Dairy products and the risk of type 2 diabetes: a systematic review and dose-response meta-analysis of cohort studies

Involvement of dietary saturated fats, from all sources or of dairy origin only, in insulin resistance and type 2 diabetes

Reducing the consumption of saturated fatty acids to a level as low as possible is a European public health recommendation to reduce the risk of cardiovascular disease. The association between dietary intake of saturated fatty acids and development and management of type 2 diabetes mellitus (T2DM), however, is a matter of debate. A literature search was performed to identify prospective studies and clinical trials in humans that explored the association between dietary intake of saturated fatty acids and risk of insulin resistance and T2DM. Furthermore, to assess whether specific foods, and not just the saturated fatty acid content of the food matrix, can have differential effects on human health, the relationship between consumption of full-fat dairy products, a main source of dietary saturated fatty acids, and risk of insulin resistance and T2DM was studied. There is no evidence that dietary saturated fatty acids from varied food sources affect the risk of insulin resistance or T2DM, nor is intake of full-fat dairy products associated with this risk. These findings strongly suggest that future studies on the effects of dietary saturated fatty acids should take into account the complexity of the food matrix. Furthermore, communication on saturated fats and their health effects should be prudent and well informed.

The scale of the evidence base on the health effects of conventional yogurt consumption: findings of a scoping review

BACKGROUND

The health effects of conventional yogurt have been investigated for over a century; however, few systematic reviews have been conducted to assess the extent of the health benefits of yogurt.

OBJECTIVE

The aim of this scoping review was to assess the volume of available evidence on the health effects of conventional yogurt.

METHODS

The review was guided by a protocol agreed a priori and informed by an extensive literature search conducted in November 2013. Randomized controlled trials were selected and categorized according to the eligibility criteria established in the protocol.

RESULTS

213 studies were identified as relevant to the scoping question. The number of eligible studies identified for each outcome were: bone health (14 studies), weight management and nutrition related health outcomes (81 studies), metabolic health (6 studies); cardiovascular health (57 studies); gastrointestinal health (24 studies); cancer (39 studies); diabetes (13 studies), Parkinson's disease risk (3 studies), all-cause mortality (3 studies), skin complaints (3 studies), respiratory complaints (3 studies), joint pain/function (2 studies); the remaining 8 studies reported a variety of other outcomes. For studies of a similar design and which assessed the same outcomes in similar population groups, we report the potential for the combining of data across studies in systematic reviews.

CONCLUSIONS

This scoping review has revealed the extensive evidence base for many outcomes which could be the focus of systematic reviews exploring the health effects of conventional yogurt consumption.

Phosphorus ingestion improves oral glucose tolerance of healthy male subjects: a crossover experiment

Background

Fasting serum phosphorus (P) was reported to be inversely related to serum glucose and insulin, while the impact of P ingestion is not well documented. The effect of P intake with or before glucose ingestion on postprandial glucose and insulin statuses was investigated.

Method

Two cross over experiments using healthy male subjects were conducted. Experiment 1: Overnight fasted subjects (n = 7) randomly received: 500 mg of P tablets, glucose (75 g) solution with placebo or 500 mg of P tablets. Experiment 2: Overnight fasted subjects (n = 8) underwent similar procedures to those of experiment 1, except that placebo or 500 mg P tablets were given 60 min prior to glucose ingestion.

Results

In both experiments, serum P decreased following glucose ingestion. Co-ingestion of P with glucose improved, at time 60 min, postprandial glucose (P < 0.05), insulin (P < 0.05), and insulin sensitivity index (p < 0.006), while P pre-ingestion failed to exert similar effect.

Conclusion

This study suggests that postprandial glucose and insulin are affected by exogenous P supply, especially when co-ingested with glucose.

No Effect of Added Sugar Consumed at Median American Intake Level on Glucose Tolerance or Insulin Resistance

Excess sugar consumption may promote adverse changes in hepatic and total body insulin resistance. Debate continues over the effects of sugars at more typically consumed levels and whether the identity of the sugar consumed is important. In the present study participants (20–60 years old) were randomly assigned to one of five groups, three that consumed low fat milk with added fructose containing sugars in amounts equivalent to the 50th percentile of fructose consumption (US), one which consumed low-fat milk sweetened with glucose, and one unsweetened low-fat milk control group. The intervention lasted ten weeks. In the entire study population there was less than 1 kg increase in weight (73.6 ± 13.0 vs. 74.5 ± 13.3 kg, p < 0.001), but the change in weight was comparable among groups (p > 0.05). There were no changes in fasting glucose (49 ± 0.4 vs. 5.0 ± 0.5 mmol/L), insulin (56.9 ± 38.9 vs. 61.8 ± 50.0 pmol/L), or insulin resistance, as measured by the Homeostasis Model Assessment method (1.8 ± 1.3 vs. 2.0 ± 1.5, all p > 0.05). These data suggest that added sugar consumed at the median American intake level does not produce changes in measures of insulin sensitivity or glucose tolerance and that no sugar has more deleterious effects than others.

Is consuming yoghurt associated with weight management outcomes? Results from a systematic review

Background:

Yoghurt is part of the diet of many people worldwide and is commonly recognised as a ‘health food'. Epidemiological studies suggest that yoghurt may be useful as part of weight management programs. In the absence of comprehensive systematic reviews, this systematic review investigated the effect of yoghurt consumption by apparently healthy adults on weight-related outcomes.

Methods:

An extensive literature search was undertaken, as part of a wider scoping review, to identify yoghurt studies. A total of 13 631 records were assessed for their relevance to weight-related outcomes.

Results:

Twenty-two publications were eligible according to the review protocol. Cohort studies (n=6) and cross-sectional studies (n=7) all showed a correlation between yoghurt and lower or improved body weight/composition. Six randomised controlled trials (RCTs) and one controlled trial had various limitations, including small size and short duration. One RCT showed significant effects of yoghurt on weight loss, but was confounded by differences in calcium intake. One trial showed nonsignificant weight gain and the remaining five trials showed nonsignificant weight losses that were greater in yoghurt consumers.

Conclusions:

Yoghurt consumption is associated with lower body mass index, lower body weight/weight gain, smaller waist circumference and lower body fat in epidemiological studies. RCTs suggest weight reduction effects, but do not permit determination of a cause–effect relationship. Well-controlled, adequately powered trials in research and community settings appear likely to identify a modest but beneficial effect of yoghurt consumption for prevention of weight gain and management of obesity. The ready availability of yoghurt (a nutrient-dense food) and its ease of introduction to most diets suggests that educating the public to eat yoghurt as part of a balanced and healthy diet may potentially contribute to improved public health. Future carefully designed RCTs could provide proof of principle and large community-based studies could determine the practical impact of yoghurt on body weight/composition.

Dairy products consumption and metabolic syndrome in adults: systematic review and meta-analysis of observational studies

The association of dairy products consumption with risk of metabolic syndrome (MetS) has been inconsistently reported in observational studies. A systematic review and meta-analysis of published observational studies was conducted to quantitatively evaluate this association. Relevant studies were identified by searching PubMed and EMBASE databases and by carefully checking the bibliographies of retrieved full reports and related reviews. Eligible studies were observational studies that investigated the association between dairy products consumption and risk of MetS in adults, with risk estimates available. Random-effects model was assigned to calculate the summary risk estimates. The final analysis included 15 cross-sectional studies, one case-control study and seven prospective cohort studies. Higher dairy consumption significantly reduced MetS by 17% in the cross-sectional/case-control studies (odds ratio = 0.83, 95% confidence interval [CI], 0.73-0.94), and by 14% (relative risk [RR] = 0.86, 95% CI, 0.79-0.92) in cohort studies. The inverse dairy-MetS association was consistent in subgroup and sensitivity analyses. The dose-response analysis of the cohort studies conferred a significant 6% (RR = 0.94, 95% CI, 0.90-0.98) reduction in the risk of MetS for each increment in dairy consumption of one serving/d. No significant publication bias was observed. Our findings suggest an inverse dose-response relationship between dairy consumption and risk of MetS.

