Whole-grain intake is favorably associated with metabolic risk factors for type 2 diabetes and cardiovascular disease in the Framingham Offspring Study

Associations of plant food, dairy product, and meat intakes with 15-y incidence of elevated blood pressure in young black and white adults: the Coronary Artery Risk Development in Young Adults (CARDIA) Study

BACKGROUND

Consumption of plant foods and dairy and meat products may moderate increases in blood pressure.

OBJECTIVE

The objective was to evaluate associations of dietary intake with the 15-y incidence of elevated blood pressure (EBP; ie, incident systolic BP >or= 130 mm Hg, diastolic BP >or= 85 mm Hg, or use of antihypertensive medication).

DESIGN

Proportional hazards regression was used to evaluate relations of dietary intake at years 0 and 7 with the 15-y incidence of EBP in the Coronary Artery Risk Development in Young Adults (CARDIA) Study of 4304 participants aged 18-30 y at baseline.

RESULTS

EBP incidence varied from 12% in white women to 33% in black men. Plant food intake (whole grains, refined grains, fruit, vegetables, nuts, or legumes) was inversely related to EBP after adjustment for age, sex, race, center, energy intake, cardiovascular disease risk factors, and other potential confounding factors. Compared with quintile 1, the relative hazards of EBP for quintiles 2-5 of plant food intake were 0.83 (95% CI: 0.68, 1.01), 0.83 (0.67, 1.02), 0.82 (0.65, 1.03), and 0.64 (0.53, 0.90), respectively; P for trend = 0.01. Dairy intake was not related to EBP (P for trend = 0.06), and positive dose-response relations for EBP were observed across increasing quintiles of meat intake (P for trend = 0.004). In subgroup analyses, risk of EBP was positively associated with red and processed meat intake, whereas it was inversely associated with intakes of whole grain, fruit, nuts, and milk. Adjustment for intermediary factors in the causal pathway attenuated these relations.

CONCLUSION

These findings are consistent with a beneficial effect of plant food intake and an adverse effect of meat intake on blood pressure.

Dietary fiber intake and risk factors for cardiovascular disease in French adults

BACKGROUND

Increased consumption of dietary fiber is widely recommended to maintain or improve health, but knowledge of the relation between dietary fiber sources and cardiovascular disease risk factors is limited.

OBJECTIVE

We examined the relation between the source or type of dietary fiber intake and cardiovascular disease risk factors in a cohort of adult men and women.

DESIGN

In a cross-sectional study, quintiles of fiber intake were determined from dietary records, separately for 2532 men and 3429 women. Age- and multivariate-controlled logistic models investigated the odds ratios of abnormal markers for quintiles 2-5 of fiber intake compared with the lowest quintile.

RESULTS

The highest total dietary fiber and nonsoluble dietary fiber intakes were associated with a significantly (P < 0.05) lower risk of overweight and elevated waist-to-hip ratio, blood pressure, plasma apolipoprotein (apo) B, apo B:apo A-I, cholesterol, triacylglycerols, and homocysteine. Soluble dietary fiber was less effective. Fiber from cereals was associated with a lower body mass index, blood pressure, and homocysteine concentration; fiber from vegetables with a lower blood pressure and homocysteine concentration; and fiber from fruit with a lower waist-to-hip ratio and blood pressure. Fiber from dried fruit or nuts and seeds was associated with a lower body mass index, waist-to-hip ratio, and fasting apo B and glucose concentrations. Fiber from pulses had no specific effect.

CONCLUSION

Dietary fiber intake is inversely correlated with several cardiovascular disease risk factors in both sexes, which supports its protective role against cardiovascular disease and recommendations for its increased consumption.

Prevention of Type 2 Diabetes by Diet and Lifestyle Modification

Diabetes mellitus is an epidemic of our time. This disease affects nearly 150 million adults worldwide and nearly 11 million in the United States in 2000. Because of the prevalence of obesity and diabetes and associated vascular complications, preventing even a small proportion of cases would save thousands of lives and billions of dollars in healthcare costs and lost productivity. Researchers have made great strides in identifying many lifestyle and dietary factors associated with diabetes, but solidifying the scientific basis for prevention and control of this disease as well as implementation at a national level remains a difficult challenge. The literature on the influence of diet and lifestyle in the development of diabetes is reviewed here, with emphasis on epidemiologic data. We outline a systematic approach to primary and secondary prevention of this disease by evaluating and prioritizing risk factors for which intervention is effective and developing a framework for application of intervention strategies. Effective interventions must target not only the affected individuals but also families, workplaces, schools and communities. Prevention of this devastating disease calls for the identification of culture-sensitive measures that can be applied to the population in general and some high-risk minority groups in particular.

The Nutritional Impact of Dairy Product Consumption on Dietary Intakes of Adults (1995–1996): The Bogalusa Heart Study

OBJECTIVE

To examine the nutritional impact of dairy product consumption on the dietary intakes of adults.

DESIGN

Dietary intakes of adults who participated in a cross-sectional survey (1995-1996) in Bogalusa, LA.

SUBJECTS

Dietary intake data were collected on 1,266 adults (61% women, 39% men; 74% white, 26% African American) in Bogalusa, LA.

STATISTICAL ANALYSIS

Analysis of covariance was used to examine the mean nutrient intake differences among four dairy consumption groups. Significance tests in multiple comparisons between any two groups were conducted using Tukey's procedure.

