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Biomedical subjects

K E Anderson

Publications and source records attributed to K E Anderson.

At least 73 records · Page 4Linked to original sources
PubMed2000

Physical activity and incidence of postmenopausal breast cancer.

Whether physical activity reduces the risk of postmenopausal breast cancer is uncertain; few studies have addressed this issue. We examined the association of leisure physical activity with breast cancer incidence among 37,105 postmenopausal participants in the Iowa Women's Health Study. Women reporting the highest level of physical activity at baseline compared with women with the lowest level of activity had an age-adjusted relative risk of breast cancer of 0.92 (95% confidence interval = 0.80-1.05). Women reporting any regular leisure-time physical activity had a relative risk of 0.97 (95% confidence interval = 0.87-1.08) compared with those reporting no such regular physical activity. Adjustment for potential confounders did not appreciably alter the findings. There is little evidence from this study that physical activity later in life is associated to any appreciable extent with breast cancer incidence.

Aged↗
PubMed2000

Immunolocalization of Dpfp1, a byssal protein of the zebra mussel Dreissena polymorpha.

The zebra mussel is one of only a few freshwater bivalves known to produce a byssus. This fibrous, proteinaceous and highly cross-linked structure allows the mussel to attach to a variety of substrata and contributes to its notoriety as a major freshwater biofouling species. We have successfully expressed a full-length version of Dreissena polymorpha foot protein 1 (Dpfp1), a putative byssal thread precursor, and have used the recombinant protein as an antigen for polyclonal antibody production. Antisera obtained from rabbits immunized with recombinant Dpfp1 recognize the protein in western blots of extracts from foot tissue and byssal threads. On the basis of this evidence, we conclude that Dpfp1 is a byssal precursor protein manufactured and stored in the foot of the mussel. Immunohistochemical localization of Dpfp1 suggests that the protein is localized in secretory granules in a large gland surrounding the ventral groove of the foot. Only a subset of these glandular cells stockpiles the protein, implying that the zebra mussel foot is a complex organ capable of several distinct secretory activities involved in byssal thread formation. The uniform distribution of Dpfp1-containing cells suggests that the protein is a significant load-bearing component of zebra mussel byssal threads, although a more rigorous test of this hypothesis awaits ultrastructural localization of the protein in mature byssal threads.

Amino Acid Sequence↗
PubMed2000

Urinary excretion of Bowman-Birk inhibitor in humans after soy consumption as determined by a monoclonal antibody-based immunoassay.

The Bowman-Birk inhibitor (BBI) found in soybeans is a serine protease inhibitor with anticarcinogenic activity. In the present study, an ELISA for BBI was developed with the use of a monoclonal antibody against a reduced form of BBI. This newly developed ELISA method was used to measure the urinary levels of BBI metabolites in nine human subjects after consumption of 36-oz or 60-oz soymilk (containing 105 or 175 mg of BBI) at two time points 36 h apart. The results demonstrate that urinary BBI excretion rates peaked within 6 h and decreased to baseline levels within 12-24 h after soymilk ingestion. The changes in BBI:creatinine ratios in urine closely paralleled the changes in urinary BBI excretion rates after soymilk consumption. These data suggest that BBI ingested p.o. is absorbed and could be bioavailable for cancer chemoprevention in other organs in addition to those in the gastrointestinal tract.

Adult↗
PubMed1999

Folic acid-PEO-labeled liposomes to improve gastrointestinal absorption of encapsulated agents.

The design of targeted oral liposomes is anticipated to improve the systemic delivery of poorly absorbed agents, such as proteins and peptides. A poly(ethylene oxide) (PEO)-folic acid (FA) derivative was prepared and evaluated for improving liposome transport across a model gastrointestinal cell line (Caco-2). FA-PEO-cholesterol (Chol) derivatives were synthesized and adsorbed at liposome surfaces encapsulating Texas Red((R))-Dextran 3000 (TR-dex), a poorly-absorbed, neutral, hydrophilic, large molecular weight (M(w)) marker. Apparent permeabilities (P(app)) of Caco-2 cells to FA-PEO conjugates, TR-dex, uncoated TR-dex liposomes, and FA-coated TR-dex liposomes were compared at 2 h post-administration. Intracellular delivery of TR-dex was detected by fluorescence microscopy. An increase in intracellular accumulation of TR-dex associated with FA-PEO-coated liposomes, but not other formulations, was evidence of the potential of FA-targeted liposomes in the oral delivery of poorly absorbed, large M(w) agents.

