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

Comparison of the impact of saturated fat from full-fat yogurt or low-fat yogurt and butter on cardiometabolic factors: a randomized cross-over trial

PURPOSE

Dairy foods are often a major contributor to dietary saturated fatty acids (SFA) intake. However, different SFA-rich foods may not have the same effects on cardiovascular risk factors. We compared full-fat yogurt with low-fat yogurt and butter for their effects on cardiometabolic risk factors in healthy individuals.

METHODS

Randomized, two-period crossover trial conducted from October 2022 to April 2023 among 30 healthy men and women (15 to receive full-fat yogurt first, and 15 to receive low-fat yogurt and butter first). Participants consumed a diet with 1.5-2 servings of full-fat (4%) yogurt or low-fat (< 1.5) yogurt and 10-15 g of butter per day for 4 weeks, with 4 weeks wash-out when they consumed 1.5-2 servings of low-fat milk. At baseline, and the end of each 4 weeks, fasting blood samples were drawn and plasma lipids, glycemic and inflammatory markers as well as expression of some genes in the blood buffy coats fraction were determined.

RESULTS

All 30 participants completed the two periods of the study. Apolipoprotein B was higher for the low-fat yogurt and butter [changes from baseline, + 10.06 (95%CI 4.64 to 15.47)] compared with the full-fat yogurt [-4.27 (95%CI, -11.78 to 3.23)] and the difference between two treatment periods was statistically significant (p = 0.004). Non-high-density lipoprotein increased for the low-fat yogurt and butter [change, + 5.06 (95%CI (-1.56 to 11.69) compared with the full-fat yogurt [change, - 4.90 (95%CI, -11.61 to 1.81), with no significant difference between two periods (p = 0.056). There were no between-period differences in other plasma lipid, insulin, and inflammatory biomarkers or leukocyte gene expression of ATP-binding cassette transporter 1 and CD36.

CONCLUSION

This study suggests that short-term intake of SFAs from full-fat yogurt compared to intake from butter and low-fat yogurt has fewer adverse effects on plasma lipid profile.

CLINICALTRIALS

GOV: NCT05589350, 10/15/2022.

Dairy product consumption and type 2 diabetes in an Argentinian population: is there an association?

Introduction

Introduction: dairy products have long been recommended as part of a healthy eating plan, but there is a controversial opinion about whether or not they should be included in the diet of people with type 2 diabetes (T2D). Objective: the aim of this study was to know if there is an association between the intake of total dairy and dairy subgroups and the chance of having T2D, and the status of markers of glucose metabolism. Methods: three hundred and forty-two adult subjects participated in the study. A validated food-frequency questionnaire was applied to establish the dairy intake. Clinical-pathological and anthropometric variables (height, weight, waist circumference and serum concentrations of blood glucose, glycated hemoglobin [HbA1c], high sensitive C-reactive protein [hs-CRP], tumor necrosis factor alpha [TNFα], interleukin [IL] 6 and IL-10) were measured. Consumption tertiles were calculated for each dairy subgroup. Correlation coefficients, multiple linear regression models and logistic regression models were used to assess the relation between dairy product consumption and markers of glucose metabolism. Results: a negative correlation was observed between the consumption of fermented dairy products and IL-10 (r = -0.27, p = 0.0206). Fermented dairy products were inversely associated with blood glucose, and HbA1c. Total dairy intake was positively associated with a lower chance of having diabetes in tertiles 2 and 3 of consumption, in relation to the reference tertile, adjusted for age, smoking habit, and alcohol intake, body mass index (BMI) and dietary variables. Conclusions: with this study, we broaden our understanding of the role of dairy intake in diabetes risk. However, more long-term studies are needed to confirm the associations and explore different confounding factors.

The effect of dairy products on liver fat and metabolic risk markers in males with abdominal obesity - a four-arm randomized controlled trial

BACKGROUND & AIMS

In recent years, epidemiological studies have reported links between the consumption of fermented dairy products, such as yogurt, and health; however, evidence from human intervention trials is scarce and inconsistent. We aimed to investigate the effect of consumption of four different types of dairy products (two fermented and two non-fermented) on liver fat (primary outcome) and metabolic risk markers in males with abdominal obesity.

METHODS

In this parallel randomized controlled trial with four arms, 100 males aged 30-70 years, with body mass index 28.0-45.0 kg/m2, and waist circumference ≥102 cm underwent a 16-weeks intervention where they were instructed to consume 400 g/day of either milk, yogurt, heat-treated yogurt, or acidified milk as part of their habitual diet. Liver fat was measured by magnetic resonance imaging.