RESULTS

Forty-eight percent of adults consumed one serving or less of dairy products, 32% consumed two servings, 12% consumed three servings, and 8% consumed four or more servings. Overall mean intake of dairy was higher in whites (mean=1.63) compared with African Americans (mean=1.22) (P<.0001), especially the consumption of milk and cheese. No differences were found in overall mean intake of dairy servings by sex after adjusting for energy intake. However, women consumed significantly more servings of cheese (P<.0001) and yogurt (P<.01) than men. There were higher intakes of total energy, saturated fat, total protein, animal protein, and lactose (P<.0001), with greater number of servings of dairy products consumed. There were lower intakes of monounsaturated and polyunsaturated fatty acids (P<.0001), vegetable protein (P<.0001), total carbohydrates (P<.01), sucrose (P<.001), fructose (P<.0001), and fiber (P<.001). The percentage of energy from saturated fat (P<.0001) and protein (P<.001) increased with increasing number of dairy servings consumed. Intakes of calcium; magnesium; potassium; zinc; sodium; folate; thiamin; riboflavin; and vitamins B-6, B-12, A, D, and E were higher with greater number of dairy servings consumed. There was lower consumption of sweetened beverages (P<.001), specifically regular soft drinks (P<.0001), with greater consumption of milk products.

CONCLUSIONS

Dairy product consumption by adults has a major influence on their vitamin and mineral intakes. The higher intakes of saturated fat, total energy, and animal protein and lower intake of fiber suggest that it may be useful to consume lower-fat dairy products and/or modify eating patterns to optimize the nutritional contributions of dairy products. Public health organizations and dietetics professionals need to educate adults on practical strategies for increasing dairy product consumption for improving the nutritional quality of adults' diets.

Dietary pattern, inflammation, and incidence of type 2 diabetes in women

BACKGROUND

Inflammation is considered a key mechanism leading to type 2 diabetes, but dietary exposures that lead to inflammation and diabetes are largely unknown.

OBJECTIVE

Our objective was to investigate the relation between a dietary pattern associated with biomarkers of inflammation and the incidence of type 2 diabetes.

DESIGN

We conducted a nested case-control study of 656 cases of type 2 diabetes and 694 controls among women in the Nurses' Health Study and 2 prospective cohort studies of 35,340 women in the Nurses' Health Study and 89,311 women in the Nurses' Health Study II who were followed for incident diabetes.

RESULTS

Through the use of reduced rank regression, we identified a dietary pattern that was strongly related to inflammatory markers in the nested case-control study. This pattern, which was high in sugar-sweetened soft drinks, refined grains, diet soft drinks, and processed meat but low in wine, coffee, cruciferous vegetables, and yellow vegetables, was associated with an increased risk of diabetes (multivariate-adjusted odds ratio comparing extreme quintiles: 3.09; 95% CI: 1.99, 4.79). We identified 1517 incident cases of confirmed type 2 diabetes in the Nurses' Health Study (458,991 person-years) and 724 incident cases in the Nurses' Health Study II (701,155 person-years). After adjustment for body mass index and other potential lifestyle confounders, the relative risks comparing extreme quintiles of the pattern were 2.56 (95% CI: 2.10, 3.12; P for trend < 0.001) in the Nurses' Health Study and 2.93 (95% CI: 2.18, 3.92; P for trend < 0.001) in the Nurses' Health Study II.

CONCLUSION

The dietary pattern identified may increase chronic inflammation and raise the risk of developing type 2 diabetes.

The effects of a low-fat, plant-based dietary intervention on body weight, metabolism, and insulin sensitivity

PURPOSE

This study investigated the effect of a low-fat, plant-based diet on body weight, metabolism, and insulin sensitivity, while controlling for exercise in free-living individuals.

SUBJECTS AND METHODS

In an outpatient setting, 64 overweight, postmenopausal women were randomly assigned to a low-fat, vegan diet or a control diet based on National Cholesterol Education Program guidelines, without energy intake limits, and were asked to maintain exercise unchanged. Dietary intake, body weight and composition, resting metabolic rate, thermic effect of food, and insulin sensitivity were measured at baseline and 14 weeks.

RESULTS

Mean +/- standard deviation intervention-group body weight decreased 5.8 +/- 3.2 kg, compared with 3.8 +/- 2.8 kg in the control group (P = .012). In a regression model of predictors of weight change, including diet group and changes in energy intake, thermic effect of food, resting metabolic rate, and reported energy expenditure, significant effects were found for diet group (P < .05), thermic effect of food (P < .05), and resting metabolic rate (P < .001). An index of insulin sensitivity increased from 4.6 +/- 2.9 to 5.7 +/- 3.9 (P = .017) in the intervention group, but the difference between groups was not significant (P = .17).

CONCLUSION

Adoption of a low-fat, vegan diet was associated with significant weight loss in overweight postmenopausal women, despite the absence of prescribed limits on portion size or energy intake.

Whole-grain consumption and the metabolic syndrome: a favorable association in Tehranian adults

BACKGROUND

Although dietary guidelines recommend increased intake of grain products to prevent chronic diseases, epidemiologic data regarding whole-grain intake association with metabolic syndrome are sparse.

OBJECTIVE

To evaluate the relationship between whole-grain intakes, metabolic syndrome and metabolic risk factors in Tehranian adults.

DESIGN

Population-based cross-sectional study.

SETTING

Tehran, the capital of Iran.

SUBJECTS

A representative sample of 827 subjects (357 men and 470 women) aged 18-74 y.