Evidence-Based Guideline of the German Nutrition Society: Fat Intake and Prevention of Selected Nutrition-Related Diseases

As nutrition-related chronic diseases have become more and more frequent, the importance of dietary prevention has also increased. Dietary fat plays a major role in human nutrition, and modification of fat and/or fatty acid intake could have a preventive potential. The aim of the guideline of the German Nutrition Society (DGE) was to systematically evaluate the evidence for the prevention of the widespread diseases obesity, type 2 diabetes mellitus, dyslipoproteinaemia, hypertension, metabolic syndrome, coronary heart disease (CHD), stroke, and cancer through the intake of fat or fatty acids. The main results can be summarized as follows: it was concluded with convincing evidence that a reduced intake of total and saturated fat as well as a larger intake of polyunsaturated fatty acids (PUFA) at the expense of saturated fatty acids (SFA) reduces the concentration of total and low-density lipoprotein cholesterol in plasma. Furthermore, there is convincing evidence that a high intake of trans fatty acids increases risk of dyslipoproteinaemia and that a high intake of long-chain polyunsaturated n-3 fatty acids reduces the triglyceride concentration in plasma. A high fat intake increases the risk of obesity with probable evidence when total energy intake is not controlled for (ad libitum diet). When energy intake is controlled for, there is probable evidence for no association between fat intake and risk of obesity. A larger intake of PUFA at the expense of SFA reduces risk of CHD with probable evidence. Furthermore, there is probable evidence that a high intake of long-chain polyunsaturated n-3 fatty acids reduces risk of hypertension and CHD. With probable evidence, a high trans fatty acid intake increases risk of CHD. The practical consequences for current dietary recommendations are described at the end of this article.

Milk Consumption and Mortality from All Causes, Cardiovascular Disease, and Cancer: A Systematic Review and Meta-Analysis

Results from epidemiological studies of milk consumption and mortality are inconsistent. We conducted a systematic review and meta-analysis of prospective studies assessing the association of non-fermented and fermented milk consumption with mortality from all causes, cardiovascular disease, and cancer. PubMed was searched until August 2015. A two-stage, random-effects, dose-response meta-analysis was used to combine study-specific results. Heterogeneity among studies was assessed with the I² statistic. During follow-up periods ranging from 4.1 to 25 years, 70,743 deaths occurred among 367,505 participants. The range of non-fermented and fermented milk consumption and the shape of the associations between milk consumption and mortality differed considerably between studies. There was substantial heterogeneity among studies of non-fermented milk consumption in relation to mortality from all causes (12 studies; I² = 94%), cardiovascular disease (five studies; I² = 93%), and cancer (four studies; I² = 75%) as well as among studies of fermented milk consumption and all-cause mortality (seven studies; I² = 88%). Thus, estimating pooled hazard ratios was not appropriate. Heterogeneity among studies was observed in most subgroups defined by sex, country, and study quality. In conclusion, we observed no consistent association between milk consumption and all-cause or cause-specific mortality.

Adaptation to Lactose in Lactase Non Persistent People: Effects on Intolerance and the Relationship between Dairy Food Consumption and Evalution of Diseases

Dairy foods contain complex nutrients which interact with the host. Yet, evolution of lactase persistence has divided the human species into those that can or cannot digest lactose in adulthood. Such a ubiquitous trait has differential effects on humanity. The literature is reviewed to explore how the divide affects lactose handling by lactase non persistent persons. There are two basic differences in digesters. Firstly, maldigesters consume less dairy foods, and secondly, excess lactose is digested by colonic microflora. Lactose intolerance in maldigesters may occur with random lactose ingestion. However, lactose intolerance without maldigestion tends to detract from gaining a clear understanding of the mechanisms of symptoms formation and leads to confusion with regards to dairy food consumption. The main consequence of intolerance is withholding dairy foods. However, regular dairy food consumption by lactase non persistent people could lead to colonic adaptation by the microbiome. This process may mimic a prebiotic effect and allows lactase non persistent people to consume more dairy foods enhancing a favorable microbiome. This process then could lead to alterations in outcome of diseases in response to dairy foods in lactose maldigesters. The evidence that lactose is a selective human prebiotic is reviewed and current links between dairy foods and some diseases are discussed within this context. Colonic adaptation has not been adequately studied, especially with modern microbiological techniques.

Milk intake is not associated with low risk of diabetes or overweight-obesity: a Mendelian randomization study in 97,811 Danish individuals

BACKGROUND

High dairy/milk intake has been associated with a low risk of type 2 diabetes observationally, but whether this represents a causal association is unknown.

OBJECTIVE

We tested the hypothesis that high milk intake is associated with a low risk of type 2 diabetes and of overweight-obesity, observationally and genetically.

DESIGN

In 97,811 individuals from the Danish general population, we examined the risk of incident type 2 diabetes and of overweight-obesity by milk intake observationally and by LCT-13910 C/T genotype [polymorphism (rs4988235) upstream from the lactase (LCT) gene], where TT and TC genotypes are associated with lactase persistence and CC with nonpersistence.

RESULTS

Observationally for any compared with no milk intake, the HR for type 2 diabetes was 1.10 (95% CI: 0.98, 1.24; P = 0.11), whereas the OR for overweight-obesity was 1.06 (1.02, 1.09; P = 0.002). Median milk intake was 5 glasses/wk (IQR: 0-10) for lactase TT/TC persistence and 3 (0-7) for CC nonpersistence. Genetically for lactase TT/TC persistence compared with CC nonpersistence, the OR was 0.96 (0.86, 1.08; P = 0.50) for type 2 diabetes and 1.06 (1.00, 1.12; P = 0.04) for overweight-obesity. In a stratified analysis for type 2 diabetes, corresponding values in those with and without milk intake were 0.88 (0.76, 1.03; P = 0.11) and 1.35 (1.07, 1.70; P = 0.01) (P-interaction: 0.002), whereas no gene-milk interaction on overweight-obesity was found. For a 1-glass/wk higher milk intake, the genetic risk ratio for type 2 diabetes was 0.99 (0.93, 1.06), and the corresponding observational risk was 1.01 (1.00, 1.01). For overweight-obesity, the corresponding values were 1.01 (1.00, 1.02) genetically and 1.00 (1.00, 1.01) observationally.

CONCLUSIONS

High milk intake is not associated with a low risk of type 2 diabetes or overweight-obesity, observationally or genetically via lactase persistence. The higher risk of type 2 diabetes in lactase-persistent individuals without milk intake likely is explained by collider stratification bias.

Association between consumption of dairy products and incident type 2 diabetes--insights from the European Prospective Investigation into Cancer study

The public health burden of type 2 diabetes has risen unabated over the past decades, fueled by obesity and lifestyle influences, including diet quality. Epidemiological evidence is accumulating for an inverse association between dairy product intake and type 2 diabetes risk; this is somewhat counterintuitive to the saturated fat and cardiometabolic disease paradigm. The present report reviews the contribution that the findings of the European Prospective Investigation into Cancer (EPIC) study have made to this debate, noting that types of dairy products, particularly fermented dairy products including yogurt, may be more relevant than overall dairy intake for the prevention of type 2 diabetes. The EPIC study has contributed evidence through complementary approaches of a large prospective study across 8 European countries with heterogeneous dietary intakes assessed using food-frequency questionnaires (EPIC-InterAct study) and through a more detailed examination of diet assessed using a 7-day food diary (EPIC-Norfolk study). The implications of these findings are placed in the wider context, including the use of individual fatty acid blood biomarkers in the EPIC-InterAct study and an appraisal of current research gaps and suggestions for future research directions.