RESULTS

In the complete case analyses (n = 80), no effects of the intervention or differences between groups were detected in anthropometry or body composition including liver fat. Moreover, no effects were detected in inflammatory markers. Main effects of time were detected in blood pressure (decrease; P < 0.001), insulin (decrease; P < 0.001), C-peptide (decrease; P = 0.040), homeostatic model assessment for insulin resistance (decrease; P < 0.001), total cholesterol (decrease; P = 0.016), low-density lipoprotein (decrease; P = 0.033), high-density lipoprotein (decrease; P = 0.006), and alanine transaminase (decrease; P = 0.019). Interactions between group and time failed to reach significance.

CONCLUSIONS

In conclusion, findings from our study do not confirm that fermented yogurt products are superior in reducing liver fat or improving metabolic risk markers compared to non-fermented milk products. In fact, all intervention products (both fermented yogurt products and non-fermented milk products) did not affect liver fat and caused largely similar modest favorable changes in some metabolic risk markers. The study was registered at www.

CLINICALTRIALS

gov (# NCT04755530).

Dairy Foods: Beneficial Effects of Fermented Products on Cardiometabolic Health

PURPOSE OF REVIEW

This review of recent observational studies and understanding of the complex nature of dairy foods is intended to reappraise the effects of different types of dairy foods on cardiovascular disease (CVD).

RECENT FINDINGS

Recent guidelines from major cardiovascular societies suggest that apart from the adverse effect of butter, consumption of more complex dairy products notably fermented varieties and yogurt in particular, appear to be inversely associated with outcomes of CVD and type 2 diabetes (T2D). Reduced fat in dairy food remains preferred for people at increased CVD risk. Changed evidence has led to new advice regarding consumption of some dairy foods. The apparent beneficial effects of fermented milk products, particularly yogurt, allow for increased consumption of nutritious staple foods. Recent national guidelines reflect this view.

The Relationship between Whole-Milk Dairy Foods and Metabolic Health Highlights an Opportunity for Dietary Fat Recommendations to Evolve with the State of the Science

The science of dietary fats has evolved, and a body of evidence indicates they are complex bioactive nutrients that have different effects on health depending on their food source, chain length, degree of saturation, and other factors that can be affected by food processing, handling, and storage. As such, it is becoming increasingly clear that the effects of foods on obesity and metabolic health cannot be predicted simply with their fat content. The aim of this opinion article is to provide a brief overview of select recent research on the effects of whole-milk dairy foods on body composition and indicators of metabolic health across the lifespan to show the gap between current knowledge and dietary guidance. As the state of the science on dietary fats and human health evolves to consider the complexity of food matrices, the total nutrient package they deliver, and the health impacts associated with dietary patterns, so too must guidelines for dietary fat.

Effects of Dairy Intake on Markers of Cardiometabolic Health in Adults: A Systematic Review with Network Meta-Analysis

The health effects of dairy products are still a matter of scientific debate owing to inconsistent findings across trials. Therefore, this systematic review and network meta-analysis (NMA) aimed to compare the effects of different dairy products on markers of cardiometabolic health. A systematic search was conducted in 3 electronic databases [MEDLINE, Cochrane Central Register of Controlled Trials (CENTRAL), and Web of Science; search date: 23 September 2022]. This study included randomized controlled trials (RCTs) with a ≥12-wk intervention comparing any 2 of the eligible interventions [e.g., high dairy (≥3 servings/d or equal amount in grams per day), full-fat dairy, low-fat dairy, naturally fermented milk products, and low dairy/control (0-2 servings/d or usual diet)]. A pairwise meta-analysis and NMA using random-effects model was performed in the frequentist framework for 10 outcomes [body weight, BMI, fat mass, waist circumference, low-density lipoprotein cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, fasting glucose, glycated hemoglobin, and systolic blood pressure]. Continuous outcome data were pooled using mean differences (MDs) and dairy interventions ranked using the surface under the cumulative ranking curve. Nineteen RCTs with 1427 participants were included. High-dairy intake (irrespective of fat content) showed no detrimental effects on anthropometric outcomes, blood lipids, and blood pressure. Both low-fat and full-fat dairy improved systolic blood pressure (MD: -5.22 to -7.60 mm Hg; low certainty) but, concomitantly, may impair glycemic control (fasting glucose-MD: 0.31-0.43 mmol/L; glycated hemoglobin-MD: 0.37%-0.47%). Full-fat dairy may increase HDL cholesterol compared with a control diet (MD: 0.26 mmol/L; 95% CI: 0.03, 0.49 mmol/L). Yogurt improved waist circumference (MD: -3.47 cm; 95% CI: -6.92, -0.02 cm; low certainty), triglycerides (MD: -0.38 mmol/L; 95% CI: -0.73, -0.03 mmol/L; low certainty), and HDL cholesterol (MD: 0.19 mmol/L; 95% CI: 0.00, 0.38 mmol/L) compared with milk. In conclusion, our findings indicate that there is little robust evidence that a higher dairy intake has detrimental effects on markers of cardiometabolic health. This review was registered at PROSPERO as CRD42022303198.