Absorption↗
PubMed1999

Does a family history of cancer increase the risk for postmenopausal endometrial carcinoma? A prospective cohort study and a nested case-control family study of older women.

BACKGROUND: As part of the hereditary nonpolyposis colon carcinoma (HNPCC) constellation of neoplasia caused by defects in mismatch repair genes, some endometrial carcinomas are known to have a genetic contribution to etiology. However, most endometrial carcinomas occur in postmenopausal women, presumably without the HNPCC defect. Consequently, the genetic contribution to these cases is unclear. The objective of this study was to determine whether family history of cancer is a risk factor for endometrial carcinoma in older women. METHODS: The authors analyzed incident endometrial carcinoma data, as well as data on family history of various cancers in first-degree relatives, from a cohort of 24,848 postmenopausal Iowa women ages 55-69 years who were cancer free at baseline in 1986. Because a positive family history is dependent on many factors, including the age of the patient, the number of relatives, and the distribution of other risk factors in relatives, the authors also conducted a nested case-control study on family members of 95 patients with endometrial carcinoma diagnosed during 1988-1989 and 91 cancer free controls who were chosen randomly from subjects matched for age (+/-1 year). RESULTS: During 10 years of follow-up of the cohort, 322 incident endometrial carcinoma cases occurred. Women who reported a positive family history of cancer overall or at any specific site (e.g., the endometrium, colon, or breast) were not at increased risk for endometrial carcinoma. Adjustment for potential confounders, such as age, obesity, parity, oral contraceptive use, and estrogen replacement therapy, did not alter these results. Analysis of the family members of the cases and controls produced little evidence to suggest that this lack of association between family history and endometrial carcinoma could be explained by unequal distribution of known risk factors among relatives. Case family members were slightly older than control family members, but no significant differences were found in body mass index (kg/m2), age at menarche, age at menopause, or number of pregnancies. Relation to a case or control was not associated with increased risk of endometrial, ovarian, breast, or colon carcinoma for family members. Controlling for a variety of potential confounders did not alter the results. CONCLUSIONS: No evidence was found that genetics contribute to the risk of postmenopausal endometrial carcinoma for women with no personal cancer history.

Aged↗
PubMed1999

Intake of fluids and methylxanthine-containing beverages: association with colon cancer.

Although diet and its constituents have been studied extensively as risk factors for colon cancer, much less is known about how specific types of fluid influence colon cancer risk. In this study, we explored associations between colon cancer and total fluids, water and methylxanthine-containing beverages such as coffee, tea and cola; data were obtained from 1,993 incident cases of colon cancer and 2,410 population-based controls living in California, Utah and Minnesota. Our primary objective was to determine the influence on associations of amount consumed, confounding and effect modification. We observed few important differences between colon cancer and fluid consumption for all subjects combined. Among men, low levels of coffee intake were associated with an increased risk of colon cancer relative to non-consumers of coffee (OR 1.32, 95% CI 1.02-1.67), while at high levels of consumption, an inverse association was observed (OR 0.81, 95% CI 0.58-1.12). The observed associations were only slightly influenced by consumption of water or other potential confounding factors, but changing the referent group to those consuming one cup of coffee per day or less resulted in a stronger association and a more significant inverse linear trend (OR 0.71, 95% CI 0.53-0.96). The associations with coffee and caffeine- and methylxanthine-containing beverages were strongest for proximal tumors in men. High levels of water intake, however, were protective for distal tumors (OR for men 0.68, 95% CI 0.49-0.96). Assessment of the impact of smoking on associations between colon cancer and coffee showed a significant interaction between smoking and coffee for both men and women.

Adult↗
PubMed1999

Comparison of DNA adduct levels associated with exogenous and endogenous exposures in human pancreas in relation to metabolic genotype.

Recently, we examined normal human pancreas tissue for DNA adducts derived from either exogenous chemical exposure and/or endogenous agents. In an effort to explain the different types and levels of DNA adducts formed in the context of individual susceptibility to cancer, we have focused on gene-environment interactions. Here, we report on the levels of hydrophobic aromatic amines (AAs), specifically those derived from 4-aminobiphenyl (ABP), and DNA adducts associated with oxidative stress in human pancreas. Although these adducts have been reported in several human tissues by different laboratories, a comparison of the levels of these adducts in the same tissue samples has not been performed. Using the same DNA, the genotypes were determined for N-acetyltransferase 1 (NAT1), the glutathione S-transferase (GST) M1, GSTP1, GSTT1, and NAD(P)H quinone reductase-1 (NQO1) as possible modulators of adduct levels because their gene products are involved in the detoxification of AAs, lipid peroxidation products and in redox cycling. These results indicate that ABP-DNA adducts, malondialdehyde-DNA adducts, and 8-oxo-2'-deoxyguanosine (8-oxo-dG) adducts are present at similar levels. Of the metabolic genotypes examined, the presence of ABP-DNA adducts was strongly associated with the putative slow NAT1*4/*4 genotype, suggesting a role for this pathway in ABP detoxification.

