Vegetarian and vegan diets in type 2 diabetes management

Polyunsaturated Fatty Acids and Glycemic Control in Type 2 Diabetes

The impact of dietary fat on the risk of cardiovascular disease (CVD) has been extensively studied in recent decades. Solid evidence indicates that replacing saturated fatty acids (SFAs) with polyunsaturated fatty acids (PUFAs) decreases blood cholesterol levels and prevents CVD and CVD mortality. Studies indicate that fat quality also may affect insulin sensitivity and hence, the risk of type 2 diabetes (T2D). A high intake of SFAs has shown to increase the risk of T2D in prospective studies, while a high intake of PUFAs reduces the risk. Whether PUFAs from marine or vegetable sources affect glycemic regulation differently in T2D remains to be elucidated. The aim of the present review was therefore to summarize research on human randomized, controlled intervention studies investigating the effect of dietary PUFAs on glycemic regulation in T2D. About half of the studies investigating the effect of fish, fish oils, vegetable oils, or nuts found changes related to glycemic control in people with T2D, while the other half found no effects. Even though some of the studies used SFA as controls, the majority of the included studies compared PUFAs of different quality. Considering that both marine and vegetable oils are high in PUFAs and hence both oils may affect glycemic regulation, the lack of effect in several of the included studies may be explained by the use of an inappropriate control group. It is therefore not possible to draw a firm conclusion, and more studies are needed.

Vegetarian Diets and the Risk of Diabetes

PURPOSE OF REVIEW

Worldwide, diabetes has increased steadily and in recent years, drastically. The majority of diabetes cases are type 2 (T2DM), caused by modifiable risk factors such as diet. Vegetarian diets have been studied over the past few decades for their preventative and therapeutic effects on diabetes and may be more beneficial than medication for diabetes management.

RECENT FINDINGS

A vegetarian diet characterized by whole plant foods is most beneficial for diabetes prevention and management. Vegetarian diets are inversely associated with risk of developing diabetes independent of the positive association of meat consumption with diabetes development. Vegetarian diets range from vegan (no animal products), lacto-ovo-vegetarian (no animal meat, but consumes milk and eggs), pesco-vegetarian (consumes fish), and semi-vegetarian (occasional meat consumption). There has been an observed difference in the extent of preventative and therapeutic effects of these different types of diets. The most important aspect of any of these types of diets is emphasizing whole grains, fruits and vegetables, legumes, and nuts and reducing saturated and trans fats.

Shifting Food Systems: Increasing Well-Being Through Plant-Based Approaches

Growing evidence reveals food production systems and consumption practices contradict goals for environmental well-being and population health. This interdisciplinary paper reviews research for impacts from diets on non-communicable human diseases, climate change, and animal well-being. With increasing pressures to innovate and reduce economic as well as emotional costs associated with ill-health, our recommendations could positively impact policy.

The Design, Development and Evaluation of the Vegetarian Lifestyle Index on Dietary Patterns among Vegetarians and Non-Vegetarians

Traditionally, healthful diets and lifestyles have been examined only in relation to single nutrients, foods, or food groups in terms of dietary exposure. An alternative approach is to conceptualize an index based on vegetarian food pyramid guidelines as a measure of overall diet and lifestyle quality. Our objectives were to: (1) develop the Vegetarian Lifestyle Index (VLI); and (2) evaluate adherence to the Vegetarian Food Guide Pyramid (VFGP) among a low-risk population of Adventists. The index was based on the operationalization of 14 dietary and lifestyle components. All components were equally weighted. Higher score reflected greater adherence to the VFGP. The analytic sample (n = 90,057) comprised 47.7% non-vegetarians, 5.6% semi-, 10.1% pesco-, and 29.0% lacto-ovo-vegetarians, and 7.7% vegans, of which 1.1% were current smokers and 9.9% were alcohol consumers. Population mean VLI score was 7.43 (SD = 1.75) ranging from 1 to 12.5. Non-vegetarians (6.14; 95% confidence interval (CI), 6.06⁻6.21) had a significantly lower mean compared to semi- (7.31; 95% CI, 7.22⁻7.40), pesco- (7.41; 95% CI, 7.32⁻7.49), and lacto-ovo-vegetarians (8.16; 95% CI, 8.08⁻8.24), as well as vegans (8.88; 95% CI, 8.78⁻8.96). Vegetarians scored on average 1.18 to 2.73 more points than their non-vegetarian counterparts. Results demonstrate that the index has strong discriminant ability across distinct dietary patterns. Additionally, the VLI provides a useful measure of diet and lifestyle adherence to further refine vegetarian food pyramid guidelines.

Comparison of Sociodemographic and Nutritional Characteristics between Self-Reported Vegetarians, Vegans, and Meat-Eaters from the NutriNet-Santé Study

BACKGROUND

There is a growing trend for vegetarian and vegan diets in many Western countries. Epidemiological evidence suggesting that such diets may help in maintaining good health is rising. However, dietary and sociodemographic characteristics of vegetarians and vegans are not well known. The aim of this cross-sectional study was to describe sociodemographic and nutritional characteristics of self-reported, adult vegetarians and vegans, compared to meat-eaters, from the French NutriNet-Santé study.

METHODS

Participants were asked if they were following a specific diet. They were then classified into three self-reported diet groups: 90,664 meat-eaters, 2370 vegetarians, and 789 vegans. Dietary data were collected using three repeated 24-h dietary records. Multivariable polytomic logistic regression models were perfomed to assess the association between the sociodemographic characteristics and type of diet. The prevalence of nutrient intake inadequacy was estimated, by sex and age for micronutrients, as well as by type of self-reported diet.

