Whole grains, bran, and germ in relation to homocysteine and markers of glycemic control, lipids, and inflammation 1.

BACKGROUND: Intake of whole grains is inversely associated with risk of diabetes and ischemic heart disease in observational studies. The lower risk associated with high whole-grain intakes may be mediated through improvements in glycemic control, lipid profiles, or reduced inflammation. OBJECTIVE: The aim was to examine whether the intake of whole grains, bran, and germ is related to homocysteine, plasma markers of glycemic control (fasting insulin, hemoglobin A1c, C-peptide, and leptin), lipids (total cholesterol, triacylglycerol, HDL cholesterol, and LDL cholesterol), and inflammation (C-reactive protein, fibrinogen, and interleukin 6). DESIGN: This was a cross-sectional study of the relations of whole grains, bran, and germ intakes with homocysteine and markers of glycemic control, lipids, and inflammation in 938 healthy men and women. RESULTS: Whole-grain intake was inversely associated with homocysteine and markers of glycemic control. Compared with participants in the bottom quintile of whole-grain intake, participants in the highest quintile had 17%, 14%, 14%, and 11% lower concentrations of homocysteine (P < 0.01), insulin (P = 0.12), C-peptide (P = 0.03), and leptin (P = 0.03), respectively. Inverse associations were also observed with total cholesterol (P = 0.02), HDL cholesterol (P = 0.05), and LDL cholesterol (P = 0.10). Whole-grain intake was not associated with the markers of inflammation. Whole-grain intake was most strongly inversely associated with markers of glycemic control in this population. CONCLUSION: The results suggest a lower risk of diabetes and heart disease in persons who consume diets high in whole grains.

Lipoprotein peroxidation and mobility limitation: results from the Health, Aging, and Body Composition Study.

BACKGROUND: Oxidative damage plays an important role in leading to major health-related events. The aim of this study was to assess the predictive value of a lipoprotein peroxidation marker, oxidized low-density lipoprotein (oxLDL) for incident mobility limitation (ML). METHODS: Data are from 2985 well-functioning elders enrolled in the Health ABC study (median follow-up, 4.1 years). All oxLDL levels were measured at the baseline assessment. The oxLDL/LDL cholesterol (LDL-C) ratio (log value) was used as a measure of lipoprotein peroxidation. Mobility limitation was defined by 2 consecutive semiannual reports of any difficulty either walking 1/4 mile or climbing up 10 steps without resting. Severe ML was defined by 2 consecutive reports of great difficulty or inability to do the same tasks. Cox proportional hazards models were performed to assess hazard ratios (HRs) and 95% confidence intervals (CIs). RESULTS: The mean (SD) age of the sample was 74.2 (2.9) years. After adjustment for potential confounders (sociodemographic factors, smoking, physical activity, body mass index, clinical conditions, biological markers, and medications), the relationship between the oxLDL/LDL-C ratio and disability events was statistically significant (per log-unit difference in the oxLDL/LDL-C ratio) (for ML: HR, 1.22; 95% CI, 1.06-1.41; for severe ML: HR, 1.43; 95% CI, 1.15-1.79). Consistent results were found when interleukin 6 level was included as a covariate in the adjusted models (ML: HR, 1.13; 95% CI, 0.98-1.31; severe ML: HR, 1.31; 95% CI, 1.05-1.64). No significant sex, race, interleukin 6 level, or clinical conditions interaction was found with the oxLDL/LDL-C ratio and mobility disability. CONCLUSIONS: Lipoprotein peroxidation predicts the onset of ML in older persons. The oxLDL predictive value for ML is partly explained by interleukin 6 levels.

Dietary glycemic index and load, measures of glucose metabolism, and body fat distribution in older adults.

BACKGROUND: Recent evidence suggests that the rate of carbohydrate digestion and absorption may influence the development of type 2 diabetes. OBJECTIVE: The aim of this study was to examine associations of dietary glycemic index and glycemic load with predictors of type 2 diabetes in older adults. DESIGN: This study evaluated cross-sectional relations of dietary glycemic index and glycemic load with measures of glucose metabolism and body fat distribution in participants of the Health, Aging and Body Composition Study, a prospective cohort study of adults aged 70-80 y (n = 2248). RESULTS: In men, dietary glycemic index was positively associated with 2-h glucose (P for trend = 0.04) and fasting insulin (P for trend = 0.004), inversely associated with thigh intramuscular fat (P for trend = 0.02), and not significantly associated with fasting glucose, glycated hemoglobin, or visceral abdominal fat. Dietary glycemic load was inversely associated in men with visceral abdominal fat (P for trend = 0.02) and not significantly associated with fasting glucose, 2-h glucose, glycated hemoglobin, fasting insulin, or thigh intramuscular fat. In women, although dietary glycemic index and load were not significantly related to any measures of glucose metabolism or body fat distribution, the association between dietary glycemic index and 2-h glucose was nearly significant (P for trend = 0.06). CONCLUSION: The findings of this cross-sectional study indicate an association between dietary glycemic index and selected predictors of type 2 diabetes in older adults, particularly in men.