Aminobiphenyl Compounds↗
PubMed1999

Prospective study of diet and ovarian cancer.

Evidence on dietary risk factors for ovarian cancer is inconsistent, but some studies have suggested positive associations with dietary fat, lactose, and cholesterol and negative associations with green and yellow vegetable intake. By using information from the Iowa Women's Health Study, the authors investigated the association of epithelial ovarian cancer with dietary factors in a prospective study of 29,083 postmenopausal women. Dietary information was ascertained via a food frequency questionnaire mailed to participants in 1986. During 10 years of follow-up (1986-1995), 139 of the women developed incident epithelial ovarian cancer. Incidence of the disease was not associated with dietary fat intake. Lactose and cholesterol showed moderately elevated risks. Multivariable-adjusted relative risks for the lowest to highest quartiles of lactose intake were 1.00, 1.38, 1.25, and 1.60 (p for trend = 0.12). For cholesterol, the corresponding values were 1.00, 1.34, 1.86, and 1.55 (p for trend = 0.06). Consumption of eggs was also associated with an increased risk of ovarian cancer. Multivariable-adjusted relative risks for increasing frequency of egg consumption were 1.00 (<1/week), 1.12 (1/week), 2.04 (2-4/week), and 1.81 (>4/week) (p for trend = 0.04). Total vegetable intake was modestly and inversely associated with the risk of ovarian cancer (p for trend = 0.21). Green leafy vegetable intake was more strongly associated with a decreased risk: multivariable-adjusted relative risks for the lowest to highest intake levels were 1.00, 0.80, 0.87, and 0.44 (p = 0.01). These findings are generally in agreement with the results from previous, mostly case-control studies of diet and epithelial ovarian cancer.

Aged↗
PubMed1999

Co-mutagenicity of coumarin (1,2-benzopyrone) with aflatoxin B1 and human liver S9 in mammalian cells.

Coumarin (1,2-benzopyrone), a natural dietary constituent and drug currently under evaluation for treatment of certain cancers and lymphedema, reduces polycyclic aromatic hydrocarbon-induced neoplasms in rodents. Because most rodents metabolize coumarin through 3,4-epoxidation, whereas 7-hydroxylation predominates in humans, their suitability as a model for coumarin effects in humans has been questioned. We examined coumarin chemoprotection against the promutagen and dietary contaminant aflatoxin B1 with human liver S9 bioactivation in the Chinese hamster ovary cell/hypoxanthine-guanine phosphoribosyltransferase mutation assay. Coumarin in the absence of aflatoxin B1 was not mutagenic or cytotoxic up to 500 microM. When included with either 1 or 10 microM aflatoxin B1, coumarin produced a dose-dependent increase in mutant frequency and cytotoxicity. At concentrations greater than 50 microM, coumarin stimulated human liver S9 bioactivation of aflatoxin B1 to the mutagenic 8,9-epoxide. This increase was 12- and fivefold at 500 microM coumarin with 1 and 10 microM aflatoxin B1, respectively, compared with incubations with aflatoxin B1 alone. These findings differ from previous results with liver S9 from other species, and indicate that coumarin co-mutagenicity with aflatoxin B1 and human liver S9 is through increased aflatoxin B1 bioactivation.

Aflatoxin B1↗
PubMed1999

Comparison of physical quality and composition of eggs from historic strains of single comb White Leghorn chickens.