RESULTS

Compared with meat-eaters, vegetarians were more likely to have a higher educational level, whereas vegans had a lower education level. Compared with meat-eaters, vegetarians were more likely to be women, younger individuals, and to be self-employed or never employed rather than managerial staff. Vegetarians and vegans substituted animal protein-dense products with a higher consumption of plant protein-dense products (e.g., soy-based products or legumes). Vegetarians had the most balanced diets in terms of macronutrients, but also had a better adherence to French dietary guidelines. Vegetarians exhibited a lower estimated prevalence of inadequacies for micronutrients such as antioxidant vitamins (e.g., for vitamin E, 28.9% for vegetarian women <55 years of age vs. 41.6% in meat-eaters) while vegans exhibited a higher estimated prevalence of inadequacies for some nutrients, in particular vitamin B12 (69.9% in men and 83.4% in women <55 years of age), compared to meat-eaters.

CONCLUSIONS

Our study highlighted that, overall, self-reported vegetarians and vegans may meet nutritional recommendations.

Position of the Academy of Nutrition and Dietetics: Vegetarian Diets

It is the position of the Academy of Nutrition and Dietetics that appropriately planned vegetarian, including vegan, diets are healthful, nutritionally adequate, and may provide health benefits for the prevention and treatment of certain diseases. These diets are appropriate for all stages of the life cycle, including pregnancy, lactation, infancy, childhood, adolescence, older adulthood, and for athletes. Plant-based diets are more environmentally sustainable than diets rich in animal products because they use fewer natural resources and are associated with much less environmental damage. Vegetarians and vegans are at reduced risk of certain health conditions, including ischemic heart disease, type 2 diabetes, hypertension, certain types of cancer, and obesity. Low intake of saturated fat and high intakes of vegetables, fruits, whole grains, legumes, soy products, nuts, and seeds (all rich in fiber and phytochemicals) are characteristics of vegetarian and vegan diets that produce lower total and low-density lipoprotein cholesterol levels and better serum glucose control. These factors contribute to reduction of chronic disease. Vegans need reliable sources of vitamin B-12, such as fortified foods or supplements.

Adherence to a Vegetarian Diet and Diabetes Risk: A Systematic Review and Meta-Analysis of Observational Studies

We quantitatively assessed the association between a vegetarian diet and diabetes risk using pooled estimates from observational studies. Electronic database searches for articles published from January 1980 to May 2016 were independently performed by two investigators, and 13 articles (14 studies) were identified. The pooled odds ratio (OR) for diabetes in vegetarians vs. non-vegetarians was 0.726 (95% confidence interval (CI): 0.608, 0.867). In the subgroup analyses, this inverse association was stronger for the studies conducted in the Western Pacific region (OR 0.514, 95% CI: 0.304, 0.871) and Europe/North America (OR 0.756, 95% CI: 0.589, 0.971) than studies conducted in Southeast Asia (OR 0.888, 95% CI: 0.718, 1.099). No study had a substantial effect on the pooled effect size in the influence analysis, and the Egger's (p = 0.465) and Begg's tests (p = 0.584) revealed no publication bias. This meta-analysis indicates that a vegetarian diet is inversely associated with diabetes risk. Our results support the need for further investigations into the effects of the motivations for vegetarianism, the duration of the adherence to a vegetarian diet, and type of vegetarian on diabetes risk.

Impact of a Plant-Based Diet and Support on Mitigating Type 2 Diabetes Mellitus in Latinos Living in Medically Underserved Areas

Purpose:

To determine the impact that a high-fiber, low-fat diet, derived from mostly plant-based sources, when coupled with support has upon self-management of type 2 diabetes mellitus in Latinos from medically underserved areas (MUAs).

Design:

Experimental randomized controlled community pilot study.

Setting:

Three community clinics in MUAs located within San Bernardino County, California.

Participants:

Thirty-two randomly assigned Latinos with A1C greater than 6.4: 15 control and 17 experimental.

Intervention:

Participants completed a 5-week education program. Researchers provided follow-up support for 17 randomly assigned experimental group participants through focus groups held at participating clinics—1, 3, and 6 months posteducation.

Measures:

Changes in fat and fiber consumption were measured using a modified Dietary Screener for Mexican Americans. Self-management was measured through the Self-Efficacy for Exercise Scale and Diabetes Quality of Life Measure.

Analysis:

Baseline characteristics for both groups were analyzed using independent t tests and χ2 tests. A 2-way repeated-measures analysis of variance was used to analyze biometric data between baseline and 6 months for both groups.

Results:

Mean A1C levels decreased from baseline to 6 months for both groups: control, μ1 = 9.57, μ2 = 9.49; experimental, μ1 = 8.53, μ2 = 7.31.

Conclusion:

The experimental group demonstrated a statistically significant reduction in mean A1C levels ( P = .002) when compared to the control group.

Vegetarian Diets in the Prevention and Management of Diabetes and Its Complications

IN BRIEF Epidemiological studies have found a lower prevalence of type 2 diabetes among vegetarians compared to nonvegetarians. This reduced risk is likely a function of improved weight status, higher intake of dietary fiber, and the absence of animal protein and heme iron in the diet. Interventional studies have shown that vegetarian diets, especially a vegan diet, are effective tools in glycemic control and that these diets control plasma glucose to a greater level than do control diets, including diets traditionally recommended for patients with diabetes (e.g., diets based on carbohydrate counting). Vegetarian diets are associated with improvement in secondary outcomes such as weight reduction, serum lipid profile, and blood pressure. Studies indicate that vegetarian diets can be universally used in type 2 diabetes prevention and as tools to improve blood glucose management.