Associations between dietary intake and glucose tolerance in clinical and metabolomics-based metabotypes

BACKGROUND

Metabotyping is a novel concept to group metabolically similar individuals. Different metabotypes may respond differently to dietary interventions; hence, metabotyping may become an important future tool in precision nutrition strategies. However, it is not known if metabotyping based on comprehensive omic data provides more useful identification of metabotypes compared to metabotyping based on only a few clinically relevant metabolites.

AIM

This study aimed to investigate if associations between habitual dietary intake and glucose tolerance depend on metabotypes identified from standard clinical variables or comprehensive nuclear magnetic resonance (NMR) metabolomics.

METHODS

We used cross-sectional data from participants recruited through advertisements aimed at people at risk of type 2 diabetes mellitus (n = 203). Glucose tolerance was assessed with a 2-h oral glucose tolerance test (OGTT), and habitual dietary intake was recorded with a food frequency questionnaire. Lipoprotein subclasses and various metabolites were quantified with NMR spectroscopy, and plasma carotenoids were quantified using high-performance liquid chromatography. We divided participants into favorable and unfavorable clinical metabotypes based on established cutoffs for HbA1c and fasting and 2-h OGTT glucose. Favorable and unfavorable NMR metabotypes were created using k-means clustering of NMR metabolites.

RESULTS

While the clinical metabotypes were separated by glycemic variables, the NMR metabotypes were mainly separated by variables related to lipoproteins. A high intake of vegetables was associated with a better glucose tolerance in the unfavorable, but not the favorable clinical metabotype (interaction, p = 0.01). This interaction was confirmed using plasma concentrations of lutein and zeaxanthin, objective biomarkers of vegetable intake. Although non-significantly, the association between glucose tolerance and fiber intake depended on the clinical metabotypes, while the association between glucose tolerance and intake of saturated fatty acids and dietary fat sources depended on the NMR metabotypes.

CONCLUSION

Metabotyping may be a useful tool to tailor dietary interventions that will benefit specific groups of individuals. The variables that are used to create metabotypes will affect the association between dietary intake and disease risk.

Effects of fermented dairy products on inflammatory biomarkers: A meta-analysis

AIM

Fermented dairy products (FDPs) are made from raw milk under the action of specific microorganisms by lactic acid bacteria fermentation or co-fermentation of lactic acid bacteria, bifidobacteria, and yeast. The aim of this study was to explore the effects of FDPs on inflammatory biomarkers.

DATA SYNTHESIS

A comprehensive search was conducted on four electronic databases, including PubMed, Web of Science, Embase, and the Cochrane Library. Finally, fourteen trials (15 arms) were included in this meta-analysis: yogurt (n = 9), fermented milk (n = 4), and kefir (n = 2). Additionally, the random effects model or fixed-effects model was used to pool the study results. Firstly, the analysis indicated that FDPs' supplementation decreased the levels of C-reactive protein (CRP) (SMD = -0.21; 95% CI: -0.40, -0.02; P = 0.033) and increased interferon-gamma (IFN-γ) levels (SMD = 0.12; 95% CI: 0.01, 0.23; P = 0.033). Furthermore, we obtained some statistically significant results in the following subgroups: CRP decreased in participants with metabolic diseases. IFN-γ increased in the intervention that lasted ≥12 weeks, Asian, yogurt, and healthy population. Finally, there was no significant effect on tumor necrosis factor-alpha, interleukin (IL)-6, IL-10, and IL-2.

CONCLUSIONS

FDPs reduced CRP and increased IFN-γ, but they had no effect on other inflammatory markers. The results showed that the consumption of FDPs was slightly associated with reduced inflammation, but because of the limited literature, these results should be interpreted with caution.

Low-fat dairy consumption improves intestinal immune function more than high-fat dairy in a diet-induced swine model of insulin resistance

PURPOSE

To understand the effects of consuming high-fat and low-fat dairy products on postprandial cardiometabolic risk factors and intestinal immune function, we used an established low birthweight (LBW) swine model of diet-induced insulin resistance.

METHODS

LBW piglets were randomized to consume one of the 3 experimental high fat diets and were fed for a total of 7 weeks: (1) Control high fat (LBW-CHF), (2) CHF diet supplemented with 3 servings of high-fat dairy (LBW-HFDairy) and (3) CHF diet supplemented with 3 servings of low-fat dairy (LBW-LFDairy). As comparison groups, normal birthweight (NBW) piglets were fed a CHF (NBW-CHF) or standard pig grower diet (NBW-Chow). At 11 weeks of age, all piglets underwent an established modified oral glucose and fat tolerance test. At 12 weeks of age, piglets were euthanized and ex vivo cytokine production by cells isolated from mesenteric lymph node (MLN) stimulated with mitogens was assessed.