The effect of long-term genetic selection on physical quality and composition of eggs was determined by analyzing eggs acquired from Agriculture Canada: Ottawa Control Strain 5 (CS5) from a 1950 base population, 7 (CS7) from a 1958 population and 10 (CS10) from a 1972 population. Eggs from the H&N "Nick Chick" current commercial strain (CCS) were also included. Eggs were collected monthly over a 62-wk laying period and analyzed for egg, albumen, shell and yolk weight; albumen protein, solids and pH; percentage yolk solids and fat; Haugh units; and specific gravity. Significant (P < 0.05) differences found between strains included a progressive increase in weight of eggs from the CS5 to CCS. Although the eggs increased in size, no significant differences were found between strains for specific gravity or percentage shell weight. Yolk weights of eggs from the strains examined did not differ. However, the percentage of yolk found in current strain eggs was significantly lower (P < 0.05), with a subsequent higher percentage albumen due to the increase in egg size of the CCS. Haugh units were significantly higher in the CS10 and CCS strains than in the other strains. No significant differences between strains were seen in albumen protein, solids, pH, or yolk solids. Mean percentage yolk fat assay values for eggs from the CS5, CS7, CS10, and CCS strains were 33.08, 32.68, 32.84, and 32.40, respectively. Percentage yolk fat values obtained from CCS were significantly lower (P < 0.05) than those obtained from the other strains. The results from this study indicate that genetic selection has produced larger eggs containing a lower percentage of yolk while overall egg quality has been maintained or improved.

Aging↗
PubMed1999

Family history, ethnicity, and relative risk of breast cancer in a prospective cohort study of older women.

In a cohort of 27,578 postmenopausal Iowa women, we examined whether the risk with a family history of breast cancer differs by self-reported ethnicity. A total of 1042 breast cancer cases occurred over 10 years of follow-up. Using a phylogenetic tree, ethnicities were combined into five groups: Scandinavian; English, Scottish, Welsh, and Dutch (ESWD); Irish; German; and Other European. The incidence of breast cancer did not differ significantly by ethnicity, although the highest rates were observed among Scandinavian women (488 per 100,000 per year) and the lowest among Irish women (353 per 100,000 per year). The prevalence of a family history of breast cancer was not significantly associated with ethnicity when only first-degree relatives were considered (P = 0.17), but inclusion of data on second-degree relatives increased the statistical significance of the association (P = 0.003). Differences in mean levels of breast cancer risk factors between ethnicities were generally small but statistically significant. Proportional hazards regression was performed to evaluate potential interactions of family history with ethnicity on breast cancer incidence. A family history of breast cancer was associated with increased relative risks among ESWD, Germans, and Other Europeans but not among Irish and Scandinavians. Relative risk estimates were not attenuated upon addition of known breast cancer risk factors to the model, implying that the distribution of these risk factors by ethnicity is unlikely to explain some of the observed ethnic-specific differences between family history and risk of breast cancer. Results of this study could have implications for studies of common genetic polymorphisms and cancer risk.

Aged↗
PubMed1998

Well-done meat intake and the risk of breast cancer.

BACKGROUND: Heterocyclic amines, mutagens formed in meats cooked at high temperatures, have been demonstrated as mammary carcinogens in animals. We conducted a nested, case-control study among 41836 cohort members of the Iowa Women's Health Study to evaluate the potential role of heterocyclic amines and intake of well-done meat in the risk for human breast cancer. METHODS: A questionnaire was mailed to individuals in the cohort who had breast cancer diagnosed during the period from 1992 through 1994 and a random sample of cancer-free cohort members to obtain information on usual intake of meats and on meat preparation practices. Color photographs showing various doneness levels of hamburger, beefsteak, and bacon were included. Multivariate analysis was performed on data from 273 case subjects and 657 control subjects who completed the survey. RESULTS: A dose-response relationship was found between doneness levels of meat consumed and breast cancer risk. The adjusted odds ratios (ORs) for very well-done meat versus rare or medium-done meat were 1.54 (95% confidence interval [CI]=0.96-2.47) for hamburger, 2.21 (95% CI=1.30-3.77) for beef steak, and 1.64 (95% CI=0.92-2.93) for bacon. Women who consumed these three meats consistently very well done had a 4.62 times higher risk (95% CI=1.36-15.70) than that of women who consumed the meats rare or medium done. Risk of breast cancer was also elevated with increasing intake of well-done to very well-done meat. CONCLUSIONS: Consumption of well-done meats and, thus, exposures to heterocyclic amines (or other compounds) formed during high-temperature cooking may play an important role in the risk of breast cancer.

Aged↗
PubMed1998

Comparison of DNA adduct levels associated with oxidative stress in human pancreas.

