Lipoproteins, nutrition, and heart disease

Effects of a low-fat vegan diet and a Step II diet on macro- and micronutrient intakes in overweight postmenopausal women

OBJECTIVE

This study investigated the nutrient intake of overweight postmenopausal women assigned to a low-fat vegan diet or a Step II diet.

METHODS

Fifty-nine overweight (body mass index, 26 to 44 kg/m2) postmenopausal women were randomly assigned to a self-selected low-fat vegan or a National Cholesterol Education Program Step II diet in a 14-wk controlled trial on weight loss and metabolism. Nutrient intake, which was measured per 1000 kcal, was the main outcome measure. Statistical analyses included within-group and between-group t tests examining changes associated with each diet.

RESULTS

Consumption of a low-fat vegan diet was associated with greater decreases in fat, saturated fat, protein, and cholesterol intakes and greater increases in carbohydrate, fiber, beta-carotene, and total vitamin A intakes than was a Step II diet. The low-fat vegan group also increased thiamin, vitamin B6, and magnesium intakes more than the Step II group, and both groups increased folic acid, vitamin C, and potassium intakes. If considering only food sources of micronutrients, the low-fat vegan group decreased vitamin D, vitamin B12, calcium, selenium, phosphorous, and zinc intakes compared with baseline. However, with incidental supplements included, decreases were evident only in phosphorous and selenium intakes. No micronutrient decreases were found in the Step II group.

CONCLUSIONS

Individuals on a low-fat vegan or Step II diet should take steps to meet the recommended intakes of vitamin D, vitamin K, folic acid, calcium, magnesium, and zinc. Individuals on a low-fat vegan diet should also ensure adequate intakes of vitamin B12, phosphorous, and selenium.

Nutrição e doenças cardiovasculares: os marcadores de risco em adultos

As doenças cardiovasculares contribuem significativamente, como grupo causal, para a taxa de mortalidade em todas as regiões brasileiras, principalmente na Região Sudeste. Além disso, constituem uma das principais causas de permanência hospitalar prolongada e são responsáveis pela principal alocação de recursos públicos em hospitalizações no Brasil. O ônus econômico das doenças cardiovasculares tem crescido exponencialmente nas últimas décadas. O risco de se desenvolver doença cardiovascular é avaliado com base na análise conjunta de características que aumentam a chance do indivíduo vir a apresentar a doença. O conhecimento desses fatores associados ao risco é de grande importância para o estabelecimento de estratégias de prevenção. Este artigo em questão revisa os principais marcadores de risco para doenças cardiovasculares em adultos, relacionados à nutrição, como os antropométricos, dietéticos e bioquímicos. Além disso, enfatiza o impacto destas morbidades na sociedade, bem como a necessidade de serem estabelecidas medidas de prevenção primária no controle das mesmas.

Lipoprotein transport in the metabolic syndrome: pathophysiological and interventional studies employing stable isotopy and modelling methods

The accompanying review in this issue of Clinical Science [Chan, Barrett and Watts (2004) Clin. Sci. 107, 221–232] presented an overview of lipoprotein physiology and the methodologies for stable isotope kinetic studies. The present review focuses on our understanding of the dysregulation and therapeutic regulation of lipoprotein transport in the metabolic syndrome based on the application of stable isotope and modelling methods. Dysregulation of lipoprotein metabolism in metabolic syndrome may be due to a combination of overproduction of VLDL [very-LDL (low-density lipoprotein)]-apo (apolipoprotein) B-100, decreased catabolism of apoB-containing particles and increased catabolism of HDL (high-density lipoprotein)-apoA-I particles. These abnormalities may be consequent on a global metabolic effect of insulin resistance, partly mediated by depressed plasma adiponectin levels, that collectively increases the flux of fatty acids from adipose tissue to the liver, the accumulation of fat in the liver and skeletal muscle, the hepatic secretion of VLDL-triacylglycerols and the remodelling of both LDL (low-density lipoprotein) and HDL particles in the circulation. These lipoprotein defects are also related to perturbations in both lipolytic enzymes and lipid transfer proteins. Our knowledge of the pathophysiology of lipoprotein metabolism in the metabolic syndrome is well complemented by extensive cell biological data. Nutritional modifications may favourably alter lipoprotein transport in the metabolic syndrome by collectively decreasing the hepatic secretion of VLDL-apoB and the catabolism of HDL-apoA-I, as well as by potentially increasing the clearance of LDL-apoB. Several pharmacological treatments, such as statins, fibrates or fish oils, can also correct the dyslipidaemia by diverse kinetic mechanisms of action, including decreased secretion and increased catabolism of apoB, as well as increased secretion and decreased catabolism of apoA-I. The complementary mechanisms of action of lifestyle and drug therapies support the use of combination regimens in treating dyslipoproteinaemia in subjects with the metabolic syndrome.