METHODS

Usual dietary intake was assessed using a food frequency questionnaire. The procedure developed by Jacobs et al was used to classify grain products into whole and refined grains. Weight and height were measured according to standard protocols and body mass index was calculated. Fasting blood samples were taken for biochemical measurements and blood pressure was assessed according to standard methods. Hypertriglyceridemia, hypercholestrolemia, high LDL, low HDL and metabolic syndrome were defined according to ATP III guidelines and hypertension based on JNC VI. Diabetes was defined as fasting plasma glucose level of > or = 126 mg/dl or 2-h postchallenge blood glucose level of > or = 200 mg/dl. Subjects were categorized based on quartile cut-points of whole- and refined-grain intake.

RESULTS

Mean (+/-s.d.) consumptions of whole and refined grains were 93+/-29 and 201+/-57 g/day, respectively. Both men and women reported higher intakes of refined grain than of whole grains. Compared with subjects in the lower quartile category, those in the upper category of whole-grain intake had lower prevalence of metabolic risk factors. Conversely, those in the higher category of refined-grain intake had higher prevalence of metabolic risk factors, except for diabetes. After controlling for confounders, a significantly decreasing trend was observed for the risk of having hypertriglyceridemia (odds ratios among quartiles: 1.00, 0.89, 0.74, 0.61, respectively), hypertension (1.00, 0.99, 0.93, 0.84) and metabolic syndrome (1.00, 0.84, 0.76, 0.68). Higher consumption of refined grains was associated with higher odds of having hypercholestrolemia (1.00, 1.07, 1.19, 1.23), hypertriglyceridemia (1.00, 1.17, 1.49, 2.01), hypertension (1.00, 1.22, 1.48, 1.69) and metabolic syndrome (1.00, 1.68, 1.92, 2.25).

CONCLUSION

Whole-grain intake is inversely and refined-grain intake is positively associated with the risk of having metabolic syndrome. Recommendations to increase whole-grain intake may reduce this risk.

Cereal grains, legumes and diabetes

This review examines the evidence for the role of whole grain foods and legumes in the aetiology and management of diabetes. MedLine and SilverPlatter ('Nutrition' and 'Food Science FSTA') databases were searched to identify epidemiological and experimental studies relating to the effects of whole grain foods and legumes on indicators of carbohydrate metabolism. Epidemiological studies strongly support the suggestion that high intakes of whole grain foods protect against the development of type II diabetes mellitus (T2DM). People who consume approximately 3 servings per day of whole grain foods are less likely to develop T2DM than low consumers (<3 servings per week) with a risk reduction in the order of 20-30%. The role of legumes in the prevention of diabetes is less clear, possibly because of the relatively low intake of leguminous foods in the populations studied. However, legumes share several qualities with whole grains of potential benefit to glycaemic control including slow release carbohydrate and a high fibre content. A substantial increase in dietary intake of legumes as replacement food for more rapidly digested carbohydrate might therefore be expected to improve glycaemic control and thus reduce incident diabetes. This is consistent with the results of dietary intervention studies that have found improvements in glycaemic control after increasing the dietary intake of whole grain foods, legumes, vegetables and fruit. The benefit has been attributed to an increase in soluble fibre intake. However, prospective studies have found that soluble fibre intake is not associated with a lower incidence of T2DM. On the contrary, it is cereal fibre that is largely insoluble that is associated with a reduced risk of developing T2DM. Despite this, the addition of wheat bran to the diets of diabetic people has not improved indicators of glycaemic control. These apparently contradictory findings might be explained by metabolic studies that have indicated improvement in glucose handling is associated with the intact structure of food. For both grains and legumes, fine grinding disrupts cell structures and renders starch more readily accessible for digestion. The extent to which the intact structure of grains and legumes or the composition of foods in terms of dietary fibre and other constituents contribute to the beneficial effect remains to be quantified. Other mechanisms to help explain improvements in glycaemic control when consuming whole grains and legumes relate to cooking, type of starch, satiety and nutrient retention. Thus, there is strong evidence to suggest that eating a variety of whole grain foods and legumes is beneficial in the prevention and management of diabetes. This is compatible with advice from around the world that recommends consumption of a wide range of carbohydrate foods from cereals, vegetables, legumes and fruits both for the general population and for people with diabetes.

Deleterious effects of omitting breakfast on insulin sensitivity and fasting lipid profiles in healthy lean women

BACKGROUND

Breakfast consumption is recommended, despite inconclusive evidence of health benefits.

OBJECTIVE

The study's aim was to ascertain whether eating breakfast (EB) or omitting breakfast (OB) affects energy intake, energy expenditure, and circulating insulin, glucose, and lipid concentrations in healthy women.

DESIGN

In a randomized crossover trial, 10 women [x+/-SD body mass index (BMI; in kg/m2): 23.2+/-1.4] underwent two 14-d EB or OB interventions separated by a 2-wk interval. In the EB period, subjects consumed breakfast cereal with 2%-fat milk before 0800 and a chocolate-covered cookie between 1030 and 1100. In the OB period, subjects consumed the cookie between 1030 and 1100 and the cereal and milk between 1200 and 1330. Subjects then consumed 4 additional meals with content similar to usual at predetermined times later in the day and recorded food intake on 3 d during each period. Fasting and posttest meal glucose, lipid, and insulin concentrations and resting energy expenditure were measured before and after each period.

