Low-fat dairy consumption reduces systolic blood pressure, but does not improve other metabolic risk parameters in overweight and obese subjects

Fructose-containing food sources and blood pressure: A systematic review and meta-analysis of controlled feeding trials

Whether food source or energy mediates the effect of fructose-containing sugars on blood pressure (BP) is unclear. We conducted a systematic review and meta-analysis of the effect of different food sources of fructose-containing sugars at different levels of energy control on BP. We searched MEDLINE, Embase and the Cochrane Library through June 2021 for controlled trials ≥7-days. We prespecified 4 trial designs: substitution (energy matched substitution of sugars); addition (excess energy from sugars added); subtraction (excess energy from sugars subtracted); and ad libitum (energy from sugars freely replaced). Outcomes were systolic and diastolic BP. Independent reviewers extracted data. GRADE assessed the certainty of evidence. We included 93 reports (147 trial comparisons, N = 5,213) assessing 12 different food sources across 4 energy control levels in adults with and without hypertension or at risk for hypertension. Total fructose-containing sugars had no effect in substitution, subtraction, or ad libitum trials but decreased systolic and diastolic BP in addition trials (P<0.05). There was evidence of interaction/influence by food source: fruit and 100% fruit juice decreased and mixed sources (with sugar-sweetened beverages [SSBs]) increased BP in addition trials and the removal of SSBs (linear dose response gradient) and mixed sources (with SSBs) decreased BP in subtraction trials. The certainty of evidence was generally moderate. Food source and energy control appear to mediate the effect of fructose-containing sugars on BP. The evidence provides a good indication that fruit and 100% fruit juice at low doses (up to or less than the public health threshold of ~10% E) lead to small, but important reductions in BP, while the addition of excess energy of mixed sources (with SSBs) at high doses (up to 23%) leads to moderate increases and their removal or the removal of SSBs alone (up to ~20% E) leads to small, but important decreases in BP in adults with and without hypertension or at risk for hypertension. Trial registration: Clinicaltrials.gov: NCT02716870.

Important food sources of fructose-containing sugars and adiposity: A systematic review and meta-analysis of controlled feeding trials

BACKGROUND

Sugar-sweetened beverages (SSBs) providing excess energy increase adiposity. The effect of other food sources of sugars at different energy control levels is unclear.

OBJECTIVES

To determine the effect of food sources of fructose-containing sugars by energy control on adiposity.

METHODS

In this systematic review and meta-analysis, MEDLINE, Embase, and Cochrane Library were searched through April 2022 for controlled trials ≥2 wk. We prespecified 4 trial designs by energy control: substitution (energy-matched replacement of sugars), addition (energy from sugars added), subtraction (energy from sugars subtracted), and ad libitum (energy from sugars freely replaced). Independent authors extracted data. The primary outcome was body weight. Secondary outcomes included other adiposity measures. Grading of Recommendations Assessment, Development, and Evaluation (GRADE) was used to assess the certainty of evidence.

RESULTS

We included 169 trials (255 trial comparisons, n = 10,357) assessing 14 food sources at 4 energy control levels over a median 12 wk. Total fructose-containing sugars increased body weight (MD: 0.28 kg; 95% CI: 0.06, 0.50 kg; P_MD = 0.011) in addition trials and decreased body weight (MD: -0.96 kg; 95% CI: -1.78, -0.14 kg; P_MD = 0.022) in subtraction trials with no effect in substitution or ad libitum trials. There was interaction/influence by food sources on body weight: substitution trials [fruits decreased; added nutritive sweeteners and mixed sources (with SSBs) increased]; addition trials [dried fruits, honey, fruits (≤10%E), and 100% fruit juice (≤10%E) decreased; SSBs, fruit drink, and mixed sources (with SSBs) increased]; subtraction trials [removal of mixed sources (with SSBs) decreased]; and ad libitum trials [mixed sources (with/without SSBs) increased]. GRADE scores were generally moderate. Results were similar across secondary outcomes.

CONCLUSIONS

Energy control and food sources mediate the effect of fructose-containing sugars on adiposity. The evidence provides a good indication that excess energy from sugars (particularly SSBs at high doses ≥20%E or 100 g/d) increase adiposity, whereas their removal decrease adiposity. Most other food sources had no effect, with some showing decreases (particularly fruits at lower doses ≤10%E or 50 g/d). This trial was registered at clinicaltrials.gov as NCT02558920 (https://clinicaltrials.gov/ct2/show/NCT02558920).

Effect of dietary approaches to stop hypertension (DASH) diet, high in animal or plant protein on cardiometabolic risk factors in obese metabolic syndrome patients: A randomized clinical trial

AIMS

This study aimed to investigate the effect of replacing plant proteins with animal proteins in the dietary approaches to stop hypertension (DASH) diet on cardiometabolic risk factors in obese metabolic syndrome participants.

METHODS

In this double-blind randomized controlled clinical trial, 90 obese patients with metabolic syndrome, aged 30-70 years were randomly allocated into the DASH diet based on plant or animal proteins for 8 weeks. Fasting blood samples were collected to assess the biochemical markers. Also, blood pressure, weight, and waist circumference (WC) were measured at the beginning and end of the trial.

RESULTS

The participants in both groups experienced significant reductions in the fasting plasma glucose (FPG), systolic blood pressure (SBP) and diastolic blood pressure (DBP), triglyceride (TG) concentrations, weight and WC. However the reduction in FPG and SBP was higher in the plant-based DASH group, compared to the animal-based DASH group, after adjustment for weight change. No significant changes were found within or between groups with regard to total cholesterol, LDL-C, HDL-C.

CONCLUSIONS

Substituting plant proteins with animal proteins in the DASH diet improves FPG and SBP in obese individuals with metabolic syndrome, independent of weight change. IRCT registration number: IRCT20090203001640N16.

Effect of Important Food Sources of Fructose-Containing Sugars on Inflammatory Biomarkers: A Systematic Review and Meta-Analysis of Controlled Feeding Trials

BACKGROUND

Fructose-containing sugars as sugar-sweetened beverages (SSBs) may increase inflammatory biomarkers. Whether this effect is mediated by the food matrix at different levels of energy is unknown. To investigate the role of food source and energy, we conducted a systematic review and meta-analysis of controlled trials on the effect of different food sources of fructose-containing sugars on inflammatory markers at different levels of energy control.

METHODS

MEDLINE, Embase, and the Cochrane Library were searched through March 2022 for controlled feeding trials ≥ 7 days. Four trial designs were prespecified by energy control: substitution (energy matched replacement of sugars); addition (excess energy from sugars added to diets); subtraction (energy from sugars subtracted from diets); and ad libitum (energy from sugars freely replaced). The primary outcome was C-reactive protein (CRP). Secondary outcomes were tumour necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6). Independent reviewers extracted data and assessed risk of bias. GRADE assessed certainty of evidence.

RESULTS

We identified 64 controlled trials (91 trial comparisons, n = 4094) assessing 12 food sources (SSB; sweetened dairy; sweetened dairy alternative [soy]; 100% fruit juice; fruit; dried fruit; mixed fruit forms; sweetened cereal grains and bars; sweets and desserts; added nutritive [caloric] sweetener; mixed sources [with SSBs]; and mixed sources [without SSBs]) at 4 levels of energy control over a median 6-weeks in predominantly healthy mixed weight or overweight/obese adults. Total fructose-containing sugars decreased CRP in addition trials and had no effect in substitution, subtraction or ad libitum trials. No effect was observed on other outcomes at any level of energy control. There was evidence of interaction/influence by food source: substitution trials (sweetened dairy alternative (soy) and 100% fruit juice decreased, and mixed sources (with SSBs) increased CRP); and addition trials (fruit decreased CRP and TNF-α; sweets and desserts (dark chocolate) decreased IL-6). The certainty of evidence was moderate-to-low for the majority of analyses.

CONCLUSIONS

Food source appears to mediate the effect of fructose-containing sugars on inflammatory markers over the short-to-medium term. The evidence provides good indication that mixed sources that contain SSBs increase CRP, while most other food sources have no effect with some sources (fruit, 100% fruit juice, sweetened soy beverage or dark chocolate) showing decreases, which may be dependent on energy control.

CLINICALTRIALS

gov: (NCT02716870).

Associations of dietary patterns with blood pressure and markers of subclinical arterial damage in adults with risk factors for CVD

OBJECTIVE

Unhealthy diet is a modifiable risk factor leading to subclinical arterial damage (SAD), high BP and CVD. It was aimed to investigate the possible associations of dietary patterns (DPs) with SAD in adults having multiple CVD risk factors.

