Antioxidants and hormone-mediated health benefits of whole grains

Behavioural, attitudinal and dietary responses to the consumption of wholegrain foods

Whole grains are important dietary constituents as they provide a plethora of nutrients and protective chemicals that may have synergistic actions in promoting health. Regular consumption of wholegrain foods has been associated with a reduced risk of several chronic diseases such as CHD and certain cancers, although their exact role in disease prevention is not yet fully elucidated. Studies reporting levels of whole grain consumption reveal that those subjects who include higher levels of whole grain foods in their diets also have many other favourable dietary and lifestyle practices. While the actions of these practices and whole grains may not be mutually exclusive, these variables do not appear to explain the reduction in risk of disease observed for high-whole grain consumers. Actual whole grain consumption levels are extremely low and many practical barriers exist to consumer uptake of these foods. Effective communication of the whole grain health message is an important strategy to increase awareness of the importance of whole grains in the diet. Increasing the variety and availability of acceptable wholegrain foods is also important. Whole grain consumption at breakfast can have an important impact on total daily nutrient intakes. This simple dietary modification is potentially relatively easy to achieve and could greatly contribute to increased whole grain intake for many individuals.

Diet and asthma in Dutch school children (ISAAC-2)

BACKGROUND

The rise in the prevalence of asthma in western societies may be related to changed dietary habits. Epidemiological studies in children have shown inverse associations of asthma related outcomes with intake of fruits, vegetables, dairy and whole grain products, and fish. In contrast to most previous studies, we used both questionnaire and clinical data to define asthma.

METHODS

Intake of the abovementioned foods was studied in relation to asthma in 598 Dutch children aged 8-13 years. Dietary intake was estimated using a parent completed semi-quantitative food frequency questionnaire. Current wheeze and current asthma were defined based on questionnaire data. More complex end points were defined using information on bronchial hyperresponsiveness (BHR) and atopic sensitisation as well. Linear associations were studied using logistic regression analysis and odds ratios presented for the highest versus the lowest tertile of intake. In the final models, adjustments were made for maternal educational level, foreign descent, and total energy intake.

RESULTS

The intake of whole grain products and of fish was inversely associated with asthma. Adjusted odds ratios for the independent associations with whole grains and fish were 0.46 (95% CI 0.19 to 1.10) and 0.34 (95% CI 0.13 to 0.85) for current asthma and 0.28 (95% CI 0.08 to 0.99) and 0.12 (95% CI 0.02 to 0.66) for atopic asthma with BHR. Similar results were observed for current wheeze and atopic wheeze with BHR. Intake of (citrus) fruits, vegetables, and dairy products showed no clear associations with asthma end points.

CONCLUSIONS

Our findings suggest that a high intake of whole grain products and fish may have a protective effect against asthma in children.

Antioxidant properties of pearled barley fractions

Two barley varieties (Falcon and AC Metcalfe) were separated by pearling into seven fractions and subsequently extracted with 80% methanol. The extracts, after solvent removal, were evaluated for their radical scavenging efficacy using Trolox equivalent antioxidant capacity (TEAC). The radical scavenging capacity of the extracts was determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, oxygen radical absorbance capacity (ORAC(FL)), and superoxide radical assays and a photoinduced chemiluminescence technique. In both barley varieties the outermost fraction (F1) yielded the highest phenolic content. In general, Falcon had a significantly higher total phenolic content than AC Metcalfe. A similar trend was observed for TEAC, DPPH, and superoxide radical scavenging capacities of the extracts. The contents of water-soluble antioxidants of Falcon and AC Metcalfe were 1.15-12.98 and 2.20-12.25 micromol of Trolox equiv/(g of defatted material), while the corresponding lipid-soluble counterparts varied from 1.44 to 4.70 micromol of alpha-tocopherol equiv/(g of defatted material). Phenolic acids, namely, vanillic, caffeic, p-coumaric, ferulic, and sinapic acids, were identified by HPLC in barley fractions.

Phytochemicals and antioxidant activity of milled fractions of different wheat varieties

The health-promoting effects of whole-grain consumption have been attributed in part to their unique phytochemical contents and profiles that complement those found in fruits and vegetables. Wheat is an important component of the human diet; however, little is known about the phytochemical profiles and total antioxidant activities of milled fractions of different wheat varieties. The objectives of this study were to investigate the distribution of phytochemicals (total phenolics, flavonoids, ferulic acid, and carotenoids) and to determine hydrophilic and lipophilic antioxidant activity in milled fractions (endosperm and bran/germ) of three different wheat varieties, two of which were grown in two environments. Grain samples of each of the wheat varieties were milled into endosperm and bran/germ fractions. Each fraction was extracted and analyzed for total phenolics, ferulic acid, flavonoids, carotenoid contents, and hydrophilic and lipophilic antioxidant activities. Total phenolic content of bran/germ fractions (2867-3120 micromol of gallic acid equiv/100 g) was 15-18-fold higher (p < 0.01) than that of respective endosperm fractions. Ferulic acid content ranged from 1005 to 1130 micromol/100 g in bran/germ fractions and from 15 to 21 micromol/100 g in the endosperm fractions. The bran/germ fraction flavonoid content was 740-940 micromol of catechin equiv/100 g. On average, bran/germ fractions of wheat had 4-fold more lutein, 12-fold more zeaxanthin, and 2-fold more beta-cryptoxanthin than the endosperm fractions. Hydrophilic antioxidant activity of bran/germ samples (7.1-16.4 micromol of vitamin C equiv/g) was 13-27-fold higher than that of the respective endosperm samples. Similarly, lipophilic antioxidant activity was 28-89-fold higher in the bran/germ fractions (1785-4669 nmol of vitamin E equiv/g). Hydrophilic antioxidant activity contribution to the total antioxidant activity (hydrophilic + lipophilic) was >80%. In whole-wheat flour, the bran/germ fraction contributed 83% of the total phenolic content, 79% of the total flavonoid content, 51% of the total lutein, 78% of the total zeaxanthin, 42% of the total beta-cryptoxanthin, 85% of the total hydrophilic antioxidant activity, and 94% of the total lipophilic antioxidant activity. Our results showed that different milled fractions of wheat have different profiles of both hydrophilic and lipophilic phytochemicals. These findings provide information necessary for evaluating contributions to good health and disease prevention from whole-wheat consumption.