Healthy aging: health promotion and disease prevention

Successful aging includes the ability to perform functional tasks. This ability to perform functional tasks, or functional ability, is influenced by musculoskeletal and cardiovascular functioning and the presence and severity of symptoms of chronic disease. Empirical evidence indicates that musculoskleletal and cardiovascular functioning and symptoms of chronic disease in later life are strongly related to lifestyle choices involving physical activity and nutritional intake. Previous researchers have demonstrated that increases in physical activity and appropriate changes in nutritional intake can be effective interventions to prevent and treat symptoms of chronic disease and improve musculoskeletal and cardiovascular functioning. As a result of this evidence, several organizations have developed physical activity and nutritional intake recommendations aimed at maintaining or increasing the functional ability of older adults. These physical activity recommendations include engaging in cardiorespiratory, flexibility, strength, and balance training 3 to 5 days per week. Broad nutritional recommendations for older adults include a low-fat, plant-based diet including fruits, vegetables, whole grains, 8 glasses of water per day, and a vitamin and mineral supplement.

Health Promotion and Cardiovascular Health in Adult Monozygotic Twins

PURPOSE

To describe relationships among cardiovascular health indicators and health-promoting behaviors in adult monozygotic (MZ) twins.

DESIGN

The descriptive, correlational design with a convenience sample of adult twins (77 twin pairs, or N = 154) obtained during a public conference held in the Midwestern United States.

METHODS

Bivariate correlational analyses with twins as their own controls and with each twin pair. This double-entry approach allowed for the creation of a symmetrical scatterplot of twin characteristics and accounted for the genuine effects of outliers. Relationships were examined among cardiovascular health indicators (systolic and diastolic blood pressures, body mass indices, serum lipids) and health-promoting behaviors.

FINDINGS

Thirteen intermeasure correlations for cardiovascular indicators were significant, and 74% of the variance in the cardiovascular health indicators was shared within each twin pair, thus indicating evidence of common behavioral and genetic influences.

CONCLUSIONS

Both behavioral and genetic factors contributed to cardiovascular health in adult MZ twins who shared close familial and environmental ties. This finding is consistent with previous literature identifying behavioral and genetic effects on the development of cardiovascular disease.

Lifestyle recommendations to prevent prostate cancer, part I: time to redirect our attention?

This article provides a foundation for clinicians willing to provide lifestyle change recommendations for the prevention of prostate cancer. In part II, more general and specific lifestyle recommendations will be provided. It is imperative to provide patients with realistic and practical recommendations that are not only consistent in the medical literature, but will improve overall compliance.

Waist circumference is a better predictor than body mass index of coronary heart disease risk in overweight premenopausal women

Waist circumference (WC) has been postulated to have stronger associations with biomarkers of coronary heart disease (CHD) than BMI. In this study, we measured the level of activity by determining steps walked per day and select biomarkers for CHD risk in 80 overweight or obese (BMI = 25-37 kg/m(2)) premenopausal women to evaluate whether these biomarkers are associated with WC or BMI. The plasma biomarkers measured, using samples from women who had fasted for 12 h, were lipids, apolipoproteins (apo), LDL peak diameter, LDL susceptibility to oxidation, glucose, leptin, and insulin. We identified subjects with the metabolic syndrome (11%) and insulin resistance (30%) to further distinguish subjects at increased risk for CHD. Both BMI and WC were positively correlated with insulin (r = 0.376 and 0.384, respectively, P < 0.05) and leptin (r = 0.614 and 0.512, respectively, P < 0.01) and negatively correlated with the number of steps taken per day (r = -0.245 and -0.354, respectively, P < 0.05). In addition, WC had positive correlations with diastolic blood pressure (r = 0.250, P < 0.05), plasma triglycerides (TG) (r = 0.270, P < 0.05), and apo C-III (r = 0.240, P < 0.05). Women with BMI > or = 30 kg/m(2) or WC > 88 cm had significantly higher leptin concentrations than women having a BMI < 30 kg/m(2) or a WC < or = 88 cm; women with WC > 88 cm also had higher diastolic pressure (P < 0.05), and higher plasma TG (P < 0.05) and apo C-III (P < 0.05) concentrations than those with WC < or = 88. In addition, subjects with the higher WC walked an average of 1000 fewer steps per day (P < 0.01). These results suggest that WC is a stronger predictor of CHD risk than BMI and is more closely associated with the level of exercise in premenopausal women.

Double-blind, randomized feedback control fails to improve the hypocholesterolemic effect of a plant-based low-fat diet in patients with moderately elevated total cholesterol levels

OBJECTIVE

To determine whether the cholesterol-lowering effect of a plant-based low-fat diet can be improved by a flexible control design that controls the extent of fat reduction based on the individual response of blood cholesterol.

DESIGN

Randomized, double-blind intervention study.

SETTING

A hotel in Prerow, Germany.

SUBJECTS

A total of 32 participants (21 female and 11 male participants) with total cholesterol level > 5.7 mmol/l.

INTERVENTION

The control group consumed a plant-based low-fat diet with constantly 20% of energy as fat; the intervention group received a diet with either 20 or 15% of energy as fat, depending on the serum cholesterol response of the preceding week. A flexible control design based on the individual cholesterol response during a run-in period of 1 week was used within a low-fat intervention.