Iron Status of Vegetarian Children: A Review of Literature

Background: Iron is considered a nutrient of concern for vegetarians. In children, inadequate iron status may lead to anemia and poor growth. Summary: Thirteen original manuscripts met the inclusion criteria. Various biochemical markers of iron status, such as hemoglobin (Hb) and serum ferritin, were used. Seven of the 13 studies reported the prevalence of iron deficiency separately for vegetarians and non-vegetarians. Five out of 7 showed a higher prevalence of iron deficiency among the vegetarian participants, while the other 2 showed a higher prevalence of iron deficiency among non-vegetarians. A wide range of iron deficiency prevalence, from 4.3% of vegetarian participants in one study to 73% having ferritin <10 µg/L in another study, was found. Hb data showed almost as wide variations from 0% of children having Hb values lower than 11 g/dL to 47.5% having Hb values below 3rd percentile. Key Messages: The prevalence of iron deficiency among vegetarian children varies considerably from one study to another. The wide variation in the prevalence of inadequate iron status was consistent for studies from industrial and developing countries. The physiological significance of low iron status among vegetarians reported in some studies is unknown.

Vitamin B12 among Vegetarians: Status, Assessment and Supplementation

Cobalamin is an essential molecule for humans. It acts as a cofactor in one-carbon transfers through methylation and molecular rearrangement. These functions take place in fatty acid, amino acid and nucleic acid metabolic pathways. The deficiency of vitamin B12 is clinically manifested in the blood and nervous system where the cobalamin plays a key role in cell replication and in fatty acid metabolism. Hypovitaminosis arises from inadequate absorption, from genetic defects that alter transport through the body, or from inadequate intake as a result of diet. With the growing adoption of vegetarian eating styles in Western countries, there is growing focus on whether diets that exclude animal foods are adequate. Since food availability in these countries is not a problem, and therefore plant foods are sufficiently adequate, the most delicate issue remains the contribution of cobalamin, which is poorly represented in plants. In this review, we will discuss the status of vitamin B12 among vegetarians, the diagnostic markers for the detection of cobalamin deficiency and appropriate sources for sufficient intake, through the description of the features and functions of vitamin B12 and its absorption mechanism.

The long-term health of vegetarians and vegans

Vegetarians, who do not eat any meat, poultry or fish, constitute a significant minority of the world's population. Lacto-ovo-vegetarians consume dairy products and/or eggs, whereas vegans do not eat any foods derived wholly or partly from animals. Concerns over the health, environmental and economic consequences of a diet rich in meat and other animal products have focussed attention on those who exclude some or all of these foods from their diet. There has been extensive research into the nutritional adequacy of vegetarian diets, but less is known about the long-term health of vegetarians and vegans. We summarise the main findings from large cross-sectional and prospective cohort studies in western countries with a high proportion of vegetarian participants. Vegetarians have a lower prevalence of overweight and obesity and a lower risk of IHD compared with non-vegetarians from a similar background, whereas the data are equivocal for stroke. For cancer, there is some evidence that the risk for all cancer sites combined is slightly lower in vegetarians than in non-vegetarians, but findings for individual cancer sites are inconclusive. Vegetarians have also been found to have lower risks for diabetes, diverticular disease and eye cataract. Overall mortality is similar for vegetarians and comparable non-vegetarians, but vegetarian groups compare favourably with the general population. The long-term health of vegetarians appears to be generally good, and for some diseases and medical conditions it may be better than that of comparable omnivores. Much more research is needed, particularly on the long-term health of vegans.

Effect of a Brown Rice Based Vegan Diet and Conventional Diabetic Diet on Glycemic Control of Patients with Type 2 Diabetes: A 12-Week Randomized Clinical Trial

Objective

Several intervention studies have suggested that vegetarian or vegan diets have clinical benefits, particularly in terms of glycemic control, in patients with type 2 diabetes (T2D); however, no randomized controlled trial has been conducted in Asians who more commonly depend on plant-based foods, as compared to Western populations. Here, we aimed to compare the effect of a vegan diet and conventional diabetic diet on glycemic control among Korean individuals.

Materials and Methods

Participants diagnosed with T2D were randomly assigned to follow either a vegan diet (excluding animal-based food including fish; n = 46) or a conventional diet recommended by the Korean Diabetes Association 2011 (n = 47) for 12 weeks. HbA1c levels were measured at weeks 0, 4, and 12, and the primary study endpoint was the change in HbA1c levels over 12 weeks.

Results

The mean HbA1c levels at weeks 0, 4, and 12 were 7.7%, 7.2%, and 7.1% in the vegan group, and 7.4%, 7.2%, and 7.2% in the conventional group, respectively. Although both groups showed significant reductions in HbA1C levels, the reductions were larger in the vegan group than in the conventional group (-0.5% vs. -0.2%; p-for-interaction = 0.017). When only considering participants with high compliance, the difference in HbA1c level reduction between the groups was found to be larger (-0.9% vs. -0.3%). The beneficial effect of vegan diets was noted even after adjusting for changes in total energy intake or waist circumference over the 12 weeks.

Conclusion

Both diets led to reductions in HbA1c levels; however, glycemic control was better with the vegan diet than with the conventional diet. Thus, the dietary guidelines for patients with T2D should include a vegan diet for the better management and treatment. However, further studies are needed to evaluate the long-term effects of a vegan diet, and to identify potential explanations of the underlying mechanisms.

Trial Registration

CRiS KCT0001771

Associations between Vitamin B-12 Status and Oxidative Stress and Inflammation in Diabetic Vegetarians and Omnivores

Diabetes is considered an oxidative stress and a chronic inflammatory disease. The purpose of this study was to investigate the correlations between vitamin B-12 status and oxidative stress and inflammation in diabetic vegetarians and omnivores. We enrolled 154 patients with type 2 diabetes (54 vegetarians and 100 omnivores). Levels of fasting glucose, glycohemoglobin (HbA1c), lipid profiles, oxidative stress, antioxidant enzymes activity, and inflammatory makers were measured. Diabetic vegetarians with higher levels of vitamin B-12 (>250 pmol/L) had significantly lower levels of fasting glucose, HbA1c and higher antioxidant enzyme activity (catalase) than those with lower levels of vitamin B-12 (≤250 pmol/L). A significant association was found between vitamin B-12 status and fasting glucose (r = −0.17, p = 0.03), HbA1c (r = −0.33, p = 0.02), oxidative stress (oxidized low density lipoprotein-cholesterol, r = −0.19, p = 0.03), and antioxidant enzyme activity (catalase, r = 0.28, p = 0.01) in the diabetic vegetarians; vitamin B-12 status was significantly correlated with inflammatory markers (interleukin-6, r = −0.33, p < 0.01) in diabetic omnivores. As a result, we suggest that it is necessary to monitor the levels of vitamin B-12 in patients with diabetes, particularly those adhering to a vegetarian diet.

