Lipid droplet size and emulsification on postprandial glycemia, insulinemia and lipidemia

Lipid emulsion structure, digestion behavior, physiology, and health: a scoping review and future directions

Research investigating the effects of the food matrix on health is needed to untangle many unresolved questions in nutritional science. Emulsion structure plays a fundamental role in this inquiry; however, the effects of oil-in-water emulsion structure on broad metabolic, physiological, and health-related outcomes have not been comprehensively reviewed. This systematic scoping review targets this gap and examines methodological considerations for the field of relating food structure and health. MEDLINE, Web of Science, and CAB Direct were searched from inception to December 2022, returning 3106 articles, 52 of which were eligible for inclusion. Many investigated emulsion lipid droplet size and/or gastric colloidal stability and their relation to postprandial weight-loss-related outcomes. The present review also identifies numerous novel relationships between emulsion structures and health-related outcomes. "Omics" endpoints present an exciting avenue for more comprehensive analysis in this area, yet interpretation remains difficult. Identifying valid surrogate biomarkers for long-term outcomes and disease risk will be a turning point for food structure research, leading to breakthroughs in the pace and utility of research that generates advancements in health. The review's findings and recommendations aim to support new hypotheses, future trial design, and evidence-based emulsion design for improved health and well-being.

Effect of Isoenergetic Substitution of Cheese with Other Dairy Products on Blood Lipid Markers in the Fasted and Postprandial State: An Updated and Extended Systematic Review and Meta-Analysis of Randomized Controlled Trials in Adults

Consumption of fat as part of a cheese matrix may differentially affect blood lipid responses when compared with other dairy foods. This systematic review was conducted to compare the impact of consuming equal amounts of fat from cheese and other dairy products on blood lipid markers in the fasted and postprandial state. Searches of PubMed (Medline), Cochrane Central and Embase databases were conducted up to mid-June 2022. Eligible human randomized controlled trials (RCTs) investigated the effect of isoenergetic substitution of hard or semi-hard cheese with other dairy products on blood lipid markers. Risk of bias (RoB) was assessed using the Cochrane RoB 2.0 tool. Random-effects meta-analyses assessed the effect of ≥2 similar dietary replacements on the same blood lipid marker. Of 1491 identified citations, 10 articles were included (RoB: all some concerns). Pooled analyses of 7 RCTs showed a reduction in fasting total cholesterol, LDL-C and HDL-C concentrations after ≥14 d mean daily intake of 135 g cheese (weighted mean difference [WMD]: -0.24 mmol/L; 95% confidence interval (CI): -0.34, -0.15; I2 = 59.8%, WMD: -0.19 mmol/L; 95% CI: -0.27, -0.12; I2 = 42.8%, and WMD: -0.04 mmol/L; 95% CI: -0.08, -0.00; I2 = 58.6%, respectively) relative to ∼52 g/d butter. We found no evidence of a benefit from replacing cheese for ≥14 d with milk on fasting blood lipid markers (n = 2). Limited postprandial RCTs, described in narrative syntheses, suggested that cheese-rich meals may induce differential fed-state lipid responses compared with some other dairy matrix structures, but not butter (n ≤ 2). In conclusion, these findings indicate that dairy fat consumed in the form of cheese has a differential effect on blood lipid responses relative to some other dairy food structures. However, owing to considerable heterogeneity and limited studies, further confirmation from RCTs is warranted. TRIAL REGISTRATION NUMBER: This systematic review protocol was registered at https://www.crd.york.ac.uk/PROSPERO/ as CRD42022299748.

Effects of dietary fat type and emulsification on carotenoid absorption: a randomized crossover trial

BACKGROUND

Although emerging evidence has suggested that the type and emulsification of dietary fat may be important to carotenoids absorption, these effects have not yet been validated in a human trial.

OBJECTIVE

This study aimed to examine the effects of dietary fat type and emulsification on the bioaccessibility and bioavailability of carotenoids from a carotenoids-rich salad.