RESULTS

During the run-in period, the consumption of a plant-based low-fat diet led to a reduction in total cholesterol by 18+/-6 mmol/l (P < 0.001), in LDL cholesterol by 19+/-9 mmol/l (P < 0.001) and triglycerides by 13+/-3 mmol/l (P < 0.001). During the feedback control period, an additional reduction in total cholesterol by 13+/-8 (P < 0.001) and in LDL cholesterol by 17+/-11 (P < 0.001) was observed compared to 15+/-15 and 7+/-18 in the control group. The effect of an additional feedback control was only marginal and not statistically significant compared to the effect of the low-fat diet alone.

CONCLUSIONS

On a level of fat intake already reduced to 20% of energy, the use of a feedback control to adapt the fat content of the diet depending on the individual serum cholesterol response was not more effective in reducing blood cholesterol levels than a plant-based low-fat diet alone.

Starvation response in mouse liver shows strong correlation with life-span-prolonging processes

We have monitored global changes in gene expression in mouse liver in response to fasting and sugar-fed conditions using high-density microarrays. From ∼20,000 different genes, the significantly regulated ones were grouped into specific signaling and metabolic pathways. Striking changes in lipid signaling cascade, insulin and dehydroepiandrosterone (DHEA) hormonal pathways, urea cycle and S-adenosylmethionine-based methyl transfer systems, and cell apoptosis regulators were observed. Since these pathways have been implicated to play a role in the aging process, and since we observe significant overlap of genes regulated upon starvation with those regulated upon caloric restriction, our analysis suggests that starvation may elicit a stress response that is also elicited during caloric restriction. Therefore, many of the signaling and metabolic components regulated during fasting may be the same as those which mediate caloric restriction-dependent life-span extension.

Associations of low density lipoprotein particle composition with atherogenicity

PURPOSE OF REVIEW

A growing body of data suggests that in addition to LDL-cholesterol concentrations, compositional properties of LDL, including size and fatty acid composition, are important in determining the relative degree of atherogenicity. This review examines current research in this field to evaluate which properties of LDL may most directly influence the risk of coronary heart disease.

RECENT FINDINGS

The presence of small dense LDL has been correlated with an increased risk of coronary heart disease, but this has not been shown to be fully independent of related factors such as elevated plasma triacylglycerol concentrations. An increased susceptibility of small dense LDL to in-vitro oxidation has also been demonstrated, but its importance to coronary heart disease risk has not been established. Other studies have found that the presence of enlarged LDL, modified (oleate enriched) fatty acyl composition of LDL, and higher numbers of LDL particles in plasma also are endpoints associated with an increased risk of coronary heart disease.

SUMMARY

LDL size may indicate a metabolic condition associated with increased CHD risk as opposed to the direct promotion of atherosclerosis by specific particle types of LDL. In most claims of detrimental effects of small dense LDL, neither LDL particle concentrations nor the fatty acid composition of the particles were established, both factors being important in contributing to the atherogenic potential of LDL. The predisposition to premature coronary heart disease cannot currently be objectively assigned to any one type of LDL particle.

Nutritional genomics: the next frontier in the postgenomic era

The interface between the nutritional environment and cellular/genetic processes is being referred to as “nutrigenomics.” Nutrigenomics seeks to provide a molecular genetic understanding for how common dietary chemicals (i.e., nutrition) affect health by altering the expression and/or structure of an individual’s genetic makeup. The fundamental concepts of the field are that the progression from a healthy phenotype to a chronic disease phenotype must occur by changes in gene expression or by differences in activities of proteins and enzymes and that dietary chemicals directly or indirectly regulate the expression of genomic information. We present a conceptual basis and specific examples for this new branch of genomic research that focuses on the tenets of nutritional genomics: 1) common dietary chemicals act on the human genome, either directly or indirectly, to alter gene expression or structure; 2) under certain circumstances and in some individuals, diet can be a serious risk factor for a number of diseases; 3) some diet-regulated genes (and their normal, common variants) are likely to play a role in the onset, incidence, progression, and/or severity of chronic diseases; 4) the degree to which diet influences the balance between healthy and disease states may depend on an individual’s genetic makeup; and 5) dietary intervention based on knowledge of nutritional requirement, nutritional status, and genotype (i.e., “individualized nutrition”) can be used to prevent, mitigate, or cure chronic disease.

Assessing the health of future physicians: an opportunity for preventive education

INTRODUCTION

Research shows that physicians who model prevention are more likely to encourage preventive behaviors in their patients. Therefore, understanding the health of medical students ought to provide insight into the development of health promotion programs that influence the way these future physicians practice medicine. A university-based General Clinical Research Center (GCRC) provides a venue well suited to the health assessment and education of medical students. This research explores the utility of a GCRC in a program measuring the prevalence of clinical risk factors and related health behaviors in first-year medical students.

METHODS

A 6-year cross-sectional study of first-year medical students measured clinical and behavioral variables associated with metabolic syndrome. Statistical testing was used to determine the prevalence of risk factors and the influence of gender in these variables.

RESULTS

This group of medical students displayed better health indicators than did the general young adult population; however a small proportion of medical students exhibited early risk factors for chronic disease. There were significant gender differences in mean values for clinical risk factors, with males displaying higher cardiovascular risk overall. Males and females demonstrated significant differences in dietary intake and exercise programs.

