Long-term soy isoflavone supplementation and cognition in women: a randomized, controlled trial.

OBJECTIVE: To determine the cognitive effects of long-term dietary soy isoflavones in a daily dose comparable to that of traditional Asian diets. METHODS: In the double-blind Women's Isoflavone Soy Health trial, healthy postmenopausal women were randomly allocated to receive daily 25 g of isoflavone-rich soy protein (91 mg of aglycone weight of isoflavones: 52 mg of genistein, 36 mg of daidzein, and 3 mg glycitein) or milk protein-matched placebo. The primary cognitive endpoint compared between groups at 2.5 years was change from baseline on global cognition, a composite of the weighted sum of 14 neuropsychological test score changes. Secondary outcomes compared changes in cognitive factors and individual tests. RESULTS: A total of 350 healthy postmenopausal women aged 45-92 years enrolled in this trial; 313 women with baseline and endpoint cognitive test data were included in intention-to-treat analyses. Adherence in both groups was nearly 90%. There was no significant between-group difference on change from baseline in global cognition (mean standardized improvement of 0.42 in the isoflavone group and 0.31 in the placebo group; mean standardized difference 0.11, 95% confidence interval [CI] -0.13 to 0.35). Secondary analyses indicated greater improvement on a visual memory factor in the isoflavone group (mean standardized difference 0.33, 95% CI 0.06-0.60) but no significant between-group differences on 3 other cognitive factors or individual test scores, and no significant difference within a subgroup of younger postmenopausal women. CONCLUSION: For healthy postmenopausal women, long-term dietary soy isoflavone supplementation in a dose comparable to that of traditional Asian diets has no effect on global cognition but may improve visual memory. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that long-term dietary supplementation with isoflavone-rich soy protein does not improve global cognition of healthy postmenopausal women.

Urinary phytoestrogen excretion and prostate cancer risk: a nested case-control study in the Multiethnic Cohort.

BACKGROUND: Phytoestrogens are of special interest in prostate cancer research because populations in Asia with a high consumption of phytoestrogens have a lower incidence of the disease than comparable populations in Western countries. METHODS: This case-control study is nested within a large multiethnic cohort in Hawaii and California. Urine samples were analysed for daidzein, genistein, equol, and enterolactone among 249 incident prostate cancer cases and 404 controls matched on age, race/ethnicity, date/time of specimen collection, and fasting status. RESULTS: The median excretion of daidzein was 0.173 nmol mg(-1) creatinine in cases and 0.291 in controls (P=0.01), and the median excretion of genistein was 0.048 in cases and 0.078 in controls (P=0.05). An inverse association was seen for daidzein overall (odds ratio for the highest vs lowest quintile=0.55, 95% confidence interval=0.31-0.98, P(trend)=0.03) and seemed to apply to localized (P(trend)=0.08) as well as advanced or high-grade cancer (P(trend)=0.09). This association was consistent across the four ethnic groups examined. Although the relationship was weaker for genistein, the odds ratios and trends were similarly inverse. Urinary excretion of equol and enterolactone was not significantly related to prostate cancer risk. CONCLUSION: Our findings suggest that high intake of isoflavones, as reflected by urinary excretion of daidzein and genistein, may be protective against prostate cancer.

Effects of dietary sesame seeds on plasma tocopherol levels.

The tocopherols, the major vitamers of vitamin E, are believed to play a role in the prevention of human aging-related diseases such as cancer and heart disease, yet little is known concerning determinants of their plasma concentrations. Evidence from animal studies suggests that the dietary source of gamma-tocopherol can significantly affect plasma levels of this tocopherol as well as its functional vitamin E activity. To determine whether plasma levels of tocopherols in humans are similarly altered, a study was undertaken in which subjects (n = 9) were fed muffins containing equivalent amounts of gamma-tocopherol from sesame seeds, walnuts, or soy oil. We observed that consumption of as little as 5 mg of gamma-tocopherol per day over a three-day period from sesame seeds, but not from walnuts or soy oil, significantly elevated serum gamma-tocopherol levels (19.1% increase, p = 0.03) and depressed plasma beta-tocopherol (34% decrease, p = 0.01). No significant changes in baseline or postintervention plasma levels of cholesterol, triglycerides, or carotenoids were seen for any of the intervention groups. All subjects consuming sesame seed-containing muffins had detectable levels of the sesame lignan sesamolin in their plasma. Consumption of moderate amounts of sesame seeds appears to significantly increase plasma gamma-tocopherol and alter plasma tocopherol ratios in humans and is consistent with the effects of dietary sesame seeds observed in rats leading to elevated plasma gamma-tocopherol and enhanced vitamin E bioactivity.