METHODS

An identical salad was used for the in vitro and the human trial. This was paired with 28 g of one of the following four different fats: i) non-emulsified olive oil; ii) emulsified olive oil; (iv) non-emulsified coconut oil; v) emulsified coconut oil. The bioaccessibility of total carotenoids (TC) was assessed by a simulated in vitro digestion model. Sixteen subjects consumed salad with four test fats in random order, and plasma triglyceride and carotenoid (lutein, zeaxanthin, α-carotene, β-carotene, and lycopene) concentrations were determined hourly for 10 hours following the consumption. The absorption of TC and individual carotenoids were evaluated by the positive incremental area under the curve (iAUC) of plasma carotenoid concentrations.

RESULTS

The bioaccessibility of TC was greater with olive oil (24.0%) than with coconut oil (14.9%), and with the oil being emulsified (23.5%) rather than non-emulsified (15.4%). Likewise, the positive iAUC_1-10h of TC, α-carotene and lycopene were 55.2%, 110.8% and 45.8%, respectively, higher with olive oil than with coconut oil. Emulsified fat induced 40.0% greater positive iAUC_1-10h of TC than non-emulsified fat.

CONCLUSIONS

The type and emulsification of dietary fat are both essential to the carotenoid absorption. Findings from this study may provide scientific support for designing excipient emulsions as potential dietary strategies to optimize the absorption of fat-soluble compounds.

CLINICAL TRIAL REGISTRY

The present trial was registered at clinicaltrials.gov (NCT04323826), link: https://clinicaltrials.gov/ct2/show/NCT04323826.

Matrix structure of dairy products results in different postprandial lipid responses: a randomized crossover trial

BACKGROUND

The dairy matrix may influence digestion and absorption of lipids and thereby risk of cardiovascular diseases (CVDs). However, few postprandial studies have compared dairy products that differed only in terms of their matrix.

OBJECTIVES

We aimed to investigate acute 8-h postprandial lipid, glycemic, and appetite responses after intake of isoenergetic dairy meals with different matrixes, but similar nutritional composition.

METHODS

Twenty-five normal-weight men (18-40 y old) were enrolled in a randomized controlled crossover trial. On 4 test days, a meal with 1 of 4 dairy products was served: cheddar cheese (Cheese), homogenized Cheese (Hom. Cheese), micellar casein isolate (MCI) with cream (MCI Drink), and a gel produced from the MCI Drink by addition of Glucono Delta-Lactone (MCI Gel). The fat- and protein-matched dairy products differed in terms of their casein network, fat droplet size, and/or texture. Blood biochemistry and appetite responses were collected.

RESULTS

Eighteen participants completed the trial. Postprandial triglycerides (TGs) (primary outcome) increased by (mean ± SEM) 0.24 ± 0.07 and 0.19 ± 0.07 mmol/L after MCI Gel compared with Cheese and Hom. Cheese, respectively (both P ≤ 0.05). Likewise, MCI Gel increased TG incremental AUC compared with Cheese and Hom. Cheese (both P < 0.05), and peak compared with Cheese (P < 0.05). ApoB-48 (primary outcome) was unaffected by dairy matrix. For free fatty acids (FFAs), glucose, and insulin, time × meal interactions were observed (all P < 0.001). During the first 2 h, FFAs were lower for Cheese than for MCI products, whereas the opposite was observed for glucose and insulin.

CONCLUSIONS

Postprandial TG but not apoB-48 response was higher after MCI Gel, indicating that the type of casein network influences lipid responses. This suggests that the dairy matrix may also affect risk factors for CVDs. Reducing fat droplet size (i.e., Hom. Cheese) did not affect blood biochemistry.This trial was registered at clinicaltrials.gov as NCT03656367.

Postprandial vascular-inflammatory and thrombotic responses to high-fat feeding are augmented by manipulating the lipid droplet size distribution

BACKGROUND AND AIMS

Postprandial responses are influenced not only by the type and amount of fat ingested, but also lipid droplet size distribution. However, little research has investigated the impact of differential lipid size distributions within a mixed-macronutrient meal context on postprandial vascular health. Therefore, we examined whether manipulating the lipid droplet size distribution within a mixed-macronutrient meal impacts vascular-inflammatory and thrombotic parameters.