DISCUSSION

A GCRC can be used to provide a health assessment of medical students. Moreover, some students may benefit from health promotion programs incorporated into medical school curricula. This study provides a foundation for further research on the health of future physicians and the development of health promotion programs for this population. It also begins to explore the use of a GCRC as a teaching resource for medical students.

The use of consumption data to assess exposure to biotechnology-derived foods and the feasibility of identifying effects on human health through post-market monitoring

The pre-market safety assessment of foods derived through biotechnology provides a scientific basis for concluding reasonable certainty of no harm and ensuring safety. At a minimum, the outcome of such an assessment provides sufficient information to estimate the likelihood of adverse effects on consumers, generally precluding the need for post-market monitoring. Post-market monitoring (PMM) may be appropriate under certain conditions where a better estimate of dietary exposure and/or nutritional consequence of a biotechnology-derived food is required, when a potential safety issue, such as allergenicity, cannot be adequately addressed through pre-market studies, or to corroborate dietary intakes of a nutritionally improved food with beneficial effects on human health. Monitoring programs must be hypothesis-driven, and are dependent upon the availability of accurate consumption data. Exposure assessment methods include both deterministic and probabilistic estimates of intakes using food supply data, individual dietary surveys, household surveys, or total diet studies. In the development of a monitoring approach, resource allocation should be dependent upon both the desired level of conservatism and the endpoint of interest. However, the cost of monitoring varies substantially, and the potential to determine causation may be limited.

Variations in body composition and plasma lipids in response to a high-carbohydrate diet

OBJECTIVE

To examine the extent to which variations in body composition modulate changes in the lipid profile in response to the ad libitum consumption of a diet rich in carbohydrates (CHOs) (high-CHO diet: 58% of energy as CHOs) or high in fat and in monounsaturated fatty acids (MUFAs) (high-MUFA diet: 40% of energy as fat, 23% as MUFAs).

RESEARCH METHODS AND PROCEDURES

Sixty-three men were randomly assigned to one of the two diets that they consumed for 6 to 7 weeks. Body composition and fasting plasma lipid levels were measured at the beginning and the end of the dietary intervention.

RESULTS

The high-CHO and high-MUFA diets induced significant and comparable reductions in body weight and waist circumference. These changes were accompanied by significant and comparable (p < 0.01) reductions in total plasma cholesterol and low-density lipoprotein cholesterol levels. However, the high-MUFA diet had more beneficial effects on plasma triglyceride concentrations (p < 0.01) and on plasma high-density lipoprotein cholesterol levels (p = 0.02) compared with the high-CHO diet. Diet-induced changes in waist circumference were significantly associated with changes in low-density lipoprotein cholesterol levels in the high-CHO group (r = 0.39, p = 0.03) but not in the high-MUFA group (r = 0.16, p = 0.38).

DISCUSSION

Improvements in plasma lipids induced by the ad libitum consumption of a high-CHO diet seem to be partly mediated by changes in body weight, whereas lipid changes induced by the high-MUFA diet seem to be independent of changes in body weight.

Relative influence of diet and physical activity on cardiovascular risk factors in urban Chinese adults

OBJECTIVE

The relative influence of dietary factors vs physical activity on cardiovascular risk factors are poorly understood. We investigated these factors in a population whose traditional diet may have both positive (high plant-based) and negative (high refined carbohydrate) aspects, and whose physical activity levels (PALs) vary widely.

DESIGN

Cross-sectional study.

SUBJECTS

A total of 130 weight stable adults aged 35-49 y (BMI 18-35 kg/m(2)) living in urban Beijing, China.

MEASUREMENTS

Dietary intake (by food frequency questionnaire), PAL as the ratio of predicted total to resting energy expenditure), percent body fat (by deuterium oxide dilution), and central adiposity (waist circumference and waist to hip ratio) were assessed. Biochemical parameters (total cholesterol, low- and high-density lipoprotein cholesterol (LDL-C; HDL-C), triglyceride (TG), apolipoproteins A-I and B, glucose, insulin, and homocysteine and its related vitamins), blood pressure and presence of the metabolic syndrome (having >/=3 risk factors of central adiposity, HDL-C, TG, glucose, blood pressure) were also examined.

RESULTS

Mean values for cardiovascular risk factors were relatively low, but 19% of subjects had the metabolic syndrome. Using validated methods for measuring food intake and energy expenditure, we found that an adverse cardiovascular risk profile was associated with a diet high in carbohydrate, low in polyunsaturated fat, and low in fruit and vegetables, independent of body fatness and its distribution. While dietary factors predicted individual cardiovascular risk factors more consistently than PAL, avoidance of low PAL reduced the risk of having the metabolic syndrome.

CONCLUSION

These results suggest that, regardless of total body fatness and fat distribution, multiple unfavorable dietary factors and low physical activity independently increase the risk for cardiovascular disease. Avoidance of a sedentary lifestyle additionally reduces the risk of developing the metabolic syndrome.

