The role of specific gut microbes in shaping body composition remains unclear. We transplanted fecal microbiota from adult female twin pairs discordant for obesity into germ-free mice fed low-fat ...mouse chow, as well as diets representing different levels of saturated fat and fruit and vegetable consumption typical of the U.S. diet. Increased total body and fat mass, as well as obesity-associated metabolic phenotypes, were transmissible with uncultured fecal communities and with their corresponding fecal bacterial culture collections. Cohousing mice harboring an obese twin's microbiota (Ob) with mice containing the lean co-twin's microbiota (Ln) prevented the development of increased body mass and obesity-associated metabolic phenotypes in Ob cage mates. Rescue correlated with invasion of specific members of Bacteroidetes from the Ln microbiota into Ob microbiota and was diet-dependent. These findings reveal transmissible, rapid, and modifiable effects of diet-by-microbiota interactions.
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 envi-ronment, such as dietary fiber, resistant starch, and oligosaccha-rides. 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 com-ponents of whole grains will be maintained when developing whole grains into acceptable food products for the public.
Effect of Wheat Bran on Glycemic Control and Risk Factors for Cardiovascular Disease in Type 2 Diabetes
David J. A. Jenkins , MD 1 2 3 4 ,
Cyril W. C. Kendall , PHD 1 3 ,
Livia S. A. Augustin , MSC 1 ...3 ,
Margaret C. Martini , PHD 5 ,
Mette Axelsen , PHD 6 ,
Dorothea Faulkner , RD 1 ,
Edward Vidgen , BSC 1 3 ,
Tina Parker , RD 1 ,
Herb Lau , MD 7 8 ,
Philip W. Connelly , PHD 2 9 10 ,
Jerome Teitel , MD 7 8 ,
William Singer , MD 2 ,
Arthur C. Vandenbroucke , PHD 7 10 ,
Lawrence A. Leiter , MD 1 2 3 4 and
Robert G. Josse , MD 1 2 3 4
1 Clinical Nutrition and Risk Factor Modification Center, St. Michael’s Hospital, Toronto, Ontario, Canada
2 Department of Medicine, Division of Endocrinology and Metabolism, St. Michael’s Hospital, Toronto, Ontario, Canada
3 Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
4 Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
5 Kraft Foods, Glenview, Illinois
6 Lundberg Laboratory for Diabetic Research, Department of Internal Medicine, Sahlgrenska University Hospital, Göteborg, Sweden
7 Department of Laboratory Medicine, Division of Clinical Biochemistry, St. Michael’s Hospital, Toronto, Ontario, Canada
8 Department of Hematology, St. Michael’s Hospital, Toronto, Ontario, Canada
9 Department of Biochemistry, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
10 Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
Abstract
OBJECTIVE —Cohort studies indicate that cereal fiber reduces the risk of diabetes and coronary heart disease (CHD). Therefore, we assessed
the effect of wheat bran on glycemic control and CHD risk factors in type 2 diabetes.
RESEARCH DESIGN AND METHODS —A total of 23 subjects with type 2 diabetes (16 men and 7 postmenopausal women) completed two 3-month phases of a randomized
crossover study. In the test phase, bread and breakfast cereals were provided as products high in cereal fiber (19 g/day additional
cereal fiber). In the control phase, supplements were low in fiber (4 g/day additional cereal fiber).
RESULTS —Between the test and control treatments, no differences were seen in body weight, fasting blood glucose, HbA 1c , serum lipids, apolipoproteins, blood pressure, serum uric acid, clotting factors, homocysteine, C-reactive protein, magnesium,
calcium, iron, or ferritin. LDL oxidation in the test phase was higher than that seen in the control phase (12.1 ± 5.4%, P < 0.034). Of the subjects originally recruited, more dropped out of the study for health and food preference reasons from
the control phase (16 subjects) than the test phase (11 subjects).
CONCLUSIONS —High-fiber cereal foods did not improve conventional markers of glycemic control or risk factors for CHD in type 2 diabetes
over 3 months. Possibly longer studies are required to demonstrate the benefits of cereal fiber. Alternatively, cereal fiber
in the diet may be a marker for another component of whole grains that imparts health advantages or a healthy lifestyle.
CHD, coronary heart disease
NCEP, National Cholesterol Education Program
Footnotes
Address correspondence and reprint requests to David J. A. Jenkins, Clinical Nutrition and Risk Factor Modification Center,
St. Michael’s Hospital, 61 Queen St. East, Toronto, Ontario, Canada, M5C 2T2. E-mail: cyril.kendall{at}utoronto.ca .
Received for publication 12 April 2002 and accepted in revised form 28 May 2002.
A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.
See accompanying editorial on p. 1652.
