of diabetes is kidney disease, which can lead to kidney failure. Substituting soy for animal protein lowers the glomerular filtration rate, a measure of kidney stress, and may slow kidney damage. |
Bill Sardi
See book keywords and concepts | | Soy isoflavones (genistein, daidzen, equol); provides phytoestrogens with small amounts of iron-binding phytic acid and omega-3 oil.
Glycine max; many trade names - Soylife
Soy phytoestrogens alone, under certain circumstances, may promote growth of tumors. was determined that lignans are mild inhibitors of estrogen production by virtue of their ability to inhibit aromatase, the enzyme responsible for estrogen production. | | Prostate 59: 141-47, 2004]
Soy fractions (genistein) and prostate cancer
Men, in their own study of soy and prostate cancer, may run across studies that show fractions of soy, such as genistein, equol and daidzein, may be potentially troublesome. For example, genistein has been shown to cause genetic damage to human cells in a lab dish, but not in humans. [American Journal Clinical Nutrition 77: 875-82, 2003]
To the contrary, genistein may be very beneficial for prostate cancer patients. | | SOY PHYTOESTROGENS
Phytoestrogens from soy (genistein, equol, daidzein) are widely promoted as cancer fighters. Much more can be said about soy than in this short report. Suffice to say that there is a royal battle going on in scientific circles over the use of soy to combat symptoms of menopause and prevent breast cancer.
There is also cause for concern. Soy phytoestrogens may stimulate growth of breast cancer cells under certain circumstances. [Journal Nutrition 133: 1983-86S, 2003] But is this concern pose a real threat? |
Elaine Magee
See book keywords and concepts |  In lab experiments using LDL isolated from adult blood samples, they found that increasing amounts of three phytoestrogens (genis-tein, daidzein, and equol) inhibited LDL oxidation; this protective effect was even more powerful when ascorbic acid (vitamin C) was present, too. Genis-tein and daidzein are the isoflavones found in soy and soy products. Pairing soy with citrus sounds like a partnership that can't miss. |
Ann M. Coulston and Carol J. Boushey
See book keywords and concepts | | Premenopausal equol excretors show plasma hormone profiles associated with lowered risk of breast cancer. Cancer Epidemiol. Biomarkers Prev. 9, 581-586.
58. Setchell, K. D. R., and Cassidy, A. (1999). Dietary isoflavones: Biological effects and relevance to human health. /. Nutr. 129, 758S-767S.
59. Cassidy, A., Brown, J. E., Hawdon, A., Faughnan, M. S., King, L. J., Millward, J., Zimmer-Nechemias, L., Wolfe, B., and Setchell, K. D. R. (2006). Factors affecting the bioavailability of soy isoflavones in humans after ingestion of physiologically relevant levels from different soy foods. J. |
Michael Friedman, ND
See book keywords and concepts |  Isoflavones, such as genistein and equol, are inhibitors of thyroid peroxidase, the thyroid follicle enzyme that makes T4 and T3. This inhibition may generate goiters, hypothyroidism, and autoimmune thyroiditis. Since isoflavones are being touted as cancer preventatives, especially for breast and prostate cancers, their addition to non-soya foods may create further thyroid challenges. Isoflavones already available in soya foods may depress thyroid function through TPO inhibition.
Another challenge to thyroid function is the situation with rT3 (reverse T3). |
Kaayla T. Daniel, PhD, CCN
See book keywords and concepts |  Sheep can efficiently convert formononetin to equol, the highly estrogenic metabolite that also comes from the soy isoflavone daidzein. In female sheep, eating clover causes endometrial damage and cervical mucus changes associated with an inability to conceive. The problems are not unique to sheep; fertility problems from phytoestrogen exposure have also been reported in birds, cows, mice, cats and dogs as well as in humans.214 Scientists have identified estrogenic activity in more than 300 plants,15 but only one of these plants commonly appears in the food supply—soy. |
Simon Mills and Kerry Bone
See book keywords and concepts | | Individuals are grouped as either low equol producers (less than 8 umo/ in 3 days) or high equol producers (over 25 umo/ in 3 days) Note: equol is substantially more oestrogenic than daidzein or O-Dma
Other studies have found the following.