DESIGN

Dietary intake was evaluated through two 24-h dietary recalls and principal component analysis was used to identify DPs. Oscillometry, applanation tonometry with pulse wave analysis and carotid ultrasound were used to assess peripheral and aortic BP, arterial stiffness and pressure wave reflections.

SETTING

Laiko University Hospital, Athens, Greece.

PARTICIPANTS

A total of 470 individuals (53·1 ± 14·2 years) with CVD risk factors were enrolled.

RESULTS

A pattern characterised by increased consumption of whole-grain cereals, white meat and reduced consumption of sugar was positively associated with common carotid compliance (β = 0·01, 95 % CI 0·00, 0·01), whereas a pattern high in refined cereals, red and processed meat was positively associated with brachial but not aortic systolic pressure (β = 1·76, 95 % CI 0·11, 3·42) and mean arterial pressure (MAP) (β = 1·18, 95 % CI 0·02, -2·38). Low consumption of low-fat dairy products, high consumption of full-fat cheese and butter was positively associated with MAP (β = 0·97, 95 % CI 0·01, 1·95). Increased consumption of vegetables, fruits, fresh juices, fish and seafood was inversely associated with augmentation index (AIx) (β = -1·01, 95 % CI -1·93, -0·09).

CONCLUSION

Consumption of whole grains, white meat, fruits/vegetables, fish/seafood and avoidance of sugar was associated with improved SAD. Preference in refined grains, red/processed meat, high-fat cheese/butter and low intake of low-fat dairy products were associated with BP elevation. Future studies are needed to confirm the present findings.

Effect of carbohydrate-restricted dietary interventions on LDL particle size and number in adults in the context of weight loss or weight maintenance: a systematic review and meta-analysis

BACKGROUND

LDL particle size and number (LDL-P) are emerging lipid risk factors. Nonsystematic reviews have suggested that diets lower in carbohydrates and higher in fats may result in increased LDL particle size when compared with higher-carbohydrate diets.

OBJECTIVES

This study aimed to systematically review available evidence and conduct meta-analyses of studies addressing the association of carbohydrate restriction with LDL particle size and LDL-P.

METHODS

We searched 6 electronic databases on 4 January, 2021 for randomized trials of any length that reported on dietary carbohydrate restriction (intervention) compared with higher carbohydrate intake (control). We calculated standardized mean differences (SMDs) in LDL particle size and LDL-P between the intervention and control groups of eligible studies, and pooled effect sizes using random-effects models. We performed prespecified subgroup analyses and examined the effect of potential explanatory factors. Internal validity and publication bias were assessed using Cochrane's risk-of-bias tool and funnel plots, respectively. Studies that could not be meta-analyzed were summarized qualitatively.

RESULTS

This review summarizes findings from 38 randomized trials including a total of 1785 participants. Carbohydrate-restricted dietary interventions were associated with an increase in LDL peak particle size (SMD = 0.50; 95% CI: 0.15, 0.86; P < 0.01) and a reduction in LDL-P (SMD = -0.24; 95% CI: -0.43, -0.06; P = 0.02). The effect of carbohydrate-restricted dietary interventions on LDL peak particle size appeared to be partially explained by differences in weight loss between intervention groups and exploratory analysis revealed a shift from small dense to larger LDL subclasses. No statistically significant association was found between carbohydrate-restricted dietary interventions and mean LDL particle size (SMD = 0.20; 95% CI: -0.29, 0.69; P = 0.37).

CONCLUSIONS

The available evidence indicates that dietary interventions restricted in carbohydrates increase LDL peak particle size and decrease the numbers of total and small LDL particles.This review was registered at www.crd.york.ac.uk/prospero/ as CRD42020188745.

The impact of diets rich in low-fat or full-fat dairy on glucose tolerance and its determinants: a randomized controlled trial

BACKGROUND

Dairy foods, particularly yogurt, and plasma biomarkers of dairy fat intake are consistently inversely associated with incident type 2 diabetes. Yet, few trials assessing the impact of dairy on glucose homeostasis include fermented or full-fat dairy foods.

OBJECTIVES

We aimed to compare the effects of diets rich in low-fat or full-fat milk, yogurt, and cheese on glucose tolerance and its determinants, with those of a limited dairy diet.

METHODS

In this parallel-design randomized controlled trial, 72 participants with metabolic syndrome completed a 4-wk wash-in period, limiting dairy intake to ≤3 servings/wk of nonfat milk. Participants were then randomly assigned to either continue the limited dairy diet, or switch to a diet containing 3.3 servings/d of either low-fat or full-fat dairy for 12 wk. Outcome measures included glucose tolerance (area under the curve glucose during an oral-glucose-tolerance test), insulin sensitivity, pancreatic β-cell function, systemic inflammation, liver-fat content, and body weight and composition.

RESULTS

In the per-protocol analysis (n = 67), we observed no intervention effect on glucose tolerance (P = 0.340). Both the low-fat and full-fat dairy diets decreased the Matsuda insulin sensitivity index (ISI) (means ± SDs -0.47 ± 1.07 and -0.25 ± 0.91, respectively) and as compared with the limited dairy group (0.00 ± 0.92) (P = 0.012 overall). Body weight also changed differentially (P = 0.006 overall), increasing on full-fat dairy (+1.0 kg; -0.2, 1.8 kg) compared with the limited dairy diet (-0.4 kg; -2.5, 0.7 kg), whereas the low-fat dairy diet (+0.3 kg; -1.1, 1.9 kg) was not significantly different from the other interventions. Intervention effects on the Matsuda ISI remained after adjusting for changes in adiposity. No intervention effects were detected for liver fat content or systemic inflammation. Findings in intent-to-treat analyses (n = 72) were consistent.

CONCLUSIONS

Contrary to our hypothesis, neither dairy diet improved glucose tolerance in individuals with metabolic syndrome. Both dairy diets decreased insulin sensitivity through mechanisms largely unrelated to changes in key determinants of insulin sensitivity.This trial was registered at clinicaltrials.gov as NCT02663544.

Role of Fluid Milk in Attenuating Postprandial Hyperglycemia and Hypertriglyceridemia

Postprandial plasma glucose and triglyceride concentrations are predictive of relative cardiovascular disease (CVD) risk, and the pathogenesis of both insulin resistance and atherosclerosis has been attributed to acute states of hyperglycemia and hypertriglyceridemia. Postprandial lipemia and hyperglycemia suppress vascular reactivity and induce endothelial dysfunction. Epidemiological studies suggest that chronically-high consumption of milk and milk products is associated with a reduced risk of type 2 diabetes, metabolic syndrome, and CVD. The addition of dairy products to meals high in carbohydrates and fat may lessen these risks through reductions in postprandial glucose and triglyceride responses. Purported mechanisms include dairy proteins and bioactive compounds, which may explain the inverse relationship between dairy consumption and cardiometabolic diseases. The current review evaluates the available literature describing the relationships between metabolic dysfunction, postprandial metabolism, and vascular dysfunction and discusses the potential role of milk and dairy products in attenuating these impairments.

Effect of dairy intake with or without energy restriction on body composition of adults: overview of systematic reviews and meta-analyses of randomized controlled trials

CONTEXT

Some studies suggest that consumption of dairy products can aid in weight loss, while others suggest a negative effect or no effect.

OBJECTIVE

An overview of systematic reviews and meta-analyses was conducted to examine the effect of dairy product consumption on changes in body composition.

DATA SOURCES

PRISMA guidelines were followed to ensure transparent reporting of evidence. The MEDLINE, Embase, Cochrane Central Database of Systematic Reviews, and Web of Science databases were searched from inception to April 2018.

STUDY SELECTION

Six systematic reviews and 47 associated meta-analyses (which included the results of 58 different randomized controlled trials) published in English or Spanish and reporting data on dairy intake and changes in weight, fat mass, lean mass, or waist circumference were included.

DATA EXTRACTION

Two authors independently extracted the data and assessed the risk of bias using the AMSTAR2 tool.

RESULTS

Dairy consumption interventions without dietary energy restriction had no significant effects on weight, fat mass, lean mass, or waist circumference. Interventions in energy-restricted settings had significant effects on fat mass and body weight.

CONCLUSIONS

Increasing total dairy intake without energy restriction in adults does not affect body composition. In the context of an energy-restricted diet, however, increased dairy intake results in lower fat mass and body weight but has no conclusive effects on waist circumference or lean mass.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number CRD42018094672.