RESULTS

Reported energy intake was significantly lower in the EB period (P=0.001), and resting energy expenditure did not differ significantly between the 2 periods. OB was associated with significantly higher fasting total and LDL cholesterol than was EB (3.14 and 3.43 mmol/L and 1.55 and 1.82 mmol/L, respectively; P=0.001). The area under the curve of insulin response to the test meal was significantly lower after EB than after OB (P<0.01).

CONCLUSION

OB impairs fasting lipids and postprandial insulin sensitivity and could lead to weight gain if the observed higher energy intake was sustained.

Magnesium may mediate the favorable impact of whole grains on insulin sensitivity by acting as a mild calcium antagonist

Recent epidemiology has linked high consumption of whole grains with reduced risk for diabetes, coronary disease, stroke, and various types of cancer; there is reason to suspect that improved insulin sensitivity is largely responsible for this protection. This phenomenon may be partially explained by the lower glycemic indices of some whole grain food products in comparison to their fiber-depleted analogs. Nonetheless, the fact that whole wheat flour promotes insulin sensitivity relative to white flour--and yet has a near-identical glycemic index--suggests that certain nutrients or phytochemicals in whole wheat, depleted by the refining process, promote preservation of insulin sensitivity. Magnesium is a likely candidate in this regard; magnesium deficiency promotes insulin resistance in rodents and in humans, whereas supplemental magnesium has been found to prevent type 2 diabetes in rodent models of this syndrome, and to improve the insulin sensitivity of elderly or diabetic humans. Magnesium-rich diets as well as above-average serum magnesium are associated with reduced diabetes risk in prospective epidemiology, and with greater insulin sensitivity in cross-sectional studies; moreover, other types of magnesium-rich foods--dairy products, legumes, and nuts--have been linked to decreased diabetes risk in prospective studies. The biochemical role of magnesium in support of insulin function is still poorly understood. In light of evidence that magnesium can function as a mild natural calcium antagonist, it is interesting to note suggestive evidence that increases in intracellular free calcium may compromise the insulin responsiveness of adipocytes and skeletal muscle, and may indeed play a pathogenic role in the insulin resistance syndrome. Thus, it is proposed that some or all of the favorable impact of good magnesium status on insulin function may reflect antagonism of the induction or effects of increased intracellular free calcium. Further research concerning the potential health benefits of long-term magnesium supplementation is clearly warranted. These considerations, however, should not detract from efforts to better inform the public regarding the strong desirability of choosing whole grain products in preference to refined grains.

Whole-grain intake and the prevalence of hypertriglyceridemic waist phenotype in Tehranian adults

BACKGROUND

Although dietary guidelines recommend increased intake of grain products to prevent chronic diseases, no epidemiologic data associate whole-grain intake with hypertriglyceridemic waist (HW) phenotype.

OBJECTIVE

We aimed to evaluate the relation between whole-grain intakes and the prevalence of HW phenotype in adults in Tehran, Iran.

DESIGN

Whole-grain intake, serum triacylglycerol concentration, and waist circumference (WC) were assessed in a population-based, cross-sectional study of 827 Iranian subjects (357 men and 470 women) aged 18-74 y. HW phenotype was defined as serum triacylglycerol concentrations > or =150 mg/dL and concurrent WC > or = 80 cm (men) and > or =79 cm (women).

RESULTS

Mean (+/-SD) consumption of whole and refined grains was 93 +/- 29 and 201 +/- 57 g/d, respectively. Subjects in the highest quartile of whole-grain intake had a significantly lower prevalence of HW (29%) than did those in the lowest quartile (44%; P < 0.05). Conversely, those in the highest quartile of refined-grain intake had a significantly higher prevalence of HW (45%) than did those in the lowest quartile (27%; P < 0.05). After control for potential confounding factors, a significantly decreasing trend was observed for the risk of HW phenotype across quartiles of whole-grain intake (odds ratios among quartiles: 1.00, 0.95, 0.90, and 0.78, respectively; P for trend = 0.02). Higher consumption of refined grains was associated with better odds of HW phenotype (by quartile: 1.00, 1.38, 1.65, and 2.1; P for trend = 0.01).

CONCLUSION

Whole-grain intake is inversely and refined-grain intake is positively associated with the risk of HW.

Food and drinking patterns as predictors of 6-year BMI-adjusted changes in waist circumference

Few studies have investigated the prospective associations between diet or drinking patterns and abdominal obesity; we therefore investigated whether food and beverage groups or patterns predicted 6-year changes in waist circumference (WC) and whether these associations were independent of concurrent changes in BMI as a measure of general obesity. The subjects were 2300 middle-aged men and women with repeated measurements of dietary intake, BMI and WC from 1982 to 1993. Intakes from ten food groups and from coffee, tea, wine, beer and spirits were assessed; gender-specific food factors were identified by factor analyses. Multiple linear regression analyses were done before and after adjustment for concurrent changes in BMI. A high intake of potatoes seemed to prevent gain in WC for men, while a high intake of refined bread was associated with gain in WC for women. The association persisted for refined bread, but not for potatoes, after adjustment for concurrent BMI changes. Among women, but not men, high intakes of beer and spirits were associated with gain in WC in both models. A high intake of coffee for women and moderate to high intake of tea for men were associated with gain in WC, but the associations were weakened, especially for women, after adjustment for BMI changes. None of the food factors was associated with WC changes. Based on the present study, we conclude that very few food items and no food patterns seem to predict changes in WC, whereas high intakes of beer and spirits among women, and moderate to high tea intake among men, may promote gain in WC.

