Dairy cheese consumption ameliorates single-meal sodium-induced cutaneous microvascular dysfunction by reducing ascorbate-sensitive oxidants in healthy older adults

Whole milk dairy foods and cardiometabolic health: dairy fat and beyond

Bovine dairy milk is a nutrient-rich matrix, but consumption of full-fat dairy food varieties has been claimed historically to be associated with poorer cardiometabolic health, a notion often attributed to the saturated fat content. However, continued investigation that includes observational studies and randomized controlled trials (RCTs) provide evidence that favorably supports full-fat dairy foods and their bioactive components on cardiometabolic health. This review addresses this controversy by examining the evidence surrounding full-fat dairy foods and their implications for human health. Dairy foods are heterogeneous, not just in their fat content but also in other compositional aspects within and between fermented (e.g., yogurt, cheese) and nonfermented products (e.g., milk) that could differentially influence cardiometabolic health. Drawing from complementary lines of evidence from epidemiological studies and RCTs, this review describes the health effects of dairy foods regarding their fat content, as well as their polar lipids that are concentrated in the milk fat globule fraction. Observational studies have limitedly supported the consumption of full-fat dairy to protect against cardiometabolic disorders. However, this framework has been disputed by RCTs indicating that dairy foods, regardless of their fat content or fermentation, are not detrimental to cardiometabolic health and may instead alleviate certain cardiometabolic risk factors. As dietary recommendations evolve, which currently indicate to avoid full-fat dairy foods, it is essential to consider the totality of evidence, especially from RCTs, while also recognizing that investigation is needed to evaluate the complexity of dairy foods within diverse dietary patterns and their impacts on cardiometabolic health.

Whole-Milk Dairy Foods: Biological Mechanisms Underlying Beneficial Effects on Risk Markers for Cardiometabolic Health

Lifestyle modifications that include adherence to healthy dietary patterns that are low in saturated fat have been associated with reduced risk for cardiovascular disease, the leading cause of death globally. Whole-milk dairy foods, including milk, cheese, and yogurt, are leading sources of saturated fat in the diet. Dietary guidelines around the world recommend the consumption of low-fat and fat-free dairy foods to obtain overall healthy dietary patterns that help meet nutrient recommendations while keeping within recommended calorie and saturated fat limitations. A body of observational and clinical evidence indicates, however, that whole-milk dairy food consumption, despite saturated fat content, does not increase the risk for cardiovascular disease. This review describes the proposed biological mechanisms underlying inverse associations between whole-milk dairy food consumption and risk markers for cardiometabolic health, such as altered lipid digestion, absorption, and metabolism; influence on the gut microflora; and regulation of oxidative stress and inflammatory responses. The dairy food matrix, a term used to describe how the macronutrients and micronutrients and other bioactive components of dairy foods are differentially packaged and compartmentalized among fluid milk, cheese, and yogurt, may dictate how each affects cardiovascular risk. Current evidence indicates consideration of dairy foods as complex food matrices, rather than delivery systems for isolated nutrients, such as saturated fatty acids, is warranted.

Cheese consumption and multiple health outcomes: an umbrella review and updated meta-analysis of prospective studies

This umbrella review aims to provide a systematic and comprehensive overview of current evidence from prospective studies on the diverse health effects of cheese consumption. We searched PubMed, Embase, and Cochrane Library to identify meta-analyses/pooled analyses of prospective studies examining the association between cheese consumption and major health outcomes from inception to August 31, 2022. We reanalyzed and updated previous meta-analyses and performed de novo meta-analyses with recently published prospective studies, where appropriate. We calculated the summary effect size, 95% prediction confidence intervals, between-study heterogeneity, small-study effects, and excess significance bias for each health outcome. We identified 54 eligible articles of meta-analyses/pooled analyses. After adding newly published original articles, we performed 35 updated meta-analyses and 4 de novo meta-analyses. Together with 8 previous meta-analyses, we finally included 47 unique health outcomes. Cheese consumption was inversely associated with all-cause mortality (highest compared with lowest category: RR = 0.95; 95% CI: 0.92, 0.99), cardiovascular mortality (RR = 0.93; 95% CI: 0.88, 0.99), incident cardiovascular disease (CVD) (RR = 0.92; 95% CI: 0.89, 0.96), coronary heart disease (CHD) (RR = 0.92; 95% CI: 0.86, 0.98), stroke (RR = 0.93; 95% CI: 0.89, 0.98), estrogen receptor-negative (ER-) breast cancer (RR = 0.89; 95% CI: 0.82, 0.97), type 2 diabetes (RR = 0.93; 95% CI: 0.88, 0.98), total fracture (RR = 0.90; 95% CI: 0.86, 0.95), and dementia (RR = 0.81; 95% CI: 0.66, 0.99). Null associations were found for other outcomes. According to the NutriGrade scoring system, moderate quality of evidence was observed for inverse associations of cheese consumption with all-cause and cardiovascular mortality, incident CVD, CHD, and stroke, and for null associations with cancer mortality, incident hypertension, and prostate cancer. Our findings suggest that cheese consumption has neutral to moderate benefits for human health.