Dairy Consumption and Metabolic Health

Milk and dairy foods are naturally rich sources of a wide range of nutrients, and when consumed according to recommended intakes, contribute essential nutrients across all stages of the life cycle. Seminal studies recommendations with respect to intake of saturated fat have been consistent and clear: limit total fat intake to 30% or less of total dietary energy, with a specific recommendation for intake of saturated fat to less than 10% of total dietary energy. However, recent work has re-opened the debate on intake of saturated fat in particular, with suggestions that recommended intakes be considered not at a total fat intake within the diet, but at a food-specific level. A large body of evidence exists examining the impact of dairy consumption on markers of metabolic health, both at a total-dairy-intake level and also at a food-item level, with mixed findings to date. However the evidence suggests that the impact of saturated fat intake on health differs both across food groups and even between foods within the same food group such as dairy. The range of nutrients and bioactive components in milk and dairy foods are found in different levels and are housed within very different food structures. The interaction of the overall food structure and the nutrients describes the concept of the 'food matrix effect' which has been well-documented for dairy foods. Studies show that nutrients from different dairy food sources can have different effects on health and for this reason, they should be considered individually rather than grouped as a single food category in epidemiological research. This narrative review examines the current evidence, mainly from randomised controlled trials and meta-analyses, with respect to dairy, milk, yoghurt and cheese on aspects of metabolic health, and summarises some of the potential mechanisms for these findings.

The Effects of Dairy Product and Dairy Protein Intake on Inflammation: A Systematic Review of the Literature

Systemic inflammation is associated with obesity and chronic disease risk. Intake of dairy foods is associated with reduced risk of type 2 diabetes and cardiovascular disease; however, the impact of dairy foods on inflammation is not well-established. The objective of this study was to conduct a systematic review to evaluate the effect of dairy product (milk, cheese, and yogurt) and dairy protein consumption on low-grade systemic inflammation in adults without severe inflammatory disorders. A literature search was completed in September 2019 using PubMed and CENTRAL as well as inspection of reference lists from relevant review articles. The search resulted in the identification of 27 randomized controlled trials which were included in this analysis. In the 19 trials which evaluated dairy products, 10 reported no effect of the intervention, while 8 reported a reduction in at least one biomarker of inflammation. All 8 trials that investigated dairy protein intake on markers of inflammation reported no effect of the intervention. The available literature suggests that dairy products and dairy proteins have neutral to beneficial effects on biomarkers of inflammation. Additional clinical studies designed using inflammatory biomarkers as the primary outcome are needed to fully elucidate the effects of dairy intake on inflammation.

Traditional plain yogurt: a therapeutic food for metabolic syndrome?

Dairy products have an important role in a healthy diet due to their high-quality protein and rich micronutrients. Yogurt, a fermented milk product, has a similar composition to milk but is a more concentrated product in terms of group B vitamins, minerals, and proteins. It is known that bioactive metabolites and live enzymes that occur by fermentation and digestion, affect the health positively by improving gut microbiota. In recent years, the prevalence of metabolic syndrome, which threatens public health, is increasing rapidly. As with other noninfectious diseases, the diet has an important effect on the prevention and treatment of metabolic syndrome. It has been demonstrated that yogurt has a high-quality amino acid pattern, reduces energy intake by stimulating satiety, and regulates blood glucose level. In addition to the rich protein variety, yogurt also contains peptides that positively affect blood pressure. Unlike milk, increased acidity during the fermentation of yogurt positively affects calcium absorption. Calcium plays an important role in the control of blood glucose and energy metabolism through insulin-dependent and non-insulin-dependent routes. In addition to reducing inflammation, calcium has a positive effect on the regulation of the blood lipid profile by increasing fecal fat excretion. There are many lipid and lipoid nutrients such as saturated fatty acids, phospholipids, sphingolipids, and conjugated linoleic acid that may affect the blood lipid profile in yogurt positively or negatively. There are seen very few randomized controlled studies that are focused on the relationship between yogurt and metabolic syndrome, and these are based on contradictory results. In this review, based on the clinical studies conducted to date, and the nutrient content of yogurt, possible mechanisms of these contradictory results are investigated.

Whole Milk and Full-Fat Dairy Products and Hypertensive Risks

Lifestyle modifications in the form of diet and exercise are generally a first-line approach to reduce hypertensive risk and overall cardiovascular disease (CVD) risk. Accumulating research evidence has revealed that consumption of non- and low-fat dairy products incorporated into the routine diet is an effective means to reduce elevated blood pressure and improve vascular functions. However, the idea of incorporating whole-fat or full-fat dairy products in the normal routine diet as a strategy to reduce CVD risk has been met with controversy. The aim of this review is to review both sides of the argument surrounding saturated fat intake and CVD risk from the standpoint of dairy intake. Throughout the review, we examined observational studies on relationships between CVD risk and dairy consumption, dietary intervention studies using non-fat and whole-fat dairy, and mechanistic studies investigating physiological mechanisms of saturated fat intake that may help to explain increases in cardiovascular disease risk. Currently available data have demonstrated that whole-fat dairy is unlikely to augment hypertensive risk when added to the normal routine diet but may negatively impact CVD risk. In conclusion, whole-fat dairy may not be a recommended alternative to non- or low-fat dairy products as a means to reduce hypertensive or overall CVD risk.

Intake of Animal Source Foods in Relation to Risk of Metabolic Syndrome

Metabolic syndrome (MetS) is a prevalent disorder associated with diabetes and cardiovascular diseases. Lifestyle and occupation can increase the risk of developing MetS. Since dietary pattern is a major component of lifestyle, this study aimed to determine the relationship between consumption of animal source foods (ASFs) and MetS among food suppliers. This cross-sectional study was conducted on 112 male food suppliers. We measured anthropometric indices, body composition, and blood pressure of the participants. Blood biochemistry was determined using 5 mL fasting blood samples. MetS was defined based on the guidelines described by the International Diabetes Federation (IDF). ASF intake, including dairy products, eggs, red meat, poultry, and fish, was assessed using food frequency questionnaires. Overall, 46.4% of participants had MetS. Participants who consumed dairy 3∼5 times/d and more than 5 times/d had lower risk of MetS [odds ratios (OR): 0.18 (confidence interval (CI) 95%: 0.05∼0.62) and OR: 0.20 (CI 95%: 0.06∼0.67), respectively] compared with participants in the lowest tertile. The risk of hypertension was significantly decreased in participants who consumed dairy products >5 times/d [OR: 0.22 (CI 95%: 0.07∼0.67)]. Other ASFs were not associated against the risk of MetS in crude and adjusted models. Our findings indicated that adhering to dairy products can decrease the risk of MetS. Higher adherence to dairy products was also protective against hypertension in these participants.

Effects of regular-fat and low-fat dairy consumption on daytime ambulatory blood pressure and other cardiometabolic risk factors: a randomized controlled feeding trial

BACKGROUND

The extent to which dairy products and their fat content influence cardiovascular health remains uncertain.

OBJECTIVE

This study aimed to assess how consumption of low-fat milk and regular-fat cheese enriched in γ-aminobutyric acid (GABA) influences daytime ambulatory blood pressure (BP) and other cardiometabolic risk factors.

METHODS

In this crossover controlled feeding study, 55 healthy men and women with high-normal daytime BP were randomly assigned to sequences of three 6-wk isoenergetic diets, each comprising 1) no dairy (control diet), 2) 3 daily servings of 1% fat milk, and 3) 1 daily serving of 31% fat cheddar cheese naturally enriched in GABA. Total proteins, carbohydrates, and fats were matched across all 3 diets. The additional 2% of energy from SFAs in the cheese diet was replaced by n-6 PUFAs in the other diets.

RESULTS

Comparison of postdiet ambulatory systolic BP revealed no difference (P = 0.34), which was also the case for ambulatory diastolic BP (P = 0.45). The cheese diet increased serum LDL-cholesterol concentrations compared with the control and milk diets (+5.8%, P = 0.006 and +7.0%, P = 0.0008, respectively) and increased LDL particle size compared with the milk diet (P = 0.02). HDL-cholesterol concentrations after the milk diet were lower than after the control diet (-4.1%; P = 0.009). The milk and cheese diets increased triglycerides compared with the control diet (+9.9%, P = 0.01 and +10.5%, P = 0.007, respectively). There was no significant difference between all diets for C-reactive protein concentrations and markers of glucose/insulin homeostasis.