Butter increased total and LDL cholesterol compared with olive oil but resulted in higher HDL cholesterol compared with a habitual diet

BACKGROUND

Butter is known to have a cholesterol-raising effect and, therefore, has often been included as a negative control in dietary studies, whereas the effect of moderate butter intake has not been elucidated to our knowledge.

OBJECTIVE

We compared the effects of moderate butter intake, moderate olive oil intake, and a habitual diet on blood lipids, high-sensitivity C-reactive protein (hsCRP), glucose, and insulin.

DESIGN

The study was a controlled, double-blinded, randomized 2 × 5-wk crossover dietary intervention study with a 14-d run-in period during which subjects consumed their habitual diets. The study included 47 healthy men and women (mean ± SD total cholesterol: 5.22 ± 0.90 mmol/L) who substituted a part of their habitual diets with 4.5% of energy from butter or refined olive oil.

RESULTS

Study subjects were 70% women with a mean age and body mass index (in kg/m²) of 40.4 y and 23.5, respectively. Butter intake increased total cholesterol and LDL cholesterol more than did olive oil intake (P < 0.05) and the run-in period (P < 0.005 and P < 0.05, respectively) and increased HDL cholesterol compared with the run-in period (P < 0.05). No difference in effects was observed for triacylglycerol, hsCRP, insulin, and glucose concentrations. The intake of saturated fatty acids was significantly higher in the butter period than in the olive oil and run-in periods (P < 0.0001).

CONCLUSIONS

Moderate intake of butter resulted in increases in total cholesterol and LDL cholesterol compared with the effects of olive oil intake and a habitual diet (run-in period). Furthermore, moderate butter intake was also followed by an increase in HDL cholesterol compared with the habitual diet. We conclude that hypercholesterolemic people should keep their consumption of butter to a minimum, whereas moderate butter intake may be considered part of the diet in the normocholesterolemic population.

Cholesterol and breast cancer risk: a systematic review and meta-analysis of prospective studies

The objective of the present study was to conduct the first systematic review and meta-analysis of prospective studies investigating the associations between total cholesterol (TC), HDL-cholesterol (HDL-C) and LDL-cholesterol (LDL-C) levels and the risk of breast cancer. Relevant studies were identified in PubMed (up to January 2014). Inclusion criteria were original peer-reviewed publications with a prospective design. Random-effects models were used to estimate summary hazard ratios (HR) and 95% CI. Distinction was made between studies that did or did not exclude cancer cases diagnosed during the first years of follow-up, thereby eliminating potential preclinical bias. Overall, the summary HR for the association between TC and breast cancer risk was 0.97 (95% CI 0.94, 1.00; dose-response per 1 mmol/l increment, thirteen studies), and that between HDL-C and breast cancer risk was 0.86 (95% CI 0.69, 1.09; dose-response per 1 mmol/l increment, six studies), with high heterogeneity (I2= 67 and 47%, respectively). For studies that eliminated preclinical bias, an inverse association was observed between the risk of breast cancer and TC (dose-response HR 0.94 (95% CI 0.89, 0.99), seven studies, I2= 78%; highest v. lowest HR 0.82 (95% CI 0.66, 1.02), nine studies, I2= 81%) and HDL-C (dose-response HR 0.81 (95% CI 0.65, 1.02), five studies, I2= 30 %; highest v. lowest HR 0.82 (95% CI 0.69, 0.98), five studies, I2= 0%). There was no association observed between LDL-C and the risk of breast cancer (four studies). The present meta-analysis confirms the evidence of a modest but statistically significant inverse association between TC and more specifically HDL-C and the risk of breast cancer, supported by mechanistic plausibility from experimental studies. Further large prospective studies that adequately control for preclinical bias are needed to confirm the results on the role of cholesterol level and its fractions in the aetiology of breast cancer.

Cheddar Cheese Ripening Affects Plasma Nonesterified Fatty Acid and Serum Insulin Concentrations in Growing Pigs

BACKGROUND

Meta-analyses of observational studies found cheese consumption to be inversely associated with risk of type 2 diabetes and metabolic syndrome. This may be attributed to the bioactive compounds produced during cheese ripening.

OBJECTIVE

The objective of this study was to investigate by means of a porcine model how cheeses with different ripening times affect blood glucose, insulin, and lipid concentrations and fecal-fat excretion.

METHODS

A parallel-arm randomized intervention study with 36 Landrace × Yorkshire × Duroc crossbred 3-mo-old female pigs was conducted. The pigs were fed a 21-d butter-rich run-in diet (143 g of butter/kg diet), followed by a 14-d intervention with 1 of 3 isocaloric diets: 4-mo ripened cheddar (4-MRC) diet, 14-mo ripened cheddar (14-MRC) diet, or 24-mo ripened cheddar (24-MRC) diet (350 g of cheese/kg diet). Serum cholesterol, triglycerides, HDL cholesterol, LDL cholesterol, and insulin; plasma nonesterified fatty acids (NEFAs) and glucose; fecal-fat excretion; and body weight were measured.

RESULTS

Plasma NEFAs were lower in the 24-MRC (201 ± 26 μEq/L) and in the 14-MRC (171 ± 19 μEq/L) diet groups than in the 4-MRC diet group (260 ± 27 μEq/L; P = 0.044 and P = 0.001). Serum insulin was lower in the 24-MRC diet group (1.04 ± 0.09 mmol/L) than in the 4-MRC diet group (1.44 ± 0.14 mmol/L; P = 0.002), but intermediate and not different from either in the 14-MRC diet group (1.25 ± 0.11 mmol/L). Likewise, homeostasis model assessment of insulin resistance was lower in the 24-MRC diet group (0.030 ± 0.003) than in the 4-MRC diet group (0.041 ± 0.005; P < 0.01), but intermediate and not different from either in the 14-MRC group (0.036 ± 0.004).

CONCLUSIONS

Intake of long-term ripened cheddar improved indicators of insulin sensitivity in growing pigs compared with short-term ripened cheddar. This may also be important for human health.

Metabolomics to Explore Impact of Dairy Intake

Dairy products are an important component in the Western diet and represent a valuable source of nutrients for humans. However, a reliable dairy intake assessment in nutrition research is crucial to correctly elucidate the link between dairy intake and human health. Metabolomics is considered a potential tool for assessment of dietary intake instead of traditional methods, such as food frequency questionnaires, food records, and 24-h recalls. Metabolomics has been successfully applied to discriminate between consumption of different dairy products under different experimental conditions. Moreover, potential metabolites related to dairy intake were identified, although these metabolites need to be further validated in other intervention studies before they can be used as valid biomarkers of dairy consumption. Therefore, this review provides an overview of metabolomics for assessment of dairy intake in order to better clarify the role of dairy products in human nutrition and health.

The Role of Nutrition and Physical Activity in Cholesterol and Aging

Cholesterol is a precursor of several substances with important biologic activities; however, it is common to associate this molecule only with bad outcomes. This article reviews the cholesterol metabolism, its functions in the human body, its pathogenicity, and its elimination. The modifications in biochemical paths of cholesterol in aging are highlighted. Finally, the role of diet, physical activity, and exercise in cholesterol management is discussed.