Lignans are involved in the antitumor activity of wheat bran in colon cancer SW480 cells

Wheat bran was shown to provide protection against colorectal cancer in human intervention and animal studies. Our recent study showed, however, that antitumor activities of wheat bran from various wheat cultivars differed significantly even when wheat fiber was equal in diets. We hypothesized that phytochemical lignans in wheat bran may account for the differences among wheat cultivars in cancer prevention. The concentration of a major lignan, secoisolariciresinol diglycoside, was determined by HPLC in 4 selected wheat cultivars (i.e., Madison, Ernie, Betty, and Arapahoe). The lignan concentrations and their antitumor activities, previously determined in APC-Min mice, were correlated (r = 0.73, P < 0.02). The cancer preventive mechanisms of 2 prominent lignan metabolites (enterolactone and enterodiol) were further studied in human colonic cancer SW480 cells. Treatment with enterolactone and enterodiol, alone or in combination, at 0-40 micromol/L resulted in dose- and time-dependent decreases in cell numbers. Although the cytotoxicity as measured by trypan blue staining in adherent cells was not affected, DNA flow cytometric analysis indicated that the treatments induced cell cycle arrest at the S-phase. Western blot analysis for cyclin A, a required protein for S/G2 transition, showed that the cyclin A protein levels decreased after treatment with enterodiol or the combination of enterolactone and enterodiol at 40 micromol/L for 72 h. Apoptosis analysis by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay showed an increased percentage of apoptotic cells in the floating cells after enterodiol alone or combined treatments. These results suggest for the first time that lignans may contribute, at least in part, to the cancer prevention by wheat bran observed in APC-Min mice. Inhibition of cancer cell growth by lignan metabolites seems to be mediated by cytostatic and apoptotic mechanisms.

Novel antioxidant peptides from fermented mushroom Ganoderma lucidum

Oxidative stress has been linked with the pathogenesis of many human diseases including cancer, aging, and atherosclerosis. The present study investigates the antioxidant activities of peptides isolated from the medicinal mushroom, Ganoderma lucidum. G. lucidum has been shown to possess potent antioxidant activity with little or no side effects. Polysaccharide, polysaccharide-peptide complex, and phenolic components of G. lucidum have been proposed to be responsible for this antioxidant effect. However, research has shown that the G. lucidum peptide (GLP) is the major antioxidant component of G. lucidum. The objective of this study was to evaluate the antioxidant activity of this peptide using different oxidation systems. GLP showed potent antioxidant activities in both lightproof soybean oil and lard systems, assessed by lipid peroxidant value. Compared to butylated hydroxytoluene, GLP showed a higher antioxidant activity in the soybean oil system. Soybean lipoxygenase activity was blocked by GLP in a dose-dependent manner with an IC50 value of 27.1 microg/mL. GLP showed scavenging activity toward hydroxyl radicals produced in a deoxyribose system with an IC50 value of 25 microg/mL, and GLP effectively quenched superoxide radical anion produced by pyrogallol autoxidation in a dose-dependent manner. Malondialdehyde level has been used as the oxidation index in many biological systems. GLP showed substantial antioxidant activity in the rat liver tissue homogenates and mitochondrial membrane peroxidation systems. The auto-hemolysis of rat red blood cells was also blocked by GLP in a dose-dependent manner. On the basis of these results, it is concluded that GLP is the major constituent responsible for the antioxidant activity of G. lucidum. GLP could play an important role in the inhibition of lipid peroxidation in biological systems through its antioxidant, metal chelating, and free radical scavenging activities.

Proposal for a dietary “phytochemical index”

There is ample reason to believe that diets rich in phytochemicals provide protection from vascular diseases and many cancers; direct antioxidant activity as well as modulation of enzyme expression or hormone activity contribute to this effect. Phytochemicals derived from diverse foods presumably can interact additively and (possibly) synergistically; thus, the total dietary load of phytochemicals may have important implications for health. As a means of very roughly quantifying this load, a "phytochemical index" (PI) is proposed, defined as the percent of dietary calories derived from foods rich in phytochemicals. Calories derived from fruits, vegetables (excluding potatoes), legumes, whole grains, nuts, seeds, fruit/vegetable juices, soy products, wine, beer, and cider - and foods compounded therefrom - would be counted in this index. Partial credit could be given for antioxidant-rich extra virgin olive oil. Other added oils, refined sugars, refined grains, potato products, hard liquors, and animal products - regrettably, the chief sources of calories in typical Western diets - would be excluded. Although the PI would provide only a very rough approximation of the quantity or quality of phytochemical nutrition, it nonetheless could aid epidemiologists in exploring the health consequences of diets high in phytochemical-rich plant foods, and could also help clinical nutritionists in their efforts to improve the phytochemical nutrition of their clients.

Phytochemical profiles and antioxidant activity of wheat varieties

Whole grain consumption has been associated with reduced risk of chronic diseases, such as cardiovascular diseases and cancer. These beneficial effects have been attributed to the unique phytochemicals of grains that complement those found in fruits and vegetables. Wheat is one of the major grains in the human diet; however, little is known about the inherent varietal differences in phytochemical profiles, total phenolic and carotenoid contents, or total antioxidant activities of different wheat varieties, which ultimately influence the associated nutritional and health benefits of wheat and wheat products. The objectives of this study were to determine the phytochemical profiles and total antioxidant activity for 11 diverse wheat varieties and experimental lines. The profiles included free, soluble-conjugated, and insoluble-bound forms of total phenolics, flavonoids, and ferulic acids and carotenoid content including lutein, zeaxanthin, and beta-cryptoxanthin. The results showed that total phenolic content (709.8-860.0 micromol of gallic acid equiv/100 g of wheat), total antioxidant activity (37.6-46.4 micromol of vitamin C/g), and total flavonoid content (105.8-141.8 micromol of catechin equiv/100 g of wheat) did not vary greatly among the 11 wheat lines. However, significant differences in total ferulic acid content (p < 0.05) and carotenoid content (p < 0.05) among the varieties were observed, with carotenoid content exhibiting the greatest range of values. Carotenoid content among the 11 wheat varieties exhibited 5-fold, 3-fold, and 12-fold differences in lutein, zeaxanthin, and beta-cryptoxanthin, respectively. A synthetic wheat experimental line, W7985, gave the lowest carotenoid concentrations of any of the genotypes in this study. Such large genotypic differences in carotenoid content may open up new opportunities for breeding wheat varieties with higher nutritional value.