RESULTS

Dairy consumption did not modulate postprandial plasma lipid, inflammatory markers and glucose concentrations. A lower production of IL-2 and TNF-α after pokeweed mitogen (PWM) stimulation was observed in LBW-CHF vs NBW-Chow (P < 0.05), suggesting impaired MLN T cell function. While feeding high-fat dairy had minimal effects, feeding low-fat dairy significantly improved the production of IL-2 and TNF-α after PWM stimulation (P < 0.05).

CONCLUSIONS

Irrespective of fat content, dairy had a neutral effect on postprandial cardiometabolic risk factors. Low-fat dairy products improved intestinal T cell function to a greater extent than high-fat dairy in this swine model of obesity and insulin resistance.

Fermented food: Should patients with cardiometabolic diseases go back to an early neolithic diet?

Fermentation has been used since the Early Neolithic period to preserve foods. It has inherent organoleptic and nutritive properties that bestow health benefits, including reducing inflammation and oxidative stress, supporting the growth of salutogenic microbiota, enhancing intestinal mucosal protection and promoting beneficial immunometabolic health effects. The fermentation of food with specific microbiota increases the production salutogenic bioactive compounds that can activate Nrf2 mediated cytoprotective responses and mitigate the effects of the 'diseasome of aging' and its associated inflammageing, which presents as a prominent feature of obesity, type-2 diabetes, cardiovascular and chronic kidney disease. This review discusses the importance of fermented food in improving health span, with special reference to cardiometabolic diseases.

Changes in Food and Nutrient Intake and Diet Quality on a Low-Fat Vegan Diet Are Associated with Changes in Body Weight, Body Composition, and Insulin Sensitivity in Overweight Adults: A Randomized Clinical Trial

BACKGROUND

Consuming different food groups and nutrients can have differential effects on body weight, body composition, and insulin sensitivity.

OBJECTIVE

The aim was to identify how food group, nutrient intake, and diet quality change relative to usual-diet controls after 16 weeks on a low-fat vegan diet and what associations those changes have with changes in body weight, body composition, and measures of metabolic health.

DESIGN

Secondary analysis of a randomized clinical trial conducted between October 2016 and December 2018 in four replications.

PARTICIPANTS/SETTING

Participants included in this analysis were 219 healthy, community-based adults in the Washington, DC, area, with a body mass index (BMI) between 28 and 40 kg/m², who were randomly assigned to follow either a low-fat vegan diet or make no diet changes.

INTERVENTION

A low-fat, vegan diet deriving approximately 10% of energy from fat, with weekly classes including dietary instruction, group discussion, and education on the health effects of plant-based nutrition. Control group participants continued their usual diets.

MAIN OUTCOME MEASURES

Changes in food group intake, macro- and micronutrient intake, and dietary quality as measured by Alternate Healthy Eating Index-2010 (AHEI-2010), analyzed from 3-day diet records, and associations with changes in body weight, body composition, and insulin sensitivity were assessed.

STATISTICAL ANALYSES PERFORMED

A repeated measure analysis of variance (ANOVA) model that included the factors group, subject, and time, was used to test the between-group differences throughout the 16-week study. Interaction between group and time (Gxt) was calculated for each variable. Within each diet group, paired comparison t-tests were calculated to identify significant changes from baseline to 16 weeks. Spearman correlations were calculated for the relationship between changes in food group intake, nutrient intake, AHEI-2010 score, and changes in body weight, body composition, and insulin sensitivity. The relative contribution of food groups and nutrients to weight loss was evaluated using linear regression.

RESULTS

Fruit, vegetable, legume, meat alternative, and whole grain intake significantly increased in the vegan group. Intake of meat, fish and poultry; dairy products; eggs; nuts and seeds; and added fats decreased. Decreased weight was most associated with increased intake of legumes (r=-0.38; p<.0001) and decreased intake of total meat, fish, and poultry (r=+0.43; p<.0001). Those consuming a low-fat vegan diet also increased their intake of carbohydrates, fiber, and several micronutrients and decreased fat intake. Reduced fat intake was associated with reduced body weight (r=+0.15; p=0.02) and, after adjustment for changes in BMI and energy intake, with reduced fat mass (r=+0.14; p=0.04). The intervention group's AHEI-2010 increased by 6.0 points on average in contrast to no significant change in the control group (treatment effect +7.2 [95% CI +3.7 to +10.7]; p<0.001). Increase in AHEI-2010 correlated with reduction in body weight (r=0.14; p=0.04), fat mass (r=-0.14; p=0.03), and insulin resistance as measured by HOMA-IR (r=-0.17; p=0.02), after adjustment for changes in energy intake.