METHODS AND RESULTS

In a randomised and counterbalanced fashion, sixteen adults (8 males; age 34 ± 7 years; BMI of 25.3 ± 4.5 kg/m²) completed three separate fasted morning-time feeding challenges, each separated by a minimum washout of 7-days. On each occasion, test-meals matched for carbohydrate and protein content differing only in fat amount and the lipid droplet size distribution were administered, such that participants consumed (1) a low-fat meal (LF) with negligible fat content, (2) an emulsified-high-fat meal with a fine lipid droplet size (FE), or (3) an emulsified-high-fat meal with a coarse lipid droplet size (CE). Periodic blood samples were retrospectively analysed for plasma triglycerides, tumour necrosis factor alpha (TNFα), tissue factor (TF), fibrinogen, and plasminogen activator inhibitor-1 (PAI-1). Triglyceride concentrations increased rapidly overtime under FE (P-time<0.05); this rise was attenuated under CE (P-time>0.05) and was comparable to LF (P-condition>0.05). Similarly, FE induced a significant rise in TNFα, TF, fibrinogen, and PAI-1 (P-time<0.05); these parameters remained unchanged under LF and CE (P-time>0.05).

CONCLUSION

A high-fat mixed-macronutrient meal with a larger lipid droplet size distribution ameliorates the associated rise in vascular-inflammatory and thrombotic parameters.

TRIAL REGISTRATION

ISRCTN88881254.

Slow digestion-oriented dietary strategy to sustain the secretion of GLP-1 for improved glucose homeostasis

Dysregulated glucose metabolism is associated with many chronic diseases such as obesity and type 2 diabetes mellitus (T2DM), and strategies to restore and maintain glucose homeostasis are essential to health. The incretin hormone of glucagon-like peptide-1 (GLP-1) is known to play a critical role in regulating glucose homeostasis and dietary nutrients are the primary stimuli to the release of intestinal GLP-1. However, the GLP-1 producing enteroendocrine L-cells are mainly distributed in the distal region of the gastrointestinal tract where there are almost no nutrients to stimulate the secretion of GLP-1 under normal situations. Thus, a dietary strategy to sustain the release of GLP-1 was proposed, and the slow digestion property and dipeptidyl peptidase IV (DPP-IV) inhibitory activity of food components, approaches to reduce the rate of food digestion, and mechanisms to sustain the release of GLP-1 were reviewed. A slow digestion-oriented dietary approach through encapsulation of nutrients, incorporation of viscous dietary fibers, and enzyme inhibitors of phytochemicals in a designed whole food matrix will be implemented to efficiently reduce the digestion rate of food nutrients, potentiate their distal deposition and a sustained secretion of GLP-1, which will be beneficial to improved glucose homeostasis and health.

New insights into in vivo gastroduodenal digestion of oil-in-water emulsions: gastric stability and in vitro digestion modeling

In this paper, effect of emulsion stability on gastroduodenal emptying/secretion was reviewed and differentiated. Moreover, novel perspectives on physiology of gastric lumen, duodenum, and gall bladder were achieved using mathematical models, being useful for designing artificial digestive systems. In this regard, numerical data for dynamic gastric emptying/secretion were offered for gastric-stable and gastric-unstable emulsion intakes. It was shown that alterations in human gastric and duodenal volume follow, respectively, linear and sinusoidal curves, with high correlation coefficients (r² > 0.93). For both emulsions, about 30-40 mL ingesta discharged rapidly from stomach upon ingestion; However, further gastric emptying was regulated for the rest of digestion period, so that 0.1 mL/min oil was passing through duodenum. Intragastric evacuation of both emulsions started with a lag phase during which stomach stored secretions incrementally by slow gastric discharge. Lag phase ended with fat layering, when emptying considerably enhanced. This reduction was gradual for stable emulsion while unstable emulsion experienced a rapid emptying before slow declining trend. Along with initial gastric emptying, 87% of gallbladder content discharged into duodenum, prolonged up to the gradual reduction phase of stomach. Supplementary investigations are needed to quantify gastroduodenal secretions, particularly pepsin and pancreas in response to emulsion ingesta.