Determination of Phytic Acid in Urine by Inductively Coupled Plasma Mass Spectrometry

An ICPMS method for the determination of phytic acid in human urine based on the total phosphorus measurement of purified extracts of phytic acid is described. Pretreatment of the sample is required to avoid interference in the ICPMS detection from other phosphorus compounds accompanying phytic acid in urine such as phosphate or pyrophosphate. This treatment consists of a simple filtration of the urine sample followed by complete separation of phytic acid from the mentioned phosphorus components using an anion-exchange solid-phase extraction. Separation/recovery conditions, optimized for standards of phytic acid prepared in water and artificial urine, were successfully applied to natural urine samples, resulting in adequate accuracy and precision. Linear range (0.02-0.6 mg of phytic acid L(-)(1)) and limit of detection (5 microg L(-)(1) phytic acid) are adequate for analysis of the usual amounts of phytic acid present in urine. Phosphate, pyrophosphate, and pH of urine samples at concentrations exceeding their normal physiological ranges do not affect the determination of phytic acid. Because of the simplicity, low sample requirement, and relatively high sample throughput (10 to 6 min per sample for runs between 50 and 100 samples, respectively), the present method presents the best alternative to current methods for phytic acid determination in urine. Results also show that the method is adequate for the differentiation of levels of phytic acid excretion from patients suffering from oxalocalcic urolithiasis and healthy controls, suggesting that low phytic acid concentrations in urine lead to elevated risk of oxalocalcic urolithiasis.

Association of consumption of products containing milk fat with reduced asthma risk in pre-school children: the PIAMA birth cohort study

BACKGROUND

Environment and lifestyle contribute to the development of asthma in children. Understanding the relevant factors in this relationship may provide methods of prevention. The role of diet in the development of asthma in pre-school children was investigated.

METHODS

Data from 2978 children participating in a prospective birth cohort study were used. Food frequency data were collected at the age of 2 years and related to asthma symptoms reported at the age of 3 years.

RESULTS

The prevalence of recent asthma at age 3 was lower in children who consumed (at age 2) full cream milk daily (3.4%) than in those who did not (5.6%) and in those who consumed butter daily (1.5%) than in those who did not (5.1%). The prevalence of recent wheeze was lower in children who consumed milk products daily (13.7%) than in those who did not (18.4%) and in children who consumed butter daily (7.7%) than in those who did not (15.4%). These effects remained in a logistic regression model including different foods and confounders (adjusted odds ratio (CI) for recent asthma: full cream milk daily v rarely 0.59 (0.40 to 0.88), butter daily v rarely 0.28 (0.09 to 0.88)). Daily consumption of brown bread was also associated with lower rates of asthma and wheeze, whereas no associations were observed with the consumption of fruits, vegetables, margarine, and fish.

CONCLUSIONS

In pre-school children, frequent consumption of products containing milk fat is associated with a reduced risk of asthma symptoms.

Turkish Tombul hazelnut (Corylus avellana L.). 1. Compositional characteristics

The quality of Tombul (Round) hazelnut, grown in the Giresun province of Turkey, was determined by measuring proximate composition, minerals, vitamins, dietary fiber, amino acids, and taste active components (free amino acids, sugars, and organic acids). Fat was the predominant component in Tombul hazelnut (approximately 61%). The major minerals were potassium, phosphorus, calcium, magnesium, and selenium. Hazelnut was also found to serve as an excellent source of vitamin E (24 mg/100 g) and a good source of water soluble (B complex) vitamins and dietary fiber. The major amino acids were glutamic acid, arginine, and aspartic acid. The three nonessential amino acids and the essential amino acids contributed 44.9 and 30.9% to the total amino acids present, respectively, while lysine and tryptophan were the limiting amino acids in Tombul hazelnut. Twenty-one free amino acids, six sugars, and six organic acids were positively identified; among these, arginine, sucrose, and malic acid predominated, respectively. These taste active components may play a significant role in the taste and flavor characteristics of hazelnut. Thus, the present results suggest that Tombul hazelnut serves as a good source of vital nutrients and taste active components.

A case-control study of dietary phytoestrogens and testicular cancer risk

A few dietary studies have found elevated testicular cancer risks for higher red meat, fat, and milk intakes and lower intakes of fruits, vegetables, and fiber. Because hormonal modulation by dietary intake of plant estrogens could affect risk of testicular cancer, we chose to explore the possible relationship between dietary phytoestrogens and testicular cancer. We conducted a hospital-based case-control study of 159 testicular cancer cases diagnosed between 1990 and 1996 and 136 adult friend-matched controls at the University of Texas M. D. Anderson Cancer Center. Amounts of phytoestrogenic compounds in foods were added to the National Cancer Institute's DietSys program and then grouped into prelignans, lignans, flavonoids, isoflavonoids, phytosterols, and coumestrol for statistical analysis, expressed per 1,000 kcal. The results of multivariate logistic regression analysis showed, after adjustment for age, education, income, ethnicity, cryptorchidism, body mass index, baldness unrelated to therapy, severe acne in adolescence, early puberty, daily fiber and fat intake, and total daily calories, no discernable monotonic increased or decreased risk estimates across quartiles of phytoestrogen intake. A U-shaped pattern was observed for lignans and coumestrol. Further evaluation of this pattern by cubic spline parameterization did fit the data, but the data were also consistent with no effect. This hypothesis-generating study does not support the premise that dietary phytoestrogens increase or decrease testicular cancer risk in young men.

Antioxidant and antiproliferative activities of common fruits

Consumption of fruits and vegetables has been associated with reduced risk of chronic diseases such as cardiovascular disease and cancer. Phytochemicals, especially phenolics, in fruits and vegetables are suggested to be the major bioactive compounds for the health benefits. However, the phenolic contents and their antioxidant activities in fruits and vegetables were underestimated in the literature, because bound phenolics were not included. This study was designed to investigate the profiles of total phenolics, including both soluble free and bound forms in common fruits, by applying solvent extraction, base digestion, and solid-phase extraction methods. Cranberry had the highest total phenolic content, followed by apple, red grape, strawberry, pineapple, banana, peach, lemon, orange, pear, and grapefruit. Total antioxidant activity was measured using the TOSC assay. Cranberry had the highest total antioxidant activity (177.0 +/- 4.3 micromol of vitamin C equiv/g of fruit), followed by apple, red grape, strawberry, peach, lemon, pear, banana, orange, grapefruit, and pineapple. Antiproliferation activities were also studied in vitro using HepG(2) human liver-cancer cells, and cranberry showed the highest inhibitory effect with an EC(50) of 14.5 +/- 0.5 mg/mL, followed by lemon, apple, strawberry, red grape, banana, grapefruit, and peach. A bioactivity index (BI) for dietary cancer prevention is proposed to provide a new alternative biomarker for future epidemiological studies in dietary cancer prevention and health promotion.