Hydroxymatairesinol, a novel enterolactone precursor with antitumor properties from coniferous tree (Picea abies).

The potential for the extraction of the plant lignan hydroxymatairesinol (HMR) in large scale from Norway spruce (Picea abies) has given us the opportunity to study the metabolism and biological actions of HMR in animals. HMR, the most abundant single component of spruce lignans, was metabolized to enterolactone (ENL) as the major metabolite in rats after oral administration. The amounts of urinary ENL increased with the dose of HMR (from 3 to 50 mg/kg), and only minor amounts of unmetabolized HMR isomers and other lignans were found in urine. HMR (15 mg/kg body wt po) given for 51 days decreased the number of growing tumors and increased the proportion of regressing and stabilized tumors in the rat dimethylbenz[a]anthracene-induced mammary tumor model. HMR (50 mg/kg body wt) did not exert estrogenic or antiestrogenic activity in the uterine growth test in immature rats. HMR also showed no antiandrogenic responses in the growth of accessory sex glands in adult male rats. Neither ENL nor enterodiol showed estrogenic or antiestrogenic activity via a classical alpha- or beta-type estrogen receptor-mediated pathway in vitro at < 1.0 microM. HMR was an effective antioxidant in vitro.

Application of HPLC coupled with ultraviolet-photodiode array detection for the analysis of phytoestrogens in biological samples.

HPLC/PDA methodology was developed for phytoestrogen analysis in human blood, urine, and breast milk. Applications of this technique in four different observational studies showed that urinary excretion rates of isoflavonoids reflects soy consumption reliably. A case-control study in Shanghai showed a decrease in risk to develop breast cancer for women with high urinary isoflavone excretion. These findings support a potential breast cancer preventive effect achieved by soy consumption in populations that eat soy foods habitually.

Effects of beta-carotene and alpha-tocopherol on bleomycin-induced chromosomal damage.

The number of bleomycin-induced chromosomal breaks in cultured peripheral blood lymphocytes has been proposed as a measure of the sensitivity of an individual to carcinogens. Although "mutagen sensitivity" (clastogenicity) may be a useful biomarker for the identification of individuals at high risk for DNA damage, there is some uncertainty whether the results of this assay can be modified by environmental factors, such as diet. We designed an intervention study to determine whether micronutrient supplementation with beta-carotene and alpha-tocopherol influenced the mutagenicity score among 22 healthy volunteers. This intervention study followed a double-blind, randomized, cross-over design. Chromatid breaks ranged from 0.30 to 2.30 per cell and were uncorrelated with plasma beta-carotene (r = -0.07; P = 0.50) and a-tocopherol (r = -0.01; P = 0.92) levels, after accounting for the time of the measurement. The average number of breaks per cell was similar (P for difference in means = 0.90) among subjects during periods of vitamin supplementation (mean = 0.87 breaks per cell) and placebo (mean = 0.86 breaks per cell), averaged over groups and after adjustment for baseline breaks. Substantial within-person variation may indicate some imprecision in the mutagen sensitivity assessment. Our results suggest that mutagen sensitivity is not affected by plasma levels of beta-carotene or alpha-tocopherol. Although mutagen sensitivity does not appear to be modified by changes in plasma levels of two common antioxidant vitamins, it may be useful for the identification of high-risk individuals for participation in large intervention studies with cancer outcomes.

Lifestyle and nutritional correlates of cytochrome CYP1A2 activity: inverse associations with plasma lutein and alpha-tocopherol.

Cytochrome CYP1A2, a liver enzyme responsible for the metabolic activation of a number of putative human carcinogens, exhibits wide inter-individual differences in activity. In order to characterize sources of variability in CYP1A2 activity, we phenotyped (with the caffeine test) 90 subjects of various ethnic backgrounds in Hawaii. Forty-three subjects were patients with in-situ colorectal cancer treated by polypectomy and 47 were healthy population controls. Subjects were also administered a detailed lifestyle questionnaire, including a quantitative food frequency questionnaire, and were assessed for plasma levels of carotenoids, tocopherols, retinol, ascorbic acid, cholesterol and triglycerides. In a stepwise multiple regression, 27% of the overall variation in CYP1A2 activity was explained by seven variables. Plasma lutein explained the largest portion of the variance (7%) and was negatively associated with CYP1A2 activity (p < 0.01), as were use of menopausal replacement estrogens (p = 0.04), plasma alpha-tocopherol (p = 0.05) and alcohol consumption (p = < 0.01). Acetaminophen use (p = 0.05), coffee consumption (p = 0.05) and plasma lycopene (p = 0.06) were positively associated with CYP1A2 activity. After adjustment for these variables, no association was found between CYP1A2 activity and sex, race, age, education, smoking, physical activity, weight, vitamin E supplements, the other plasma micronutrients measured, and dietary intakes of red meat, processed meat and cruciferous vegetables. Results were similar for colorectal cancer cases and controls. Almost two-thirds (73%) of the variability in CYP1A2 activity remained unexplained. This study confirms an enhancing effect of acetaminophen and coffee on CYP1A2 activity and suggests and inhibitory effect of estrogens, alcohol and food sources of lutein and alpha-tocopherol on this enzyme.