Effect of Replacing Animal Protein with Plant Protein on Glycemic Control in Diabetes: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Previous research on the effect of replacing sources of animal protein with plant protein on glycemic control has been inconsistent. We therefore conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) to assess the effect of this replacement on glycemic control in individuals with diabetes. We searched MEDLINE, EMBASE, and Cochrane databases through 26 August 2015. We included RCTs ≥ 3-weeks comparing the effect of replacing animal with plant protein on HbA1c, fasting glucose (FG), and fasting insulin (FI). Two independent reviewers extracted relevant data, assessed study quality and risk of bias. Data were pooled by the generic inverse variance method and expressed as mean differences (MD) with 95% confidence intervals (CIs). Heterogeneity was assessed (Cochran Q-statistic) and quantified (I²-statistic). Thirteen RCTs (n = 280) met the eligibility criteria. Diets emphasizing a replacement of animal with plant protein at a median level of ~35% of total protein per day significantly lowered HbA1c (MD = -0.15%; 95%-CI: -0.26, -0.05%), FG (MD = -0.53 mmol/L; 95%-CI: -0.92, -0.13 mmol/L) and FI (MD = -10.09 pmol/L; 95%-CI: -17.31, -2.86 pmol/L) compared with control arms. Overall, the results indicate that replacing sources of animal with plant protein leads to modest improvements in glycemic control in individuals with diabetes. Owing to uncertainties in our analyses there is a need for larger, longer, higher quality trials.

TRIAL REGISTRATION

ClinicalTrials.gov registration number: NCT02037321.

Is vitamin B12 deficiency a risk factor for cardiovascular disease in vegetarians?

The goal of this paper is to describe the role of vitamin B12 deficiency in cardiovascular disease development among vegetarians. Vegetarians have a high prevalence of vitamin B12 deficiency. Deficiency of this vitamin is associated with a variety of atherogenic processes that are mainly, but not exclusively, due to vitamin B12 deficiency-induced hyperhomocysteinemia. Each 5-μmol/L increase above 10 μmol/L of serum homocysteine is associated with a 20% increased risk of circulatory health problems. Mean homocysteine concentration >10 μmol/L among vegetarians was reported in 32 of 34 reports. Macrocytosis associated with vitamin B12 deficiency is also associated with fatal and non-fatal coronary disease, myocardial infarction, stroke, and other circulatory health problems. Compared with non-vegetarians, vegetarians have an improved profile of the traditional cardiovascular disease risk factors, including serum lipids, blood pressure, serum glucose concentration, and weight status. However, not all studies that assessed cardiovascular disease incidence among vegetarians reported a protective effect. Among studies that did show a lower prevalence of circulatory health problems, the effect was not as pronounced as expected, which may be a result of poor vitamin B12 status due to a vegetarian diet. Vitamin B12 deficiency may negate the cardiovascular disease prevention benefits of vegetarian diets. In order to further reduce the risk of cardiovascular disease, vegetarians should be advised to use vitamin B12 supplements.

Improved clinical outcomes of patients with type 2 diabetes mellitus utilizing integrative medicine: a case report

This case report demonstrates a successful approach to managing patients with type 2 diabetes mellitus (DM2). Botanical herbs (including Gymnema sylvestre) and nutrients (including alpha lipoic acid and chromium) were used alongside metformin to help improve insulin sensitization; however, the greatest emphasis of treatment for this patient centered on a low-carbohydrate, whole-foods diet and regular exercise that shifted the focus to the patient's role in controlling their disease. Research on DM2 often focuses on improving drug efficacy while diet and lifestyle are generally overlooked as both a preventive and curative tool. During the 7 months of treatment, the patient's hemoglobin A1c and fasting glucose significantly decreased to within normal ranges and both cholesterol and liver enzyme markers normalized. A significant body of evidence already exists advocating for disease management using various diets, including Mediterranean, low-carb, and low-fat vegan diets; however, no clear dietary standards have been established. This study supports the use of naturopathic medicine as well as dietary and lifestyle changes to develop the most efficacious approach for the treatment of DM2.

Vegetarian diets and glycemic control in diabetes: a systematic review and meta-analysis

INTRODUCTION

Previous studies have suggested an association between vegetarian diets and improvements in glycemic control in diabetes, although this relationship is not well established. No meta-analysis of these studies has been performed.

METHODS

To conduct a systematic review and meta-analysis of controlled clinical trials examining the association between vegetarian diets and glycemic control in type 2 diabetes.

DATA SOURCE

The electronic databases Medline, Web of Science, Excerpta Medica Database (EMBASE), and Cochrane Central Register of Controlled Trials were searched for articles published in any language through December 9, 2013.

STUDY SELECTION

The following criteria were used for study inclusion: (I) age of participants >20 years; (II) vegetarian diet as intervention; (III) mean difference in hemoglobin A1c (HbA1c) and/or fasting blood glucose levels used as outcomes; and (IV) controlled trials, duration ≥4 weeks. Exclusion criteria were: (I) not an original investigation; (II) duplicate samples; (III) diabetes other than type 2; (IV) multiple interventions; and (V) uncontrolled studies.

DATA EXTRACTION AND SYNTHESIS

The data collected included study design, baseline population characteristics, dietary data, and outcomes. Data were pooled using a random-effects model.

MAIN OUTCOMES AND MEASURES

Differences in HbA1c and fasting blood glucose levels associated with vegetarian diets were assessed.