Dairy foods and dairy proteins in the management of type 2 diabetes: a systematic review of the clinical evidence

Type 2 diabetes mellitus (T2DM) is a growing public health concern affecting hundreds of millions of people worldwide and costing the global economy hundreds of billions of dollars annually. This chronic disease damages the blood vessels and increases the risk of other cardiometabolic ailments such as cardiovascular disease and stroke. If left unmanaged it can also lead to nerve damage, kidney damage, blindness, and amputation. For the most part, many of these symptoms can be prevented or reduced through simple dietary modifications and proper nutrition. Therefore, identifying relatively inexpensive and easily implementable dietary modifications for the prevention and management of T2DM is of considerable value to human health and healthcare modalities around the globe. Protein-rich dairy products have consistently been shown in epidemiologic studies to be beneficial for reducing the risk of developing T2DM. The clinical evidence regarding both dairy foods and dairy proteins (i.e., casein and whey protein) have shown promise for improving insulin secretion in individuals with T2DM. However, the clinical research on dairy protein supplementation in subjects with T2DM has been limited to acute studies. These studies have been mostly descriptive and have not been focused on important T2DM endpoints such as prevention, management, or treatment. Long-term studies are clearly needed to help researchers and medical professionals better understand the effects of consistent dairy protein intake on the metabolic health of humans with T2DM.

Associations between dairy products consumption and risk of type 2 diabetes: Tehran lipid and glucose study

We aimed to examine the relationship between total dairy and dairy subtypes with the risk of type 2 diabetes (T2DM) in an Asian population. A nested case-control study of 178 cases of incident T2DM and 520 matched controls was conducted within the Tehran lipid and glucose study (TLGS). A 27% lower risk of T2DM was found per 100 g/d total dairy consumption that tend to be significant (95% CI: 0.52-1.02). Milk intake was inversely associated with diabetes after adjustment for confounders (p-trend: 0.042). Milk intake was associated with decreased T2DM risk in men (p-trend: 0.025), but not in women (p-trend: 0.527). Each 100 g/d increase in milk intake corresponded to 41% lower T2DM risk in fully adjusted model (95% CI: 0.39-0.89) in men. In conclusion, there is no significant association between diabetes and total dairy intake in the present study, but high intake of milk may reduce T2DM risk among men.

Food sources of fat may clarify the inconsistent role of dietary fat intake for incidence of type 2 diabetes

BACKGROUND

Dietary fats could affect glucose metabolism and obesity development and, thereby, may have a crucial role in the cause of type 2 diabetes (T2D). Studies indicated that replacing saturated with unsaturated fats might be favorable, and plant foods might be a better choice than animal foods. Nevertheless, epidemiologic studies suggested that dairy foods are protective.

OBJECTIVE

We hypothesized that, by examining dietary fat and its food sources classified according to fat type and fat content, some clarification regarding the role of dietary fat in T2D incidence could be provided.

DESIGN

A total of 26,930 individuals (61% women), aged 45-74 y, from the Malmö Diet and Cancer cohort were included in the study. Dietary data were collected by using a modified diet-history method. During 14 y of follow-up, 2860 incident T2D cases were identified.

RESULTS

Total intake of high-fat dairy products (regular-fat alternatives) was inversely associated with incident T2D (HR for highest compared with lowest quintiles: 0.77; 95% CI: 0.68, 0.87; P-trend < 0.001). Most robust inverse associations were seen for intakes of cream and high-fat fermented milk (P-trend < 0.01) and for cheese in women (P-trend = 0.02). High intake of low-fat dairy products was associated with increased risk, but this association disappeared when low- and high-fat dairy were mutually adjusted (P-trend = 0.18). Intakes of both high-fat meat (P-trend = 0.04) and low-fat meat (P-trend < 0.001) were associated with increased risk. Finally, we did not observe significant association between total dietary fat content and T2D (P-trend = 0.24), but intakes of saturated fatty acids with 4-10 carbons, lauric acid (12:0), and myristic acid (14:0) were associated with decreased risk (P-trend < 0.01).

CONCLUSIONS

Decreased T2D risk at high intake of high- but not of low-fat dairy products suggests that dairy fat partly could have contributed to previously observed protective associations between dairy intake and T2D. Meat intake was associated with increased risk independently of the fat content.

Plasma phospholipid very-long-chain saturated fatty acids and incident diabetes in older adults: the Cardiovascular Health Study

BACKGROUND

Circulating saturated fatty acids (SFAs) are integrated biomarkers of diet and metabolism that may influence the pathogenesis of diabetes. In epidemiologic studies, circulating levels of palmitic acid (16:0) are associated with diabetes; however, very-long-chain SFAs (VLSFAs), with 20 or more carbons, differ from palmitic acid in their biological activities, and little is known of the association of circulating VLSFA with diabetes.

OBJECTIVE

By using data from the Cardiovascular Health Study, we examined the associations of plasma phospholipid VLSFA levels measured at baseline with subsequent incident diabetes.

DESIGN

A total of 3179 older adults, with a mean age of 75 y at study baseline (1992-1993), were followed through 2011. We used multiple proportional hazards regression to examine the associations of arachidic acid (20:0), behenic acid (22:0), and lignoceric acid (24:0) with diabetes.

RESULTS

Baseline levels of each VLSFA were cross-sectionally associated with lower triglyceride levels and lower circulating palmitic acid. We identified 284 incident diabetes cases during follow-up. Compared with the lowest quartile, levels of arachidic acid in the highest quartile of the fatty acid distribution were associated with a 47% lower risk of diabetes (95% CI: 23%, 63%; P-trend: <0.001), after adjustment for demographics, lifestyle factors, and clinical conditions. In analogous comparisons, levels of behenic and lignoceric acid were similarly associated with 33% (95% CI: 6%, 53%; P-trend: 0.02) and 37% (95% CI: 11%, 55%; P-trend: 0.01) lower diabetes risk, respectively. Adjustment for triglycerides and palmitic acid attenuated the associations toward the null, and only the association of arachidic acid remained statistically significant (32% lower risk for fourth vs. first quartile; P-trend: 0.04).

CONCLUSIONS

These results suggest that circulating VLSFAs are associated with a lower risk of diabetes, and these associations may be mediated by lower triglycerides and palmitic acid. The study highlights the need to distinguish the effects of different SFAs and to explore determinants of circulating VLSFAs. This trial was registered at clinicaltrials.gov as NCT00005133.

Association between intake of dairy products and short-term memory with and without adjustment for genetic and family environmental factors: A twin study

BACKGROUND & AIMS

Previous studies have indicated associations between intake of dairy products and better cognitive function and reduced risk of dementia. However, these studies did not adjust for genetic and family environmental factors that may influence food intake, cognitive function, and metabolism of dairy product nutrients. In the present study, we investigated the association between intake of dairy products and short-term memory with and without adjustment for almost all genetic and family environmental factors using a genetically informative sample of twin pairs.

METHODS

A cross-sectional study was conducted among twin pairs aged between 20 and 74. Short-term memory was assessed as primary outcome variable, intake of dairy products was analyzed as the predictive variable, and sex, age, education level, marital status, current smoking status, body mass index, dietary alcohol intake, and medical history of hypertension or diabetes were included as possible covariates. Generalized estimating equations (GEE) were performed by treating twins as individuals and regression analyses were used to identify within-pair differences of a twin pair to adjust for genetic and family environmental factors. Data are reported as standardized coefficients and 95% confidence intervals (CI).

RESULTS

Analyses were performed on data from 78 men and 278 women. Among men, high intake of dairy products was significantly associated with better short-term memory after adjustment for the possible covariates (standardized coefficients = 0.22; 95% CI, 0.06-0.38) and almost all genetic and family environmental factors (standardized coefficients = 0.38; 95% CI, 0.07-0.69). Among women, no significant associations were found between intake of dairy products and short-term memory. Subsequent sensitivity analyses were adjusted for small samples and showed similar results.

CONCLUSIONS

Intake of dairy product may prevent cognitive declines regardless of genetic and family environmental factors in men.

Associations of dairy intake with glycemia and insulinemia, independent of obesity, in Brazilian adults: the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

BACKGROUND

Inverse associations between dairy intake and the risk of type 2 diabetes have been shown, but more studies are needed, especially from low- and middle-income countries.