Reproducibility of erythrocyte polyamine measurements and correlation with plasma micronutrients in an antioxidant vitamin intervention study.

Erythrocyte polyamine measurements have been previously investigated as candidate biomarkers for hyperproliferation and recently as a potential intermediate endpoint in clinical chemoprevention trials with difluoromethylornithine, an inhibitor of polyamine biosynthesis. This study was performed to determine the reproducibility of erythrocyte polyamine measurements and their possible correlation with plasma micronutrients in seven healthy adults in an antioxidant vitamin intervention study. As part of this cross-over intervention study, three subjects took beta-carotene (31.4 mg/day) plus D-alpha-tocopherol acetate (720 IU/day) supplements during the first 3 months and four subjects took the supplements during the second 3 months. Heparinized blood samples were collected at baseline and every month over total 6 months for simultaneous determination of erythrocyte polyamines and plasma micronutrients by the high-performance liquid chromatographic method. For all the measures of erythrocyte polyamines the intraindividual variation was smaller than that between subjects, and three or four measurements required to accurately characterize long-term erythrocyte polyamines for an individual. The intra-class correlations were moderately high for all erythrocyte polyamine measurements, indicating a good reproducibility for intra-individual erythrocyte polyamine measurements. Based on monthly values, significant inverse correlations were found between erythrocyte spermidine and the plasma levels of retinol (r = -0.50) and lutein (r = -0.52). There were also significant inverse associations between erythrocyte spermine and plasma levels of alpha-tocopherol (r = -0.29), lutein (r = -0.44), lycopene (r = -0.29), beta-cryptoxanthin (r = -0.30), and total carotenoids (r = -0.29). The effects of supplementation upon the associations between erythrocyte polyamines and plasma nutrient levels were additionally addressed. The results indicate an acceptable longitudinal reproducibility of erythrocyte polyamine measurements, support the hypothesis that erythrocyte polyamine measurements may be correlated with plasma levels of certain nutrients, and suggest a further biomarker application in cancer prevention trials involving dietary modifications or specific relevant micronutrients.

Correlations between mutagen sensitivity and plasma nutrient levels of healthy individuals.

Increased mutagen sensitivity and decreased intake of antioxidant-rich fruits and vegetables have been associated with an increased risk of upper aerodigestive tract cancers. The objective of this study was to investigate the intraindividual variation in mutagen sensitivity and its possible correlation with plasma nutrient levels in a group of 25 healthy individuals in Hawaii. Mutagen sensitivity, as assessed by bleomycin-induced chromosomal breaks in cultured peripheral blood lymphocytes and plasma nutrient levels were measured monthly for 11 months. The monthly numbers of chromosomal breaks/cell ranged from 0.04 to 0.80 and showed considerable intraindividual variation. Based on individual means, significant inverse correlations were found between mutagen sensitivity scores and the plasma levels of alpha-carotene (r = -0.64), total carotenoids (r = -0.41), and ascorbic acid (r = -0.40). There were also significant inverse associations between monthly mean plasma levels of alpha-carotene (r = -0.58), beta-carotene (r = -0.76) and total carotenoids (r = -0.72) and monthly mean chromosomal breaks. In contrast, there was a significant positive correlation between monthly mean plasma triglyceride level (r = 0.60) and monthly mean mutagen sensitivity. These results suggest that mutagen sensitivity as assessed by the bleomycin assay may be influenced by plasma levels of certain nutrients and could potentially be modified by dietary interventions or micronutrient supplementation.

Seasonal variations in plasma micronutrients and antioxidants.