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.

Whole grain intake and cardiovascular disease: A review

Prospective epidemiologic and feeding studies find possible health benefits of whole cereal grain foods (which include the bran, germ, and endosperm in their naturally occurring proportions), especially for prevention of atherosclerotic cardiovascular diseases and type 2 diabetes. We review 17 articles that consistently found a 20% to 40% reduction in long-term risk of these diseases comparing habitual consumers of whole grains to those who rarely eat these foods. Another 12 studies found a similar risk reduction according to amount of cereal fiber consumed. Feeding studies show improvements in risk factors for these diseases when whole grain foods are consumed. Some authors have tried to explain the reduced risk by invoking cereal fiber, with no attention to nonfiber constituents. We interpret the data as supportive of a synergy of the whole grain constituents, including fiber as only one such constituent.

Whole grain intake and insulin sensitivity: evidence from observational studies

Observational studies have found that diets rich in whole-grain foods are associated with improved insulin sensitivity. The improved insulin sensitivity may be mediated in part by magnesium and dietary fiber, two nutrients found in whole-grain foods. By incorporating whole-grain foods into the diet, therefore, insulin sensitivity might be improved.

Functional foods, herbs and nutraceuticals: towards biochemical mechanisms of healthy aging

Aging is associated with mitochondrial dysfunctions, which trigger membrane leakage, release of reactive species from oxygen and nitrogen and subsequent induction of peroxidative reactions that result in biomolecules' damaging and releasing of metals with amplification of free radicals discharge. Free radicals induce neuronal cell death increasing tissue loss, which could be associated with memory detriment. These pathological events are involved in cardiovascular, neurodegenerative and carcinogenic processes. Dietary bioactive compounds from different functional foods, herbs and nutraceuticals (ginseng, ginkgo, nuts, grains, tomato, soy phytoestrogens, curcumin, melatonin, polyphenols, antioxidant vitamins, carnitine, carnosine, ubiquinone, etc.) can ameliorate or even prevent diseases. Protection from chronic diseases of aging involves antioxidant activities, mitochondrial stabilizing functions, metal chelating activities, inhibition of apoptosis of vital cells, and induction of cancer cell apoptosis. Functional foods and nutraceuticals constitute a great promise to improve health and prevent aging-related chronic diseases.

Diet composition and the risk of type 2 diabetes: epidemiological and clinical evidence

In the last 10 years nutritional research on diabetes has improved dramatically in terms of both number of studies produced and quality of methodologies employed. Therefore, it is now possible to attempt to provide the evidence on which nutritional recommendations for the prevention of type 2 diabetes could be based. We therefore performed a literature search and, among the papers published in indexed journals, we selected relevant epidemiological (mostly prospective) and controlled intervention studies. Lifestyle factors that have, so far, been consistently associated with increased risk of type 2 diabetes are overweight and physical inactivity. However, recent evidence from epidemiological studies has shown that the risk of type 2 diabetes is also associated with diet composition, particularly with: (1) low fibre intake; (2) a high trans fatty acid intake and a low unsaturated:saturated fat intake ratio; (3) absence of or excess alcohol consumption. All these factors are extremely common in Western populations and therefore the potential impact of any intervention on them is large: indeed, >90 % of the general population has one or more of these risk factors. The ability to correct these behaviours in the population is estimated to reduce the incidence of diabetes by as much as 87 %. Recent intervention studies have shown that type 2 diabetes can be prevented by lifestyle changes aimed at body-weight reduction, increased physical activity and multiple changes in the composition of the diet. Within this context, the average amount of weight loss needed is not large, about 5 % initial weight, which is much less than the weight loss traditionally considered to be clinically significant for prevention of type 2 diabetes. In conclusion, new emphasis on prevention by multiple lifestyle modifications, including moderate changes in the composition of the habitual diet, might limit the dramatic increase in incidence of type 2 diabetes envisaged worldwide.

Position of the American Dietetic Association and Dietitians of Canada: Nutrition and Women’s Health

It is the position of the American Dietetic Association (ADA) and Dietitians of Canada (DC) that women have specific nutritional needs and vulnerabilities and, as such, are at unique risk for various nutrition-related diseases and conditions. Therefore, the ADA and the DC strongly support research, health promotion activities, health services, and advocacy efforts that will enable women to adopt desirable nutrition practices for optimal health. Women are at risk for numerous chronic diseases and conditions that affect the duration and quality of their lives. Although women's health-related issues are multifaceted, nutrition has been shown to influence significantly the risk of chronic disease and to assist in maintaining optimal health status. Dietetics professionals strongly support research, health promotion activities, health services, and advocacy efforts that will enable women to adopt desirable nutrition practices for optimal health.

Carbohydrate nutrition, insulin resistance, and the prevalence of the metabolic syndrome in the Framingham Offspring Cohort

OBJECTIVE

The aim of this study was to examine the relation between carbohydrate-related dietary factors, insulin resistance, and the prevalence of the metabolic syndrome in the Framingham Offspring Cohort.

RESEARCH DESIGN AND METHODS

We examined cross-sectional associations between carbohydrate-related dietary factors, insulin resistance, and the prevalence of the metabolic syndrome in 2,834 subjects at the fifth examination (1991-1995) of the Framingham Offspring Study. Homeostasis model assessment of insulin resistance (HOMA-IR) was calculated using the following formula (fasting plasma insulin x plasma glucose)/22.5. The metabolic syndrome was defined using the National Cholesterol Education Program criteria.