• Soya isoflavones are 85% degraded in the intestine.329
• Differences in faecal flora account for the differing metabolism of soya isoflavones.330
• Faecal flora could completely degrade genistein and daidzein. |
John Boik
See book keywords and concepts |  One phytoestrogen, equol, has a low affinity for estrogen receptors, but is produced in high quantity from diets rich in soy foods (Setchell et al., 1984). equol has a biologic estrogen activity approximately 0.2% that of estradiol. However, by sheer numbers, equol may compete with estrogen receptors, and thus lower the bioavailability of circulating estrogen. Soy products appear to have an estrogenic effect on postmenopausal women, and an antiestrogenic effect on premenopausal women who have relatively high estrogen levels (Messina and Barnes, 1991). |
Simon Mills and Kerry Bone
See book keywords and concepts | | Individuals are grouped as either low equol producers (less than 8 umo/ in 3 days) or high equol producers (over 25 umo/ in 3 days) Note: equol is substantially more oestrogenic than daidzein or O-Dma
Other studies have found the following.
• Soya isoflavones are 85% degraded in the intestine.329
• Differences in faecal flora account for the differing metabolism of soya isoflavones.330
• Faecal flora could completely degrade genistein and daidzein. |
Kaayla T. Daniel, PhD, CCN
See book keywords and concepts | | Whether in early life the bacterial enzymes which in adults are responsible for the conversion of daidzein-glycoside in soya to equol are present, remains to be established. If so the infant may be subjected to concentrations of this weak estrogen which are well in excess of endogenous estrogen levels and if not it is probable that the precursor daidzein, itself a weak estrogen may be absorbed and excreted in the urine as the glucuronide conjugate, as shown in adults. | | The 'contraceptive' effect in animals suggests to us that it may be of interest to investigate the dietary habits and urinary excretion of equol in women with unexplained infertility or disorders of the menstrual cycle."19
Similarly, Setchell once proposed that women with menstrual cycle disorders and fertility problems consider their consumption of soy "in view of the various reproductive disorders in animals that have been associated with the ingestion of a variety of phytoestrogens."20
The soy industry has not publicized these recommendations. | | Interestingly, some people are equol producers while others are not. It seems that different people excrete different phytoestrogen metabolites even when the quality and quantity of soy food eaten is tightly controlled. Retests tend to be consistent in individuals. Populations of gut flora are highly individual and seem to play key roles in the metabolism and bioavailability of isoflavones. Antibiotics, dysbiosis or bowel disease also modify isoflavone metabolism. | | The importance of the microflora in the metabolic handling of isoflavones is well illustrated from observations that antibiotic administration blocks metabolism, germfree animals do not excrete the metabolites, and infants fed soy infant formulas in the first four months of life cannot form appreciable amounts of equol."12
This last is cited as evidence of soy formula's safety for infants although Setchell's own work has shown that infants can and will absorb other forms of isoflavones. | | Furthermore, green tea drinking might be needed to improve the capacity for equol production.73
Soy proponents rarely tell men that the reason why soy might protect them against prostate cancer is because it has a feminizing effect. Levels of soy that might be useful in prostate cancer prevention or treatment will significantly decrease testosterone and androgen and increase estrogen.74 77 Doctors believe that prostate cancer depends on exposure to male reproductive hormones and thus recommend soy because its estrogens perturb natural hormone concentrations and ratios. |
Laurie Deutsch Mozian, M.S., R.D.
See book keywords and concepts |  Genis-tein and daidzein, the major isoflavones found largely in legumes and soy products, lead to the production of equol in people and some animals. equol is a weak estrogen possessing about 0.2 percent of the biological activity of estradiol, one of the major estrogens found in the body. Depending upon a person's own estrogen production and the tissue in question, the weak estrogenic effects of isoflavones can either hinder or enhance the action of natural estrogens in the body. |
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