DIABETES CARE
The glycemic index (GI) is an indicator of the relative human glycemic response to dietary carbohydrates in a food. It is determined using a costly and time-consuming in vivo method. We describe an ...in vitro analytical method that allows the accurate prediction of the GI of a food product. The method involves digestion of the food product using HCl and enzymes, followed by HPLC analysis of sugars and sugar alcohols. Data from the HPLC analysis combined with the product's compositional information are treated using an artificial neural network to produce a predicted value for the GI of the food product. For the sample set examined (n = 72) consisting of a variety of food types, r2 = 0.93 and the root mean square error of correlation (RMSEC) = 5 GI units. Twenty-fold cross-validation yields CVR2 = 0.89, indicating good predictive ability for samples outside the calibration set. The relative standard deviation of the method is 6.6%. This method is rapid and low cost relative to in vivo testing. Due to good ability to predict in vivo GI, it may be a valuable screening tool for determining the relative effect of food ingredients on the glycemic index of a food product.
Dietary isoflavone and lignan phytoestrogens are potential chemopreventive agents. This has led to a need to monitor exposure
to these compounds in human populations and to determine which components ...of a mixed diet contribute to the exposure. Typically,
urinary isoflavonoid excretion is associated with soy consumption and that of lignans is associated with whole grains. However,
other plant foods are known to contain phytoestrogen precursors. The purpose of this study was to examine the association
between urinary isoflavonoid and lignan excretion and intakes of vegetables and fruits (V&F). Isoflavonoids (genistein, daidzein,
O -desmethylangolensin, and equol) and lignans (enterolactone, enterodiol, and matairesinol) were measured in urine collected
for 3 days from 49 male and 49 female volunteers (age, 18–37 years) reporting a wide range of habitual V&F intakes. Dietary
intakes were assessed using 5-day diet records and a food frequency questionnaire. V&F groupings (total V&F, total V, total
F, soyfoods, and V&F grouped by botanical families) were used to assess the relationship between V&F intake and urinary isoflavonoid
and lignan excretion. Pearson correlations were performed. Intake of soyfoods was correlated significantly with urinary genistein
( r = 0.40; P = 0.0001), O -desmethylangolensin ( r = 0.37; P = 0.0002), daidzein ( r = 0.34; P = 0.0007), and the sum of isoflavonoids ( r = 0.39; P = 0.0001). There was no association between equol excretion and soy intake or between the isoflavonoids and any other V&F
groupings. In addition, isoflavonoid excretion was correlated positively with intake of high-fat and processed meats, particularly
among men who did not consume soy. This suggests that, even in the United States, on a Western diet, soyfoods are the primary
contributors to isoflavone intake; however, additional “hidden sources” of soy may also contribute to exposure. In contrast,
a variety of fiber-containing foods contributed to lignan excretion; the sum of the urinary lignans, enterodiol, enterolactone,
and matairesinol, was associated with intake of total F ( r = 0.27; P = 0.008), total V&F ( r = 0.25; P = 0.01), soyfoods ( r = 0.28; P = 0.006), and dietary fiber ( r = 0.36; P = 0.0003). Overall, urinary phytoestrogens (isoflavonoids + lignans) were significantly higher in “high” compared with “low”
V&F consumers. Compared with the “low” V&F group, the “high” group consumed diets that were, on average, higher in fiber and
carbohydrate and soyfoods and lower in fat; thus, the urinary phytoestrogens may also be a useful marker of healthier dietary
patterns.
Dietary estrogens, such as lignans, are similar in structure to
endogenous sex steroid hormones and may act in vivo to
alter hormone metabolism and subsequent cancer risk. The objective of
this study ...was to examine the effect of dietary intake of a lignan-rich
plant food (flaxseed) on urinary lignan excretion in postmenopausal
women. This randomized, cross-over trial consisted of three 7-week
feeding periods during which 31 healthy postmenopausal women, ages
52–82 years, consumed their habitual diets plus 0, 5, or 10 grams of
ground flaxseed per day. Urine samples collected for 2 consecutive days
during the last week of each feeding period were analyzed for lignan
content (enterodiol, enterolactone, and matairesinol) by isotope
dilution gas chromatography/mass spectrometry. Compared with the 0-gram
flaxseed diet, consumption of 5 or 10 grams of flaxseed significantly
increased excretion of enterodiol by 1,009 and 2,867 nmol/day,
respectively; significantly increased excretion of enterolactone by
21,242 and 52,826 nmol/day, respectively; and significantly increased
excretion of total lignans (enterodiol + enterolactone + matairesinol)
by 24,333 and 60,640 nmol/day, respectively. Excretion of matairesinol
was not significantly altered by flaxseed consumption.
Consumption of flax, a significant source of dietary estrogens, in
addition to their habitual diets increased excretion of enterodiol and
enterolactone, but not matairesinol, in a dose-dependent manner in this
group of postmenopausal women. Urinary excretion of lignan metabolites
is a dose-dependent biomarker of flaxseed intake within the context of
a habitual diet.