Plasma samples were collected at monthly intervals for a period of 1 year from a group of healthy nonsmoking men and women (n = 21) living in Honolulu, HI. Analysis of plasma cholesterol and triglyceride levels showed marked seasonal variations, with higher mean levels in winter months and lower values in the summer. Cholesterol and triglycerides were highly and inversely correlated with plasma levels of the provitamin A carotenoids. Mean beta- and alpha-carotene levels were highest in late summer and fall. Plasma retinol levels were significantly lower in the summer and higher in the winter. Variations (either between individuals or seasonally) in plasma retinol were unrelated to plasma provitamin A carotenoid levels. Plasma levels of alpha-tocopherol, gamma-tocopherol, beta-cryptoxanthin, and lutein were also higher in the winter and lower in the summer. Significant seasonal correlations, both positive and negative, with environmental variables, such as temperature, solar UV radiation, and rainfall, are noted for many of these plasma micronutrients. The number of samples required to accurately characterize long-term plasma levels for an individual generally ranged from 1 to 4. However, plasma retinol levels exhibited the highest ratio of intra- to interindividual variability, suggesting the need for multiple sampling (> 8 samples) for this micronutrient. Some of this variability for retinol was associated with seasonal changes. Assessment by a diet history of food and supplement intake of micronutrients and phytochemicals for 1 year showed good agreement with 1-year mean plasma levels for most carotenoids, vitamin C, and alpha-tocopherol. Retinol, gamma-tocopherol, cholesterol, and triglyceride levels in plasma were unrelated to estimates of dietary intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Rapid HPLC analysis of dietary phytoestrogens from legumes and from human urine.

Due to growing evidence suggesting that phytoestrogens might protect against various cancers, particularly against breast and prostate cancer, it is important to measure the exposure of populations to these compounds by determining levels in food and in human tissue or body fluids to assess the possible cancer protective properties of these agents. Therefore, we developed a simple and fast procedure to extract and simultaneously hydrolyze phytoestrogens and their conjugates from food items, and present a fast and selective high-performance liquid chromatography (HPLC) method for precise determinations of the most common dietary phytoestrogens genistein, biochanin-A, daidzein, formononetin, and coumestrol using flavone as internal standard. For the first time HPLC was applied to measure these phytoestrogens and their most abundant metabolites equol and O-desmethyl-angolensin from human urine. The proposed methodology has been evaluated for losses due to thermal degradation during extraction and hydrolysis and due to sample handling during the entire work-up including solid phase extraction, and values are given for inter- and intra-assay variability. We present isoflavonoid levels of most common peas and beans used in "western" and "eastern" diets and compare isoflavonoid and coumestrol levels of raw, canned, and cooked foods which can be used in future epidemiological studies. We also determined human urinary levels with our methodology comparing values before and after soybean intake.

High-performance liquid chromatographic assay of isoflavonoids and coumestrol from human urine.

A rapid, sensitive and precise diode-array reversed-phase HPLC method was developed for human urine analysis of the most common dietary isoflavones daidzein, genistein, formononetin and biochanin-A, their mammalian metabolites equol and O-desmethylangolensin, and of coumestrol, another commonly occurring phytoestrogen. Analytes were isolated and concentrated by solid-phase extraction and separated by HPLC followed by identification through retention times and UV scans, and in the case of coumestrol additionally by fluorometric response. This method was applied to monitor changes in urinary excretion of these analytes after challenge with soybeans and was evaluated for precision and recovery of analytes.

Effects of micronutrients and antioxidants on lipid peroxidation in human plasma and in cell culture.

Plasma levels of triglycerides, retinol, cholesterol, lipid-phase antioxidants (alpha-, gamma-tocopherols, beta-carotene, alpha-carotene, lycopene, beta-cryptoxanthin and lutein/zeaxanthin), and thiobarbituric acid-reactive substances (TBA-RS), as an indicator of lipid peroxidation, were repeatedly determined in nine individuals over a 3-month period. Levels of TBA-RS were positively correlated with plasma triglycerides and gamma-tocopherol, and negatively correlated with plasma carotenoids. These results were consistent with in vitro cell culture studies which showed increased TBA-RS for cells supplemented with linolenic acid and decreased levels when treated with beta-carotene. We conclude that TBA-RS measurements in plasma accurately reflect the level of peroxidizable substrate as modified by the presence of a variety of dietary antioxidants, particularly carotenoids. Although the inter- and intra-individual variabilities for TBA-RS are comparable with the micronutrients and antioxidants measured in this study, high interassay variability and the strong association with the more commonly measured plasma triglycerides suggest the TBA-RS assay to be of limited use in epidemiologic studies. However, this assay does appear to be useful in cell culture studies where experimental conditions can be better controlled. Low ratios of inter- to intra-individual variability in some of the plasma micronutrient and lipid-phase antioxidants measured suggest that multiple samples may be required to characterize individuals in studies evaluating the relation between these plasma constituents and disease incidence.