CONCLUSIONS

When compared with participants' usual diets, intake of plant foods increased, and consumption of animal foods, nuts and seeds, and added fats decreased on a low-fat vegan diet. Increased legume intake was the best single food group predictor of weight loss. Diet quality as measured by AHEI-2010 improved on the low-fat vegan diet, which was associated with improvements in weight and metabolic outcomes. These data suggest that increasing low-fat plant foods and minimizing high-fat and animal foods is associated with decreased body weight and fat loss, and that a low-fat vegan diet can improve measures of diet quality and metabolic health.

Akt: A Potential Drug Target for Metabolic Syndrome

The serine/threonine kinase Akt, also known as protein kinase B (PKB), is one of the key factors regulating glucose and lipid energy metabolism, and is the core focus of current research on diabetes and metabolic diseases. Akt is mostly expressed in key metabolism-related organs and it is activated in response to various stimuli, including cell stress, cell movement, and various hormones and drugs that affect cell metabolism. Genetic and pharmacological studies have shown that Akt is necessary to maintain the steady state of glucose and lipid metabolism and a variety of cellular responses. Existing evidence shows that metabolic syndrome is related to insulin resistance and lipid metabolism disorders. Based on a large number of studies on Akt-related pathways and reactions, we believe that Akt can be used as a potential drug target to effectively treat metabolic syndrome.

The impact of low-fat and full-fat dairy foods on symptoms of gastroesophageal reflux disease: an exploratory analysis based on a randomized controlled trial

PURPOSE

Gastroesophageal reflux disease (GERD) is a widely prevalent condition. High consumption of dairy foods and dietary fat are associated with worse GERD symptoms. However, existing data are inconsistent and mostly based on observational studies. The purpose of this exploratory analysis of a randomized controlled trial was to investigate the impact of low-fat and full-fat dairy food consumption on GERD symptoms.

METHODS

Seventy-two participants with metabolic syndrome completed a 4-week wash-in diet during which dairy intake was limited to three servings of nonfat milk per week. Participants were then randomized to either continue the limited dairy diet or switch to a diet containing 3.3 servings per day of either low-fat or full-fat milk, yogurt and cheese for 12 weeks. Here, we report intervention effects on the frequency of acid reflux, and the frequency and severity of heartburn, exploratory endpoints assessed by a questionnaire administered before and after the 12-week intervention.

RESULTS

In the per-protocol analysis (n = 63), there was no differential intervention effect on a cumulative heartburn score (p = 0.443 for the time by diet interaction in the overall repeated measures analysis of variance). Similarly, the intervention groups did not differentially affect the odds of experiencing acid regurgitation (p = 0.651). The intent-to-treat analyses (n = 72) yielded similar results.

CONCLUSION

Our exploratory analyses suggest that, in men and women with the metabolic syndrome, increasing the consumption of either low-fat or full-fat dairy foods to at least three servings per day does not affect common symptoms of GERD, heartburn and acid regurgitation compared to a diet limited in dairy.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02663544, registered on January 26, 2016.

Assessing the validity of plasma phospholipid fatty acids as biomarkers of dairy fat intake using data from a randomized controlled intervention trial

BACKGROUND

Plasma phospholipid pentadecanoic acid (C15:0), heptadecanoic acid (C17:0), and trans-palmitoleic acid (trans-C16:1n-7) are correlates of dairy fat intake. However, their relative concentrations may be influenced by other endogenous factors, such as liver fat content, and their validity as biomarkers of dairy fat intake has yet to be established.

OBJECTIVES

We investigated whether liver fat content modifies relations between concentrations of C15:0, C17:0, and trans-C16:1n-7 (alone and in combination with iso-C17:0) and known dairy fat intake in the context of a randomized controlled intervention study. We further examined the proportion of dairy fat intake explained by these fatty acids on their own and when considering liver fat content.

METHODS

We used data from a 12-wk intervention trial in which participants (n = 62) consumed diets limited in dairy (0.3 g/d of dairy fat), rich in low-fat dairy (8.7 g/d of dairy fat), or rich in full-fat dairy (28.5 g/d of dairy fat). We used linear regression models to examine relations between relative fatty acid concentrations and grams per day of dairy fat intake, liver fat percentage, and their interaction.

RESULTS

Only trans-C16:1n-7 in isolation (β: 0.0004 ± 0.0002, P = 0.03) and combined with iso-C17:0 (β: 0.002 ± 0.0005, P < 0.0001) were consistently positively associated with dairy fat intake regardless of liver fat content. Trans-C16:1n-7 combined with iso-C17:0 also explained the greatest proportion of variation (35.4%) in dairy fat intake. C15:0 and C17:0 were not associated with dairy fat intake after adjusting for liver fat and were predicted to be higher in relation to increased dairy fat intake only among individuals with elevated liver fat.

CONCLUSIONS

The potential for liver fat to affect relative plasma phospholipid concentrations of C15:0 and C17:0 raises questions about their validity as biomarkers of dairy fat intake. Of the fatty acid measures tested, trans-C16:1n-7 combined with iso-C17:0, especially with adjustment of liver fat, age, and sex, may provide the most robust estimate of dairy fat consumption.