RESULTS

After adjustment for potential confounding variables, intakes of total dietary fiber, cereal fiber, fruit fiber, and whole grains were inversely associated, whereas glycemic index and glycemic load were positively associated with HOMA-IR. The prevalence of the metabolic syndrome was significantly lower among those in the highest quintile of cereal fiber (odds ratio [OR] 0.62; 95% CI 0.45-0.86) and whole-grain (0.67; 0.48-0.91) intakes relative to those in the lowest quintile category after adjustment for confounding lifestyle and dietary factors. Conversely, the prevalence of the metabolic syndrome was significantly higher among individuals in the highest relative to the lowest quintile category of glycemic index (1.41; 1.04-1.91). Total carbohydrate, dietary fiber, fruit fiber, vegetable fiber, legume fiber, glycemic load, and refined grain intakes were not associated with prevalence of the metabolic syndrome.

CONCLUSIONS

Whole-grain intake, largely attributed to the cereal fiber, is inversely associated with HOMA-IR and a lower prevalence of the metabolic syndrome. Dietary glycemic index is positively associated with HOMA-IR and prevalence of the metabolic syndrome. Given that both a high cereal fiber content and lower glycemic index are attributes of whole-grain foods, recommendation to increase whole-grain intake may reduce the risk of developing the metabolic syndrome.

Becoming Proactive With the Whole-Grains Message

Whole-grain foods have always been considered a healthy part of the diet. Only recently have epidemiologic and other data shown that whole grains have a role in preventing cardiovascular disease, diabetes, some types of cancer, and even obesity. What nearly all consumers and most health professionals fail to realize is that whole grains deliver as many if not more phytochemicals and antioxidants than do fruits and vegetables. Healthy People 2010 (DHHS) recommends 3 servings of whole grains per day. Because the average intake in the United States is less than 1 serving per day, health professionals must mount an active campaign to help consumers better understand the important health benefits of whole grains and work to increase their intake in the diet.

Applying the theory of planned behavior to promotion of whole-grain foods by dietitians

The objective of this preliminary study was to apply the theory of planned behavior to explain dietitians' intentions to promote whole-grain foods. Surveys were mailed to a random national sample of registered dietitians to assess knowledge and attitudinal, normative, and control beliefs regarding intention to promote whole-grain foods, with a 39% return rate (n=776, with 628 usable surveys from those working in direct patient care). About half of the respondents had a master's degree, and 58% had substantial experience in the dietetics field. The theory of planned behavior explained intention to promote whole grains to a moderate extent (df=3, F=74.5, R(2)=0.278, P<.001). Most were positive about the health benefits, and few perceived barriers to promotion. However, many had low levels of knowledge and self-efficacy regarding ability to help clients consume more whole-grain foods. Continuing education for dietitians should use strategies that enhance self-efficacy regarding ability to promote whole-grain foods.

Dietary Fiber Reduces Peripheral Arterial Disease Risk in Men

We prospectively evaluated the relationship between dietary fiber and peripheral arterial disease risk (PAD) among 46,032 men, aged 40 to 75 y, in 1986. Subjects answered a vascular disease questionnaire and completed a validated 131-item food frequency questionnaire, and were free of PAD, cardiovascular disease and diabetes. During 12 y of follow-up 308 incident PAD cases were documented. After adjusting for age, smoking, hypertension, hypercholesterolemia, family history of early coronary heart disease, alcohol consumption, BMI, physical activity and energy intake, PAD risk in each quintile of cereal fiber intake compared with the lowest quintile was 0.69, 95% CI 0.49-0.97 for quintile 2; 0.65, 95% CI 0.45-0.94 for quintile 3; 0.68, 95% CI 0.47-0.98 for quintile 4; and 0.67, 95% CI 0.47-0.97 for quintile 5. In a nonlinear model the overall inverse association (P = 0.02) and nonlinear components (P = 0.03) were significant. Fruit, vegetable and total fiber intakes were not associated with PAD risk. These results suggest an inverse association between cereal fiber intake and PAD risk in men. Increasing cereal fiber intake may prevent PAD.

Whole-grain intake and insulin sensitivity: the Insulin Resistance Atherosclerosis Study

BACKGROUND

Increased intake of whole-grain foods has been related to a reduced risk of developing diabetes and heart disease. One underlying pathway for this relation may be increased insulin sensitivity.

OBJECTIVE

We assessed the relation between dietary intake of whole grain-containing foods and insulin sensitivity (S(I)).

DESIGN

We evaluated data from the Insulin Resistance Atherosclerosis Study (IRAS Exam I, 1992-1994). Usual dietary intakes in 978 middle-aged adults with normal (67%) or impaired (33%) glucose tolerance were ascertained by using an interviewer-administered, validated food-frequency questionnaire. Whole-grain intake (servings per day) was derived from dark breads and high-fiber and cooked cereals. S(I) was assessed by minimal model analyses of the frequently sampled intravenous-glucose-tolerance test. Fasting insulin was measured by using a radioimmunoassay. We modeled the relation of whole-grain intake to log(S(I) + 1) and to log(insulin) by using multivariable linear regression.