The effect of acute intradermal administration of ascorbate on heat loss responses in older adults with uncomplicated controlled hypertension

NEW FINDINGS

What is the central question of this study? Does acute intradermal administration of the antioxidant ascorbate augment local forearm cutaneous vasodilatation and sweating via nitric oxide synthase (NOS)-dependent mechanisms during exercise-heat stress in older adults with uncomplicated controlled hypertension? What is the main finding and its importance? Relative to control site, ascorbate had no effect on forearm cutaneous vascular conductance (CVC) and sweat rate, although CVC was reduced with NOS-inhibition in older adults with hypertension. We showed that acute local administration of ascorbate to forearm skin does not modulate heat loss responses during exercise-heat stress in older adults with hypertension.

ABSTRACT

Nitric oxide synthase (NOS) contributes to the heat loss responses of cutaneous vasodilatation and sweating during exercise. However, the contribution of NOS may be attenuated in individuals with uncomplicated, controlled hypertension due to elevated oxidative stress, which can reduce NO bioavailability. We evaluated the hypothesis that the acute local intradermal administration of the antioxidant ascorbate would enhance cutaneous vasodilatation and sweating via NOS-dependent mechanisms during an exercise-heat stress in adults with hypertension. Habitually active adults who were normotensive (n = 14, 7 females, 62 ± 4 years) or had uncomplicated, controlled hypertension (n = 13, 6 females, 62 ± 5 years) performed 30-min of moderate-intensity (50% of their pre-determine peak oxygen uptake) semi-recumbent cycling in the heat (35°C, 20% relative humidity). Cutaneous vascular conductance and sweat rate were assessed at four forearm skin sites continuously perfused with either: 1) lactated Ringer (Control), 2) 10 mM antioxidant ascorbate, 3) 10 mM L-NAME, a non-selective NOS inhibitor, or 4) a combination of ascorbate and L-NAME. Relative to Control, no effect of ascorbate was observed on cutaneous vascular conductance or sweating in either group (P = 0.619). However, L-NAME reduced cutaneous vascular conductance relative to Control in both groups (P ≤ 0.038). No effect of any treatment on sweating was observed (P ≥ 0.306). Thus, acute local administration of ascorbate to forearm skin does not enhance the activation of heat loss responses of cutaneous vasodilatation and sweating in older adults, and those with hypertension during an exercise-heat stress (236/250 words) This article is protected by copyright. All rights reserved.

Association between dairy consumption and ischemic heart disease among Chinese adults: a prospective study in Qingdao

BACKGROUND

Previous studies linking dairy consumption with ischemic heart disease (IHD) are almost from western countries, with little from China. The present study was to explore the relationship between dairy consumption and IHD among Chinese adults.

METHODS

The data for the present study was from the prospective cohort study of China Kadoorie Biobank in Qingdao, a total of 33,355 participants in the present study. An interviewer-administered laptop-based questionnaire was used to collect information on the consumption frequency of dairy, incident IHD cases were identified through Disease Surveillance Point System and the new national health insurance databases. Cox regression analyses were performed to estimate adjusted hazard ratios (HRs) and confidence interval for the relationship between the incidence of IHD and dairy consumption.