RESULTS

Of 477 studies identified, six met the inclusion criteria (n=255, mean age 42.5 years). Consumption of vegetarian diets was associated with a significant reduction in HbA1c [-0.39 percentage point; 95% confidence interval (CI), -0.62 to -0.15; P=0.001; I(2)=3.0; P for heterogeneity =0.389], and a non-significant reduction in fasting blood glucose concentration (-0.36 mmol/L; 95% CI, -1.04 to 0.32; P=0.301; I(2)=0; P for heterogeneity =0.710), compared with consumption of comparator diets.

CONCLUSIONS

Consumption of vegetarian diets is associated with improved glycemic control in type 2 diabetes. PROSPERO registration number is CRD42013004370.

The health advantage of a vegan diet: exploring the gut microbiota connection

This review examines whether there is evidence that a strict vegan diet confers health advantages beyond that of a vegetarian diet or overall healthy eating. Few studies include vegan subjects as a distinct experimental group, yet when vegan diets are directly compared to vegetarian and omnivorous diets, a pattern of protective health benefits emerges. The relatively recent inclusion of vegan diets in studies of gut microbiota and health allows us the opportunity to assess whether the vegan gut microbiota is distinct, and whether the health advantages characteristic of a vegan diet may be partially explained by the associated microbiota profile. The relationship between diet and the intestinal microbial profile appears to follow a continuum, with vegans displaying a gut microbiota most distinct from that of omnivores, but not always significantly different from that of vegetarians. The vegan gut profile appears to be unique in several characteristics, including a reduced abundance of pathobionts and a greater abundance of protective species. Reduced levels of inflammation may be the key feature linking the vegan gut microbiota with protective health effects. However, it is still unclear whether a therapeutic vegan diet can be prescribed to alter the gut microflora for long-term health benefits.

Values, attitudes, and frequency of meat consumption. Predicting meat-reduced diet in Australians

Reduced consumption of meat, particularly red meat, is associated with numerous health benefits. While past research has examined demographic and cognitive correlates of meat-related diet identity and meat consumption behaviour, the predictive influence of personal values on meat-consumption attitudes and behaviour, as well as gender differences therein, has not been explicitly examined, nor has past research focusing on 'meat' generally addressed 'white meat' and 'fish/seafood' as distinct categories of interest. Two hundred and two Australians (59.9% female, 39.1% male, 1% unknown), aged 18 to 91 years (M = 31.42, SD = 16.18), completed an online questionnaire including the Schwartz Values Survey, and measures of diet identity, attitude towards reduced consumption of each of red meat, white meat, and fish/seafood, as well as self-reported estimates of frequency of consumption of each meat type. Results showed that higher valuing of Universalism predicted more positive attitudes towards reducing, and less frequent consumption of, each of red meat, white meat, and fish/seafood, while higher Power predicted less positive attitudes towards reducing, and more frequent consumption of, these meats. Higher Security predicted less positive attitudes towards reducing, and more frequent consumption, of white meat and fish/seafood, while Conformity produced this latter effect for fish/seafood only. Despite men valuing Power more highly than women, women valuing Universalism more highly than men, and men eating red meat more frequently than women, gender was not a significant moderator of the value-attitude-behaviour mediations described, suggesting that gender's effects on meat consumption may not be robust once entered into a multivariate model of MRD attitudes and behaviour. Results support past findings associating Universalism, Power, and Security values with meat-eating preferences, and extend these findings by articulating how these values relate specifically to different types of meat.

Differential acute postprandial effects of processed meat and isocaloric vegan meals on the gastrointestinal hormone response in subjects suffering from type 2 diabetes and healthy controls: a randomized crossover study

BACKGROUND

The intake of meat, particularly processed meat, is a dietary risk factor for diabetes. Meat intake impairs insulin sensitivity and leads to increased oxidative stress. However, its effect on postprandial gastrointestinal hormone (GIH) secretion is unclear. We aimed to investigate the acute effects of two standardized isocaloric meals: a processed hamburger meat meal rich in protein and saturated fat (M-meal) and a vegan meal rich in carbohydrates (V-meal). We hypothesized that the meat meal would lead to abnormal postprandial increases in plasma lipids and oxidative stress markers and impaired GIH responses.

METHODS

In a randomized crossover study, 50 patients suffering from type 2 diabetes (T2D) and 50 healthy subjects underwent two 3-h meal tolerance tests. For statistical analyses, repeated-measures ANOVA was performed.

RESULTS

The M-meal resulted in a higher postprandial increase in lipids in both groups (p<0.001) and persistent postprandial hyperinsulinemia in patients with diabetes (p<0.001). The plasma glucose levels were significantly higher after the V-meal only at the peak level. The plasma concentrations of glucose-dependent insulinotropic peptide (GIP), peptide tyrosine-tyrosine (PYY) and pancreatic polypeptide (PP) were higher (p<0.05, p<0.001, p<0.001, respectively) and the ghrelin concentration was lower (p<0.001) after the M-meal in healthy subjects. In contrast, the concentrations of GIP, PYY and PP were significantly lower after the M-meal in T2D patients (p<0.001). Compared with the V-meal, the M-meal was associated with a larger increase in lipoperoxidation in T2D patients (p<0.05).

CONCLUSION/INTERPRETATION

Our results suggest that the diet composition and the energy content, rather than the carbohydrate count, should be important considerations for dietary management and demonstrate that processed meat consumption is accompanied by impaired GIH responses and increased oxidative stress marker levels in diabetic patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01572402.

Vegetarian diets and cardiovascular risk factors in black members of the Adventist Health Study-2

OBJECTIVE

To compare cardiovascular risk factors between vegetarians and non-vegetarians in black individuals living in the USA.

DESIGN

A cross-sectional analysis of a sub-set of 592 black women and men enrolled in the Adventist Health Study-2 (AHS-2) cohort of Seventh-day Adventists.