CONCLUSIONS

These results suggest that short-term consumption of dairy products, whether low or regular in fat, has no overall effect on daytime ambulatory BP compared with a dairy-free diet. Other cardiometabolic risk factors may be differently modified according to the fat content of the dairy product. This trial was registered at clinicaltrials.gov as NCT02763930.

Dairy intake and type 2 diabetes risk factors: A narrative review

AIM

The interest regarding the potential role of dairy products in the prevention of type 2 diabetes (T2D) has emerged. Although results remain mixed, numerous cohort studies have shown that increased dairy consumption is inversely associated with T2D risk. This narrative review evaluates the recent evidence of dairy products intake on T2D risk factors for the prevention of T2D.

MATERIAL AND METHOD

The review is framed within the systematic review and meta-analyses of cohort studies and the individual randomized controlled trials evidence. We searched for existing meta-analyses of cohort studies that addressed the association of dairy intake with incidence of T2D in adults using the MEDLINE (via PubMed) database. For the interventional studies, the literature searched was conducted using MEDLINE (via PubMed) with the following Medical Subjects Heading (MeSH) terms i.e. dairy OR milk OR cheese OR yogurt AND glucose OR diabetes OR insulin resistance OR insulin sensitivity OR pre-diabetes.

RESULTS

Most of the meta-analyses and systematic reviews of the cohort studies point to a reduced risk of T2D with dairy intake of 3 servings per day. This effect was mainly attributed to low-fat dairy, particularly yogurt and cheese. However, there is no evidence in cohort studies that high-fat dairy intake poses any harm.

CONCLUSION

Dairy products, when incorporated into a healthy diet, likely do not have detrimental effects on glucose-related outcomes. The potential impact of dairy consumption on glucose tolerance tests, insulin levels, insulin sensitivity measures, and plasma glucose levels warrant future investigation.

Effect of high compared with low dairy intake on blood pressure in overweight middle-aged adults: results of a randomized crossover intervention study

BACKGROUND

Observational studies suggest that high dairy intake is associated with a lower blood pressure (BP).

OBJECTIVE

We aimed to investigate the effect of a high-dairy diet (HDD) as compared with a low-dairy diet (LDD) on BP in overweight middle-aged adults.

METHODS

Fifty-two overweight men and women were included in a randomized crossover intervention study. Each subject consumed 2 isocaloric diets for 6 wk, an LDD (≤1 dairy portion per day) and an HDD (6 or 5 reduced-fat dairy portions for men and women, respectively), with a 4-wk washout period in between the diets during which the subjects consumed their habitual diet. BP was measured at the start and at the end of the intervention diets. The effect of the intervention study was evaluated by 2-sample t tests. Mixed-model analyses were used for adjustment for the potential influence of changes in dietary protein and mineral intake and risk factors for hypertension including body weight and plasma cholesterol.

RESULTS

Consumption of an HDD as compared with an LDD resulted in a reduction of both systolic BP (mean ± SD: 4.6 ± 11.2 mm Hg, P < 0.01) and diastolic BP (3.0 ± 6.7 mm Hg, P < 0.01). In further analyses, these reductions appeared dependent on the concomitant increase in calcium intake.

CONCLUSIONS

This intervention study shows that an HDD results in a reduction of both systolic and diastolic BP in overweight middle-aged men and women. If the results of our study are reproduced by other studies, advice for high dairy intake may be added to treatment and prevention of high BP. This trial was registered at trialregister.nl as NTR4899.

Full-Fat Dairy Food Intake is Associated with a Lower Risk of Incident Diabetes Among American Indians with Low Total Dairy Food Intake

BACKGROUND

Diet plays a key role in development of diabetes, and there has been recent interest in better understanding the association of dairy food intake with diabetes.

OBJECTIVE

This study examined the associations of full-fat and low-fat dairy food intake with incident diabetes among American Indians-a population with a high burden of diabetes.

METHODS

The study included participants from the Strong Heart Family Study (SHFS), a family-based study of cardiovascular disease in American Indians, free of diabetes at baseline (2001-2003) (n = 1623). Participants were 14-86-y-old at baseline and 60.8% were female. Dairy food intake was assessed using a Block food frequency questionnaire. Incident diabetes was defined using American Diabetes Association criteria. Parametric survival models with a Weibull distribution were used to evaluate the associations of full-fat and low-fat dairy food intake with incident diabetes. Serving sizes were defined as 250 mL for milk and 42.5 g for cheese.

RESULTS

We identified 277 cases of diabetes during a mean follow-up of 11 y. Reported intake of dairy foods was low [median full-fat dairy food intake: 0.11 serving/1000 kcal; median low-fat dairy food intake: 0.03 serving/1000 kcal]. Participants who reported the highest full-fat dairy food intake had a lower risk of diabetes compared to those who reported the lowest full-fat food dairy intake [HR (95% CI): 0.79 (0.59, 1.06); P-trend = 0.03, comparing extreme tertiles, after adjustment for age, sex, site, physical activity, education, smoking, diet quality, and low-fat dairy food intake]. Low-fat dairy food intake was not associated with diabetes.

CONCLUSIONS

American Indians who participated in the SHFS reported low dairy food intake. Participants who reported higher full-fat dairy food intake had a lower risk of diabetes than participants who reported lower intake. These findings may be of interest to populations with low dairy food intake.

Long-term yogurt consumption and risk of incident hypertension in adults

OBJECTIVE

To evaluate the relation between yogurt consumption as well as cheese, milk, and total dairy, and high blood pressure (HBP) in two Nurses' Health Study cohorts (NHS, n = 69 298), NHS II (n = 84 368) and the Health Professionals Follow-Up Study (HPFS, n = 30 512).

METHODS

NHS, NHS II, and HPFS participants were followed for incident HBP for up to 30, 20, and 24 years, respectively. Hazard ratios were calculated using time-dependent multivariate-adjusted Cox proportional hazards models. Pooled risk estimates were derived from fixed effects meta-analyses.

RESULTS

Participants consuming at least five servings per week (vs. <1 serving per month) of yogurt in NHS, NHS II, and HPFS had 19% (95% CI 0.75-0.87), 17% (95% CI 0.77-0.90), and 6% (95% CI 0.83-1.07) lower HBP risks, respectively. In pooled analyses of these cohorts, higher yogurt consumption was linked with 16% (95% CI 0.80-0.88) lower HBP risk; higher total dairy (3 to <6 vs. <0.5 servings/day), milk (2 to <6/day vs. <4/week) and cheese (1 to 4/day vs. <1/week) were associated with 16% (95% CI 0.81-0.87), 12% (95% CI 0.86-0.90), and 6% (95% CI 0.90-0.97) lower HBP risks, respectively. After controlling for BMI as a possible causal intermediate, total dairy, yogurt, milk, and cheese were associated with 13, 10, 8, and 8% lower HBP risks, respectively. The combination of higher yogurt intake and higher DASH ('Dietary Approaches to Stop Hypertension') diet scores was associated with 30% (95% CI 0.66-0.75) lower HBP risk compared with lower levels of both factors.

CONCLUSION

Higher total dairy intake, especially in the form of yogurt, was associated with lower risk of incident HBP in middle-aged and older adult men and women.

The effect of high compared with low dairy consumption on glucose metabolism, insulin sensitivity, and metabolic flexibility in overweight adults: a randomized crossover trial

BACKGROUND

Dairy products contain many nutritious components that may benefit metabolic health. There are indications that glucose metabolism and insulin sensitivity, which are generally disturbed in overweight and obese individuals, may improve by increased dairy intake. This may also affect one's metabolic flexibility.

OBJECTIVE

The aim of this study was to investigate the effects of high compared with low dairy intake on glucose metabolism, insulin sensitivity, and metabolic flexibility in overweight adults (aged 45-65 y).

METHODS

In this randomized intervention study, subjects consumed a high- and a low-dairy diet [HDD (5-6 dairy portions) and LDD (≤1 dairy portion), respectively] for 6 wk in a crossover design, with a washout period of 4 wk. Dairy portions were 200 g semi-skimmed yoghurt, 30 g reduced-fat (30+) cheese, and 250 mL semiskimmed milk and buttermilk. After 6 wk, a 75-g oral-glucose-tolerance test (13C-labeled) and a subsequent fasting challenge were performed. Metabolic flexibility was studied by determining the respiratory quotient (RQ) using indirect calorimetry. Fasting and postprandial plasma concentrations of glucose and insulin were analyzed. The dual isotope technique enabled calculation of glucose kinetics.