Antioxidant activity of grains

Epidemiological studies have shown that consumption of whole grains and grain-based products is associated with reduced risk of chronic diseases. The health benefits of whole grains are attributed in part to their unique phytochemical composition. However, the phytochemical contents in grains have been commonly underestimated in the literature, because bound phytochemicals were not included. This study was designed to investigate the complete phytochemical profiles in free, soluble conjugated, and insoluble bound forms, as well as their antioxidant activities in uncooked whole grains. Corn had the highest total phenolic content (15.55 +/- 0.60 micromol of gallic acid equiv/g of grain) of the grains tested, followed by wheat (7.99 +/- 0.39 micromol of gallic acid equiv/g of grain), oats (6.53 +/- 0.19 micromol of gallic acid equiv/g of grain), and rice (5.56 +/- 0.17 micromol of gallic acid equiv/g of grain). The major portion of phenolics in grains existed in the bound form (85% in corn, 75% in oats and wheat, and 62% in rice), although free phenolics were frequently reported in the literature. Ferulic acid was the major phenolic compound in grains tested, with free, soluble-conjugated, and bound ferulic acids present in the ratio 0.1:1:100. Corn had the highest total antioxidant activity (181.42 +/- 0.86 micromol of vitamin C equiv/g of grain), followed by wheat (76.70 +/- 1.38 micromol of vitamin C equiv/g of grain), oats (74.67 +/- 1.49 micromol of vitamin C equiv/g of grain), and rice (55.77 +/- 1.62 micromol of vitamin C equiv/g of grain). Bound phytochemicals were the major contributors to the total antioxidant activity: 90% in wheat, 87% in corn, 71% in rice, and 58% in oats. Bound phytochemicals could survive stomach and intestinal digestion to reach the colon. This may partly explain the mechanism of grain consumption in the prevention of colon cancer, other digestive cancers, breast cancer, and prostate cancer, which is supported by epidemiological studies.

Protective effect of a lignan-containing flaxseed extract against CCl(4)-induced hepatic injury

Carbon tetrachloride (CCl(4)) -induced hepatotoxicity is a commonly used model for investigating lipid peroxidation-related tissue injury. In the present study, the effect of flaxseed extract was observed on histological sections, glutathione-content and DNA strand breaks. Lignan-containing flaxseed extract (1.6 g/kg body weight/day) was daily administered with intragastric injection to rats for three days, on the fourth day, CCl(4) (2 g/kg) was intraperitoneally injected. Liver tissue was sampled at 24 hr after administering CCl(4). Liver-necrosis was observed in CCl(4)-injected rats without pretreatment of flaxseed extract. Pretreatment of flaxseed extract reduced extent of the necrosis found 24 hr after the intraperitoneal administration of CCl(4). Pretreatment of flaxseed extract protect against CCl(4)-induced decrease of reduced glutathione-content measured from reactions with 5,5'-dithiobis-(2-nitrobenzoic acid) and also protect against the elevation of DNA strand breaks in the liver cells measured by comet assay. Flaxseed-extract appears to protect liver cells against CCl(4)-induced necrosis.

Can dietary factors explain differences in serum cholesterol profiles among different ethnic groups (Chinese, Malays and Indians) in Singapore?

In Singapore. there exists differences in risk factors for coronary heart disease among the three main ethnic groups: Chinese, Malays and Indians. This study aimed to investigate if differences in dietary intakes of fat, types of fat, cholesterol, fruits, vegetables and grain foods could explain the differences in serum cholesterol levels between the ethnic groups. A total of 2408 adult subjects (61.0% Chinese, 21.4% Malays and 17.6% Indians) were selected systematically from the subjects who took part in the National Health Survey in 1998. The design of the study was based on a cross-sectional study. A food frequency questionnaire was used to assess intakes of energy, total fat, saturated fat, polyunsaturated fat, monounsaturated fat, cholesterol, fruits, vegetables and cereal-based foods. The Hegsted score was calculated. Serum total cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol were analysed and the ratio of total cholesterol to high density lipoprotein cholesterol was computed. The results showed that on a group level (six sex-ethnic groups), Hegsted score, dietary intakes of fat, satutrated fat, cholesterol, vegetables and grain foods were found to be correlated to serum cholesterol levels. However, selected dietary factors did not explain the differences in serum cholesterol levels between ethnic groups when multivariate regression analysis was performed, with adjustment for age, body mass index, waist-hip ratio, cigarette smoking, occupation, education level and physical activity level. This cross-sectional study shows that while selected dietary factors are correlated to serum cholesterol at a group level, they do not explain the differences in serum cholesterol levels between ethnic groups independently of age, obesity, occupation, educational level and other lifestyle risk factors.

Effects of oat and wheat cereals on endothelial responses

BACKGROUND

This study was undertaken to determine the effects of month-long whole grain oat and wheat cereal supplementation on endothelial function following a fatty meal as measured by brachial artery reactivity studies.

METHODS

Fifty healthy adult subjects underwent brachial artery reactivity studies before and after a high-fat meal along with alpha-tocopherol (vitamin E), oats, or a comparable bowl of wheat cereal and were again tested after the high-fat meal following month-long supplementation with oat or wheat cereal in a random crossover with interim washout.

RESULTS

In the acute phase, the fatty meal attenuated the hyperemic brachial artery flow response when administered concurrently with wheat cereal (-13.4%; P = 0.02), whereas hyperemic flow was maintained by concurrent administration of either oatmeal or alpha-tocopherol. Following month-long supplementation, postprandial peak flow (wheat +3.88 +/- 5.62%; oat -10.78 +/- 7.15%), and peak diameter (wheat -1.40 +/- 0.96%; oat -0.86 +/- 0.88%) did not differ from preprandial values. Oat and wheat treatments did not differ when directly compared.

CONCLUSIONS

Month-long, daily supplementation with either whole-grain oat or wheat cereal may prevent postprandial impairment of vascular reactivity in response to a high-fat meal.

Grain processing and nutrition

Whole grains provide a wide range of nutrients and phytochemicals that optimize health. Epidemiologic studies support the protectiveness of whole grain consumption for cardiovascular disease and cancer. Dietary guidance endorses increased whole grains in our diet. A crucial question remaining is the effect of processing of whole grains on their content of nutrients and phytochemicals. Although processing is often considered to be a negative attribute in nutrition, and some forms of processing reduce nutritional value, many factors support the importance of processing of grains to enhance grain consumption. First, whole grains as harvested are generally not consumed directly by humans but require some processing prior to consumption. While refining, that is, removal of the bran and the germ, reduces the nutrient content of grain, milling of grains otherwise concentrates desirable grain components and removes poorly digested compounds and contaminants. Cooking of grains generally increases digestibility of nutrients and phytochemicals. Studies in both animal models and humans support the notion that processed grains are often nutritionally superior to unprocessed grains, probably because of enhanced nutrient bioavailability in processed grains. Processing of grains also provides shelf-stable products that are convenient and good tasting for consumers.