OBJECTIVE

The objective was to describe the association between dairy products and direct measures of glycemic status in adults without known diabetes.

DESIGN

The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) includes 15,105 adults, aged 35-74 y, enrolled from universities and research institutions in 6 Brazilian capital cities. We excluded participants with a known diabetes diagnosis, cardiovascular diseases, and cancer. Dairy consumption was assessed by a food-frequency questionnaire, and we computed servings per day for total and subgroups of dairy. Associations with fasting blood glucose (FG) and fasting insulin, 2-h postload glucose (PG), 2-h postload insulin (PI), glycated hemoglobin (Hb A1c), and homeostasis model assessment of insulin resistance (HOMA-IR) were assessed through multivariable linear regression analysis with adjustment for demographic characteristics, behavioral risk factors, other dietary factors, and anthropometric measurements.

RESULTS

The sample size after exclusions was 10,010. The intake of total dairy was inversely associated with FG (linear β for dairy servings/d = -0.46 ± 0.2 mg/dL), PG (-1.25 ± 0.5 mg/dL), PI (-1.52 ± 0.6 mg/dL), Hb A1c (-0.02 ± 0.0%), and HOMA-IR (-0.04 ± 0.0) after adjustment for all covariates (P < 0.05 for all). The findings were consistent across categories of sex, race, obesity status, and dairy fat amount (reduced-fat vs. full-fat dairy). Fermented dairy products showed particularly strong inverse associations with the outcomes, with adjusted differences for a 1-serving/d increment of -0.24 (95% CI: -0.46, -0.02) mg/dL for FG, -0.86 (-1.42, -0.30) mg/dL for PG, and -0.01% (-0.02%, 0.00%) for Hb A1c. Myristic acid was the only nutrient that appeared to mediate the association between dairy intake and glycemia.

CONCLUSION

Dairy intake, especially fermented dairy, was inversely associated with measures of glycemia and insulinemia in Brazilian adults without diagnosed diabetes. This trial was registered at clinicaltrials.com as NCT02320461.

Dairy proteins, dairy lipids, and postprandial lipemia in persons with abdominal obesity (DairyHealth): a 12-wk, randomized, parallel-controlled, double-blinded, diet intervention study

BACKGROUND

Abdominal obesity and exaggerated postprandial lipemia are independent risk factors for cardiovascular disease (CVD) and mortality, and both are affected by dietary behavior.

OBJECTIVE

We investigated whether dietary supplementation with whey protein and medium-chain saturated fatty acids (MC-SFAs) improved postprandial lipid metabolism in humans with abdominal obesity.

DESIGN

We conducted a 12-wk, randomized, double-blinded, diet intervention study. Sixty-three adults were randomly allocated to one of 4 diets in a 2 × 2 factorial design. Participants consumed 60 g milk protein (whey or casein) and 63 g milk fat (with high or low MC-SFA content) daily. Before and after the intervention, a high-fat meal test was performed. We measured changes from baseline in fasting and postprandial triacylglycerol, apolipoprotein B-48 (apoB-48; reflecting chylomicrons of intestinal origin), free fatty acids (FFAs), insulin, glucose, glucagon, glucagon-like peptide 1 (GLP-1), and gastric inhibitory polypeptide (GIP). Furthermore, changes in the expression of adipose tissue genes involved in lipid metabolism were investigated. Two-factor ANOVA was used to examine the difference between protein types and fatty acid compositions, as well as any interaction between the two.

RESULTS

Fifty-two participants completed the study. We found that the postprandial apoB-48 response decreased significantly after whey compared with casein (P = 0.025) independently of fatty acid composition. Furthermore, supplementation with casein resulted in a significant increase in the postprandial GLP-1 response compared with whey (P = 0.003). We found no difference in postprandial triacylglycerol, FFA, insulin, glucose, glucagon, or GIP related to protein type or MC-SFA content. We observed no interaction between milk protein and milk fat on postprandial lipemia.

CONCLUSION

We found that a whey protein supplement decreased the postprandial chylomicron response compared with casein in persons with abdominal obesity, thereby indicating a beneficial impact on CVD risk. This trial was registered at clinicaltrials.gov as NCT01472666.

Fruit and vegetable consumption and risk of type 2 diabetes mellitus: a dose-response meta-analysis of prospective cohort studies

BACKGROUND AND AIMS

We conducted a dose-response meta-analysis to summarize the evidence from prospective cohort studies regarding the association of fruit and vegetable consumption with risk of type 2 diabetes mellitus (T2DM).

METHODS AND RESULTS

Pertinent studies were identified by searching Embase and PubMed through June 2014. Study-specific results were pooled using a random-effect model. The dose-response relationship was assessed by the restricted cubic spline model and the multivariate random-effect meta-regression. We standardized all data using a standard portion size of 106 g. The Relative Risk (95% confidence interval) [RR (95% CI)] of T2DM was 0.99 (0.98-1.00) for every 1 serving/day increment in fruit and vegetable (FV) (P = 0.18), 0.98 (0.95-1.01) for vegetable (P = 0.12), and 0.99 (0.97-1.00) for fruit (P = 0.05). The RR (95%CI) of T2DM was 0.99 (0.97-1.01), 0.98 (0.96-1.01), 0.97 (0.93-1.01), 0.96 (0.92-1.01), 0.96 (0.91-1.01) and 0.96 (0.91-1.01) for 1, 2, 3, 4, 5 and 6 servings/day of FV (P(for non-linearity) = 0.44). The T2DM risk was 0.96 (0.95-0.99), 0.94 (0.90-0.98), 0.94 (0.89-0.98), 0.96 (0.91-1.01), 0.98 (0.92-1.05) and 1.00 (0.93-1.08) for 1, 2, 3, 4, 5 and 6 servings/day of vegetable (P(for non-linearity) < 0.01). The T2DM risk was 0.95 (0.93-0.97), 0.91 (0.89-0.94), 0.88 (0.85-0.92), 0.92 (0.88-0.96) and 0.96 (0.92-1.01) for 0.5, 1, 2, 3 and 4 servings/day of fruit (P(for non-linearity) < 0.01).

CONCLUSIONS

Two-three servings/day of vegetable and 2 servings/day of fruit conferred a lower risk of T2DM than other levels of vegetable and fruit consumption, respectively.

Impact of milk consumption on cardiometabolic risk in postmenopausal women with abdominal obesity

Background

The impact of dairy intake on cardiometabolic risk factors associated with metabolic syndrome (MetS) needs further research.

Objective

To investigate the impact of milk consumption on a wide array of cardiometabolic risk factors associated with MetS (blood lipids, cholesterol homeostasis, glucose homeostasis, systemic inflammation, blood pressure, endothelial function) in postmenopausal women with abdominal obesity.

Methods

In this randomized, crossover study, 27 women with abdominal obesity consumed two 6-week diets based on the National Cholesterol Education Program (NCEP), one with 3.2 servings/d of 2% fat milk per 2000 kcal (MILK) and one without milk or other dairy (NCEP). The macronutrient composition of both diets was comparable (55% carbohydrates, 15% proteins, 30% fat and 10% saturated fat).

Results

The MILK diet had no significant effect on LDL-C, triglycerides, LDL size, CRP and cell adhesion molecule concentrations and on indicators of insulin sensitivity. The MILK diet reduced HDL-C, adiponectin, endothelin and fasting glucose levels as well blood pressure (all P ≤ 0.01), but those changes were comparable to those seen with the NCEP milk-free diet (all between-diet P ≥ 0.07). Finally, the MILK diet was associated with lower VLDL apolipoprotein B fractional catabolic rate (−13.4%; P = 0.04) and plasma sterol concentrations (−12.0%; P = 0.04) compared with the control NCEP milk-free diet.