Effects of calcium pyruvate supplementation during training on body composition, exercise capacity, and metabolic responses to exercise.

OBJECTIVE: We evaluated the effects of calcium pyruvate supplementation during training on body composition and metabolic responses to exercise. METHODS: Twenty-three untrained females were matched and assigned to ingest in a double blind and randomized manner either 5 g of calcium pyruvate (PYR) or a placebo (PL) twice daily for 30 d while participating in a supervised exercise program. Prior to and following supplementation, subjects had body composition determined via hydrodensiometry; performed a maximal cardiopulmonary exercise test; and performed a 45-min walk test at 70% of pre-training VO2 max in which fasting pre- and post exercise blood samples determined. RESULTS: No significant differences were observed between groups in energy intake or training volume. Univariate repeated measures ANOVA revealed that subjects in the PYR group gained less weight (PL 1.2 +/- 0.3, PYR 0.3 +/- 0.3 kg, P = 0.04), lost more fat (PL 1.1 +/- 0.5; PYR -0.4 +/- 0.5 kg, P = 0.03), and tended to lose a greater percentage of body fat (PL 1.0 +/- 0.7; PYR -0.65 +/- 0.6%, P = 0.07), with no differences observed in fat-free mass (PL 0.1 +/- 0.5; PYR 0.7 +/- 0.3 kg, P = 0.29). However, these changes were not significant when body composition data were analyzed by MANOVA (P = 0.16). There was some evidence that PYR may negate some of the beneficial effects of exercise on HDL values. No significant differences were observed between groups in maximal exercise responses or metabolic responses to submaximal walking. CONCLUSIONS: Results indicate that PYR supplementation during training does not significantly affect body composition or exercise performance and may negatively affect some blood lipid levels.

Intakes of whole grains, bran, and germ and the risk of coronary heart disease in men.

BACKGROUND: Previous studies have suggested that a daily intake of 3 servings of whole-grain foods is associated with a reduced risk of coronary heart disease (CHD). However, methods for the assessment of whole-grain intake differ. Furthermore, any additional effects of added bran and germ, which are components of whole grains, have not been reported. OBJECTIVE: The objective was to evaluate the association of whole-grain, bran, and germ intakes (with the use of new quantitative measures) with the incidence of CHD. DESIGN: This was a prospective cohort study of 42,850 male health professionals aged 40-75 y at baseline in 1986 who were free from cardiovascular disease, cancer, and diabetes. Daily whole-grain, bran, and germ intakes were derived in grams per day from a detailed semiquantitative dietary questionnaire. RESULTS: During 14 y of follow-up, we documented 1818 incident cases of CHD. After cardiovascular disease risk factors and the intakes of bran and germ added to foods were controlled for, the hazard ratio of CHD between extreme quintiles of whole-grain intake was 0.82 (95% CI: 0.70, 0.96; P for trend=0.01). The hazard ratio of CHD in men with the highest intake of added bran was 0.70 (95% CI: 0.60, 0.82) compared with men with no intake of added bran (P for trend < or = 0.001). Added germ was not associated with CHD risk. CONCLUSION: This study supports the reported beneficial association of whole-grain intake with CHD and suggests that the bran component of whole grains could be a key factor in this relation.

Changes in whole-grain, bran, and cereal fiber consumption in relation to 8-y weight gain among men.

BACKGROUND: Epidemiologic studies that directly examine changes in whole-grain consumption in relation to weight gain are sparse, and characterization of this association has been obscured by methodologic inconsistencies in the assessment of whole grains. OBJECTIVE: We aimed to ascertain the associations between changes in new quantitative estimates of whole-grain intake and 8-y weight gain among US men. DESIGN: The study was conducted in a prospective cohort of 27 082 men aged 40-75 y at baseline in 1986. Data on lifestyle factors were obtained periodically by using self-reported questionnaires, and participants measured and reported their body weight in 1986 and 1994. RESULTS: In multivariate analyses, an increase in whole-grain intake was inversely associated with long-term weight gain (P for trend < 0.0001). A dose-response relation was observed, and for every 40-g/d increment in whole-grain intake from all foods, weight gain was reduced by 0.49 kg. Bran that was added to the diet or obtained from fortified-grain foods further reduced the risk of weight gain (P for trend = 0.01), and, for every 20 g/d increase in intake, weight gain was reduced by 0.36 kg. Changes in cereal and fruit fiber were inversely related to weight gain. No associations were observed between changes in refined-grain or added germ consumption and body weight. CONCLUSIONS: The increased consumption of whole grains was inversely related to weight gain, and the associations persisted after changes in added bran or fiber intakes were accounted for. This suggests that additional components in whole grains may contribute to favorable metabolic alterations that may reduce long-term weight gain.