A comparison of whole wheat, refined wheat and wheat bran as inhibitors of heterocyclic amines in the Salmonella mutagenicity assay and in the rat colonic aberrant crypt focus assay

Refined wheat, unrefined whole wheat, and wheat bran were studied for their ability to protect against heterocyclic amines (HCAs) in vitro and in vivo. Wheat bran, which binds HCAs in vitro, as well as refined wheat and unrefined whole wheat, inhibited the mutagenic activities of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) when they were co-incubated and the supernatant (minus grain) was added to the Salmonella assay. The water-soluble fraction alone from refined and unrefined wheat, but not bran, also inhibited against these mutagens in vitro. In vivo, AIN-93G diets containing refined wheat or unrefined wheat were examined for their ability to inhibit IQ-induced colonic aberrant crypt foci (ACF) in the Fischer 344 rat. A slight increase in the number of AC/ACF (aberrant crypts/ACF) was seen after 16 weeks in rats treated post-initiation with refined wheat (P < 0.05), and fewer foci with two or three aberrant crypts (ACF-2) were found in rats given unrefined whole wheat post-initiation compared with animals treated with the same diet during the initiation phase (P < 0.05). There was no significant difference in the profile of IQ urinary metabolites or excretion of promutagens 0-48 h after carcinogen dosing, and grains had no effect on hepatic cytochrome P4501A1 (CYP1A1), CYP1A2, aryl sulfotransferase or N-acetyltransferase activities; however, a slightly higher UDP-glucuronosyl transferase activity was observed in rats fed unrefined wheat compared with refined wheat diets (P < 0.05). Thus, despite their antimutagenic activities in vitro, only marginal effects were seen with refined and unrefined wheat in vivo with respect to hepatic enzyme activities, carcinogen metabolism and IQ-induced ACF in the rat colon.

Diet and chronic obstructive pulmonary disease: independent beneficial effects of fruits, whole grains, and alcohol (the MORGEN study)

BACKGROUND

In recent years antioxidants, foods rich in antioxidants (e.g. fruits, vegetables) and fish have been suggested to protect against chronic obstructive pulmonary disease (COPD). There are also indications for a protective effect of whole grain intake and of consuming moderate amounts of alcohol. It is, however, not clear whether the effects of the different dietary factors on COPD are independent of each other and if so, whether their effects are additive.

OBJECTIVE

To gain more insight into the potential protective effect of diet on COPD, we studied fruit, vegetable, fish, alcohol and whole grain consumption simultaneously in relation to pulmonary function and COPD symptoms.

METHODS

Analysed were cross-sectional data collected in 13 651 men and women aged 20-59 years participating between 1994 and 1997 in the MORGEN study (monitoring project on risk factors and health in The Netherlands). Regression models were adjusted for age, gender, height (for pulmonary function only), smoking, BMI and energy intake.

RESULTS

Fruit and whole grain intake showed independent beneficial associations with COPD (P-trend < 0.001). Furthermore, in subjects with low alcohol consumption (1-30 g/day) the forced expiratory volume in 1 s (FEV1) was higher and the prevalence of COPD symptoms lower than in non-drinkers (P < 0.001). The effects of a favourable intake of fruits (> 180 g/day), whole grains (> 45 g/day) and alcohol (1-30 g/day) were largely additive. In the 2998 subjects with a favourable intake of the three foods, the FEV1 was 139 mL higher and the prevalence of COPD symptoms lower (odds ratio (OR) = 0.44) than in subjects (n = 1406) with unfavourable intakes of fruits, whole grains and alcohol (P < 0.001). A similar effect was observed in those who had never smoked. Fish and vegetable intake did not show independent beneficial associations with COPD.

CONCLUSIONS

Our results suggest independent beneficial effects of fruits, whole grains and alcohol on COPD that are largely additive and cannot be explained by smoking habits.

Whole-grain intake and cancer: an expanded review and meta-analysis

Whole grains are nutrient rich and may protect against chronic disease. To study this, we previously reviewed 14 case-control studies of colorectal, gastric, and endometrial cancers and found consistently lower risk in those with high than in those with low whole-grain intake. Questions remained concerning other cancers, dietary assessment, quantity consumed, confounding, and differential study quality. Here we expand the review to 40 case-control studies of 20 cancers and colon polyps. Odds ratios are < 1 for 46 of 51 mentions of whole-grain intake and for 43 of 45 after exclusion of 6 mentions with design/reporting flaws or low intake. The pooled odds ratio for high vs. low whole-grain intake among the 45 mentions was 0.66 (95% confidence interval = 0.60-0.72); they range from 0.59 to 0.78 across four types of dietary questionnaires. Odds ratios were < 1 in 9 of 10 mentions of studies of colorectal cancers and polyps, 7 of 7 mentions of gastric and 6 of 6 mentions of other digestive tract cancers, 7 of 7 mentions of hormone-related cancers, 4 of 4 mentions of pancreatic cancer, and 10 of 11 mentions of 8 other cancers. Most pooled odds ratios for specific cancers were in the range of 0.5-0.8, notable exceptions being breast (0.86) and prostate (0.90). The pooled odds ratio was similar in studies that adjusted for few and many covariates. Dose-response associations were stronger in studies using food-frequency questionnaires than in more quantitative questionnaires. The case-control evidence is supportive of the hypothesis that whole-grain intake protects against various cancers.

Phytochemicals for the prevention of breast and endometrial cancer

Although there is evidence that phytochemicals decrease the incidence of breast and endometrial cancer, many observations are only phenomenologic, and much work needs to be done to explore basic mechanisms and the strategic exploitation of their interactions. The multiplicity of phytochemical actions at different sites in the process of tumorigenesis may eventually lead to the development of a multiagent strategy designed to maximize the complementary effects of different agents. A number of effects with possible relevance to cancer chemoprevention have been excluded from this review, including effects of phytochemicals on the immune response; the question of dietary restriction, which has a profound effect on tumorigenesis; the relatively low methionine levels in some phytochemicals such as soy, which may limit the synthesis of polyamines necessary for tumor growth [151]; and the fact that diets higher in plant products are usually lower in fat and result in leaner individuals with less potential for the synthesis of estradiol in adipose tissue. Also, many studies dealing solely with in vitro mutagenesis were excluded.