Conclusions

These data suggest that short-term consumption of low fat milk in the context of a prudent NCEP diet has no favorable nor deleterious effect on cardiometabolic risk factors associated with MetS in postmenopausal women with abdominal obesity.

Electronic supplementary material

The online version of this article (doi:10.1186/1475-2891-14-12) contains supplementary material, which is available to authorized users.

Dietary substitutions for refined carbohydrate that show promise for reducing risk of type 2 diabetes in men and women

Both genetics and lifestyle contribute to type 2 diabetes (T2D), a condition of elevated circulating glucose induced by a collection of metabolic defects including peripheral insulin resistance, elevated hepatic glucose output, and impaired pancreatic insulin secretion. Because the prevalence of T2D and its modifiable risk factors (overweight/obesity, dyslipidemia, hypertension, and physical inactivity) have been increasing in recent decades, there has been growing interest in lifestyle interventions that target T2D management and prevention. Although it is increasingly recognized that lifestyle interventions aimed at encouraging physical activity and reducing body weight can improve insulin sensitivity, nutritional contributions to T2D risk reduction are less clear. Evidence from prospective cohort and randomized controlled trials suggests that diets rich in refined dietary carbohydrate [particularly those with a high glycemic index (GI)] may elevate T2D risk; however, the appropriate combination of macronutrients to optimize metabolic health has not been fully described. To date, the collective evidence suggests that diets rich in low-GI carbohydrates, cereal fiber, resistant starch, fat from vegetable sources (unsaturated fat), and lean sources of protein should be emphasized, whereas refined sugars and grains (high-GI carbohydrates) are to be avoided in order to lower risk of T2D and its related risk factors and comorbidities.

Dairy consumption and insulin sensitivity: a systematic review of short- and long-term intervention studies

AIM

Evidence from epidemiological studies suggests that higher consumption of dairy products may be inversely associated with risk of type 2 diabetes and other components of the metabolic syndrome, although the evidence is mixed. Intervention studies that increase dairy intake often involve lifestyle changes, including weight loss, which alone will improve insulin sensitivity. The aim of this review was to examine weight stable intervention studies that assess the effect of an increased intake of dairy products or dairy derived supplements on glucose metabolism and insulin sensitivity.

DATA SYNTHESIS

An electronic search was conducted using MEDLINE, EMBASE, the Cochrane Database and Web of Science for randomised controlled trials altering only dairy intake in humans with no other lifestyle or dietary change, particularly no weight change, and with measurement of glucose or insulin. Healthy participants and those with features of the metabolic syndrome were included. Chronic whey protein supplementation was also included. Ten studies were included in this systematic review.

CONCLUSIONS

In adults, four of the dairy interventions showed a positive effect on insulin sensitivity as assessed by Homeostasis Model Assessment (HOMA); one was negative and five had no effect. As the number of weight stable intervention studies is very limited and participant numbers small, these findings need to be confirmed by larger trials in order to conclusively determine any relationship between dairy intake and insulin sensitivity.

Serum pentadecanoic acid (15:0), a short-term marker of dairy food intake, is inversely associated with incident type 2 diabetes and its underlying disorders

BACKGROUND

Growing evidence suggests that dairy consumption is associated with lower type 2 diabetes risk. However, observational studies have reported inconsistent results, and few have examined dairy's association with the underlying disorders of insulin resistance and β-cell dysfunction.

OBJECTIVE

We investigated the association of the dairy fatty acid biomarkers pentadecanoic acid (15:0) and trans-palmitoleic acid (trans 16:1n-7) with type 2 diabetes traits by evaluating 1) prospective associations with incident diabetes after 5 y of follow-up and 2) cross-sectional associations with directly measured insulin resistance and β-cell dysfunction.

DESIGN

The study analyzed 659 adults without diabetes at baseline from the triethnic multicenter Insulin Resistance Atherosclerosis Study (IRAS). Diabetes status was assessed by using oral-glucose-tolerance tests. Frequently sampled intravenous-glucose-tolerance tests measured insulin sensitivity (SI) and β-cell function [disposition index (DI)]. Serum fatty acids were quantified by using gas chromatography. Logistic and linear regression models were adjusted for demographic, lifestyle, and dietary variables.

RESULTS

Serum 15:0 was a significant biomarker for total dairy intake in the IRAS cohort. It was associated with a decreased incident diabetes risk (OR: 0.73, P = 0.02) and was positively associated with log SI (β: 0.84, P = 0.03) and log DI (β: 2.21, P = 0.02) in fully adjusted models. trans 16:1n-7 was a marker of total partially hydrogenated dietary fat intake and was not associated with outcomes in fully adjusted models.

CONCLUSIONS

Serum 15:0, a marker of short-term intake of this fatty acid, was inversely associated with diabetes risk in this multiethnic cohort. This study may contribute to future recommendations regarding the benefits of dairy products on type 2 diabetes risk.

Associations between dairy intake and metabolic risk parameters in a healthy French-Canadian population

Observational studies support that dairy product intake is associated with a reduced risk of developing type 2 diabetes; however, several clinical studies report conflicting results on the association between dairy product consumption and metabolic parameters. The aim of this study was to determine associations between dairy product consumption and metabolic profile. Dietary data, using a validated food frequency questionnaire, and fasting blood samples were collected from 233 French Canadians. Plasma phospholipid (PL) fatty acids (FA) concentrations were determined by gas chromatography. Subjects consumed 2.5 ± 1.4 portions of dairy products daily, including 1.6 ± 1.3 portions of low-fat (LF) and 0.90 ± 0.70 portions of high-fat (HF) dairy products. Trans-palmitoleic acid level in plasma PL was related to HF dairy consumption (r = 0.15; p = 0.04). Total (r = –0.21; p = 0.001) and LF dairy (r = –0.20; p = 0.003) intakes were inversely correlated with fasting plasma glucose level. Total dairy intake was inversely associated to systolic blood pressure (r = –0.17; p = 0.008) and diastolic blood pressure (r = –0.14; p = 0.03). LF dairy intake was also inversely correlated with systolic blood pressure (r = –0.17; p = 0.009). Total dairy intake was correlated with plasma C-reactive protein (CRP) (r = 0.15; p = 0.03). No association was found between HF dairy consumption and the risk factors studied. In conclusion, dairy intake is inversely associated with glycaemia and blood pressure; yet, it may modify CRP levels. Moreover, trans-palmitoleic FA levels in plasma PL may be potentially used to assess full-fat dairy consumption.

Dairy consumption and risk of type 2 diabetes: 3 cohorts of US adults and an updated meta-analysis

BACKGROUND

The relation between consumption of different types of dairy and risk of type 2 diabetes (T2D) remains uncertain. Therefore, we aimed to evaluate the association between total dairy and individual types of dairy consumptions and incident T2D in US adults.

METHODS

We followed 41,436 men in the Health Professionals Follow-Up Study (1986 to 2010), 67,138 women in the Nurses' Health Study (1980 to 2010), and 85,884 women in the Nurses' Health Study II (1991 to 2009). Diet was assessed by validated food-frequency questionnaires, and data were updated every four years. Incident T2D was confirmed by a validated supplementary questionnaire.

RESULTS

During 3,984,203 person-years of follow-up, we documented 15,156 incident T2D cases. After adjustment for age, body mass index (BMI) and other lifestyle and dietary risk factors, total dairy consumption was not associated with T2D risk and the pooled hazard ratio (HR) (95% confidence interval (CI)) of T2D for one serving/day increase in total dairy was 0.99 (0.98, 1.01). Among different types of dairy products, neither low-fat nor high-fat dairy intake was appreciably associated with risk of T2D. However, yogurt intake was consistently and inversely associated with T2D risk across the three cohorts with the pooled HR of 0.83 (0.75, 0.92) for one serving/day increment (P for trend <0.001). We conducted a meta-analysis of 14 prospective cohorts with 459,790 participants and 35,863 incident T2D cases; the pooled relative risks (RRs) (95% CIs) were 0.98 (0.96, 1.01) and 0.82 (0.70, 0.96) for one serving total dairy/day and one serving yogurt/day, respectively.