Common gene polymorphisms and nutrition: emerging links with pathogenesis of multifactorial chronic diseases (review)

Rapid progress in human genome decoding has accelerated search for the role of gene polymorphisms in the pathogenesis of complex multifactorial diseases. This review summarizes the results of recent studies on the associations of common gene variants with multifactorial chronic conditions strongly affected by nutritional factors. Three main individual sections discuss genes related to energy homeostasis regulation and obesity, cardiovascular disease (CVD), and cancer. It is evident that several major chronic diseases are closely related (often through obesity) to deregulation of energy homeostasis. Multiple polymorphic genes encoding central and peripheral determinants of energy intake and expenditure have been revealed over the past decade. Food intake control may be affected by polymorphisms in the genes encoding taste receptors and a number of peripheral signaling peptides such as insulin, leptin, ghrelin, cholecystokinin, and corresponding receptors. Polymorphic central regulators of energy intake include hypothalamic neuropeptide Y, agouti-related protein, melanocortin pathway factors, CART (cocaine- and amphetamine-regulated transcript), some other neuropeptides, and receptors for these molecules. Potentially important polymorphisms in the genes encoding energy expenditure modulators (alpha- and beta- adrenoceptors, uncoupling proteins, and regulators of adipocyte growth and differentiation) are also discussed. CVD-related gene polymorphisms comprising those involved in the pathogenesis of atherosclerosis, blood pressure regulation, hemostasis control, and homocysteine metabolism are considered in a separate section with emphasis on multiple polymorphisms affecting lipid transport and metabolism and their interactions with diet. Cancer-associated polymorphisms are discussed for groups of genes encoding enzymes of xenobiotic metabolism, DNA repair enzymes, factors involved in the cell cycle control, hormonal regulation-associated proteins, enzymes related to DNA methylation through folate metabolism, and angiogenesis-related factors. There is an apparent progress in the field with hundreds of new gene polymorphisms discovered and characterized, however firm evidence consistently linking them with pathogenesis of complex chronic diseases is still limited. Ways of improving the efficiency of candidate gene approach-based studies are discussed in a short separate section. Successful unraveling of interaction between dietary factors, polymorphisms, and pathogenesis of several multifactorial diseases is exemplified by studies of folate metabolism in relation to CVD and cancer. It appears that several new directions emerge as targets of research on the role of genetic variation in relation to diet and complex chronic diseases. Regulation of energy homeostasis is a fundamental problem insufficiently investigated in this context so far. Impacts of genetic variation on systems controlling angiogenesis, inflammatory reactions, and cell growth and differentiation (comprising regulation of the cell cycle, DNA repair, and DNA methylation) are also largely unknown and need thorough analysis. These goals can be achieved by complex simultaneous analysis of multiple polymorphic genes controlling carefully defined and selected elements of relevant metabolic and regulatory pathways in meticulously designed large-scale studies.

Effects of dietary conjugated linoleic acid on fatty acid composition and cholesterol content of hen egg yolks

The main objectives of the present study were to determine the effect of dietary conjugated linoleic acid (CLA) isomers on the fatty acid composition and cholesterol content of egg-yolk lipids. Forty-five 25-week-old laying hens were randomly distributed into five groups of nine hens each and maintained in individual laying cages, throughout 12 weeks of the experiment. They were assigned to the five treatments that consisted of commercial layer diets containing 0, 5, 10, 15 or 20 g pure CLA/kg. Feed intake of hens varied little and insignificantly. Egg mass was uniformly lower (P<0.05) in the hens fed the CLA-enriched diets. Feed conversion efficiency, when expressed per kg eggs, was impaired (P<0.05), although without obvious relation to the dietary CLA concentration. Feeding the CLA-enriched diets resulted in gradually increasing deposition of CLA isomers (P<0.01) in egg-yolk lipids. Saturated fatty acids were increased (P<0.01) and monounsaturated fatty acids decreased (P<0.01). Polyunsaturated fatty acids (PUFA), when expressed as non-CLA PUFA, were also significantly decreased (P<0.01). The most striking effects (P<0.01) were observed for palmitic (16 : 0) and stearic (18 : 0) acids, which increased from 23.6 to 34 % and from 7.8 to 18 %, respectively. On the other hand, oleic acid (18 : 1n-9) decreased from 45.8 to 24.3 %. Among non-CLA PUFA, linoleic (18 : 2n-6) and alpha-linolenic (18 : 3n-3) acids were strongly (P<0.01) decreased, from 14.2 to 7.7 % and from 1.3 to 0.3 %, respectively. The same was true for arachidonic (20:4n-6) and docosahexaenoic (22 : 6n-3) acids. The cholesterol content of egg yolks, when expressed in mg/g yolk, was not affected by the dietary CLA concentrations. In conclusion, unless the adverse effects of CLA feeding to laying hens on the fatty acid profile of egg yolks are eliminated, the CLA-enriched eggs cannot be considered functional food products.