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.

Acute effects of oats and vitamin E on endothelial responses to ingested fat

OBJECTIVE

To assess the effects of oats and vitamin E on endothelial function following a high-fat meal in healthy adults as measured by brachial artery reactivity studies (BARS).

METHODS

A total of 25 men and 25 women (N=50) were recruited from a community population to participate in this randomized, crossover study. All subjects were free of known vascular disease, and female subjects were postmenopausal. Subjects underwent BARS before and after a high-fat meal (50 gm fat) on three occasions 1 week apart, one each with vitamin E 800 IU, oatmeal containing 3 gm beta-glucan, or a comparable bowl of wheat cereal serving as a placebo, in random sequence. The ultrasonographer was blinded to treatment status.

RESULTS

Endothelial function, as measured by brachial artery peak flow during one minute of post-occlusive hyperemia, declined significantly from baseline when the high-fat meal was consumed with the wheat cereal (-13.4%; p=0.02). There was no difference in brachial artery flow change before and after a high-fat meal with oats (+0.37%; p=0.77) or a high-fat meal with vitamin E (+1.87%; p=0.42). No significant differences in flow-mediated vasodilation before and after the high-fat meal were detected among the three supplements.

CONCLUSIONS

Endothelial dysfunction induced by acute fat ingestion in healthy adults is apparently prevented by concomitant ingestion of oats or vitamin E, but not wheat. Nutrient distribution and meal composition may have important implications for cardiovascular health.

Wheat aleurone flour increases cecal beta-glucuronidase activity and butyrate concentration and reduces colon adenoma burden in azoxymethane-treated rats

Processed wheat aleurone flour (WAF) is a source of insoluble fermentable dietary fiber that comes from the outer layers of the wheat kernel. A study was designed to evaluate WAF, wheat bran (WB) and alpha-cellulose as the source of dietary fiber (5 g/100 g of diet) in a semipurified high fat (20 g/100 g of as 1:1 lard/sunflower seed oil) diet fed to male Sprague-Dawley rats in which intestinal tumors were induced using azoxymethane (AOM). WAF at 33 g/100 g of diet (WAF33) and WB at 16 g/100 g of diet (WB16) increased the weight of feces and produced significantly higher concentrations in the cecum of the short-chain fatty acid butyrate (P < 0.001) than did no fiber (NF) and WAF added at only 10 g/100 g (1.5 g of dietary fiber) (WAF10). Cecal and fecal pH were both significantly lower in the WAF33 and WB16 treatments relative to control and no fiber treatments (P < 0.001). The intestinal tumors in the rats were assessed at 6 mo after the study began, and the WAF33- or WB16-fed rats showed a trend (P = 0.06) with 43% fewer colon adenomas relative to control. There was a significant inverse relationship between ss-glucuronidase activity and colon adenomas in the rat colon (r2 = 0.37, P = 0.001). WAF fiber influenced some metabolic markers of fermentation in the colon in a manner similar to that of WB, which, independent of the bulking effect, was associated with a trend to reduced colon adenomas. Significantly increased cecal ss-glucuronidase activity and/or butyrate concentrations may have protective influences in this context by mechanisms not yet fully elucidated.

The therapeutic potential of phytoestrogens

Phytoestrogens, such as the soya isoflavones genistein and daidzein, are currently being extensively investigated through both molecular, preclinical and clinical studies to determine their potential health benefits. Phytoestrogens may protect against chronic diseases such as hormone-dependent cancer (e.g., breast and prostate cancer), cardiovascular disease and osteoporosis. Investigations of phytoestrogen metabolism and bioavailability are also of great relevance. Conversion by gut microflora of daizein to its isoflavan metabolite equol, which is a more potent oestrogen and anti-oxidant, occurs only in some individuals (about 35% of subjects tested are equol excretors). This has considerable implications for daidzein bioavailability and also for cancer risk. Oxidative damage has been implicated in the development of heart disease and cancer and soya phytoestrogens have been reported to decrease plasma F(2)-isoprostane concentrations (biomarker for in vivo lipid peroxidation) and increase low density lipoprotein oxidation resistance. This anti-oxidant action of phytoestrogens could potentially contribute to their therapeutic efficacy. The findings from the current ongoing studies are all likely to contribute to determining the potential use of phytoestrogens as therapeutic agents.

Potential of wheat-based breakfast cereals as a source of dietary antioxidants

Whole wheat- and wheat bran-based ready-to-eat breakfast cereals could be important sources of dietary antioxidants. Of the antioxidants in wheat, free and esterified phenolic acids seem to have the greatest potential to be beneficial to health. Phenolic acids from breakfast cereals possess strong antioxidant activity in vitro at concentrations that would be obtained from a normal serving of whole wheat cereal. In addition, acid conditions and enzymic hydrolysis increase the solubility and activity of wheat phenolics suggesting that the digestive process could be important in altering the antioxidant potential of wheat-based foods. Current research on the antioxidant activity of wheat phenolics suggests that further research is warranted to determine the potential benefits of these dietary antioxidants. In addition, identification of both biological (e.g. digestion) and food processing conditions that impact the distribution, stability and activity of wheat antioxidants is needed in order to be able to produce food products with maximum health benefits.

Antioxidant content of whole grain breakfast cereals, fruits and vegetables

BACKGROUND

Considerable scientific evidence suggests that whole grains, as commonly consumed in the United States and Europe, reduce risk for chronic disease including cancer and heart disease. Whole grains provide a wide range of nutrients and phytochemicals that may work synergistically to optimize human health. Fruits and vegetables provide protection against age related diseases. It is believed their high content of antioxidant compounds is key to such protection.

OBJECTIVE

This research compares the antioxidant activity of whole grain, ready-to-eat (RTE) breakfast cereals to that of fruits and vegetables.

METHOD

Antioxidant activity was determined by dispersing finely ground samples in a 50% aqueous methanol solution of the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). DPPH, which forms a deep purple solution, reacts with antioxidants and color loss at 515 nm correlates to antioxidant content, which is expressed as Trolox equivalents/100 grams (TE).

RESULTS

Whole grain breakfast cereals analyzed in this study contained from 2,200-3,500 TE. By comparison, fruits generally ranged from 600-1,700 TE, with a high of 2,200 TE for red plums. Berries averaged 3,700 TE and. vegetables averaged 450 TE with a high of 1,400 TE for red cabbage. A 41 gram average serving of RTE breakfast cereal provides 1,120 TE, while an average 85 gram serving of vegetables or fruits provides 380 and 1,020 TE, respectively.