CONCLUSIONS

Higher intake of yogurt is associated with a reduced risk of T2D, whereas other dairy foods and consumption of total dairy are not appreciably associated with incidence of T2D.

How calorie-focused thinking about obesity and related diseases may mislead and harm public health. An alternative

Prevailing thinking about obesity and related diseases holds that quantifying calories should be a principal concern and target for intervention. Part of this thinking is that consumed calories – regardless of their sources – are equivalent; i.e. ‘a calorie is a calorie’. The present commentary discusses various problems with the idea that ‘a calorie is a calorie’ and with a primarily quantitative focus on food calories. Instead, the authors argue for a greater qualitative focus on the sources of calories consumed (i.e. a greater focus on types of foods) and on the metabolic changes that result from consuming foods of different types. In particular, the authors consider how calorie-focused thinking is inherently biased against high-fat foods, many of which may be protective against obesity and related diseases, and supportive of starchy and sugary replacements, which are likely detrimental. Shifting the focus to qualitative food distinctions, a central argument of the paper is that obesity and related diseases are problems due largely to food-induced physiology (e.g. neurohormonal pathways) not addressable through arithmetic dieting (i.e. calorie counting). The paper considers potential harms of public health initiatives framed around calorie balance sheets – targeting ‘calories in’ and/or ‘calories out’ – that reinforce messages of overeating and inactivity as underlying causes, rather than intermediate effects, of obesity. Finally, the paper concludes that public health should work primarily to support the consumption of whole foods that help protect against obesity-promoting energy imbalance and metabolic dysfunction and not continue to promote calorie-directed messages that may create and blame victims and possibly exacerbate epidemics of obesity and related diseases.

Dairy product consumption has no impact on biomarkers of inflammation among men and women with low-grade systemic inflammation

BACKGROUND

Randomized controlled trials specifically designed to assess inflammation-related outcomes in response to dairy consumption are lacking.

OBJECTIVE

We investigated the impact of dairy food consumption on biomarkers of inflammation in healthy men and women with low-grade systemic inflammation.

METHODS

In a multicenter randomized crossover study, 112 adult men and women with high-sensitivity C-reactive protein (hs-CRP) values >1 mg/L consumed 3 servings/d of dairy (375 mL low-fat milk, 175 g low-fat yogurt, and 30 g regular-fat cheddar cheese) or energy-matched control (fruit juice, vegetable juice, cashews, and 1 cookie) products as part of prudent 4-wk diets, each separated by a 4- to 8-wk washout period. Serum concentrations of inflammation biomarkers were measured at the beginning and end of each dietary phase. Expression levels of key inflammatory genes and transcription factors in whole blood cells were assessed at the end of each diet by real-time polymerase chain reaction in a random subset of 53 subjects.

RESULTS

Analysis of within-diet changes (post- vs. prediet values) showed a significant reduction in hs-CRP concentrations after the control diet (-11.7%, P = 0.05) but no change after the dairy diet (-7.3%, P = 0.47). As a result, changes in hs-CRP differed between the dairy and control diets (P = 0.04). Both the control and dairy diets similarly reduced interleukin-6 concentrations compared with diet-specific baseline values (-17.6% and -19.9%, respectively; P < 0.0001 for both, P = 0.77 for between-diet comparison). No between- or within-diet difference was observed in adiponectin concentrations, and there was also no between-diet difference in the expression of inflammatory genes and transcription factors.

CONCLUSION

Consistent with data from previous work, these results suggest that short-term consumption of a combination of low- and high-fat dairy products as part of a healthy diet has no adverse effects on inflammation. This trial was registered at www.clinicaltrials.gov as NCT01444326.

Diets high in protein or saturated fat do not affect insulin sensitivity or plasma concentrations of lipids and lipoproteins in overweight and obese adults

BACKGROUND

Previous human studies reported inconsistent effects of dietary protein and branched-chain amino acids (BCAAs) on insulin action and glucose metabolism. Similarly, it is unclear whether saturated fat (SF) intake influences these metabolic variables.

OBJECTIVE

The objective of this study was to test the effects of high [30% of energy (%E)] vs. moderate (20%E) intakes of protein (primarily whey) on insulin action and lipid and lipoprotein concentrations in the context of both high (15%E) and low (7%E) SF diets.

METHODS

The study was conducted as a randomized controlled trial in 158 overweight and obese men and women. After a 4-wk baseline diet [55%E carbohydrate, 15%E protein, 30%E fat (7%E SF)], participants were randomly assigned to 4 wk of either the baseline diet or 1 of 4 test diets containing 35%E carbohydrate and either 20%E or 30%E protein and either 7%E or 15%E SF. Frequently sampled i.v. glucose tolerance tests were administered after each dietary period.

RESULTS

Other than significantly higher fasting glucose concentrations for high vs. moderate protein intakes with a low-fat diet (difference ± SE: 0.47 ± 0.14 mmol/L; P = 0.001), there were no significant effects of dietary protein or SF on glucose metabolism, plasma insulin, or concentrations of lipids and lipoproteins. Changes in plasma BCAAs across all diets were negatively correlated with changes in the metabolic clearance rate of insulin (ρ = -0.18, P = 0.03) and positively correlated with changes in the acute insulin response to glucose (ρ = 0.15, P = 0.05).

CONCLUSIONS

These findings suggest that short-term intake of BCAAs can influence insulin dynamics. However, in this group of overweight and obese individuals, neither high protein nor SF intake affected insulin sensitivity or plasma concentrations of lipids and lipoproteins. This trial was registered at clinicaltrials.gov as NCT00508937.

Substitution of red meat with legumes in the therapeutic lifestyle change diet based on dietary advice improves cardiometabolic risk factors in overweight type 2 diabetes patients: a cross-over randomized clinical trial

BACKGROUND/OBJECTIVE

The objective of this study was to determine the effects of substitution of red meat with legumes in the Therapeutic Lifestyle Change (TLC) diet on cardiometabolic risk factors in type 2 diabetes patients based on dietary education.

SUBJECTS/METHODS

This study was a randomized, controlled, cross-over trial. Thirty-one participants (24 women and 7 men; age: 58.1 ± 6.0 years) with type 2 diabetes were randomly assigned to consume a control diet (legume-free TLC diet) and legume-based TLC diet for 8 weeks. Legume-based TLC diet was the same as the control diet, but the legume-based TLC group was advised to replace two servings of red meat with legumes, 3 days per week. After the interventional period, a washout period was conducted for 4 weeks. The groups were then advised to follow the alternate treatment for 8 weeks. Cardiometabolic risk factors were measured.

RESULTS

Compared with the legume-free TLC diet, the legume-based TLC diet significantly decreased fasting blood glucose (P=0.04), fasting insulin (P=0.04), triglyceride concentrations (P=0.04) and low-density lipoprotein cholesterol (P=0.02). Total cholesterol concentrations decreased after consumption of both TLC diet and legume TLC diet; however, the data did not differ significantly between the two diets. body mass index (BMI), waist circumference, systolic and diastolic blood pressures did not change significantly after consumption of either the legume-free TLC diet or the legume-based TLC diet.

CONCLUSIONS

Dietary advice given for substitution of red meat with legume intakes within a TLC diet-improved lipid profiles and glycemic control among diabetes patients, which were independent from BMI change. This trial was registered in the Iranian Registry of Clinical Trials (http://www.irct.ir) as IRCT201202251640N7.