Grape polyphenols decrease plasma triglycerides and cholesterol accumulation in the aorta of ovariectomized guinea pigs

Female ovariectomized guinea pigs, a model for menopausal women, were fed either a control diet or a diet containing 10 g/100 g of a lyophilized grape preparation for 12 wk. The macronutrient composition of the grape preparation was: simple carbohydrates, 90 g/100 g; protein, 4 g/100 g; and dietary fiber, 6 g/100 g. Control and grape diets had the same composition except for the percentage of macronutrients provided by the grape preparation. Polyphenols were present in the grape preparation at 0.58 g/100 g and included flavans, anthocyanins, quercetin, myricetin, kaempferol and resveratrol. Dietary cholesterol was 0.33 g/100 g to raise plasma cholesterol concentrations and ensure the development of atherosclerosis. Plasma LDL cholesterol concentrations did not differ between groups, whereas plasma triglycerides and VLDL cholesterol were 39 and 50% lower, respectively in guinea pigs fed the grape diet compared with controls (P < 0.05). Significant modifications in LDL particles included 58 and 30% lower triglycerides and phospholipids, respectively (P < 0.0001). Hepatic acyl CoA:cholesteryl acyltransferase activity was 27% lower (P < 0.05) in the grape diet-fed group compared with controls. In addition, concentrations of cholesterol in the aorta were 33% lower (P < 0.05) in guinea pigs fed the grape diet. These results suggest that grape intake in ovariectomized guinea pigs alters hepatic cholesterol metabolism, which may affect VLDL secretion rates and result in less accumulation of cholesterol in the aorta.

Lipoxins in chronic inflammation

The discovery of endogenous molecules involved in counterregulation of inflammatory responses that may lead to tissue injury provides an opportunity to explore new therapeutic approaches based on manipulation of new pathways. Natural counterregulatory pathways may reduce the possibility of unwanted toxic side-effects. Lipoxins are trihydroxytetraene-containing eicosanoids that are generated within the vascular lumen during platelet-leukocyte interactions and at mucosal surfaces via leukocyte-epithelial cell interactions. During cell-cell interactions, transcellular biosynthetic pathways are the major lipoxin biosynthetic routes, and thus, in humans, lipoxins are formed in vivo during multicellular responses, such as inflammation and asthma. This branch of the eicosanoid cascade generates specific tetraene-containing products that serve as "stop signals" for neutrophils that regulate key steps in leukocyte trafficking and prevent neutrophil-mediated tissue injury. These novel anti-inflammatory lipid mediators also appear to facilitate the resolution of the acute inflammatory response. In this review, recent findings and new concepts pertaining to the generation of lipoxins and their impact on the resolution of acute inflammation, and organ protection from leukocyte-mediated injury, are presented. The parallels and possible associations with periodontal diseases are discussed.

Carbohydrate intake and biomarkers of glycemic control among US adults: the third National Health and Nutrition Examination Survey (NHANES III)

BACKGROUND

Recommendations for preventing and treating type 2 diabetes include consuming carbohydrates, predominantly from whole grains, fruit, vegetables, and low-fat milk. However, the quantity and type of carbohydrates consumed may contribute to disorders of glycemic control.

OBJECTIVE

We evaluated the association between carbohydrate intakes and biomarkers of glycemic control in a nationally representative sample of healthy US adults who participated in a cross-sectional study, the third National Health and Nutrition Examination Survey.

DESIGN

The sample (5730 men and 6125 women aged > or = 20 y) was divided into quintiles of carbohydrate intake (as a percentage of energy). Carbohydrate intakes were examined in relation to glycated hemoglobin (Hb A(1c)), plasma glucose, serum C-peptide, and serum insulin concentrations by using logistic regression.

RESULTS

Carbohydrate intakes were not associated with Hb A(1c), plasma glucose, or serum insulin concentrations in men or women after adjustment for confounding variables. Carbohydrate intakes were inversely associated with serum C-peptide concentrations in men and women. Odds ratios for elevated serum C-peptide concentrations for increasing quintiles of carbohydrate intake were 1.00, 0.88, 0.57, 0.39, and 0.75 (P for trend = 0.016) in men, and 1.00, 0.69, 0.57, 0.36, and 0.41 (P for trend = 0.007) in women. When carbohydrate intakes were further adjusted for intakes of total and added sugar, the association of serum C-peptide with carbohydrate intakes was strengthened in men.

CONCLUSIONS

Carbohydrate intakes were not associated with Hb A(1c), plasma glucose, or serum insulin concentrations but were inversely associated with the risk of elevated serum C-peptide; this supports current recommendations regarding carbohydrate intake in healthy adults.

A randomized trial of a low-carbohydrate diet for obesity

BACKGROUND

Despite the popularity of the low-carbohydrate, high-protein, high-fat (Atkins) diet, no randomized, controlled trials have evaluated its efficacy.

METHODS

We conducted a one-year, multicenter, controlled trial involving 63 obese men and women who were randomly assigned to either a low-carbohydrate, high-protein, high-fat diet or a low-calorie, high-carbohydrate, low-fat (conventional) diet. Professional contact was minimal to replicate the approach used by most dieters.