CONCLUSION

Whole grain breakfast cereals, fruits and vegetables are all important dietary sources of antioxidants.

Mechanisms for the impact of whole grain foods on cancer risk

Dietary guidance recommends consumption of whole grains for the prevention of cancer. Epidemiologic studies find that whole grains are protective against cancer, especially gastrointestinal cancers such as gastric and colonic, and hormonally-dependent cancers including breast and prostate. Four potential mechanisms for the protectiveness of whole grains against cancer are described. First, whole grains are concentrated sources of dietary fiber, resistant starch, and oligosaccharides, fermentable carbohydrates thought to protect against cancer. Fermentation of carbohydrates in the colon results in production of short chain fatty acids that lower colonic pH and serve as an energy source for the colonocytes. Secondly, whole grains are rich in antioxidants, including trace minerals and phenolic compounds, and antioxidants have been proposed to be important in cancer prevention. Thirdly, whole grains are significant sources of phytoestrogens that have hormonal effects related to cancer protection. Phytoestrogens are thought to be particularly important in the prevention of hormonally-dependent cancers such as breast and prostate. Finally, whole grains mediate glucose response, which has been proposed to protect against colon and breast cancer.

Cancer incidence in patients treated surgically for Dupuytren's contracture

Our aim was to study risk factors for Dupuytren's contracture (DC) by assessing cancer morbidity in a group of Swedish patients treated surgically for Dupuytren's contracture. The risk of cancer was determined in 15,212 patients operated on for Dupuytren's contracture, identified in the nationwide Swedish Inpatient Register during the period 1965 to 1994 by means of record linkage to the Swedish Cancer Register. Standardized incidence ratios (SIRs) were computed using age-, sex- and period-specific incidence rates derived from the entire Swedish population. The overall relative risk of cancer was increased by 24%. There were significantly increased risks for malignancies related to smoking such as buccal, oesophageal, gastric, lung and pancreatic cancers. Significantly increased risks were present for both prostate and rectal cancer in men and an increase risk for breast cancer in women was noted 1 year or more after surgery for Dupuytren's contracture. The present study confirms smoking and alcohol abuse as probable risk factors for DC. There are characteristics in patients with DC that alter the risks for other malignancies compared with the general population.

Antioxidant capacity of oat (Avena sativa L.) extracts. 1. Inhibition of low-density lipoprotein oxidation and oxygen radical absorbance capacity

Milled oat groat pearlings, trichomes, flour, and bran were extracted with methanol and the fractions tested in vitro for antioxidant capacity against low-density lipoprotein (LDL) oxidation and R-phycoerythrin protein oxidation in the oxygen radical absorbance capacity (ORAC) assay. The oxidative reactions were generated by 2,2'-azobis(2-amidinopropane) HCl (AAPH) or Cu(2+) in the LDL assay and by AAPH or Cu(2+) + H(2)O(2) in the ORAC assay and calibrated against a Trolox standard to calculate Trolox equivalents (1 Trolox equivalent = 1 TE = activity of 1 micromol of Trolox). The antioxidant capacity of the oat fractions was generally consistent with a potency rank of pearlings (2.89-8.58 TE/g) > flour (1.00-3.54 TE/g) > trichome (1.74 TE/g) = bran (1.02-1.62 TE/g) in both LDL and ORAC assays regardless of the free radical generator employed. A portion of the oat antioxidant constituents may be heat labile as the greatest activity was found among non-steam-treated pearlings. The contribution of oat tocols from the fractions accounted for <5% of the measured antioxidant capacity. AAPH-initiated oxidation of LDL was inhibited by the oat fractions in a dose-dependent manner, although complete suppression was not achieved with the highest doses tested. In contrast, Cu(2+)-initiated oxidation of LDL stimulated peroxide formation with low oat concentrations but completely inhibited oxidation with higher doses. Thus, oats possess antioxidant capacity most of which is likely derived from polar phenolic compounds in the aleurone.

Plausible mechanisms for the protectiveness of whole grains

Dietary guidelines recommend the consumption of whole grains to prevent chronic diseases. Epidemiologic studies support the theory that whole grains are protective against cancer, especially gastrointestinal cancers such as gastric and colon can-cer, and cardiovascular disease. Components in whole grains that may be protective include compounds that affect the gut environment, such as dietary fiber, resistant starch, and oligosaccharides. Whole grains are also rich in compounds that function as antioxidants, such as trace minerals and phenolic compounds, and phytoestrogens, with potential hormonal effects. Other potential mechanisms whereby whole grains may protect against disease include binding of carcinogens and modulation of the glycemic response. Clearly, the range of protective substances in whole grains is impressive and advice to consume additional whole grains is justified. Further study is needed regarding the mechanisms behind this protection so that the most potent protective components of whole grains will be maintained when developing whole grains into acceptable food products for the public.

Wholewheat flour ensures higher mineral absorption and bioavailability than white wheat flour in rats

Consumption of unrefined whole flour is thought to affect mineral bioavailability because it contains high levels of fibre and phytic acid. The present experiment was designed to study the absorption of minerals from diets based on wholewheat flour and white wheat flour in rats. Two groups of male Wistar rats were fed on the diets for 3 weeks and absorption and tissue retention of minerals were studied. The rats fed on the wholewheat flour diet had significantly greater food intake, weight gain, faecal excretion and intestinal fermentation than those fed on the white flour diet. Mineral intakes, except for Ca, were significantly greater in rats fed on the wholewheat flour diet (4-fold for Mg, 2-fold for Fe and Zn). A significant rise in the apparent absorption of Fe (%) and a significant decrease in the apparent absorption of Zn (%) were observed. The amounts of minerals absorbed (mg/d) were significantly enhanced (excepted for Ca) with the wholewheat flour diet. Moreover, plasma and tibia levels of Mg and plasma, liver and tibia levels of Fe were significantly increased in rats fed on the wholewheat flour diet compared with those fed on the white flour diet. In conclusion, wholewheat flour, rich in phytic acid and minerals, did not have a negative effect on mineral absorption, but rather improved the bioavailability of some minerals. Human studies are needed to confirm these rat results before extrapolation to human nutrition.