SETTING

Members of the AHS-2 cohort, who lived in all states of the USA and provinces of Canada.

SUBJECTS

Black/African-American members of two sub-studies of AHS-2 where blood and physiological measurements were obtained.

RESULTS

Of these women and men, 25% were either vegan or lacto-ovo-vegetarians (labelled 'vegetarian/vegans'), 13% were pesco-vegetarian and 62% were non-vegetarian. Compared with non-vegetarians, the vegetarian/vegans had odds ratios for hypertension, diabetes, high blood total cholesterol and high blood LDL-cholesterol of 0·56 (95% CI 0·36, 0·87), 0·48 (95% CI 0·24, 0·98), 0·42 (95% CI 0·27, 0·65) and 0·54 (95% CI 0·33, 0·89), respectively, when adjusted for age, gender, education, physical activity and sub-study. Corresponding odds ratios for obesity in vegetarian/vegans and pesco-vegetarians, compared with non-vegetarians, were 0·43 (95% CI 0·28, 0·67) and 0·47 (95% CI 0·27, 0·81), respectively; and for abdominal obesity 0·54 (95% CI 0·36, 0·82) and 0·50 (95% CI 0·29, 0·84), respectively. Results for pesco-vegetarians did not differ significantly from those of non-vegetarians for other variables. Further adjustment for BMI suggested that BMI acts as an intermediary variable between diet and both hypertension and diabetes.

CONCLUSIONS

As with non-blacks, these results suggest that there are sizeable advantages to a vegetarian diet in black individuals also, although a cross-sectional analysis cannot conclusively establish cause.

Effect of diet on type 2 diabetes mellitus: a review

Type 2 diabetes mellitus is one of the fastest growing diseases; the number of people affected by diabetes will soon reach 552 million worldwide, with associated increases in complications and healthcare expenditure. Lifestyle and medical nutrition therapy are considered the keystones of type 2 diabetes prevention and treatment, but there is no definite consensus on how to treat this disease with these therapies. The American Diabetes Association has made several recommendations regarding the medical nutrition therapy of diabetes; these emphasize the importance of minimizing macrovascular and microvascular complications in people with diabetes. Four types of diets were reviewed for their effects on diabetes: the Mediterranean diet, a low-carbohydrate/high-protein diet, a vegan diet and a vegetarian diet. Each of the four types of diet has been shown to improve metabolic conditions, but the degree of improvement varies from patient to patient. Therefore, it is necessary to evaluate a patient's pathophysiological characteristics in order to determine the diet that will achieve metabolic improvement in each individual. Many dietary regimens are available for patients with type 2 diabetes to choose from, according to personal taste and cultural tradition. It is important to provide a tailor-made diet wherever possible in order to maximize the efficacy of the diet on reducing diabetes symptoms and to encourage patient adherence. Additional randomized studies, both short term (to analyse physiological responses) and long term, could help reduce the multitude of diets currently recommended and focus on a shorter list of useful regimens.

Key elements of plant-based diets associated with reduced risk of metabolic syndrome

Approximately 20 %-25 % of adults worldwide have metabolic syndrome. Vegetarian and vegan diets have demonstrated effectiveness in improving body weight, glycemic control, and cardiovascular risk factors, as compared with conventional therapeutic approaches, and are potentially useful in the prevention of metabolic syndrome. This article consists of two steps: (1) a review of the literature on studies examining vegetarian and vegan diets and metabolic syndrome and (2) a review of foods and nutrients that are protective against or associated with metabolic syndromes that may help to explain the beneficial effects of plant-based dietary approaches for metabolic syndrome. The present review found eight observational research studies, and no intervention studies, examining the association of plant-based dietary approaches with metabolic syndrome. These studies, conducted mostly in Asian populations, yielded varying results. The majority, however, found better metabolic risk factors and lowered risk of metabolic syndrome among individuals following plant-based diets, as compared with omnivores. Some dietary components that are lower in the diets of vegetarians, such as energy intake, saturated fat, heme iron, and red and processed meat, may influence metabolic syndrome risk. In addition, plant-based diets are higher in fruits, vegetables, and fiber, which are protective against the development of metabolic syndrome.

Serum hyperglycemia might be not related to fat composition of diet and vegetable composition of diet might improve sugar control in taiwanese diabetic subjects

OBJECTIVE

This is an Asian study, which was designed to examine the correlations between biochemical data and food composition of diabetic patients in Taiwan.

METHODS

One hundred and seventy Taiwanese diabetic patients were enrolled. The correlations between biochemical data and diet composition (from 24-hour recall of intake food) of these patients were explored (Spearman correlation, p < 0.05). Diet components were also correlated with each other to show diet characteristics of diabetic patients in Taiwan. Linear regression was also performed for the significantly correlated groups to estimate possible impacts from diet composition to biochemical data.

RESULTS

Postprandial serum glucose level was negatively correlated with fat percentage of diet, intake amount of polyunsaturated fatty acid and fiber diet composition. Hemoglobin A1c was negatively correlated with fat diet, polyunsaturated fatty acid and vegetable diet. Fat composition, calorie percentage accounted by polyunsaturated fatty acid and monounsaturated fatty acid in diet seemed to be negatively correlated with sugar percentage of diet and positively correlated with vegetable and fiber composition of diet. Linear regression showed that intake amount of polyunsaturated fatty acid, calorie percentage accounted by polyunsaturated fatty acid, fat percentage of diet, vegetable composition of diet would predict lower hemoglobin A1c and postprandial blood sugar. Besides, higher percentage of fat diet composition could predict higher percentage of vegetable diet composition in Taiwanese diabetic patients.

CONCLUSION

Fat diet might not elevate serum glucose. Vegetable diet and polyunsaturated fatty acid diet composition might be correlated with better sugar control in Taiwanese diabetic patients.