Dairy Product Consumption in Relation to Incident Prediabetes and Longitudinal Insulin Resistance in the Rotterdam Study

Evidence suggests neutral or moderately beneficial effects of dairy intake on type 2 diabetes mellitus risk. Nevertheless, evidence on associations with early phases of type 2 diabetes remains inconsistent. We aimed to examine associations between dairy-type intake with prediabetes risk and longitudinal insulin resistance. The analytic sample consisted of 6770 participants (aged 62 ± 4 years, 59% female) free of (pre-)diabetes at baseline from the prospective population-based Rotterdam Study. Dairy intake was measured at baseline using food frequency questionnaires. Data on prediabetes (fasting blood glucose 6.1-6.9 mmol/L or non-fasting 7.7-11.1 mmol/L) and the longitudinal homeostatic model assessment of insulin resistance (HOMA-IR) were available from 1993-2015. Associations with these outcomes were analyzed with dairy intake in quartiles (Q4 vs. Q1) and continuous using multivariable Cox proportional hazard models and linear mixed models. During a mean follow-up of 11.3 ± 4.8 years, 1139 incident prediabetes cases were documented (18.8%). In models adjusting for sociodemographic, lifestyle and dietary factors, a higher intake of high-fat yogurt was associated with lower prediabetes risk (HRQ4vsQ1 0.70, 95% CI 0.54-0.91 and HRserving/day 0.67, 0.51-0.89). In addition, a higher intake of high-fat milk was associated with lower prediabetes risk (HRQ4vsQ1 0.81, 0.67-0.97, HRserving/day 0.88, 0.79-0.99). Associations were found for low-fat dairy, low-fat milk and total cheese with a higher prediabetes risk (HRserving/day ranging from 1.05-1.07, not significant in quartiles). Associations with longitudinal HOMA-IR were similar to prediabetes for high-fat yogurt, low-fat dairy and low-fat milk. Fermented dairy, low-fat yogurt, high-fat cheese, cream and ice cream were not associated with the outcomes. In conclusion, a higher intake of high-fat yogurt was associated with a lower prediabetes risk and lower longitudinal insulin resistance. Additionally, high-fat milk was associated with a lower prediabetes risk. Some low-fat dairy types were inconsistently associated with these outcomes. Studies are needed to confirm associations and to examine the influence of confounding by population characteristics.

Dairy matrix: is the whole greater than the sum of the parts?

Dairy foods are a heterogeneous group of products that vary in physical state and structure; profile and amounts of essential nutrients, bioactive ingredients, and other constituents; the extent of alteration of these constituents by processing, whether they are fermented or aged; and addition of constituents during manufacture. The complexity of the dairy matrix is associated with a heterogeneous impact on health outcomes from increased, decreased, or neutral effects for specific dairy products and specific health outcomes. Researchers must become more nuanced and systematic in their study of the role of dairy products in health to develop meaningful dietary recommendations. This review of the evidence for the dairy matrix and health points out the dearth of randomized controlled trials and of mechanistic insights. The variable effects of dairy-product consumption on health suggest possibilities for personalized nutrition advice.

Whole-fat dairy products do not adversely affect adiposity or cardiometabolic risk factors in children in the Milky Way Study: a double-blind randomized controlled pilot study

BACKGROUND

Limited evidence supports the common public health guideline that children >2 y of age should consume dairy with reduced fat content.

OBJECTIVES

We aimed to investigate the effects of whole-fat compared with reduced-fat dairy intake on measures of adiposity and biomarkers of cardiometabolic risk in healthy 4- to 6-y-old children.

METHODS

The Milky Way Study enrolled 49 children (mean ± SD age: 5.2 ± 0.9 y; 47% girls) who were habitual consumers of whole-fat dairy, then randomly assigned them in a double-blind fashion to remain on whole-fat dairy or switch their dairy consumption to reduced-fat products for 3 mo. Primary endpoints included measures of adiposity, body composition, blood pressure, fasting serum lipids, blood glucose, glycated hemoglobin (HbA1c), and C-reactive protein (CRP) and were assessed at baseline and study end. Pre- and postintervention results were compared using linear mixed models, adjusted for growth, age, and sex.

RESULTS

Dairy fat intake was reduced by an adjusted (mean ± SEM) 12.9 ± 4.1 g/d in the reduced-fat compared with the whole-fat dairy group (95% CI: -21.2, -4.6 g/d; P = 0.003), whereas dietary energy intakes remained similar (P = 0.936). We found no significant differential changes between dairy groups in any measure of adiposity, body composition, blood pressure, or fasting serum lipids, glucose, HbA1c, and CRP.