RESULTS

Subjects on the low-carbohydrate diet had lost more weight than subjects on the conventional diet at 3 months (mean [+/-SD], -6.8+/-5.0 vs. -2.7+/-3.7 percent of body weight; P=0.001) and 6 months (-7.0+/-6.5 vs. -3.2+/-5.6 percent of body weight, P=0.02), but the difference at 12 months was not significant (-4.4+/-6.7 vs. -2.5+/-6.3 percent of body weight, P=0.26). After three months, no significant differences were found between the groups in total or low-density lipoprotein cholesterol concentrations. The increase in high-density lipoprotein cholesterol concentrations and the decrease in triglyceride concentrations were greater among subjects on the low-carbohydrate diet than among those on the conventional diet throughout most of the study. Both diets significantly decreased diastolic blood pressure and the insulin response to an oral glucose load.

CONCLUSIONS

The low-carbohydrate diet produced a greater weight loss (absolute difference, approximately 4 percent) than did the conventional diet for the first six months, but the differences were not significant at one year. The low-carbohydrate diet was associated with a greater improvement in some risk factors for coronary heart disease. Adherence was poor and attrition was high in both groups. Longer and larger studies are required to determine the long-term safety and efficacy of low-carbohydrate, high-protein, high-fat diets.

One-year results from a brief, computer-assisted intervention to decrease consumption of fat and increase consumption of fruits and vegetables

BACKGROUND

Current cancer prevention recommendations include reducing consumption of fat and increasing consumption of fruits and vegetables.

METHODS

Healthy women health maintenance organization members (n = 616) ages 40-70 were randomly assigned to either a nutrition intervention or a control intervention unrelated to diet. Intervention included two 45-min counseling sessions plus two brief follow-up telephone contacts. Counseling sessions included a 20-min, interactive, computer-based intervention using a touch-screen format. Intervention goals were reducing dietary fat and increasing fruit and vegetable consumption. Outcome measures included a food frequency questionnaire and the Fat and Fiber Behavior Questionnaire (FFBQ). Total serum cholesterol was also measured at baseline and 12 months.

RESULTS

Twelve-month follow-up data showed improvements on all dietary outcome variables. Compared to the control, intervention participants reported significantly less fat consumption (3.75 points less for percentage of energy from fat), significantly greater consumption of fruit and vegetables combined (0.93 more servings per day), and a significant reduction in a behavioral measure of fat consumption (0.20 point change in the FFBQ). Group differences in total serum cholesterol, while in the desired direction, were not significant.

CONCLUSIONS

In appropriate circumstances, moderate-intensity dietary interventions can show significant effects for periods of at least 1 year.

Effects of dietary saturated, monounsaturated and n-3 fatty acids on fasting lipoproteins, LDL size and post-prandial lipid metabolism in healthy subjects

BACKGROUND

The influence of the quality of dietary fat on some aspects of lipid metabolism-i.e. lipoprotein concentrations, post-prandial lipids and LDL size-is not completely understood, especially in healthy individuals.

OBJECTIVES

Aim of this study was to evaluate the effects of different types of dietary fat (monounsaturated vs. saturated fatty acids, and n-3 or placebo supplementation) on fasting lipoproteins, LDL size and post-prandial lipids in healthy people.

DESIGN

One hundred and sixty-two individuals were randomly assigned to follow two isoenergetic diets, one rich in saturated fatty acids (SFA diet) and the other in monounsaturated fatty acids (MUFA diet). Each group was further randomised to receive supplementation with fish oil (3.6 g/day) or placebo.

RESULTS

The type of diet significantly affected LDL cholesterol and triacylglycerol content, which was higher with the SFA diet and lower with the MUFA diet. The changes between the two diets were statistically significant for cholesterol (P<0.01) and triacylglycerol (P<0.03). VLDL cholesterol and triacylglycerol were significantly reduced and LDL cholesterol significantly increased by fish oil supplementation. Plasma triacylglycerol was significantly lower in those taking n-3 fatty acids, also 1 and 3 h after a test-meal. Neither type of diet nor n-3 supplementation affected LDL size.

CONCLUSIONS

A moderate substitution of saturated fatty acids with monounsaturated fatty acids has beneficial effects on lipid metabolism also in healthy individuals. A moderate supplementation of long-chain n-3 fatty acids in healthy individuals reduces both fasting and post-prandial triacylglycerol concentrations but increases LDL cholesterol, irrespective of the type of diet.

Dietary fat predicts coronary heart disease events in subjects with type 2 diabetes

OBJECTIVE

To investigate whether quantity or quality of dietary fat predicts coronary heart disease (CHD) events in middle-aged type 2 diabetic subjects.

RESEARCH DESIGN AND METHODS

The dietary habits of 366 type 2 diabetic men and 295 women, aged 45-64 years and free from CHD, were assessed with a 53-item food frequency questionnaire. They were followed up for 7 years.

RESULTS

Men in the highest tertile of the polyunsaturated/saturated fat (P/S) ratio (>0.28) had a significantly lower risk for CHD death than men in the two lowest tertiles (5.0 vs. 14.2%, P = 0.009). The risk for all CHD events was 14.2 vs. 23.2%, respectively (P = 0.044). P/S ratio did not predict CHD events in women. In Cox multiple regression analyses taking into account other cardiovascular risk factors, the highest P/S ratio tertile was associated with the lowest rate of CHD death in men (P = 0.048).

CONCLUSIONS

Low P/S ratio in men predicted future CHD events in type 2 diabetic subjects independently of conventional CHD risk factors.