Effects of feeding whole cottonseed on composition of milk.

Complete mixed diets containing 0, 10, 15, or 20% whole cottonseed were fed to 12 cows in a 4 X 4 Latin square design. Cows were assigned to the Latin square by production status resulting in one square each for cows in early first lactation and older cows either in early or late lactation. Diets were fed for ad libitum intake, and periods were 21 days. Percentages of milk fat and total solids increased, and protein percentage decreased with cottonseed feeding. Milk casein nitrogen decreased from .387 to .375% with cottonseed feeding. Nitrogen in whey remained unchanged, and nonprotein nitrogen increased. Proportion of total nitrogen in casein and whey fractions was not altered, but proportion of nonprotein nitrogen increased. Cottonseed decreased proportions of short-chain fatty acids (carbon-6 to carbon-16) in milk and increased stearic and oleic acids. Actual yield of milk was not affected by cottonseed feeding, but yields of fat-corrected milk and milk fat were increased. Production status affected milk composition with older cows in early lactation producing milk of lower fat, total solids, and protein content compared with cows in other groups. Casein nitrogen was highest for first-lactation and lowest for older, high-producing cows. Whey nitrogen was highest for older, low-producing cows. First-lactation cows had the highest proportion of nitrogen in the casein fraction, and older, low-producing cows had the lowest. Milk fatty acid composition changed little with status.

Sources and Content of Iodine in California Milk and Dairy Products 1.

In recent years, milk and milk products have been implicated as a major contributor to dietary iodine. The possible sources of iodine in milk are supplemental iodine in dairy feeds, iodophor-containing sanitizers used at the dairy farm and/or the processing plant, iodophor-containing teat dips used to control the spread of mastitis among dairy cows, and iodine-containing medications used by veterinarians. A five-year program to determine the California raw milk iodine concentration and identify the sources of adventitious iodine has resulted in the California dairy industry deciding late in 1980 to reduce iodine supplementation of dairy feeds. This resulted in a decrease in milk iodine concentration in samples received in 1981 to 256 ± 234 µg/kg compared to 1980, when the concentration was 474 ± 304 µg/kg. The industry has set up a program to monitor the raw milk iodine concentration at the producer level, thus ensuring that the concentration will continue to decline.

Digestibility and effects of whole cottonseed fed to lactating cows.

Four lactating Holstein cows producing about 21 kg milk/day were fed complete rations containing 0, 5, 15, and 25% whole cottonseed in a 4 X 4 Latin square design. Diets were fed ad libitum. Periods were 21 days in length with total collections of feces and urine during the last 7 days of each period. Digestibilities o nitrogen, lipid, and energy increased with increasing cottonseed in the diet. There were no significant effects of cottonseed on digestibility or availability of fiber components, calcium, phosphorous, and magnesium. Cottonseed feeding did not affect dry matter intake or milk yield but did increase yields of milk fat and fat-corrected milk and decrease milk protein and solids-not-fat percentages. Synthesis of fatty acid in the mammary gland was depressed by about 50% on the 25% cottonseed diet, but transfer of dietary fat resulted in twofold increases in yields of stearic and oleic acids. Hydrogenation of cottonseed fatty acid in the rumen resulted in a fourfold increase in yield of trans oleic acid in milk fat. Samples from bulk milk tank and data collected from 55 commercial dairies showed similar changes in fatty acid composition of milk from cows fed whole cottonseed. There was no apparent effect of feeding up to 2.9 kg cottonseed dry matter per cow per day on calving interval or on incidence of displaced abomasum, ketosis, milk, fever, or retained placenta.

Effects of feeding protected tallow on composition of milk and milk fat.

Official methods were used to analyze composite samples of milk collected during the first 15 wk of lactation from 21 Holstein cows fed a milled ration containing 0 (basal), 15% (medium, or 30% (high) protected-tallow supplement (seven cows per treatment). Protein fractions and amino acid composition of the total proteins were determined from samples of individual milking. Melting characteristics of pooled samples were determined by nuclear magnetic resonance. Milk yield was similar for the three treatments, but percent fat and fat yield were higher for cows fed protected tallow. Percentages and yields of protein and solids-not-fat were decreased on the protected tallow treatments, especially for high tallow. The decrease in protein was in the casein fraction. Amino acid composition of the total proteins was similar for the three treatments. Feeding protected tallow caused decreases in all fatty acids except 4:0, 16:1, 18:0, and 18:1 which increased. Nuclear magnetic resonance indicated that butter from the basal group would be harder than that from cows fed protected tallow.