CONCLUSIONS

Our results suggest that although changing from whole-fat to reduced-fat dairy products does reduce dairy fat intake, it does not result in changes to markers of adiposity or cardiometabolic disease risk in healthy children.This trial was registered at www.anzctr.org.au as ACTRN12616001642471.

Exploring the Links between Diet and Inflammation: Dairy Foods as Case Studies

Systemic chronic inflammation may be a contributing factor to many noncommunicable diseases, including diabetes, cardiovascular disease, and obesity. With the rapid rise of these conditions, identifying the causes of and treatment for chronic inflammation is an important research priority, especially with regard to modifiable lifestyle factors such as diet. An emerging body of evidence indicates that consuming certain foods, including dairy foods like milk, cheese, and yogurt, may be linked to a decreased risk for inflammation. To discuss both broader research on diet and inflammation as well as research on links between individual foods and inflammation, the National Dairy Council sponsored a satellite session entitled "Exploring the Links between Diet and Inflammation: Dairy Foods as Case Studies" at the American Society for Nutrition's 2020 LIVE ONLINE Conference. This article, a review based on the topics discussed during that session, explores the links between diet and inflammation, focusing most closely on the relations between intake of dairy fat and dairy foods like milk, cheese, and yogurt, and biomarkers of inflammation from clinical trials. While there is currently insufficient evidence to prove an "anti-inflammatory" effect of dairy foods, the substantial body of clinical research discussed in this review indicates that dairy foods do not increase concentrations of biomarkers of chronic systemic inflammation.

Dairy Product Consumption and Cardiovascular Health: a Systematic Review and Meta-Analysis of Prospective Cohort Studies

The association between dairy product consumption and cardiovascular health remains highly debated. We quantitatively synthesized prospective cohort evidence on the associations between dairy consumption and risk of hypertension (HTN), coronary heart disease (CHD) and stroke. We systematically searched PubMed, Embase, and Web of Science through August 1st, 2020 to retrieve prospective cohort studies that reported on dairy consumption and risk of HTN, CHD or stroke. We used random-effects models to calculate the pooled relative risk (RR) and 95% confidence interval (CI) for the highest vs the lowest category of intake and for 1 serving/day increase in consumption. We rated the quality of evidence using NutriGrade. Fifty-five studies were included. Total dairy consumption was associated with a lower risk of HTN (RR for highest vs lowest level of intake: 0.91, 95% CI: 0.86-0.95, I2 = 73.5%; RR for 1 serving/day increase: 0.96, 95% CI: 0.94-0.97, I2 = 66.5%), CHD (highest vs lowest level of intake: 0.96, 95% CI: 0.92-1.00, I2 = 46.6%; 1 serving/day increase: 0.98, 95% CI: 0.95-1.00, I2 = 56.7%), and stroke (highest vs lowest level of intake: 0.90, 95% CI: 0.85-0.96, I2 = 60.8%; 1 serving/day increase: 0.96, 95% CI: 0.93-0.99, I2 = 74.7%). Despite moderate to considerable heterogeneity, these associations remained consistent across multiple subgroups. Evidence on the relationship between total dairy and risk of HTN and CHD were of moderate quality and of low quality for stroke. Low-fat dairy consumption was associated with lower risk of HTN and stroke, and high-fat dairy with a lower risk of stroke. Milk, cheese, or yogurt consumption showed inconsistent associations with the cardiovascular outcomes in high vs. low intake and dose-response meta-analyses. Total dairy consumption was associated with a modestly lower risk of hypertension, CHD and stroke. Moderate to considerable heterogeneity was observed in the estimates and the overall quality of the evidence was low to moderate.

Dairy Consumption and 3-Year Risk of Type 2 Diabetes after Myocardial Infarction: A Prospective Analysis in the Alpha Omega Cohort

Population-based studies suggest a role for dairy, especially yogurt, in the prevention of type 2 diabetes (T2D). Whether dairy affects T2D risk after myocardial infarction (MI) is unknown. We examined associations of (types of) dairy with T2D incidence in drug-treated, post-MI patients from the Alpha Omega Cohort. The analysis included 3401 patients (80% men) aged 60-80 y who were free of T2D at baseline (2002-2006). Dairy intakes were assessed using a validated food-frequency questionnaire. Incident T2D was ascertained through self-reported physician diagnosis and/or medication use. Multivariable Cox models were used to calculate Hazard ratios (HRs) and 95% confidence intervals (CI) for T2D with dairy intake in categories and per 1-standard deviation (SD) increment. Most patients consumed dairy, and median intakes were 264 g/d for total dairy, 82 g/d for milk and 41 g/d for yogurt. During 40 months of follow-up (10,714 person-years), 186 patients developed T2D. After adjustment for confounders, including diet, HRs per 1-SD were 1.06 (95% CI 0.91-1.22) for total dairy, 1.02 (0.88-1.18) for milk and 1.04 (0.90-1.20) for yogurt. Associations were also absent for other dairy types and in dairy categories (all p-trend > 0.05). Our findings suggest no major role for dairy consumption in T2D prevention after MI.