Dietary monounsaturated versus polyunsaturated fatty acids: which is really better for protection from coronary heart disease?

PURPOSE OF REVIEW

The purpose is to evaluate recent findings concerning dietary fats and the risk of coronary heart disease. Monounsaturated fatty acids are often regarded as healthy, and many have recommended their consumption instead of saturated fatty acids and polyunsaturated fatty acids. Support for the benefits of monounsaturated fatty acids comes largely from epidemiological data, but they have not been an isolated, single variable in such studies. Beneficial effects on the plasma lipid profile and LDL oxidation rates have also been identified. More recent findings have questioned the impact of suspected beneficial effects on coronary heart disease, indicating that studies with more conclusive endpoints are needed.

RECENT FINDINGS

Human dietary studies often produce conflicting results regarding the effects of monounsaturated and polyunsaturated fatty acids on the plasma lipid profile. Monounsaturated and polyunsaturated fatty acids both appear to reduce total and LDL-cholesterol compared with saturated fatty acids; however, the effect on HDL is less clear. Lowered HDL levels in response to low-fat or polyunsaturated fatty acid diets and the decreased protection from oxidation of polyunsaturated fatty acid-enriched LDL may not indicate increased coronary heart disease risk. Several lines of evidence also suggest that polyunsaturated fatty acids may protect against atherosclerosis.

SUMMARY

Recommendations to substitute monounsaturated fatty acids for polyunsaturated fatty acids or a low-fat carbohydrate diet seem premature without more research into the effects on the development of atherosclerosis. Current opinions favoring monounsaturated fatty acids are based on epidemiological data and risk factor analysis, but are questioned by the demonstrated detrimental effects on atherosclerosis in animal models.

Kinetic studies of lipoprotein metabolism in the metabolic syndrome including effects of nutritional interventions

Nutritional interventions may favourably regulate dyslipoproteinemia and, hence, decrease cardiovascular disease risk. Lipoprotein kinetic studies afford a powerful approach to understanding and defining the mechanisms by which such interventions modulate lipoprotein metabolism. Stable isotope tracers and compartment models are now commonly employed for such studies. We review the recent application of tracer methodologies to the study of dyslipoproteinemia in the metabolic syndrome. We also focus on the effects of nutritional intervention studies that have addressed the effects of weight loss, n-3 fatty acids, plant sterols and alcohol on very low density lipoprotein, LDL and HDL metabolism. The potential for statin treatment as an adjunct to dietary modification is also discussed. New tracer methodologies are discussed, specifically those referring to reverse cholesterol transport. The nutritional interventions discussed in this review are readily transferable into clinical preventive practice. The potential benefits to be gained by weight loss and fish oil supplementation in the metabolic syndrome extend beyond their specific and positive effects on lipoprotein metabolism. Furthermore, recent developments in tracer methodologies afford new tools for probing the in-vivo pathways of lipoprotein metabolism in future studies.

Children and genetically engineered food: potentials and problems

Changes in food production and dietary practices are occurring faster than our understanding of their potential impact on children's health. Traditionally, pediatric gastroenterologists have studied food with respect to its nutritive value and digestibility, its influence on metabolism, its growth-promoting characteristics, and its relationship to risk and severity of disease. Biotechnology is now expanding the science of food to include disease prevention and treatment, as well as the feeding of children on a global scale. Bioengineered ("genetically modified", or "transgenic") plants were initially developed to enhance the food supply by increasing crop yields. Such previously developed transgenic plants are now prevalent worldwide and appear in many processed food products. The implementation of the technology of genetic modulation of food plants has led to considerable fear, controversy, and confusion as the understanding of the technology is poor in the general population. This review presents an overview of genetically modified food crops and their potential unique benefits and risks to children's health. Political, economical, and ecological issues related to transgenic crops are not discussed.

Diagnosis and management of lipoprotein abnormalities

Abnormal lipid and lipoprotein cholesterol values have been defined as a low-density lipoprotein (LDL) cholesterol (C) value of 160 mg/dL (4.1 mmol/L) or greater, a high-density lipoprotein (HDL) C value less than 40 mg/dL (1.0 mmol/L), triglycerides (TG) 150 mg/dL (1.7 mmol/L) or greater, and a lipoprotein (a) (Lp(a)) of 30 mg/dl or greater. Such values all increase coronary heart disease (CHD) risk. The National Cholesterol Education Program Adult Treatment Panel III guidelines continue to focus on optimizing LDL-C values (established as < 100 mg/dL or 2.6 mmol/L), especially in those with established CHD, diabetes, or a 10-year CHD risk over 20%. Dietary saturated fat (< 7% of calories) and cholesterol (< 200 mg/day) restriction, and the use of 3-hydroxy-3 methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors are the mainstays of treatment in this regard. Such treatment substantially reduces CHD risk. Severe hypertriglyceridemia (> 1000 mg/dL or 11.0 mmol/L) is associated with pancreatitis, and fat restriction, control of glucose, and fibrate therapy are indicated in such patients. Niacin is currently the most effective agent for lowering Lp(a) and raising HDL-C. Current recommendations for treatment by diet and drugs are outlined.