Effect of Nutrient and Micronutrient Intake on Chylomicron Production and Postprandial Lipemia

Postprandial lipemia, which is one of the main characteristics of the atherogenic dyslipidemia with fasting plasma hypertriglyceridemia, low high-density lipoprotein cholesterol and an increase of small and dense low-density lipoproteins is now considered a causal risk factor for atherosclerotic cardiovascular disease and all-cause mortality. Postprandial lipemia, which is mainly related to the increase in chylomicron production, is frequently elevated in individuals at high cardiovascular risk such as obese or overweight patients, type 2 diabetic patients and subjects with a metabolic syndrome who share an insulin resistant state. It is now well known that chylomicron production and thus postprandial lipemia is highly regulated by many factors such as endogenous factors: circulating factors such as hormones or free fatty acids, genetic variants, circadian rhythms, or exogenous factors: food components, dietary supplements and prescription drugs. In this review, we focused on the effect of nutrients, micronutrients and phytochemicals but also on food structure on chylomicron production and postprandial lipemia.

Effect of the food form and structure on lipid digestion and postprandial lipaemic response

As the food matrix is a determinant of the rate of fat digestion and absorption, it is important for the modulation of postprandial triglyceridaemia. High postprandial triglyceride levels are associated with an increase in inflammation, oxidative stress, an imbalance in the lipoprotein profile and an increase in the risk of developing chronic diseases. This study was designed to assess the in vitro digestion patterns and the postprandial lipaemic responses to test foods with the same nutrient composition but differing in the form and structure. A liquid, a semi-solid and a solid test food with the same nutrient and energy composition were designed. The digestion profiles of the three foods were assessed using a dynamic in vitro model. The foods were also consumed by healthy young adults who donated blood samples after an overnight fast and again 0.5, 1, 2, 3, 4 and 6 h after consuming each of the test foods and who were also assessed for appetite sensations. The solid food showed phase separation during gastric digestion and a lower release of fatty acids during intestinal digestion than the liquid and semi-solid foods. During the postprandial feeding experiments, the solid food caused a lower increase in serum triglycerides than the liquid food and produced higher fullness and satisfaction. In conclusion, the food form and structure modulated fat release, postprandial triglyceridaemia and appetite sensations independent of the nutrient and energy content. Thus, manipulation of the food structure and form may be used in designing strategies for improving metabolic markers and satiety.

Oral administration of lipid oil-in-water emulsions performed with synthetic or protein-type emulsifiers differentially affects post-prandial triacylglycerolemia in rats

In this study, we compared the impact of administration of size-calibrated lipid emulsions prepared with either synthetic or natural emulsifiers on the post-absorptive plasma triacylglycerol responses in rats. We did this using four types of size-calibrated (10 μm diameter) and metastable (3 days) emulsions with 20% of an oleic acid-rich sunflower oil and 1% of either synthetic emulsifiers (Tween 80 or sodium 2-stearoyl-lactylate) or two proteins (β-lactoglobulin or sodium caseinate). An oral fat tolerance test was performed in fasted rats by oral administration of each of these formulations in continuous or emulsified forms. Kinetic parameters (AUC_0-inf., AUC_0-6h, C_max, T_max, and T_1/2) for the description of the plasma triacylglycerol responses were calculated. AUC_0-6h and AUC_0-inf. calculated for the protein groups were significantly lower than those of the control and the synthetic groups. These lower values were associated with significant decreases in the C_max, exacerbated by the emulsion form and with marked decreases in the T_max as compared to the control group. T_1/2 values were differentially affected by the lipid administration forms and by the nature of the emulsifiers. As compared with the control group, T_1/2 was largely increased in the sodium stearoyl-2-lactylate group, but on the contrary, largely lowered in the casein group. We concluded that the use of proteins as natural emulsifiers in lipid emulsions decreased the magnitude of post-prandial triacylglycerolemia for the same amount of ingested lipids, when the emulsion size is controlled for. Proteins could be a promising alternative to the widespread use of synthetic emulsifiers in the food industry.