Impact of low-fat and full-fat dairy foods on fasting lipid profile and blood pressure: exploratory endpoints of a randomized controlled trial

BACKGROUND

Dietary guidelines traditionally recommend low-fat dairy because dairy's high saturated fat content is thought to promote cardiovascular disease (CVD). However, emerging evidence indicates that dairy fat may not negatively impact CVD risk factors when consumed in foods with a complex matrix.

OBJECTIVE

The aim was to compare the effects of diets limited in dairy or rich in either low-fat or full-fat dairy on CVD risk factors.

METHODS

In this randomized controlled trial, 72 participants with metabolic syndrome completed a 4-wk run-in period, limiting their dairy intake to ≤3 servings/wk of nonfat milk. Participants were then randomly assigned to 1 of 3 diets, either continuing the limited-dairy diet or switching to a diet containing 3.3 servings/d of either low-fat or full-fat milk, yogurt, and cheese for 12 wk. Exploratory outcome measures included changes in the fasting lipid profile and blood pressure.

RESULTS

In the per-protocol analysis (n = 66), there was no intervention effect on fasting serum total, LDL, and HDL cholesterol; triglycerides; free fatty acids; or cholesterol content in 38 isolated plasma lipoprotein fractions (P > 0.1 for all variables in repeated-measures ANOVA). There was also no intervention effect on diastolic blood pressure, but a significant intervention effect for systolic blood pressure (P = 0.048), with a trend for a decrease in the low-fat dairy diet (-1.6 ± 8.6 mm Hg) compared with the limited-dairy diet (+2.5 ± 8.2 mm Hg) in post hoc testing. Intent-to-treat results were consistent for all endpoints, with the exception that systolic blood pressure became nonsignificant (P = 0.08).

CONCLUSIONS

In men and women with metabolic syndrome, a diet rich in full-fat dairy had no effects on fasting lipid profile or blood pressure compared with diets limited in dairy or rich in low-fat dairy. Therefore, dairy fat, when consumed as part of complex whole foods, does not adversely impact these classic CVD risk factors. This trial was registered at clinicaltrials.gov as NCT02663544.

Tissue and Circulating Fatty Acids as Biomarkers to Evaluate Long-Term Fat Intake Are Tissue and Sex Dependent in CD-1 Mice

BACKGROUND

There is currently no consensus on which tissues are optimal for assessing specific diet-derived fatty acids (FAs) as biomarkers for long-term dietary studies.

OBJECTIVES

This study measured the content of unique diet-derived FAs from dairy, echium, and fish in tissues (adipose, muscle, liver, erythrocyte membranes, and plasma phospholipids, cholesterol esters, triglycerides, and free fatty acids) after long-term feeding in CD-1 mice.

METHODS

Beginning at weaning, mice (n = 10-11/sex/diet) were fed 1 of 4 diets (40% kcal/total energy) that only differed in FA composition: control fat blend (CON), reflecting the FA profile of the average US American diet, or CON supplemented with 30% of fish oil (FO), dairy fat (DF), or echium oil (EO). After 13 mo, tissues were collected to determine FAs via gas-liquid chromatography. Tissue FAs were analyzed via 2-factor ANOVA, and relationships between FA intake and tissue content were assessed with Spearman correlations.

RESULTS

As anticipated, 20:5n-3 (ω-3) tissue content was ≤32-fold greater in FO- compared with CON-fed mice (P < 0.05). In addition, 20:5n-3 intake strongly correlated with its content in all tissues (ρ = 0.67-0.76; P < 0.05). Echium oil intake also influenced tissue FA content in mice as expected. For example, 18:3n-6 was ≤25-fold greater in adipose, muscle, and liver tissues of EO-fed compared with CON-fed mice (P < 0.05). Tissue content of FAs typically considered biomarkers of dairy fat intake (15:0, 16:1 t9, and 17:0) was often not greater in mice fed DF than other diet groups, although 18:2 c9, t11 content was ≤6-fold greater in tissues from DF-fed compared with CON-fed mice (P < 0.05). The content of dairy-derived FAs in blood fractions of females was up to 2-fold greater compared with males, whereas docosapentaenoic acid content was up to 1-fold greater in all blood fractions and in liver tissue of males compared with females (P < 0.05). In adipose, muscle, and liver tissue, the content of γ-linolenic acid and stearidonic acid was less than 1-fold greater in females than in males (P < 0.05).

CONCLUSIONS

Our study indicates that the distribution of dietary FAs is tissue and sex dependent in aged CD-1 mice. Research using FA biomarkers should assess a combination of FA biomarkers to accurately validate patterns of FA intake and source.