Lignans, similar in structure to endogenous sex steroid hormones, may act in vivo to alter hormone metabolism and subsequent cancer risk. The objective of this study was to examine effects of dietary ...intake of a lignan-rich plant food (flaxseed) on serum concentrations of endogenous hormones and binding proteins (estrone, estrone sulfate, 17β-estradiol, sex hormone-binding globulin, progesterone, prolactin, dehydroepiandrosterone sulfate, dehydroepiandrosterone, androstenedione, testosterone, and free testosterone) in postmenopausal women. This randomized, crossover trial consisted of three seven-week feeding periods, during which 28 postmenopausal women, aged 52-82 yr, consumed their habitual diets plus 0, 5, or 10 g of ground flaxseed. Serum samples collected during the last week of each feeding period were analyzed for serum hormones using standard diagnostic kits. The flaxseed diets significantly reduced serum concentrations of 17β-estradiol by 3.26 pg/ml (12.06 pmol/l) and estrone sulfate by 0.09 ng/ml (0.42 nmol/l) and increased prolactin by 1.92 μg/l (0.05 IU/ml). Serum concentrations of androstenedione, estrone, sex hormone-binding globulin, progesterone, testosterone, free testosterone, dehydroepiandrosterone, and dehydroepiandrosterone sulfate were not altered with flaxseed feeding. In this group of postmenopausal women, consuming flaxseed in addition to their habitual diets influenced their endogenous hormone metabolism by decreasing serum 17β-estradiol and estrone sulfate and increasing serum prolactin concentrations.
Estrogen is metabolized along two competing pathways to form the
2-hydroxylated and the 16α-hydroxylated metabolites. Based on
proposed differences in biological activities, the ratio of these
...metabolites, 2-hydroxyestrogen:16α-hydroxyestrone
(2:16α-OHE1), has been used as a biomarker for breast cancer risk.
Women with an elevated 2:16α-OHE1 ratio are hypothesized to be at a
decreased risk of breast cancer. Flaxseed, the most significant source
of plant lignans, and wheat bran, an excellent source of dietary fiber,
have both been shown to have chemoprotective benefits. Some of these
benefits may be attributable to their influence on endogenous sex
hormone production and metabolism. We examined the effect of flaxseed
consumption alone and in combination with wheat bran on urinary
estrogen metabolites in premenopausal women. Sixteen premenopausal
women were studied for four feeding treatments lasting two menstrual
cycles each in a randomized cross-over design. During the four feeding
treatments, subjects consumed their usual diets supplemented with baked
goods containing no flaxseed or wheat bran, 10 g of flaxseed,
28 g of wheat bran, or 10 g of flaxseed plus 28 g of
wheat bran/day. Urinary excretion of 2-hydroxyestrogen and
16α-hydroxyestrone, as well as their ratio, 2:16α-OHE1, were
measured by enzyme immunoassay. Flaxseed supplementation significantly
increased the urinary 2:16α-OHE1 ratio ( P =
0.034), but wheat bran had no effect. These results suggest that
flaxseed may be chemoprotective in premenopausal women.
Midfollicular and midluteal dietary intakes of 18 women were evaluated between four and six ovulatory menstrual cycles. Phase lengths were established by basal body temperatures and urinary ...luteinizing hormone excretion. Midfollicular and midluteal diet records were collected 6-8 d after menstrual onset and 6-8 d after ovulation, respectively. Significant increases in energy 0.66 MJ (159 kcal), P = 0.003, protein (6.1 g, P = 0.02), carbohydrate (15.3 g, P = 0.04), and fat (8.6 g, P = 0.002) intakes were observed in midluteal phase when compared with midfollicular phase. Intakes of vitamin D, riboflavin, potassium, phosphorus, and magnesium also were significantly higher during midluteal phase (P < 0.05). These results support the regulation of food intake by menstrual cycle hormones and suggest that it is essential to consider phase of menstrual cycle in studies of nutrient intake performed in premenopausal women.
Urinary lignan and isoflavonoid excretion were examined in 11 men and 9 women consuming four nine-day controlled experimental diets: basal (vegetable free), carotenoid vegetable (carrot and spinach), ...cruciferous vegetable (broccoli and cauliflower), and soy (tofu and textured vegetable protein product). Three-day urine collections (Days 7-9) were analyzed for lignans and isoflavonoids with use of isotope-dilution gas chromatography-mass spectrometry. Urinary excretion of the lignans enterodiol and enterolactone was higher during the carotenoid and cruciferous vegetable diets than during the basal diet (p = 0.0001), suggesting that these vegetables may provide a source of mammalian lignan precursors. Urinary excretion of the isoflavonoids equol, O-desmethylangolensin, daidzein, and genistein was higher when subjects consumed soy diets than when they consumed the other test diets (p < 0.02). Gender differences in lignan excretion were observed. Men excreted more enterolactone (p = 0.006) and less enterodiol (p = 0.013) than women, implying a gender difference in colonic bacterial metabolism of lignans. There was no effect of gender on isoflavonoid excretion.
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