RESULTS

The study was completed by 45 overweight men and postmenopausal women [age 58.9 ± 4.3 y, BMI 27.9 ± 1.9 kg/m2 (mean ± SD)]. Fasting RQ and ΔRQ, reflecting metabolic flexibility, did not differ after both diets. Fasting glucose concentrations were similar, whereas fasting insulin concentrations were lower after the LDD (LDD: 8.1 ± 2.8 mU/L; HDD: 8.9 ± 3.3 mU/L; P = 0.024). This resulted in a higher HOMA-IR after the HDD (P = 0.027). Postprandial glucose and insulin responses as well as glucose kinetics were similar after both diets.

CONCLUSIONS

The amount of dairy intake during a 6-wk period had a neutral effect on metabolic flexibility or postprandial glucose metabolism in middle-aged overweight subjects. More trials are needed to study the effects of specific dairy types and to differentiate between metabolic subgroups. This trial was registered at trialregister.nl as NTR4899.

Dairy product consumption and its association with metabolic disturbance in a prospective study of urban adults

The role of dairy foods and related nutrients in cardiometabolic health aetiology is poorly understood. We investigated longitudinal associations between the metabolic syndrome (MetS) and its components with key dairy product exposures. We used prospective data from a bi-racial cohort of urban adults (30-64 years at baseline (n 1371)), the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS), in Baltimore City, MD (2004-2013). The average of two 24-h dietary recalls measured 4-10 d apart was computed at baseline (V1) and follow-up (V2) waves. Annual rates of change (Δ) in dairy foods and key nutrients were estimated. Incident obesity, central obesity and the MetS were determined. Among key findings, in the overall urban adult population, both cheese and yogurt (V1 and Δ) were associated with an increased risk of central obesity (hazard ratio (HR) 1·13; 95 % CI 1·05, 1·23 per oz equivalent of cheese (V1); HR 1·21; 95 % CI 1·01, 1·44 per fl oz equivalent of yogurt (V1)]. Baseline fluid milk intake (V1 in cup equivalents) was inversely related to the MetS (HR 0·86; 95 % CI 0·78, 0·94), specifically to dyslipidaemia-TAG (HR 0·89; 95 % CI 0·81, 0·99), although it was directly associated with dyslipidaemia-HDL-cholesterol (HR 1·10; 95 % CI 1·01, 1·21). Furthermore, ΔCa and ΔP were inversely related to dyslipidaemia-HDL and MetS incidence, respectively, whereas Δdairy product fat was positively associated with incident TAG-dyslipidaemia and HDL-cholesterol-dyslipidaemia and the MetS. A few of those associations were sex and race specific. In sum, various dairy product exposures had differential associations with metabolic disturbances. Future intervention studies should uncover how changes in dairy product components over time may affect metabolic disorders.

High dietary intake of whole milk and full-fat dairy products does not exert hypotensive effects in adults with elevated blood pressure

Regular consumption of low- and nonfat dairy products reduces blood pressure (BP) in adults with elevated BP. Currently, it is unknown if conventional full-fat dairy products exert similar hypotensive effects. We hypothesized that adding full-fat dairy products to the normal routine diet would reduce seated office and ambulatory BP (primary outcome) in adults with elevated BP when compared with a no dairy control. Using a randomized controlled crossover design, 60 adults with elevated systolic BP (systolic/diastolic BP: 120-159/<99 mm Hg) participated in a 4-week high-dairy (4 servings a day of full-fat dairy products + regular diet) and a 4-week no-dairy condition (plant-based food items + regular diet) separated by a 2-week washout period. Data were analyzed based on time, condition, and sex. Seated office systolic BP did not change significantly in either condition. There were no changes in systolic BP in male or female participants across either dietary period. Ambulatory (24-hour) systolic BP did not change significantly in the high-dairy (133 ± 2 vs 131 ± 1 mm Hg) or no-dairy conditions (132 ± 2 vs 131 ± 1 mm Hg). No significant changes were observed for diastolic BP or pulse pressure during condition for office or ambulatory measures. The solitary addition of full-fat dairy products to the normal routine diet does not exert hypotensive effects in adults with elevated BP when compared to the no-dairy control.

Effects of Dairy Products Consumption on Body Weight and Body Composition Among Adults: An Updated Meta-Analysis of 37 Randomized Control Trials

SCOPE

Effects of dairy consumption on body weight and body composition have been inconsistently observed in randomized control trials (RCTs). Our meta-analysis aims to systematically evaluate the effects of dairy consumption on body weight and body composition among the adults.

METHODS AND RESULTS

We conducted a comprehensive search of the Cochrane Library, PubMed, and Embase databases of the relevant studies from 1966 to Mar 2017 regarding dairy consumption on body weight and body composition including body fat, lean mass, and waist circumference (WC). The summary results are pooled by using a random-effects meta-analysis. Thirty-seven RCTs with 184 802 participants are included in this meta-analysis. High dairy intervention increased body weight (0.01, 95% CI: -0.25, 0.26, I² = 78.3%) and lean mass (0.37, 95% CI: 0.11, 0.62, I² = 83.4%); decreased body fat (-0.23, 95% CI: -0.48, 0.02, I² = 78.2%) and WC (-1.37, 95% CI: -2.28, -0.46, I² = 98.9%) overall. In the subgroup analysis, we found that consumption of dairy products increases body weight (0.36, 95% CI: 0.01, 0.70, I² = 83.1%) among participants without energy restriction. Dairy consumption decreases body weight (-0.64, 95% CI: -1.05, -0.24, I² = 60.2%), body fat (-0.56, 95%CI: -0.95, -0.17, I² = 66.6%), and waist circumference (-2.18, 95%CI: -4.30, -0.06, I² = 99.0%) among the adults with energy restriction.

CONCLUSIONS

This meta-analysis suggests a beneficial effect of energy-restricted dairy consumption on body weight and body composition. However, high dairy consumption in the absence of caloric restriction may increase body weight.

Food sources of fructose-containing sugars and glycaemic control: systematic review and meta-analysis of controlled intervention studies

OBJECTIVE

To assess the effect of different food sources of fructose-containing sugars on glycaemic control at different levels of energy control.

DESIGN

Systematic review and meta-analysis of controlled intervention studies.

DATA SOURCES

Medine, Embase, and the Cochrane Library up to 25 April 2018.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Controlled intervention studies of at least seven days' duration and assessing the effect of different food sources of fructose-containing sugars on glycaemic control in people with and without diabetes were included. Four study designs were prespecified on the basis of energy control: substitution studies (sugars in energy matched comparisons with other macronutrients), addition studies (excess energy from sugars added to diets), subtraction studies (energy from sugars subtracted from diets), and ad libitum studies (sugars freely replaced by other macronutrients without control for energy). Outcomes were glycated haemoglobin (HbA1c), fasting blood glucose, and fasting blood glucose insulin.

DATA EXTRACTION AND SYNTHESIS

Four independent reviewers extracted relevant data and assessed risk of bias. Data were pooled by random effects models and overall certainty of the evidence assessed by the GRADE approach (grading of recommendations assessment, development, and evaluation).

RESULTS

155 study comparisons (n=5086) were included. Total fructose-containing sugars had no harmful effect on any outcome in substitution or subtraction studies, with a decrease seen in HbA1c in substitution studies (mean difference -0.22% (95% confidence interval to -0.35% to -0.08%), -25.9 mmol/mol (-27.3 to -24.4)), but a harmful effect was seen on fasting insulin in addition studies (4.68 pmol/L (1.40 to 7.96)) and ad libitum studies (7.24 pmol/L (0.47 to 14.00)). There was interaction by food source, with specific food sources showing beneficial effects (fruit and fruit juice) or harmful effects (sweetened milk and mixed sources) in substitution studies and harmful effects (sugars-sweetened beverages and fruit juice) in addition studies on at least one outcome. Most of the evidence was low quality.

CONCLUSIONS

Energy control and food source appear to mediate the effect of fructose-containing sugars on glycaemic control. Although most food sources of these sugars (especially fruit) do not have a harmful effect in energy matched substitutions with other macronutrients, several food sources of fructose-containing sugars (especially sugars-sweetened beverages) adding excess energy to diets have harmful effects. However, certainty in these estimates is low, and more high quality randomised controlled trials are needed.

STUDY REGISTRATION

Clinicaltrials.gov (NCT02716870).