RESULTS

On average, IRAS participants consumed 0.8 servings of whole grains/d. Whole-grain intake was significantly associated with S(I) (beta = 0.082, P = 0.0005) and insulin (beta = -0.0646, P = 0.019) after adjustment for demographics, total energy intake and expenditure, smoking, and family history of diabetes. The addition of body mass index and waist circumference attenuated but did not explain the association with S(I). The addition of fiber and magnesium resulted in a nonsignificant association that is consistent with the hypothesis that these constituents account for some of the effect of whole grains on S(I).

CONCLUSION

Higher intakes of whole grains were associated with increases in insulin sensitivity.

Dietary intake and food sources of whole grains among US children and adolescents: data from the 1994-1996 Continuing Survey of Food Intakes by Individuals

OBJECTIVE

This study characterizes whole grain consumption among a nationally representative sample of US children and adolescents.

DESIGN

Data used in this study were collected as part of the 1994-1996 US Department of Agriculture Continuing Survey of Food Intakes by Individuals (CSFII).

SUBJECTS/SETTING

CSFII was designed to obtain a nationally representative sample of noninstitutionalized persons of all ages residing in the United States. Analyses reported in this article are limited to participants aged 2 to 18 years with two days of dietary recall data (n=4,802). Foods reported in the survey were quantified in servings as defined by the Food Guide Pyramid using the US Department of Agriculture Pyramid Servings Database, which contains reference data for each food reported in CSFII in servings per 100 g for 30 Pyramid food groups, including whole grain and total grain.

STATISTICAL ANALYSES

Means, frequencies, and logistic regression analyses were conducted as appropriate.

RESULTS

Average whole grain intake ranged from 0.8 servings per day for preschool-aged children to 1.0 servings per day for adolescents. Ready-to-eat cereals, corn and other chips, and yeast breads were found to be the major food sources of whole grains accounting for 30.9%, 21.7%, and 18.1% of whole grain intake respectively among those aged two to 18 years.

APPLICATIONS/CONCLUSIONS

Given the apparent low level of whole grain intake among most children and adolescents in the United States, interventions are needed to increase intake of whole-grain foods.

Prior short-term consumption of resistant starch enhances postprandial insulin sensitivity in healthy subjects

AIMS/HYPOTHESIS

Diets rich in insoluble-fibre are linked to a reduced risk of both diabetes and cardiovascular disease; however, the mechanism of action remains unclear. The aim of this study was to assess whether acute changes in the insoluble-fibre (resistant starch) content of the diet would have effects on postprandial carbohydrate and lipid handling.

METHODS

Ten healthy subjects consumed two identical, low-residue diets on separate occasions for 24 h (33% fat; <2 g dietary fibre). Of the diets one was supplemented with 60 g resistant starch (Novelose 260). On the following morning a fibre-free meal tolerance test (MTT) was carried out (59 g carbohydrate; 21 g fat; 2.1 kJ) and postprandial insulin sensitivity (SI(ORAL)) assessed using a minimal model approach.

RESULTS

Prior resistant starch consumption led to lower postprandial plasma glucose (p=0.037) and insulin (p=0.038) with a higher insulin sensitivity(44+/-7.5 vs 26+/-3.5 x 10(-4) dl kg(-1) min(-1) per micro Uml(-1); p=0.028) and C-peptide-to-insulin molar ratio (18.7+/-6.5 vs 9.7+/-0.69; p=0.017). There was no effect of resistant starch consumption on plasma triacylglycerol although non-esterified fatty acid and 3-hydroxybutyrate levels were suppressed 5 h after the meal tolerance test.

CONCLUSION

Prior acute consumption of a high-dose of resistant starch enhanced carbohydrate handling in the postprandial period the following day potentially due to the increased rate of colonic fermentation.

High- versus low-fat diets in human diseases

PURPOSE OF REVIEW

To evaluate the evidence with regard to high-versus low-fat diets in the context of the prevention and management of obesity, type 2 diabetes and coronary heart disease.

RECENT FINDINGS

Despite the increasing prevalence of obesity, there is no evidence to support the view that this is caused by an increased intake of fat. Fat sensors play an important role in regulating energy balance and lipid metabolism, and hypoenergetic diets containing 30-35% energy from fat promote weight loss. High intakes of carbohydrates with a high glycaemic index can result in insulin resistance, but this effect can be modulated by increased physical activity.

SUMMARY

Although arguments to decrease the intake of trans and saturated fatty acids are cogent, the scientific basis for a reduction in the proportion of energy from fat below 30% energy is not supported by experimental evidence. A modest reduction in fat intake to 30-35% energy, with the bulk of carbohydrates being derived from complex carbohydrates from unrefined sources, would appear to be the best option for the prevention of obesity and cardiovascular disease. Increased physical activity appears to be particularly important in modulating the adverse effects associated with high-carbohydrate low-fat diets.

Types of carbohydrates and risk of cardiovascular disease

The purpose of this review is to provide an overview of the role of dietary carbohydrates in the etiology of cardiovascular disease (CVD) among women. Many factors are thought to affect insulin resistance, and little is known about the role of diet. Through effects on postprandial glucose and insulin, dietary glycemic load may have an important role in the insulin resistance syndrome (IRS). Dietary fiber, through its influence on the glycemic load or through other pathways, may also have important effects on this syndrome. Many short-term experimental studies have supported these hypotheses. Interestingly, associations may be stronger among overweight individuals than among nonoverweight individuals. Similar to findings for fruits and vegetables, whole grain intake has been found to be consistently associated with a reduction in risk of coronary heart disease (CHD) among both men and women. Several large randomized trials of primary and secondary prevention to date have demonstrated the efficacy of diets based on an abundance of plant foods and, therefore, high carbohydrate quality. The recommendations to follow a diet including an abundance of fiber-rich foods in order to prevent CVD and diabetes are based on a wealth of consistent scientific evidence. More long-term controlled trials are needed to improve our understanding of efficacy and mechanisms. Women and a variety of racial/ethnic groups should be represented in these studies whenever possible.