RESULTS

The baseline survey reported that 32.4% of males and 34.6% of females consumed dairy regularly (i.e. ≥ 4 days/week). Over an average of 9.2 years follow-up, 2712 new-onset IHD were documented. Compared with participants who never or rarely consume dairy, the HR of consumed dairy regularly was 0.85(0.73-0.98) for males (P < 0.05), while no significant benefits were identified for females.

CONCLUSIONS

Regular dairy consumption had an inverse association to the onset of IHD among males, with no similar findings for females.

Dairy Foods and Dairy Fats: New Perspectives on Pathways Implicated in Cardiometabolic Health

Low-fat and nonfat dairy products have been promoted as part of a healthy dietary pattern by both US dietary guidelines and professional organizations for several decades. The basis for this recommendation stems in part from the putative negative cardiometabolic effects associated with saturated fat consumption. However, as nutrition research has shifted from a single nutrient to a whole-food/dietary pattern approach, the role of dairy foods and dairy fat in the diet-disease relationship is being reexamined. Most observational and experimental evidence does not support a detrimental relationship between full-fat dairy intake and cardiometabolic health, including risks of cardiovascular disease and type 2 diabetes. Indeed, an expanded understanding of the dairy food matrix and the bioactive properties of dairy fats and other constituents suggests a neutral or potentially beneficial role in cardiometabolic health. To consider how consuming dairy foods, including full-fat dairy, is associated with cardiometabolic health, this review provides an innovative perspective on mechanisms that link dairy consumption to 3 main biological systems at the core of metabolic health, the gastrointestinal, hepatic, and vascular systems.

Controlled Feeding of an 8-d, High-Dairy Cheese Diet Prevents Sodium-Induced Endothelial Dysfunction in the Cutaneous Microcirculation of Healthy, Older Adults through Reductions in Superoxide

BACKGROUND

While excess dietary sodium impairs vascular function by increasing oxidative stress, the dietary incorporation of dairy foods improves vascular health. We demonstrated that single-meal cheese consumption ameliorates acute, sodium-induced endothelial dysfunction. However, controlled feeding studies examining the inclusion of cheese, a dairy product that contains both bioactive constituents and sodium, are lacking.

OBJECTIVES

We tested the hypothesis that microcirculatory endothelium-dependent dilation (EDD) would be impaired by a high-sodium diet, but a sodium-matched diet high in dairy cheese would preserve EDD through oxidant stress mechanisms.

METHODS

We gave 11 adults without salt-sensitive blood pressure (<10 mmHg Δ mean arterial pressure; 64 ± 2 y) 4 separate 8-d controlled dietary interventions in a randomized, crossover design: a low-sodium, no-dairy intervention (LNa; 1500 mg/d sodium); a low-sodium, high-cheese intervention (LNaC; 1500 mg/d sodium, 170 g/d cheese); a high-sodium, no-dairy intervention (HNa; 5500 mg/d sodium); and a high-sodium, high-cheese intervention (HNaC; 5500 mg/d sodium, 170 g/d cheese). On Day 8 of each diet, EDD was assessed through a localized infusion (intradermal microdialysis) of acetylcholine (ACh), both alone and during coinfusion of NG-nitro-L-arginine methyl ester (NO synthase inhibitor), L-ascorbate (nonspecific antioxidant), apocynin [NAD(P)H oxidase inhibitor], or tempol (superoxide scavenger).

RESULTS

Compared with LNa, microvascular responsiveness to ACh was attenuated during HNa (LNa: -4.82 ± 0.20 versus HNa: -3.21 ± 0.55 M logEC50; P = 0.03) but not LNaC (-5.44 ± 0.20 M logEC50) or HNaC (-4.46 ± 0.50 M logEC50). Further, ascorbate, apocynin, and tempol administration each increased ACh-induced vasodilation during HNa only (Ringer's: 38.9 ± 2.4; ascorbate: 48.0 ± 2.5; tempol: 45.3 ± 2.7; apocynin: 48.5 ± 2.6% maximum cutaneous vascular conductance; all P values < 0.01).

CONCLUSIONS

These results demonstrate that incorporating dairy cheese into a high-sodium diet preserves EDD by decreasing the concentration of superoxide radicals. Consuming sodium in cheese, rather than in nondairy sources of sodium, may be an effective strategy to reduce cardiovascular disease risk in salt-insensitive, older adults. This trial was registered at clinicaltrials.gov as NCT03376555.