Consumption of regular-fat vs reduced-fat cheese reveals gender-specific changes in LDL particle size - a randomized controlled trial

Background

Regular-fat cheese does not seem to increase low density lipoprotein cholesterol (LDL-C) concentrations compared to reduced-fat cheese. However, plasma LDL-C concentrations do not reflect levels and size of LDL particles, which might be a better predictor of cardiovascular risk.

Methods

The aim was to compare the effects of regular-fat cheese vs reduced-fat cheese and carbohydrate-rich foods on LDL particle size distribution in adults with ≥ 2 metabolic syndrome (MetS) risk factors. The study was part of a 12 weeks’ randomized controlled trial in which subjects had been randomly allocated to 1 of 3 intervention groups; regular-fat cheese (REG), reduced-fat cheese (RED) or a no-cheese/carbohydrate (CHO) group. Subjects in the REG and RED groups consumed 80 g cheese/d per 10 MJ, whereas subjects in the CHO consumed bread and jam corresponding to 90 g/d and 25 g/d per 10 MJ, respectively. Fasting blood samples at wk. 0 (baseline) and wk. 12 were analyzed for LDL particle size distribution and cholesterol content using nuclear magnetic resonance (NMR) spectroscopy.

Results

A total of 85 subjects [mean ± SD age: 54.0 ± 12.8 y; BMI: 28.7 ± 3.6 kg/m²] completed the study. Overall, regular-fat cheese did not impact lipoprotein particle number and size differently than reduced-fat cheese. In men (n = 23), the REG diet decreased total LDL particle number (LDL-P, − 223.2 ± 91.1 nmol/l, P = 0.01) compared with the RED diet. The reduction was primarily in the medium-sized LDL fraction (− 128.5 ± 51.8 nmol/l, P = 0.01). In women (n = 62), the REG diet increased the concentration of cholesterol in the small high density lipoprotein (HDL) particles compared with the CHO diet (2.9 ± 1.0 mg/dl, P = 0.006).

Conclusion

Overall, regular-fat cheese did not alter LDL particle size distribution compared to reduced-fat cheese after a 12 wk. intervention in subjects with ≥2 MetS risk factors. However, our results suggest that lipoprotein response to cheese intake is gender-specific. This warrants further investigation.

Trial registration

This trial was registered at Clinicaltrials.gov as NCT0261471. Registered 30 November 2015 - Retrospectively registered.

Dairy food consumption is associated with a lower risk of the metabolic syndrome and its components: a systematic review and meta-analysis

A systematic review and a meta-analysis of observational studies were performed to assess the dose–response relationship between specific types of dairy foods and the risk of the metabolic syndrome (MetS) and its components. Studies of dairy foods and the risk of the MetS and its components published up to June 2016 were searched using PubMed, EMBASE and a reference search. Random-effects models were used to estimate the pooled relative risks (RR) with 95 % CI. Finally, ten cross-sectional studies, two nested case–control studies and twenty-nine cohort studies were included for the analysis. In a dose–response analysis of cohort studies and cross-sectional studies, the pooled RR of the MetS for a one-serving/d increment of total dairy food (nine studies) and milk (six studies) consumption (200 g/d) were 0·91 (95 % CI 0·85, 0·96) and 0·87 (95 % CI 0·79, 0·95), respectively. The pooled RR of the MetS for yogurt (three studies) consumption (100 g/d) was 0·82 (95 % CI 0·73, 0·91). Total dairy food consumption was associated with lower risk of MetS components, such as hyperglycaemia, elevated blood pressure, hypertriacylglycerolaemia and low HDL- cholesterol. A one-serving/d increment of milk was related to a 12 % lower risk of abdominal obesity, and a one-serving/d increment of yogurt was associated with a 16 % lower risk of hyperglycaemia. These associations were not significantly different by study design, study location or adjustment factors. This meta-analysis showed that specific types of dairy food consumption such as milk and yogurt as well as total dairy food consumption were inversely related to risk of the MetS and its components.

Effect of increased calcium consumption from fat-free milk in an energy-restricted diet on the metabolic syndrome and cardiometabolic outcomes in adults with type 2 diabetes mellitus: a randomised cross-over clinical trial

We investigated the effects of high-Ca fat-free milk phase (MD) (prescription of approximately 1500 mg of Ca/d) v. low-Ca phase (CD) (prescription of approximately 800 mg of Ca/d) in an energy-restricted diet on the metabolic syndrome (MetS) and cardiometabolic measures in individuals with type 2 diabetes mellitus (T2DM) and low habitual Ca consumption (<600 mg/d). In this randomised cross-over design, fourteen adults with T2DM (49·5 (sd 8·6) years, BMI 29·4 (sd 4·5) kg/m2) consumed either MD or CD for 12 weeks, with a washout of 18 weeks between phases. A breakfast shake containing 700 mg (MD) or 6·4 mg (CD) of Ca was consumed in the laboratory. In addition, energy-restricted diets were prescribed (800 mg of dietary Ca/d). Waist circumference (WC), fasting glucose, fasting TAG, systolic (SBP) and diastolic blood pressure (DBP), fasting total cholesterol, fasting LDL-cholesterol, fasting HDL-cholesterol, HDL:LDL ratio, HDL:TAG ratio and lipid accumulation product (LAP) index were assessed at baseline and after each phase. Ca consumption during the study was equivalent to 1200 mg/d during MD and 525 mg/d during CD. There was a greater reduction in WC, SBP, DBP and LAP index after MD compared with CD. HDL:LDL ratio increased and total cholesterol, LDL-cholesterol, SBP, DBP and LAP index decreased only in MD. The consumption of approximately 1200 mg of Ca/d (700 mg from fat-free milk+500mg from other dietary sources) associated with an energy-restricted diet decreased some of the MetS components and cardiometabolic measures in adults with T2DM.

Dairy Fats and Cardiovascular Disease: Do We Really Need to be Concerned?

Cardiovascular diseases (CVD) remain a major cause of death and morbidity globally and diet plays a crucial role in the disease prevention and pathology. The negative perception of dairy fats stems from the effort to reduce dietary saturated fatty acid (SFA) intake due to their association with increased cholesterol levels upon consumption and the increased risk of CVD development. Institutions that set dietary guidelines have approached dairy products with negative bias and used poor scientific data in the past. As a result, the consumption of dairy products was considered detrimental to our cardiovascular health. In western societies, dietary trends indicate that generally there is a reduction of full-fat dairy product consumption and increased low-fat dairy consumption. However, recent research and meta-analyses have demonstrated the benefits of full-fat dairy consumption, based on higher bioavailability of high-value nutrients and anti-inflammatory properties. In this review, the relationship between dairy consumption, cardiometabolic risk factors and the incidence of cardiovascular diseases are discussed. Functional dairy foods and the health implications of dairy alternatives are also considered. In general, evidence suggests that milk has a neutral effect on cardiovascular outcomes but fermented dairy products, such as yoghurt, kefir and cheese may have a positive or neutral effect. Particular focus is placed on the effects of the lipid content on cardiovascular health.

Yogurt and Cardiometabolic Diseases: A Critical Review of Potential Mechanisms

Associations between yogurt intake and risk of diet-related cardiometabolic diseases (CMDs) have been the subject of recent research in epidemiologic nutrition. A healthy dietary pattern has been identified as a pillar for the prevention of weight gain and CMDs. Epidemiologic studies suggest that yogurt consumption is linked to healthy dietary patterns, lifestyles, and reduced risk of CMDs, particularly type 2 diabetes. However, to our knowledge, few to no randomized controlled trials have investigated yogurt intake in relation to cardiometabolic clinical outcomes. Furthermore, there has been little attempt to clarify the mechanisms that underlie the potential beneficial effects of yogurt consumption on CMDs. Yogurt is a nutrient-dense dairy food and has been suggested to reduce weight gain and prevent CMDs by contributing to intakes of protein, calcium, bioactive lipids, and several other micronutrients. In addition, fermentation with bacterial strains generates bioactive peptides, resulting in a potentially greater beneficial effect of yogurt on metabolic health than nonfermented dairy products such as milk. To date, there is little concrete evidence that the mechanisms proposed in observational studies to explain positive results of yogurt on CMDs or parameters are valid. Many proposed mechanisms are based on assumptions that commercial yogurts contain strain-specific probiotics, that viable yogurt cultures are present in adequate quantities, and that yogurt provides a minimum threshold dose of nutrients or bioactive components capable of exerting a physiologic effect. Therefore, the primary objective of this review is to investigate the plausibility of potential mechanisms commonly cited in the literature in order to shed light on the inverse associations reported between yogurt intake and various cardiometabolic health parameters that are related to its nutrient profile, bacterial constituents, and food matrix. This article reviews current gaps and challenges in identifying such mechanisms and provides a perspective on the research agenda to validate the proposed role of yogurt in protecting against CMDs.