Fat versus carbohydrate in insulin resistance, obesity, diabetes and cardiovascular disease

PURPOSE OF REVIEW

This review assesses the relative effect of fat versus carbohydrate and the differences between fatty acids and types of carbohydrate on insulin resistance and associated risk factors for diabetes and cardiovascular disease.

RECENT FINDINGS

The debate continues over whether high-carbohydrate or high-fat diets have the more deleterious metabolic effects. Large randomized controlled trials have shown that a reduction of fat intake as part of a healthy lifestyle combined with weight reduction and exercise reduce the risk of type 2 diabetes. Carbohydrate as fruit and vegetable together with low-fat dairy products reduce blood pressure. The results of trials of fatty acid type continue to favor the use of monounsaturated fats. However, the advantages over carbohydrate have not always been clear. In terms of carbohydrate, the glycemic index appears to be a better predictor of the metabolic effects of a diet than the sugar content. The fiber content of the carbohydrate food appears to confer benefits in terms of diabetic control. Lower cholesterol and postprandial blood glucose results are associated with viscous fibers.

SUMMARY

Diets that are higher in monounsaturated fatty acids, fiber and low glycemic index foods appear to have advantages in insulin resistance, glycemic control and blood lipids in a number of studies. The division of nutrients into total fat (regardless of fatty acids) versus carbohydrate (type and quantity not specified) appears to be less helpful in predicting outcomes.

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.

Epidemiological support for the protection of whole grains against diabetes

The epidemic of type 2 diabetes among children, adolescents and adults is increasing along with the increasing prevalence of overweight and obesity. Overweight is the most powerful modifiable risk factor for type 2 diabetes. Intake of wholegrain foods may reduce diabetes risk. Three prospective studies in 160000 men and women examined the relationship of whole-grain or cereal-fibre intake with the risk of type 2 diabetes. Each study used a mailed Willett food-frequency questionnaire and similar methods of quantifying wholegrain foods and cereal fibre. The self-reported incident diabetes outcome was more reliably determined in the two studies of health-care professionals than in the study of Iowa women. Risk for incident type 2 diabetes was 21-27% lower for those in the highest quintile of whole-grain intake, and 30-36% lower in the highest quintile of cereal-fibre intake, each compared with the lowest quintile. Risk reduction persisted after adjustment for the healthier lifestyle found among habitual whole-grain consumers. Observations in non-diabetic individuals support an inverse relationship between whole-grain consumption and fasting insulin levels. In feeding studies in non-diabetic individuals insulin resistance was reduced using whole grains or diets rich in whole grains. Glucose control improved with diets rich in whole grains in feeding studies of subjects with type 2 diabetes. There is accumulating evidence to support the hypothesis that whole-grain consumption is associated with a reduced risk of incident type 2 diabetes; it may also improve glucose control in diabetic individuals.

Bioactive compounds in foods: their role in the prevention of cardiovascular disease and cancer

"Bioactive compounds" are extranutritional constituents that typically occur in small quantities in foods. They are being intensively studied to evaluate their effects on health. The impetus sparking this scientific inquiry was the result of many epidemiologic studies that have shown protective effects of plant-based diets on cardiovascular disease (CVD) and cancer. Many bioactive compounds have been discovered. These compounds vary widely in chemical structure and function and are grouped accordingly. Phenolic compounds, including their subcategory, flavonoids, are present in all plants and have been studied extensively in cereals, legumes, nuts, olive oil, vegetables, fruits, tea, and red wine. Many phenolic compounds have antioxidant properties, and some studies have demonstrated favorable effects on thrombosis and tumorogenesis and promotion. Although some epidemiologic studies have reported protective associations between flavonoids or other phenolics and CVD and cancer, other studies have not found these associations. Various phytoestrogens are present in soy, but also in flaxseed oil, whole grains, fruits, and vegetables. They have antioxidant properties, and some studies demonstrated favorable effects on other CVD risk factors, and in animal and cell culture models of cancer. However, because phytoestrogens act both as partial estrogen agonists and antagonists, their effects on cancer are likely complex. Hydroxytyrosol, one of many phenolics in olives and olive oil, is a potent antioxidant. Resveratrol, found in nuts and red wine, has antioxidant, antithrombotic, and anti-inflammatory properties, and inhibits carcinogenesis. Lycopene, a potent antioxidant carotenoid in tomatoes and other fruits, is thought to protect against prostate and other cancers, and inhibits tumor cell growth in animals. Organosulfur compounds in garlic and onions, isothiocyanates in cruciferous vegetables, and monoterpenes in citrus fruits, cherries, and herbs have anticarcinogenic actions in experimental models, as well as cardioprotective effects. In summary, numerous bioactive compounds appear to have beneficial health effects. Much scientific research needs to be conducted before we can begin to make science-based dietary recommendations. Despite this, there is sufficient evidence to recommend consuming food sources rich in bioactive compounds. From a practical perspective, this translates to recommending a diet rich in a variety of fruits, vegetables, whole grains, legumes, oils, and nuts.