Decreases in dietary glycemic index are related to weight loss among individuals following therapeutic diets for type 2 diabetes

This study assessed the effect of changes in glycemic index (GI) and load (GL) on weight loss and glycated hemoglobin (HbA1c) among individuals with type 2 diabetes beginning a vegan diet or diet following the 2003 American Diabetes Association (ADA) recommendations. The study was a 22-wk, randomized trial of 99 participants with type 2 diabetes who were counseled to follow 1 of 2 diet treatments. GI and GL changes were assessed based on 3-d dietary records. The relationships between GI/GL and changes in weight and HbA1C were calculated. In an intention-to-treat analysis (n = 99), the vegan group reduced GI to a greater extent than the ADA group (P < 0.05), but GL was reduced further in the ADA than the vegan group (P < 0.001). GI predicted changes in weight (P = 0.001), adjusting for changes in fiber, carbohydrate, fat, alcohol, energy intake, steps per day, group, and demographics, such that for every point decrease in GI, participants lost ~0.2 kg (0.44 lb). GI was not a predictor for changes in HbA1C after controlling for weight loss (P = 0.33). Weight loss was a predictor of changes in HbA1C (P = 0.047). GL was not related to weight loss or changes in HbA1C. A low-GI diet appears to be one of the determinants of success of a vegan or ADA diet in reducing body weight among people with type 2 diabetes. The reduction of body weight, in turn, was predictive of decreasing HbA1C.

A pilot study of the Spanish Ketogenic Mediterranean Diet: an effective therapy for the metabolic syndrome

The "Spanish Ketogenic Mediterranean Diet" (SKMD) has been shown to promote potential therapeutic properties for the metabolic syndrome. The purpose of this study was to evaluate the potential therapeutic properties under free-living conditions of the SKMD in patients with metabolic syndrome (following the International Diabetes Federation consensus guidelines) over a 12-week period. A prospective study was carried out in 22 obese subjects with metabolic syndrome (12 men and 10 women) with the inclusion criteria whose body mass index of 36.58 ± 0.54 kg/m² and age was 41.18 ± 2.28 years. Statistical differences between the parameters studied before and after the administration of the SKMD (week 0 and 12, respectively) were analyzed by paired Student's t test. There was an extremely significant (P < .001) improvement in low-density lipoprotein cholesterol (from 126.25 mg/dL to 103.87 mg/dL) and all the parameters studied associated with metabolic syndrome: body weight (from 106.41 kg to 91.95 kg), body mass index (from 36.58 kg/m² to 31.69 kg/m²), waist circumference (from 111.97 cm to 94.70 cm), fasting plasma glucose (from 118.81 mg/dL to 91.86 mg/dL), triacylglycerols (from 224.86 mg/dL to 109.59 mg/dL), high-density lipoprotein cholesterol (from 44.44 to 57.95 mg/dL), systolic blood pressure (from 141.59 mm Hg to 123.64 mm Hg), and diastolic blood pressure (from 89.09 mm Hg to 76.36 mm Hg). The most affected parameter was the triacylglycerols (51.26% reduction). After the diet all the subjects were free of metabolic syndrome according to the International Diabetes Federation definition, and 100% of them had normal triacylglycerols and high-density lipoprotein cholesterol levels, in spite of the fact that 77.27% of them still had a body mass index of > 30 kg/m². We conclude that the SKMD could be an effective and safe way to cure patients suffering from metabolic syndrome. Future research should include a larger sample size, a longer-term use, and a comparison with other ketogenic diets.

Vegetarian diet improves insulin resistance and oxidative stress markers more than conventional diet in subjects with Type 2 diabetes

AIMS

The aim of this study was to compare the effects of calorie-restricted vegetarian and conventional diabetic diets alone and in combination with exercise on insulin resistance, visceral fat and oxidative stress markers in subjects with Type 2 diabetes.

METHODS

A 24-week, randomized, open, parallel design was used. Seventy-four patients with Type 2 diabetes were randomly assigned to either the experimental group (n = 37), which received a vegetarian diet, or the control group (n = 37), which received a conventional diabetic diet. Both diets were isocaloric, calorie restricted (-500 kcal/day). All meals during the study were provided. The second 12 weeks of the diet were combined with aerobic exercise. Participants were examined at baseline, 12 weeks and 24 weeks. Primary outcomes were: insulin sensitivity measured by hyperinsulinaemic isoglycaemic clamp; volume of visceral and subcutaneous fat measured by magnetic resonance imaging; and oxidative stress measured by thiobarbituric acid reactive substances. Analyses were by intention to treat.

RESULTS

Forty-three per cent of participants in the experimental group and 5% of participants in the control group reduced diabetes medication (P < 0.001). Body weight decreased more in the experimental group than in the control group [-6.2 kg (95% CI -6.6 to -5.3) vs. -3.2 kg (95% CI -3.7 to -2.5); interaction group × time P = 0.001]. An increase in insulin sensitivity was significantly greater in the experimental group than in the control group [30% (95% CI 24.5-39) vs. 20% (95% CI 14-25), P = 0.04]. A reduction in both visceral and subcutaneous fat was greater in the experimental group than in the control group (P = 0.007 and P = 0.02, respectively). Plasma adiponectin increased (P = 0.02) and leptin decreased (P = 0.02) in the experimental group, with no change in the control group. Vitamin C, superoxide dismutase and reduced glutathione increased in the experimental group (P = 0.002, P < 0.001 and P = 0.02, respectively). Differences between groups were greater after the addition of exercise training. Changes in insulin sensitivity and enzymatic oxidative stress markers correlated with changes in visceral fat.

CONCLUSIONS

A calorie-restricted vegetarian diet had greater capacity to improve insulin sensitivity compared with a conventional diabetic diet over 24 weeks. The greater loss of visceral fat and improvements in plasma concentrations of adipokines and oxidative stress markers with this diet may be responsible for the reduction of insulin resistance. The addition of exercise training further augmented the improved outcomes with the vegetarian diet.