Bidirectional Relationship between Gastric Emptying and Plasma Glucose Control in Normoglycemic Individuals and Diabetic Patients

Gastric emptying and glycemic control pathways are closely interrelated processes. Gastric chyme is transferred into the duodenum with velocities depending on its solid or liquid state, as well as on its caloric and nutritional composition. Once nutrients enter the intestine, the secretion of incretins (hormonal products of intestinal cells) is stimulated. Among incretins, glucagon-like peptide-1 (GLP-1) has multiple glycemic-regulatory effects that include delayed gastric emptying, thus triggering a feedback loop lowering postprandial serum glucose levels. Glycemic values also influence gastric emptying; hyperglycemia slows it down, and hypoglycemia accelerates it, both limiting glycemic fluctuations. Disordered gastric emptying in diabetes mellitus is understood today as a complex pathophysiological condition, with both irreversible and reversible components and high intra- and interindividual variability of time span and clinical features. While limited delays may be useful for reducing postprandial hyperglycemias, severely hindered gastric emptying may be associated with higher glycemic variability and worsened long-term glycemic control. Therapeutic approaches for both gastric emptying and glycemic control include dietary modifications of meal structure or content and drugs acting as GLP-1 receptor agonists. In the foreseeable future, we will probably witness a wider range of dietary interventions and more incretin-based medications used for restoring both gastric emptying and glycemic levels to nearly physiological levels.

Differential impact of the cheese matrix on the postprandial lipid response: a randomized, crossover, controlled trial

Background: In a simulated gastrointestinal environment, the cheese matrix modulates dairy fat digestion. However, to our knowledge, the impact of the cheese matrix on postprandial lipemia in humans has not yet been evaluated.Objective: In healthy subjects, we compared the impact of dairy fat provided from firm cheese, soft cream cheese, and butter on the postprandial response at 4 h and on the incremental area under the curve (iAUC) of plasma triglycerides.Design: Forty-three healthy subjects were recruited to this randomized, crossover, controlled trial. In random order at intervals of 14 d and after a 12-h fast, subjects ingested 33 g fat from a firm cheese (young cheddar), a soft cream cheese (cream cheese), or butter (control) incorporated into standardized meals that were matched for macronutrient content. Plasma concentrations of triglycerides were measured immediately before the meal and 2, 4, 6, and 8 h after the meal.Results: Cheddar cheese, cream cheese, and butter induced similar increases in triglyceride concentrations at 4 h (change from baseline: +59%, +59%, and +62%, respectively; P = 0.9). No difference in the triglyceride iAUC_{0-8 h} (P-meal = 0.9) was observed between the 3 meals. However, at 2 h, the triglyceride response caused by the cream cheese (change from baseline: +44%) was significantly greater than that induced by butter (change from baseline: +24%; P = 0.002) and cheddar cheese (change from baseline: +16%; P = 0.0004). At 6 h, the triglyceride response induced by cream cheese was significantly attenuated compared with that induced by cheddar cheese (change from baseline: +14% compared with +42%; P = 0.0004).Conclusion: This study demonstrates that the cheese matrix modulates the impact of dairy fat on postprandial lipemia in healthy subjects. This trial was registered at clinicaltrials.gov as NCT02623790.

Postprandial lipemia: factoring in lipemic response for ranking foods for their healthiness

One of the limitations for ranking foods and meals for healthiness on the basis of the glycaemic index (GI) is that the GI is subject to manipulation by addition of fat. Postprandial lipemia, defined as a rise in circulating triglyceride containing lipoproteins following consumption of a meal, has been recognised as a risk factor for the development of cardiovascular disease and other chronic diseases. Many non-modifiable factors (pathological conditions, genetic background, age, sex and menopausal status) and life-style factors (physical activity, smoking, alcohol and medication use, dietary choices) may modulate postprandial lipemia. The structure and the composition of a food or a meal consumed also plays an important role in the rate of postprandial appearance and clearance of triglycerides in the blood. However, a major difficulty in grading foods, meals and diets according to their potential to elevate postprandial triglyceride levels has been the lack of a standardised marker that takes into consideration both the general characteristics of the food and the food’s fat composition and quantity. The release rate of lipids from the food matrix during digestion also has an important role in determining the postprandial lipemic effects of a food product. This article reviews the factors that have been shown to influence postprandial lipemia with a view to develop a novel index for ranking foods according to their healthiness. This index should take into consideration not only the glycaemic but also lipemic responses.