Changes in body weight and body fat distribution as risk factors for clinical diabetes in US men.

Although previous studies have linked obesity to diabetes, the risks associated with weight gain or changes in body fat distribution have not been fully elucidated. The authors therefore prospectively examined the relations between changes in body weight and body fat distribution (1986-1996) and the subsequent risk of diabetes (1996-2000) among 22,171 men in the Health Professionals Follow-up Study. Weight gain was monotonically related to risk, and for every kilogram of weight gained, risk increased by 7.3%. A gain in abdominal fat was positively associated with risk, independent of the risk associated with weight change. Compared with men who had a stable waist, men who increased waist circumference by 14.6 cm or more had 1.7 (95% confidence interval: 1.0, 2.8) times the risk of diabetes after controlling for weight gain. In contrast, men who lost more than 4.1 cm in hip girth had 1.5 (95% confidence interval: 1.0, 2.3) times the risk of diabetes compared with men with stable hip circumference. Fifty-six percent of the cases of diabetes in this cohort could be attributed to weight gain greater than 7 kg, and 20 percent of the cases could be attributed to a waist gain exceeding 2.5 cm. Our findings underscore the critical importance of maintaining weight and waist to reduce the risk of diabetes.

Prospective study of the association of changes in dietary intake, physical activity, alcohol consumption, and smoking with 9-y gain in waist circumference among 16 587 US men.

BACKGROUND: Although it is known that abdominal obesity increases the risk of chronic diseases, prospective data examining the relation between lifestyle factors and the accumulation of abdominal adipose tissue are sparse. OBJECTIVE: The objective of the study was to determine the associations of changes in diet, physical activity, alcohol consumption, and smoking with 9-y waist gain among US men. DESIGN: A prospective cohort comprised 16 587 US men aged 40-75 y at baseline in 1986. Data on lifestyle factors were provided periodically with the use of self-reported questionnaires, and participants measured and reported their waist circumference in 1987 and 1996. RESULTS: In multivariate analyses, a 2% increment in energy intake from trans fats that were isocalorically substituted for either polyunsaturated fats or carbohydrates was significantly associated with a 0.77-cm waist gain over 9 y (P < 0.001 for each comparison). An increase of 12 g total fiber/d was associated with a 0.63-cm decrease in waist circumference (P < 0.001), whereas smoking cessation and a 20-h/wk increase in television watching were associated with a 1.98-cm and 0.59-cm waist gain, respectively (P < 0.001). Increases of 25 metabolic equivalent tasks (METs) * h/wk in vigorous physical activity and of >/= 0.5 h/wk in weight training were associated with 0.38-cm and 0.91-cm decreases in waist circumference, respectively (P < 0.001 for each comparison). These associations remained significant after further adjustment for concurrent change in body mass index. Changes in total fat and alcohol consumption and in walking volume were not significantly related to waist gain. CONCLUSIONS: Waist gain may be modulated by changes in trans fat and fiber consumption, smoking cessation, and physical activity.

Whole grain consumption and weight gain: a review of the epidemiological evidence, potential mechanisms and opportunities for future research.

The epidemiological data that directly examine whole grain v. refined grain intake in relation to weight gain are sparse. However, recently reported studies offer insight into the potential role that whole grains may play in body-weight regulation due to the effects that the components of whole grains have on hormonal factors, satiety and satiation. In both clinical trials and observational studies the intake of whole-grain foods was inversely associated with plasma biomarkers of obesity, including insulin, C-peptide and leptin concentrations. Whole-grain foods tend to have low glycaemic index values, resulting in lower postprandial glucose responses and insulin demand. High insulin levels may promote obesity by altering adipose tissue physiology and by enhancing appetite. The fibre content of whole grains may also affect the secretion of gut hormones, independent of glycaemic response, that may act as satiety factors. Future studies may examine whether whole grain intake is directly related to body weight, and whether the associations are primarily driven by components of the grain, including dietary fibre, bran or germ.