Effects of dairy protein and fat on the metabolic syndrome and type 2 diabetes

The incidence of the metabolic syndrome (MetS) and type 2 diabetes (T2D) is increasing worldwide. Evidence supports a negative relationship between the consumption of dairy products and risk of MetS and T2D. Dairy proteins are known to have a directly beneficial effect on hypertension, dyslipidemia, and hyperglycemia, but a detailed understanding of the underlying mechanisms is missing. It has been confirmed by observations that the insulinotropic effect of dairy proteins is associated with the amino acid composition; in particular branched-chain amino acids (BCAA) seem to be of vital importance. Dairy protein-derived peptides may also contribute to the insulinotropic effect via dipeptidyl peptidase-4 (DPP-4) inhibitory activity, and may lower the blood pressure (BP). The lipid metabolism may be improved by whey protein (WP), which acts to reduce the postprandial triglyceride (TG) response. The effect of dairy fat is much more controversial because of the potentially harmful effect exerted by saturated fatty acid (SFA) on metabolic health. Recent observations suggest less adverse effects of SFA on metabolic health than previous assumed. However, little is known about dairy lipid fractions belonging to the groups of monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), and phospholipids (PL). Dairy fat seems to act differently depending on the dairy product and the composition of macronutrients in the meal. Therefore, for a better understanding of the mechanisms behind the dairy protein and fat effect on MetS, we suggest that more human studies should be carried out to clarify the interactions of dairy protein and fat with macronutrients in the meal and other dairy components, such as micronutrients and microorganisms from fermented products.

Definitions and potential health benefits of the Mediterranean diet: views from experts around the world

The Mediterranean diet has been linked to a number of health benefits, including reduced mortality risk and lower incidence of cardiovascular disease. Definitions of the Mediterranean diet vary across some settings, and scores are increasingly being employed to define Mediterranean diet adherence in epidemiological studies. Some components of the Mediterranean diet overlap with other healthy dietary patterns, whereas other aspects are unique to the Mediterranean diet. In this forum article, we asked clinicians and researchers with an interest in the effect of diet on health to describe what constitutes a Mediterranean diet in different geographical settings, and how we can study the health benefits of this dietary pattern.

Vitamin D and L-cysteine levels correlate positively with GSH and negatively with insulin resistance levels in the blood of type 2 diabetic patients

Background/Objectives:

Vitamin D, L-cysteine (LC) and glutathione (GSH) levels are lower in the blood of diabetic patients. This study examined the hypothesis that the levels of vitamin D and LC correlate with those of GSH in the blood of type 2 diabetic patients (T2D), and that vitamin D and LC upregulate glutamate–cysteine ligase (GCLC), which catalyzes GSH biosynthesis, in cultured monocytes.

Subjects/Methods:

Fasting blood was obtained after written informed consent from T2D (n=79) and healthy controls (n=22). U937 monocytes were pretreated with 1,25 (OH)₂ vitamin D (0–25 nM) or LC (0–500 μM) for 24 h and then exposed to control or high glucose (25 mM) for 4 h.

Results:

Plasma levels of vitamin D, LC, GSH and GCLC protein were significantly lower in T2D versus those in age-matched healthy controls. Multiple linear regression analyses and adjustment for body weight showed a significant positive correlation between plasma levels of vitamin D (r=0.26, P=0.05) and LC (r=0.81, P=0.001) and that of GSH, and between LC and vitamin D (r=0.27, P=0.045) levels. Plasma levels of GSH (r=−0.34, P=0.01) and LC (r=−0.33, r=0.01) showed a negative correlation with triglyceride levels. Vitamin D correlated inversely with HbA_1C (−0.30, P=0.01) and homeostatic model assessment insulin resistance (r=−0.31, P=0.03), which showed a significant positive correlation with triglycerides (r=0.44, P=0.001) in T2D. Cell culture studies demonstrate that supplementation with vitamin D and LC significantly increased GCLC expression and GSH formation in control and high-glucose-treated monocytes.

Conclusions:

This study suggests a positive relationship between the concentrations of the micronutrients vitamin D and LC and that of GSH. Some of the beneficial effects of vitamin D and LC supplementation may be mediated by an increase in the levels of GSH and a decrease in triglyceride levels in T2D patients.

Dietary dairy product intake and incident type 2 diabetes: a prospective study using dietary data from a 7-day food diary

AIM/HYPOTHESIS

The aim of this study was to investigate the association between total and types of dairy product intake and risk of developing incident type 2 diabetes, using a food diary.

METHODS

A nested case-cohort within the EPIC-Norfolk Study was examined, including a random subcohort (n = 4,000) and cases of incident diabetes (n = 892, including 143 cases in the subcohort) followed-up for 11 years. Diet was assessed using a prospective 7-day food diary. Total dairy intake (g/day) was estimated and categorised into high-fat (≥3.9%) and low-fat (<3.9% fat) dairy, and by subtype into yoghurt, cheese and milk. Combined fermented dairy product intake (yoghurt, cheese, sour cream) was estimated and categorised into high- and low-fat. Prentice-weighted Cox regression HRs were calculated.

RESULTS

Total dairy, high-fat dairy, milk, cheese and high-fat fermented dairy product intakes were not associated with the development of incident diabetes. Low-fat dairy intake was inversely associated with diabetes in age- and sex-adjusted analyses (tertile [T] 3 vs T1, HR 0.81 [95% CI 0.66, 0.98]), but further adjustment for anthropometric, dietary and diabetes risk factors attenuated this association. In addition, an inverse association was found between diabetes and low-fat fermented dairy product intake (T3 vs T1, HR 0.76 [95% CI 0.60, 0.99]; p(trend) = 0.049) and specifically with yoghurt intake (HR 0.72 [95% CI 0.55, 0.95]; p(trend) = 0.017) in multivariable adjusted analyses.

CONCLUSIONS/INTERPRETATION

Greater low-fat fermented dairy product intake, largely driven by yoghurt intake, was associated with a decreased risk of type 2 diabetes development in prospective analyses. These findings suggest that the consumption of specific dairy types may be beneficial for the prevention of diabetes, highlighting the importance of food group subtypes for public health messages.

Associations between dairy foods, diabetes, and metabolic health: potential mechanisms and future directions

Epidemiological evidence supports an inverse relationship between adequate intake of dairy foods and susceptibility to type 2 diabetes (T2D). The biological mechanisms responsible for this association remain to be established. This review provides a current perspective on proposed mechanisms that may underlie these effects, and highlights how randomized clinical trials can be applied to investigate these relationships. Results from epidemiological studies generally support that consumption of milk and dairy products is associated with a lower incidence of T2D or improvements in glucose homeostasis indices, and studies of animal and cell models support a positive effect of dairy-rich diets or components on metabolic and inflammation factors relevant to T2D and insulin resistance. Emerging evidence indicates that dairy components that alter mitochondrial function (e.g., leucine actions on silent information regulator transcript 1 (SIRT1)-associated pathways), promote gut microbial population shifts, or influence inflammation and cardiovascular function (e.g., Ca-regulated peptides calcitonin gene-related peptide [CGRP] or calcitonin) should be considered as possible mechanistic factors linking dairy intake with lower risk for T2D. The possibility that dairy-derived trans-palmitoleic acid (tC16:1) has metabolic bioactivities has also been proposed. Pre-clinical and clinical studies focusing specifically on these parameters are needed to validate hypotheses regarding the potential roles of dairy products and their components on the determinants of glucose tolerance, particularly insulin sensitivity, pancreatic endocrine function, and inflammation in individuals at-risk for T2D development. Such experiments would complement epidemiological studies and add to the evidence base for recommendations regarding consumption of dairy products and their individual components.