Does dietary fat affect inflammatory markers in overweight and obese individuals?-a review of randomized controlled trials from 2010 to 2016

Background

Obesity, a major cause of death and disability, is increasing worldwide. Obesity is characterized by a chronic, low-grade inflammatory state which is suggested to play a critical role in the development of obesity-related diseases like cardiovascular diseases and type 2 diabetes. In fact, in the hours following consumption of a meal, a transient increase in inflammatory markers occurs, a response that is exaggerated in obese subjects. Dietary composition, including content of dietary fatty acids, may affect this inflammatory response both acutely and chronically, and thereby be predictive of progression of disease. The aim of the review was to summarize the literature from 2010 to 2016 regarding the effects of dietary fat intake on levels of inflammatory markers in overweight and obesity in human randomized controlled trials.

Methods and results

We performed a literature search in MEDLINE, EMBASE, and PubMed databases. The literature search included human randomized controlled trials, both postprandial and long-term interventions, from January 2010 to September 2016. In total, 37 articles were included. Interventions with dairy products, vegetable oils, or nuts showed minor effects on inflammatory markers. The most consistent inflammatory-mediating effects were found in intervention with whole diets, which suggests that many components of the diet reduce inflammation synergistically. Furthermore, interventions with weight reduction and different fatty acids did not clearly show beneficial effects on inflammatory markers.

Conclusion

Most interventions showed either no or minor effects of dietary fat intake on inflammatory markers in overweight and obese subjects. To progress our understanding on how diet and dietary components affect our health, mechanistic studies are required. Hence, future studies should include whole diets and characterization of obese phenotypes at a molecular level, including omics data and gut microbiota.

Invited review: The anti-inflammatory properties of dairy lipids

Dairy product consumption is often associated with negative effects because of its naturally high levels of saturated fatty acids. However, recent research has shown that dairy lipids possess putative bioactivity against chronic inflammation. Inflammation triggers the onset of several chronic diseases, including cardiovascular disease, type 2 diabetes mellitus, obesity, and cancer. This review discusses the anti-inflammatory properties of dairy lipids found in milk, yogurt, and cheese, and it examines them in relation to their implications for human health: their protective effects and their role in pathology. We also consider the effect of lipid profile alteration in dairy products-by using ruminant dietary strategies to enrich the milk, or by lipid fortification in the products. We critically review the in vivo, in vitro, ex vivo, and epidemiological studies associated with these dairy lipids and their role in various inflammatory conditions. Finally, we discuss some suggestions for future research in the study of bioactive lipids and dairy products, with reference to the novel field of metabolomics and epidemiological studies.

Dairy consumption, systolic blood pressure, and risk of hypertension: Mendelian randomization study

Objective To examine whether previous observed inverse associations of dairy intake with systolic blood pressure and risk of hypertension were causal.Design Mendelian randomization study using the single nucleotide polymorphism rs4988235 related to lactase persistence as an instrumental variable.Setting CHARGE (Cohorts for Heart and Aging Research in Genomic Epidemiology) Consortium.Participants Data from 22 studies with 171 213 participants, and an additional 10 published prospective studies with 26 119 participants included in the observational analysis.Main outcome measures The instrumental variable estimation was conducted using the ratio of coefficients approach. Using meta-analysis, an additional eight published randomized clinical trials on the association of dairy consumption with systolic blood pressure were summarized.Results Compared with the CC genotype (CC is associated with complete lactase deficiency), the CT/TT genotype (TT is associated with lactose persistence, and CT is associated with certain lactase deficiency) of LCT-13910 (lactase persistence gene) rs4988235 was associated with higher dairy consumption (0.23 (about 55 g/day), 95% confidence interval 0.17 to 0.29) serving/day; P<0.001) and was not associated with systolic blood pressure (0.31, 95% confidence interval -0.05 to 0.68 mm Hg; P=0.09) or risk of hypertension (odds ratio 1.01, 95% confidence interval 0.97 to 1.05; P=0.27). Using LCT-13910 rs4988235 as the instrumental variable, genetically determined dairy consumption was not associated with systolic blood pressure (β=1.35, 95% confidence interval -0.28 to 2.97 mm Hg for each serving/day) or risk of hypertension (odds ratio 1.04, 0.88 to 1.24). Moreover, meta-analysis of the published clinical trials showed that higher dairy intake has no significant effect on change in systolic blood pressure for interventions over one month to 12 months (intervention compared with control groups: β=-0.21, 95% confidence interval -0.98 to 0.57 mm Hg). In observational analysis, each serving/day increase in dairy consumption was associated with -0.11 (95% confidence interval -0.20 to -0.02 mm Hg; P=0.02) lower systolic blood pressure but not risk of hypertension (odds ratio 0.98, 0.97 to 1.00; P=0.11).Conclusion The weak inverse association between dairy intake and systolic blood pressure in observational studies was not supported by a comprehensive instrumental variable analysis and systematic review of existing clinical trials.

Associations between dairy food consumption and chronic kidney disease in older adults

We aimed to assess the association between dairy product consumption and calcium intake with the prevalence and 10-year incidence of chronic kidney disease (CKD). 1185 participants aged ≥50 years at baseline were examined between 1992–4 and 2002–4. Dietary data were collected using a food frequency questionnaire, and servings of dairy food consumption were calculated. Baseline biochemistry including serum creatinine was measured. CKD was defined as Modification of Diet in Renal Disease Study estimated glomerular filtration rate <60 mL·min^−1.1.73 m⁻². Cross-sectional analysis showed that older adults in the highest quintile compared to the lowest quintile (reference group) of low/reduced fat dairy food consumption had reduced odds of CKD, multivariable-adjusted odds ratio, OR, 0.64 (95% confidence intervals, CI, 0.43–0.96). Increasing total intake of dietary calcium was associated with reduced odds of CKD (P-trend = 0.02); comparing highest versus lowest quintile: OR 0.62 (95% CI 0.42–0.92). Participants in the second versus first quintile of low/reduced fat dairy food consumption at baseline had 49% reduced risk of CKD 10 years later, OR 0.51 (95% CI 0.29–0.89). Higher consumption of low/reduced fat dairy foods was independently associated with lower risk of CKD. Additional population-based studies are warranted to confirm these findings.

Comprehensive Review of the Impact of Dairy Foods and Dairy Fat on Cardiometabolic Risk

Because regular-fat dairy products are a major source of cholesterol-raising saturated fatty acids (SFAs), current US and Canadian dietary guidelines for cardiovascular health recommend the consumption of low-fat dairy products. Yet, numerous randomized controlled trials (RCTs) have reported rather mixed effects of reduced- and regular-fat dairy consumption on blood lipid concentrations and on many other cardiometabolic disease risk factors, such as blood pressure and inflammation markers. Thus, the focus on low-fat dairy in current dietary guidelines is being challenged, creating confusion within health professional circles and the public. This narrative review provides perspective on the research pertaining to the impact of dairy consumption and dairy fat on traditional and emerging cardiometabolic disease risk factors. This comprehensive assessment of evidence from RCTs suggests that there is no apparent risk of potential harmful effects of dairy consumption, irrespective of the content of dairy fat, on a large array of cardiometabolic variables, including lipid-related risk factors, blood pressure, inflammation, insulin resistance, and vascular function. This suggests that the purported detrimental effects of SFAs on cardiometabolic health may in fact be nullified when they are consumed as part of complex food matrices such as those in cheese and other dairy foods. Thus, the focus on low-fat dairy products in current guidelines apparently is not entirely supported by the existing literature and may need to be revisited on the basis of this evidence. Future studies addressing key research gaps in this area will be extremely informative to better appreciate the impact of dairy food matrices, as well as dairy fat specifically, on cardiometabolic health.

Dairy food products: good or bad for cardiometabolic disease?