The Postprandial Appearance of Features of Cardiometabolic Risk: Acute Induction and Prevention by Nutrients and Other Dietary Substances

The purpose of this review is to provide an overview of diets, food, and food components that affect postprandial inflammation, endothelial function, and oxidative stress, which are related to cardiometabolic risk. A high-energy meal, rich in saturated fat and sugars, induces the transient appearance of a series of metabolic, signaling and physiological dysregulations or dysfunctions, including oxidative stress, low-grade inflammation, and endothelial dysfunction, which are directly related to the amplitude of postprandial plasma triglycerides and glucose. Low-grade inflammation and endothelial dysfunction are also known to cluster together with insulin resistance, a third risk factor for cardiovascular diseases (CVD) and type-II diabetes, thus making a considerable contribution to cardiometabolic risk. Because of the marked relevance of the postprandial model to nutritional pathophysiology, many studies have investigated whether adding various nutrients and other substances to such a challenge meal might mitigate the onset of these adverse effects. Some foods (e.g., nuts, berries, and citrus), nutrients (e.g., l-arginine), and other substances (various polyphenols) have been widely studied. Reports of favorable effects in the postprandial state have concerned plasma markers for systemic or vascular pro-inflammatory conditions, the activation of inflammatory pathways in plasma monocytes, vascular endothelial function (mostly assessed using physiological criteria), and postprandial oxidative stress. Although the literature is fragmented, this topic warrants further study using multiple endpoints and markers to investigate whether the interesting candidates identified might prevent or limit the postprandial appearance of critical features of cardiometabolic risk.

Acute ultraviolet radiation exposure attenuates nitric oxide-mediated vasodilation in the cutaneous microvasculature of healthy humans

5-methyltetrahydrofolate (5-MTHF) is important for nitric oxide (NO)-mediated cutaneous microvascular vasodilation. Ultraviolet B (UVB) radiation may deplete 5-MTHF, either directly or via production of reactive oxygen species (ROS), decreasing NO-mediated vasodilation. We hypothesized that 1) acute UVB exposure would attenuate NO-dependent cutaneous vasodilation, 2) local perfusion of 5-MTHF or ascorbate (ASC; anti-oxidant) would augment NO-dependent vasodilation after UVB, and 3) darker skin pigmentation would be UVB-protective. Three intradermal microdialysis fibers placed in each forearm of 21 healthy young adults (23±1 yr; 8M/13F) locally delivered lactated Ringer's (control), 5mM 5-MTHF, or 10mM ASC. One arm was UVB-exposed (300mJ/cm²), the other served as non-exposed control (CON). Following UVB exposure, a standardized local heating (42˚C) protocol induced cutaneous vasodilation. After attaining a plateau blood flow, 15mM N^G-nitro-L-arginine methyl ester (L-NAME; nitric oxide synthase inhibiter) was infused at all sites to quantify the NO contribution. Red cell flux was measured at each site by laser-Doppler flowmetry (LDF) and cutaneous vascular conductance (CVC=LDF/MAP) was expressed as a percentage of maximum (%CVC_max; 28mM sodium nitroprusside+43°C). UVB attenuated NO-mediated vasodilation compared to CON (23.1±3.6 vs 33.9±3.4 %; p=0.001). Delivery of 5-MTHF or ASC improved NO-mediated vasodilation versus lactated Ringer's in the UVB-exposed arm (MTHF: 30.1±4.8 vs 23.1±3.8 %; p=0.03; ASC: 30.9±4.3 vs 23.1±3.8 %; p=0.02). Neither treatment affected the response in the non-exposed arm (p≥0.09). Skin pigmentation (M-index) was not predictive of the UVB response (p≥0.34). These data suggest that acute UVB exposure attenuates NO-mediated vasodilation via direct and/or ROS-induced reductions in 5-MTHF, independent of skin pigmentation.