Flaxseed and lignans increase cecal beta-glucuronidase activity in rats

Flaxseed has been shown in previous studies to decrease some early markers of colon cancer risk in part because of its lignans. This study determined whether the intake of flaxseed and lignans is related to the activity of bacterial beta-glucuronidase, an enzyme suggested to increase colon cancer risk. Seven groups of six female rats each were fed, for four weeks, a basal high-fat (20%) diet (BD), BD supplemented with 2.5%, 5.0%, or 10.0% flaxseed, or BD with daily gavage of 0.75, 1.5, or 3.0 mg of secoisolariciresinol diglycoside (SDG), the major mammalian lignan precursor. The specific and total activities of beta-glucuronidase in the cecum were significantly related to the levels of flaxseed (r = 0.539, p < 0.008 and r = 0.599, p < 0.002, respectively) and SDG (r = 0.567, p < 0.007 and r = 0.435, p < 0.04, respectively). The urinary mammalian lignan excretion also increased with increasing flaxseed or SDG levels and thus was significantly related to the specific activity (r = 0.38, p < 0.017) and total activity (r = 0.429, p < 0.007) of beta-glucuronidase. Because flaxseed and lignans are colon cancer protective, it is concluded that, in contrast to other studies, beta-glucuronidase activity may play a beneficial role in their presence by increasing mammalian lignan absorption and enterohepatic circulation.

Is whole grain intake associated with reduced total and cause-specific death rates in older women? The Iowa Women's Health Study

OBJECTIVES

This study sought to determine whether nutrient-rich whole grains reduce mortality risk.

METHODS

The study included 38,740 Iowa women, aged 55 to 69 years. A food frequency questionnaire was used to obtain data on grain intake.

RESULTS

Median whole grain intake quintiles ranged from a median of 0.2 to more than 3 servings per day. Women with higher intakes had healthier lifestyles and less baseline disease. The total death rate decreased in increasing quintiles, and the pattern repeated for cancer, cardiovascular disease, and other causes combined. Adjusted for lifestyle and baseline disease, the relative hazard rate ratio for total death was about 0.85 in daily consumers of whole grain. Findings persisted in strata of baseline healthy and diseased and were not explained by dietary fiber. Rates of total mortality, but not cardiovascular disease mortality, were higher among frequent consumers of refined grain.

CONCLUSIONS

Total mortality risk was inversely associated with whole grain intake and positively associated with refined grain intake. Refined grains contributed more than 20% of energy intake, and whole grains contributed 1%. Substitution of whole for refined grain may reduce chronic disease risk in the United States.

The bioavailability of non-nutrient plant factors: dietary flavonoids and phyto-oestrogens

The bioavailability in human subjects of non-nutrient plant factors, including dietary flavonoids and phyto-oestrogens, is of great importance relative to their reported health protective effects. These effects include protection against heart disease, and also in the case of the phyto-oestrogens, hormone-dependent cancers. Epidemiological studies have shown flavonoid intake (mostly quercetin) to be inversely associated with mortality from CHD. Quercetin is a potent antioxidant in vitro, and protection against the oxidative damage to LDL implicated in atherogenesis has been suggested as a possible mechanism. Human subjects can absorb significant amounts of quercetin (particularly in the glucoside form) and it would appear to be sufficiently bioavailable to act as an antioxidant in vivo; however, following our recent study (J O'Reilly, TAB Sanders and H Wiseman, unpublished results), it is currently less clear whether quercetin really can act as an antioxidant in vivo. The isoflavone phyto-oestrogens genistein and daidzein are much less effective antioxidants than quercetin in vitro, however, they are well-absorbed by human subjects and appear to be sufficiently bioavailable to act as antioxidants in vivo. In our recent study (O'Reilly et al. 1998) lower plasma isoprostane concentrations and increased resistance of LDL to oxidation were observed following the high-isoflavone dietary phase compared with the low-isoflavone dietary phase. Considerable inter-individual variation in isoflavone metabolite excretion has been observed, in particular the production of equol (the gut bacterial metabolite of daidzein; a more potent antioxidant and more oestrogenic than daidzein), and this appears to be influenced by habitual diet. Further studies on the bioavailability of these non-nutrient plant factors and related influencing factors are clearly still required.

Studies on the genotoxicity of the mammalian lignans enterolactone and enterodiol and their metabolic precursors at various endpoints in vitro

The mammalian lignans enterolactone (ENL) and enterodiol (END) are formed by intestinal bacteria from the plant lignans matairesinol (MAT) and secoisolariciersinol (SEC), respectively, which are ingested with different types of food. ENL and END are weak estrogens. According to epidemiological and biochemical studies, lignans may act as anticarcinogens, but little is known about their genotoxic potential. We have therefore investigated the effects of ENL, END, MAT and SEC on cell-free microtubule assembly and at the following genetic endpoints in cultured male Chinese hamster V79 cells: disruption of the cytoplasmic microtubule complex, induction of mitotic arrest, induction of micronuclei and their characterization by CREST staining, and mutagenicity at the HPRT gene locus. The lignans were tested at concentrations of 200 microM in the cell-free system and 100 microM in cultured cells, which represents the limit of solubility in each assay. The established aneuploidogen diethylstilbestrol and the clastogen 4-nitroquinoline-N-oxide were used as positive reference compounds. As none of the four lignans had any activity at the endpoints studied, we conclude that ENL, END, MAT and SEC are devoid of aneuploidogenic and clastogenic potential under the experimental conditions used in this study.

Phytochemicals: guardians of our health

Consuming a diet rich in plant foods will provide a milieu of phytochemicals, nonnutritive substances in plants that possess health-protective benefits. Nuts, whole grains, fruits, and vegetables contain an abundance of phenolic compounds, terpenoids, pigments, and other natural antioxidants that have been associated with protection from and/or treatment of chronic disease such as heart disease, cancer, diabetes, and hypertension as well as other medical conditions. The foods and herbs with the highest anticancer activity include garlic, soybeans, cabbage, ginger, licorice, and the umbelliferous vegetables. Citrus, in addition to providing an ample supply of vitamin C, folic acid, potassium, and pectin, contains a host of active phytochemicals. The phytochemicals in grains reduce the risk of cardiovascular disease and cancer.

Antioxidant activity of phytoestrogenic isoflavones

The aim of this work was to determine the antioxidant activities of a range of phytoestrogenic isoflavones. The antioxidant activity in the aqueous phase was determined by means of the ABTS.+ total antioxidant activity assay. The results show that the order of reactivity in scavenging the radical in the aqueous phase is genistein > daidzein = genistin approximately equal to biochanin A = daidzin > formononetin approximately equal to ononin, the latter displaying no antioxidant activity. The importance of the single 4'-hydroxyl group in the reactivity of the isoflavones, as scavengers of aqueous phase radicals, as well as the 5'7-dihydroxy structure is demonstrated. Examination of their abilities to enhance the resistance of low density lipoproteins to oxidation supports the observation that genistein is the most potent antioxidant among this family of compound studied, both in the aqueous and in the lipophilic phases.