Health behavior modification after electron beam computed tomography and physician consultation

This study aimed to determine whether participants reported altering health behaviors (physical activity, diet, and alcohol consumption) after seeing results from an electron-beam computed tomography (EBCT) scan for coronary artery calcium and reviewing these results with a physician. Clinicians attempt to motivate patients to control cardiovascular risk factors by adopting healthy behaviors and reducing harmful actions. Asymptomatic patients (N = 510) were evaluated by EBCT for the extent of coronary artery calcium. Information pertaining to demographics, health history, and lifestyle/health behaviors was obtained from each participant at the time of the EBCT scan. Patients were given their numerical calcium score, shown images of their coronary arteries, and counseled by a physician for lifestyle and medical risk modification based on their coronary artery calcium score. Approximately 6 years after the scan, participants completed a follow-up questionnaire related to lifestyle modifications. In multivariable analysis, the presence and extent of coronary artery calcium was significantly associated with beneficial health behavior modifications. Specifically, the greater a patient's coronary artery calcium score, the more likely they were to report increasing exercise (odds ratio = 1.34, P = 0.02), changing diet (odds ratio = 1.40, P < 0.01), and changing alcohol intake (odds ratio = 1.46, P = 0.05). This study suggests that seeing and being counseled on the presence and extent of coronary artery calcium is significantly associated with behavior change.

Plant and animal protein intake and its association with overweight and obesity among the Belgian population

The objective of the present study was to assess animal and plant protein intakes in the Belgian population and to examine their relationship with overweight and obesity (OB). The subjects participated in the Belgian National Food Consumption Survey conducted in 2004. Food consumption was assessed by using two non-consecutive 24 h dietary recalls. About 3083 participants ( ≥ 15 years of age; 1546 males, 1537 females) provided completed dietary information. Animal protein intake (47 g/d) contributed more to total protein intakes of 72 g/d than plant protein intake, which accounted for 25 g/d. Meat and meat products were the main contributors to total animal protein intakes (53 %), whereas cereals and cereal products contributed most to plant protein intake (54 %). Males had higher animal and plant protein intakes than females (P < 0·001). Legume and soya protein intakes were low in the whole population (0·101 and 0·174 g/d, respectively). In males, animal protein intake was positively associated with BMI (β = 0·013; P = 0·001) and waist circumference (WC; β = 0·041; P = 0·002). Both in males and females, plant protein intake was inversely associated with BMI (males: β = − 0·036; P < 0·001; females: β = − 0·046; P = 0·001) and WC (male: β = − 0·137; P < 0·001; female: β = − 0·096; P = 0·024). In conclusion, plant protein intakes were lower than animal protein intakes among a representative sample of the Belgian population and decreased with age. Associations with anthropometric data indicated that plant proteins could offer a protective effect in the prevention of overweight and OB in the Belgian population.

A plant-based diet for type 2 diabetes: scientific support and practical strategies

PURPOSE

The purpose of this review is to provide educators with the knowledge and tools to utilize plant-based nutrition education as an intervention for type 2 diabetes. Scientific support for the efficacy, acceptability, and nutritional adequacy of a plant-based diet for people with type 2 diabetes is presented, and practical considerations such as medication adjustment and risk of hypoglycemia are reviewed.

CONCLUSIONS

Plant-based meal planning is an acceptable and effective strategy that educators can use to improve diabetes management and reduce risk of complications. Studies show that dietary changes that are effective for reducing cardiac risk may also be helpful for management of type 2 diabetes. A low-fat, plant-based diet reduces body weight and improves glycemic control, and has been shown to be remarkably well accepted by patients.

Usefulness of vegetarian and vegan diets for treating type 2 diabetes

Significant benefits for diabetes prevention and management have been observed with vegetarian and especially vegan diets. This article reviews observational studies and intervention trials on such diets, and discusses their efficacy, nutritional adequacy, acceptability, and sustainability. Research to date has demonstrated that a low-fat, plant-based nutritional approach improves control of weight, glycemia, and cardiovascular risk. These studies have also shown that carefully planned vegan diets can be more nutritious than diets based on more conventional diet guidelines, with an acceptability that is comparable with that of other therapeutic regimens. Current intervention guidelines from professional organizations offer support for this approach. Vegetarian and vegan diets present potential advantages in managing type 2 diabetes that merit the attention of individuals with diabetes and their caregivers.

Identification of biochemical changes in lactovegetarian urine using 1H NMR spectroscopy and pattern recognition

A vegetarian diet has been demonstrated to have a profound influence on human metabolism as well as to aid the prevention of several chronic diseases relative to an omnivorous diet. However, there have been no systematic metabolomic studies on all of the biochemical changes induced in human subjects by long-term vegetarianism. In this study, (1)H NMR spectroscopy in combination with multivariate statistical analysis was applied to explore the variability in the metabolic urinary profiles of healthy populations from four groups: lactovegetarian male (VEGMALE), lactovegetarian female (VEGFEMALE), omnivorous male (OMNMALE), and omnivorous female (OMNFEMALE). Differences in metabolic profiles were examined in relation to diet and gender by principal component analysis (PCA) and spectral integrals. It was found that the most influential low molecular weight metabolites responsible for the differences between the diet groups were N-acetyl glycoprotein (NAG), succinate, citrate, trimethylamine-N-oxide (TMAO), taurine, glycine, hippurate, phenylalanine, methylhistidine and formate, whereas for the differences in gender groups the most discriminatory metabolites were NAG, succinate, creatinine, arginine, TMAO, taurine, hippurate, mannitol, phenylalanine, and methylhistidine. The results from the PCA of all four groups indicated that diet plays a greater role in influencing metabolite differences than gender. As an exploration, this work shows the potential of metabolomics when applied to nutritional and physiological studies, and it will aid further studies.