Endothelial function is impaired in the cutaneous microcirculation of adults with psoriasis through reductions in nitric oxide-dependent vasodilation

Psoriasis is an independent risk factor for cardiovascular disease; however, the underlying mechanisms are not fully understood. Deficits in conduit arterial function are evident in patients with psoriasis, but potential impairments in microcirculatory endothelial function remain unclear. We hypothesized that cutaneous microvascular dysfunction would be detectable in otherwise healthy individuals with psoriasis. Two intradermal microdialysis fibers were placed in (nonlesional) forearm skin of nine patients (3 men and 6 women, 39 ± 5 yr) with moderate (16 ± 2% of body surface area) plaque psoriasis and nine healthy (nonpsoriatic) control subjects (3 men and 6 women, 38 ± 5 yr) for local delivery of 1) lactated Ringer solution (control) and 2) 10 mM l-ascorbate (a nonspecific antioxidant). An index of skin blood flow was measured using laser-Doppler flowmetry during local heating (42°C). Nitric oxide (NO)-dependent vasodilation was directly quantified after perfusion of the nonspecific NO synthase inhibitor N^G-nitro-l-arginine methyl ester (15 mM). A third fiber was perfused with increasing concentrations (10^-10 - 10^-2 M) of norepinephrine to elicit adrenoreceptor-mediated cutaneous vasoconstriction. NO-dependent vasodilation was attenuated in patients with psoriasis (57 ± 5% and 39 ± 7% maximum cutaneous vascular conductance in control subjects and adults with psoriasis, respectively, P < 0.01). l-Ascorbate did not improve NO-dependent vasodilation ( P > 0.05). There was no group difference in maximal vasoconstriction or microvascular sensitivity to norepinephrine ( P > 0.05). These data suggest that NO bioavailability is reduced in otherwise healthy individuals with psoriasis, which contributes to systemic microvascular dysfunction. NEW & NOTEWORTHY In adults with psoriasis, reduced nitric oxide bioavailability mediates impaired endothelium-dependent vasodilation, independent of increases in oxidative stress. Furthermore, the degree of psoriatic symptomology is directly related to greater reductions in nitric oxide-dependent vasodilation.

Effects of vehicle microdialysis solutions on cutaneous vascular responses to local heating

Microdialysis is a minimally invasive technique often paired with laser Doppler flowmetry to examine cutaneous microvascular function, yet presents with several challenges, including incompatibility with perfusion of highly lipophilic compounds. The present study addresses this methodological concern, with an emphasis on the independent effects of commonly used vehicle dialysis solutions to improve solubility of pharmacological agents with otherwise low aqueous solubility. Four microdialysis fibers were placed in the ventral forearm of eight subjects (4 men, 4 women; 25 ± 1 yr) with sites randomized to serve as 1) control (lactated Ringer's), 2) Sodium carbonate-bicarbonate buffer administered at physiological pH [SCB-HCl; pH 7.4, achieved via addition of hydrochloric acid (HCl)], 3) 0.02% ethanol, and 4) 2% dimethyl sulfoxide (DMSO). After baseline (34°C), vehicle solutions were administered throughout a standardized local heating protocol to 42°C. Laser Doppler flowmetry provided an index of blood flow. Cutaneous vascular conductance was calculated and normalized to maximum (%CVC_max, sodium nitroprusside and 43°C local heat). The SCB-HCl solution increased baseline %CVC_max (control: 9.7 ± 0.8; SCB-HCl: 21.5 ± 3.5%CVC_max; P = 0.03), but no effects were observed during heating or maximal vasodilation. There were no differences with perfusion of ethanol or DMSO at any stage of the protocol ( P > 0.05). These data demonstrate the potential confounding effects of some vehicle dialysis solutions on cutaneous vascular function. Notably, this study provides evidence that 2% DMSO and 0.02% ethanol are acceptable vehicles with no confounding local vascular effects to a standardized local heating protocol at the concentrations presented. NEW & NOTEWORTHY This study examined the independent effects of common vehicle solutions on cutaneous vascular responses. A basic buffer (SCB-HCl) caused baseline vasodilation; 2% DMSO and 0.02% ethanol had no effects. This highlights the need for considering potential confounding effects of solubilizing solutions when combined with low aqueous soluble pharmacological agents. Importantly, DMSO and ethanol do not appear to influence cutaneous vascular function during baseline or local heating at the concentrations studied, allowing their use without confounding effects.