DNA adducts associated with oxidative stress are believed to involve the formation of endogenous reactive species generated by oxidative damage and lipid peroxidation. Although these adducts have been reported in several human tissues by different laboratories, a comparison of the levels of these adducts in the same tissue samples has not been carried out. In this study, we isolated DNA from the pancreas of 15 smokers and 15 non-smokers, and measured the levels of 1,N6-etheno(2'-deoxy)guanosine (edA), 3, N4-etheno(2'-deoxy)cytidine (edC), 8-oxo-2'-deoxyguanosine (8-oxo-dG), and pyrimido[1,2-alpha]purin-10(3H)-one (m1G). Using the same DNA, the glutathione S-transferase (GST) M1, GSTT1, and NAD(P)H quinone reductase-1 (NQO1) genotypes were determined in order to assess the role of their gene products in modulating adduct levels through their involvement in detoxification of lipid peroxidation products and redox cycling, respectively. The highest adduct levels observed were for m1G, followed by 8-oxo-dG, edA, and edC, but there were no differences in adduct levels between smokers and non-smokers and no correlation with the age, sex or body mass index of the subject. Moreover, there was no correlation in adduct levels between edA and eC, or between edA or edC and m1G or 8-oxo-dG. However, there was a significant correlation (r=0.76; p<0.01) between the levels of 8-oxo-dG and m1G in human pancreas DNA. Neither GSTM1 nor NQO1 genotypes were associated with differences in any of the adduct levels. Although the sample set was limited, the data suggest that endogenous DNA adduct formation in human pancreas is not clearly derived from cigarette smoking or from (NQO1)-mediated redox cycling. Further, it appears that neither GSTM1 nor GSTT1 appreciably protects against endogenous adduct formation. Together with the lack of correlation between m1G and edA or edC, these data indicate that the malondialdehyde derived from lipid peroxidation may not contribute significantly to m1G adduct formation. On the other hand, the apparent correlation between m1G and 8-oxo-dG and their comparable high levels are consistent with the hypothesis that m1G is formed primarily by reaction of DNA with a base propenal, which, like 8-oxo-dG, is thought to be derived from hydroxyl radical attack on the DNA.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1998

Translocation of PDK-1 to the plasma membrane is important in allowing PDK-1 to activate protein kinase B.

BACKGROUND: Protein kinase B (PKB) is involved in the regulation of apoptosis, protein synthesis and glycogen metabolism in mammalian cells. Phosphoinositide-dependent protein kinase (PDK-1) activates PKB in a manner dependent on phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3), which is also needed for the translocation of PKB to the plasma membrane. It has been proposed that the amount of PKB activated is determined exclusively as a result of its translocation, and that a constitutively active pool of membrane-associated PDK-1 simply phosphorylates all the PKB made available. Here, we have investigated the effects of membrane localisation of PDK-1 on PKB activation. RESULTS: Ectopically expressed PDK-1 translocated to the plasma membrane in response to platelet-derived growth factor (PDGF) and translocation was sensitive to wortmannin, an inhibitor of phosphoinositide 3-kinase. Translocation of PDK-1 also occurred upon its co-expression with constitutively active phosphoinositide 3-kinase, but not with an inactive form. Overexpression of PDK-1 enhanced the ability of PDGF to activate PKB. PDK-1 disrupted in the pleckstrin homology (PH) domain which did not translocate to the membrane did not increase PKB activity in response to PDGF, whereas membrane-targeted PDK-1 activated PKB to the extent that it could not be activated further by PDGF. CONCLUSIONS: In response to PDGF, binding of Ptdlns (3,4,5)P3 and/or Ptdlns(3,4)P2 to the PH domain of PDK-1 causes its translocation to the plasma membrane where it co-localises with PKB, significantly contributing to the scale of PKB activation.

3-Phosphoinositide-Dependent Protein Kinases↗
PubMed1998

Coumarin chemoprotection against aflatoxin B1-induced gene mutation in a mammalian cell system: a species difference in mutagen activation and protection with chick embryo and rat liver S9.