Prevalence of type 2 diabetes mellitus (T2DM) is rapidly increasingly and is a key risk for CVD development, now recognised as the leading cause of death globally. Dietary strategies to reduce CVD development include reduction of saturated fat intake. Milk and dairy products are the largest contributors to dietary saturated fats in the UK and reduced consumption is often recommended as a strategy for risk reduction. However, overall evidence from prospective cohort studies does not confirm a detrimental association between dairy product consumption and CVD risk. The present review critically evaluates the current evidence on the association between milk and dairy products and risk of CVD, T2DM and the metabolic syndrome (collectively, cardiometabolic disease). The effects of total and individual dairy foods on cardiometabolic risk factors and new information on the effects of the food matrix on reducing fat digestion are also reviewed. It is concluded that a policy to lower SFA intake by reducing dairy food consumption to reduce cardiometabolic disease risk is likely to have limited or possibly negative effects. There remain many uncertainties, including differential effects of different dairy products and those of differing fat content. Focused and suitably designed and powered studies are needed to provide clearer evidence not only of the mechanisms involved, but how they may be beneficially influenced during milk production and processing.

New perspectives on dairy and cardiovascular health

CVD are the leading cause of mortality and morbidity worldwide. One of the key dietary recommendations for CVD prevention is reduction of saturated fat intake. Yet, despite milk and dairy foods contributing on average 27 % of saturated fat intake in the UK diet, evidence from prospective cohort studies does not support a detrimental effect of milk and dairy foods on risk of CVD. The present paper provides a brief overview of the role of milk and dairy products in the diets of UK adults, and will summarise the evidence in relation to the effects of milk and dairy consumption on CVD risk factors and mortality. The majority of prospective studies and meta-analyses examining the relationship between milk and dairy product consumption and risk of CVD show that milk and dairy products, excluding butter, are not associated with detrimental effects on CVD mortality or risk biomarkers that include serum LDL-cholesterol. In addition, there is increasing evidence that milk and dairy products are associated with lower blood pressure and arterial stiffness. These apparent benefits of milk and dairy foods have been attributed to their unique nutritional composition, and suggest that the elimination of milk and dairy may not be the optimum strategy for CVD risk reduction.

The Association of Dairy Intake With Metabolic Syndrome and Its Components in Adolescents: Tehran Lipid and Glucose Study

BACKGROUND

Epidemiological studies have shown that consumption of dairy product plays an important role in prevention and treatment of Metabolic Syndrome (MetS).

OBJECTIVES

The objective of this study was to examine the association of dairy intake with MetS and its components in Tehranian adolescents.

PATIENTS AND METHODS

In this cross-sectional study, 785 adolescent aged 10 to 19 years, participated from the fourth phase of the Tehran Lipid and Glucose Study. Usual dietary intake was assessed using a valid semi quantitative food frequency questionnaire. Total dairy, low fat and high fat dairy, milk, yoghurt and cheese were evaluated. Assessment of anthropometric, biochemical and blood pressure was performed and MetS was defined according to the de Ferranti criteria.

RESULTS

The mean age of subjects was 14.8 ± 2.9 years. The prevalence of MetS was 22.2% (girls: 19.5% and boys: 25.2%). The most prevalent risk factor for MetS in boys was high waist circumference (53.4%) and among girls was low HDL-C (53.1%). Energy density and intake of protein, total fat, saturated fat, cholesterol, calcium and phosphor were higher in the highest quartile of dairy consumption than the lowest quartile. After adjustments for confounders, odds ratios with 95% confidence interval for MetS in the highest quartile of total dairy, low fat dairy, high fat dairy, milk, yoghurt and cheese compared with lowest quartile were respectively 0.97 (0.57 - 1.66), 1.44 (0.83 - 2.49), 0.97 (0.56 - 1.67), 0.70 (0.42 - 1.18), 1.62 (0.99 - 2.64) and 0.72 (0.44 - 1.18).

CONCLUSIONS

Results of this study did not support the hypothesis that dairy products consumption protects against MetS and its components.

Red meat, dairy, and insulin sensitivity: a randomized crossover intervention study

BACKGROUND

Epidemiologic studies have linked high consumption of red and processed meat with risk of developing type 2 diabetes, whereas high dairy consumption has been associated with decreased risk, but interventions have been limited.

OBJECTIVE

We compared the effects on insulin sensitivity of consuming a diet high in lean red meat with minimal dairy, a diet high in primarily low-fat dairy (from milk, yogurt, or custard) with no red meat, and a control diet that contained neither red meat nor dairy.

DESIGN

A randomized crossover study was undertaken with 47 overweight and obese men and women divided into 2 groups as follows: those with normal glucose tolerance and those with impaired fasting glucose or impaired glucose tolerance. Participants followed the 3 weight-stable dietary interventions for 4 wk with glucose, insulin, and C-peptide measured by using oral-glucose-tolerance tests at the end of each diet.

RESULTS

Fasting insulin was significantly higher after the dairy diet than after the red meat diet (P < 0.01) with no change in fasting glucose resulting in a decrease in insulin sensitivity after the high-dairy diet (P < 0.05) as assessed by homeostasis model assessment of insulin resistance (HOMA-IR). A significant interaction between diet and sex was observed such that, in women alone, HOMA-IR was significantly lower after the red meat diet than after the dairy diet (1.33 ± 0.8 compared with 1.71 ± 0.8, respectively; P < 0.01). Insulin sensitivity calculated by using the Matsuda method was 14.7% lower in women after the dairy diet than after the red meat diet (P < 0.01) with no difference between diets in men. C-peptide was not different between diets.

CONCLUSION

In contrast to some epidemiologic findings, these results suggest that high consumption of dairy reduces insulin sensitivity compared with a diet high in lean red meat in overweight and obese subjects, some of whom had glucose intolerance. This trial was registered at the Australian New Zealand Clinical Trials Registry as ACTRN12613000441718.

Effects of non-fat dairy products added to the routine diet on vascular function: a randomized controlled crossover trial

BACKGROUND AND AIMS

High consumption of low- and non-fat dairy products is associated with reduced risk of high blood pressure (BP) and central arterial stiffness. However, interventional studies to determine if the addition of non-fat dairy products to the diet is capable of reducing central BP and improving vascular function are lacking. The aim of this study was to determine if the solitary addition of non-fat dairy products to the normal routine diet would reduce central BP and improve vascular function in middle-aged and older adults with elevated BP.

METHODS AND RESULTS

Using a randomized, crossover intervention study design, forty-nine adults (44% men, 53 ± 2 years, 170 ± 2 cm, 88 ± 3 kg; mean ± SEM) with elevated BP (134 ± 1/81 ± 1 mm Hg) underwent a High Dairy condition (+4 servings/day of conventional non-fat dairy products) and No Dairy condition (+4 servings/day fruit products) in which all dairy products were removed. Both dietary conditions lasted 4 weeks with a 2-week washout before crossing over into the alternate condition. The High Dairy condition produced reductions in central systolic BP (-3 ± 1 mm Hg) and carotid-femoral pulse wave velocity (-0.5 ± 0.1 m/sec), with a concomitant increase in brachial flow-mediated dilation (+1.1 ± 0.4%) and cardiovagal baroreflex sensitivity (+5 ± 1 ms/mm Hg) (P < 0.05 for all vs. baseline). In the No Dairy condition, brachial flow-mediated dilation was reduced (-1.0 ± 0.1%, P < 0.05 vs. baseline).

CONCLUSIONS

The solitary manipulation of conventional dairy products in the normal routine diet modulates levels of central BP and vascular function in middle-aged and older adults with elevated BP.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01577030.

Dairy product consumption and the metabolic syndrome

AIMS

To briefly summarize findings from epidemiological studies on the relationship between dairy product consumption and the metabolic syndrome(MetS).

MATERIALS AND METHODS

A search for relevant literature was undertaken on Web of Science, Google scholar, Pubmed (2000 to July 2013), to identify observational studies which examined the association between dairy intake and MetS (prevalence or incidence), and for any randomized controlled trials investigating the effect of dairy intake on MetS.

RESULTS

Here we review the physiological effects and possible mechanisms involved of three main dairy constituents (calcium (Ca), protein, fat) on important components of the MetS. Effects of Ca may be related to intestinal binding to fatty acids or bile acids, or to changes in intracellular Ca metabolism by suppressing calciotropic hormones. Dietary proteins may increase satiety in both the short and longer term, which may result in a reduced energy intake. Dairy proteins are precursors of angiotensin-I converting enzyme-inhibitory peptides, which may lower blood pressure. To reduce the intake of saturated fatty acids (SFA), the consumption of low-fat instead of high-fat dairy products is recommended.

CONCLUSION

More research is warranted to better understand the physiological effects and the mechanisms involved of dairy products in the prevention and treatment of the MetS.

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.

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.