Coumarin (1,2-benzopyrone), a natural food constituent, prevents polycyclic aromatic hydrocarbon-induced neoplasms in rats and mice, but has not been studied with other chemical carcinogens. We examined coumarin chemoprotection against aflatoxin B1 using the 6-thioguanine resistance mutation assay in two different Chinese hamster ovary cell lines (K1BH4 and AS52) with liver S9 from rats and 19-day-old chick embryos for aflatoxin B1 bioactivation. Laboratory rodents metabolize coumarin through 3-hydroxylation, whereas 7-hydroxylation predominates in chick embryos and humans. Chick embryo liver S9 was approximately 25-fold more effective in activating aflatoxin B1 to the mutagenic and cytotoxic metabolite(s) than rat liver S9. Coumarin added at 50 and 500 microM with chick embryo liver S9 reduced the mutant frequency of 1 microM aflatoxin B1 by 40 and 85%, respectively. Coumarin up to 500 microM had no effect on aflatoxin B1 mutagenicity with rat liver S9. When liver S9 from chick embryos pretreated with coumarin was used for aflatoxin B1 bioactivation, mutant frequency and cytotoxicity were decreased compared to liver S9 from vehicle-treated controls. Liver S9 from coumarin-treated rats did not significantly affect mutant frequency or cytotoxicity. HPLC analysis of chick embryo liver S9 incubated with 1 microM aflatoxin B1 showed a dose-dependent decrease by coumarin of aflatoxin B1 activation to the 8,9-epoxide ranging from 70% of controls at 5 microM coumarin to 4% of controls at 500 microM coumarin. In contrast, coumarin produced a dose-dependent increase in 20 microM aflatoxin B1 activation by rat liver S9, reaching twice the control levels at 500 microM coumarin. These findings, using a mammalian cell system as a mutagenic endpoint, demonstrate marked species differences in chemoprotection by coumarin.

Aflatoxin B1↗
PubMed1998

Diet and risk of colon cancer in a large prospective study of older women: an analysis stratified on family history (Iowa, United States).

OBJECTIVE: The purpose was to investigate whether dietary associations with risk of colon cancer in women differ by family history of the disease. METHODS: Data were analyzed from a prospective cohort study of 35,216 Iowa (United States) women aged 55 to 69 years at baseline. Through 31 December 1995, 241 colon cancers were identified through record linkage with the State Health Registry. The cohort was stratified on family history of colon cancer in first-degree relatives; nutrient intakes were divided into tertiles. RESULTS: Analyses using Cox regression revealed that the association of most dietary components with colon cancer incidence were similar for individuals with and without a family history. However, total calcium intake was associated inversely with colon cancer among women with a negative family history (relative risk [RR] = 0.50 for upper cf lower tertile, P < 0.001), but was unrelated to incidence for women with a positive family history (RR = 1.1 for upper cf lower tertile, P = 0.69). Similarly, total vitamin E intake was associated with lower risk among women with a negative family history (RR = 0.67 for upper cf lower tertile, P = 0.04), but not among women with a positive family history (RR = 0.87 for upper cf lower tertile, P = 0.67). High intakes of fiber, fruits, and vegetables were each weakly inversely associated with risk among family-history negative women, but not among family-history positive women. CONCLUSIONS: These data, if corroborated, suggest that dietary factors typically associated with lower risk may be less effective risk-reduction interventions against colon cancer for individuals with a family history of colon cancer.

Age Factors↗
PubMed1998

Sex and long-term soy diets affect the metabolism and excretion of soy isoflavones in humans.

Soybean consumption may be protective against hormone-dependent cancers, possibly in part because of the isoflavones daidzein and genistein, which are weakly estrogenic. This paper reviews our studies of the metabolism and disposition of these phytoestrogens in humans. During 1 mo of daily soy ingestion in a metabolic unit [1.065 L (36 oz) soymilk, providing 80-210 mg of each isoflavone daily], women initially excreted more isoflavone conjugates in urine than did men. Recoveries of conjugates of genistein, daidzein, and equol were 24%, 66%, and 28% of the amounts ingested in women, respectively, and 15%, 47%, and 15%, respectively, of those in men. A progressive decrease in urinary excretion of genistein and daidzein was observed in women but not in men during the study. At least 10% of ingested daidzin was excreted in urine as equol conjugate in one man and one woman after the first soy ingestion. Three more women but no more men developed the ability to produce and excrete large amounts of equol. Absorption rate constants (k(e)) of the isoflavones were estimated to be 0.24-0.50 h(-1). The elimination rates (k(e)) for genistein, daidzein, and equol were 0.1, 0.16, and 0.08 h(-1), respectively, in women and 0.19, 0.25, and 0.13 h(-1), respectively, in men. Thus, the excretion half-life values of genistein were longer in women (7, 4, and 9 h, respectively) than in men (4, 3, and 5 h, respectively) after the first soy ingestion. The excretion half-life shortened progressively in women but lengthened progressively in men over the study period. Thus, isoflavone metabolism and disposition were affected by the duration of soy ingestion and by sex.

Adult↗