Kacie Dickinson

Effects of a low-salt diet on flow-mediated dilatation in humans

BACKGROUND The effect of salt reduction on vascular function, assessed by brachial artery flow-mediated dilatation (FMD), is unknown. OBJECTIVE Our aim was to compare the effects of a low-salt (LS; 50 mmol Na/d) diet with those of a usual-salt (US; 150 mmol Na/d) diet on FMD. DESIGN This was a randomized crossover design in which 29 overweight and obese normotensive men and women followed an LS diet and a US diet for 2 wk. Both diets had similar potassium and saturated fat contents and were designed to ensure weight stability. After each intervention, FMD, pulse wave velocity, augmentation index, and blood pressure were measured. RESULTS FMD was significantly greater (P = 0.001) with the LS diet (4.89 +/- 2.42%) than with the US diet (3.37 +/- 2.10%), systolic blood pressure was significantly (P = 0.02) lower with the LS diet (112 +/- 11 mm Hg) than with the US diet (117 +/- 13 mm Hg), and 24-h sodium excretion was significantly lower (P = 0.0001) with the LS diet (64.1 +/- 41.3 mmol) than with the US diet (156.3 +/- 56.7 mmol). There was no correlation between change in FMD and change in 24-h sodium excretion or change in blood pressure. No significant changes in augmentation index or pulse wave velocity were observed. CONCLUSIONS Salt reduction improves endothelium-dependant vasodilation in normotensive subjects independently of the changes in measured resting clinic blood pressure. These findings suggest additional cardioprotective effects of salt reduction beyond blood pressure reduction. The trial is registered with the Australian and New Zealand Clinical Trials Registry (unique identifier: ANZCTR12607000381482; http://www.anzctr.org.au/trial_view.aspx?ID=82159).

Endothelial function is impaired after a high-salt meal in healthy subjects

BACKGROUND Dietary salt is related to blood pressure (BP), and cardiovascular disease and increased sodium intakes have been shown to impair vascular function. The effect of salt on endothelial function postprandially is unknown. OBJECTIVE The aim was to investigate the postprandial effect of dietary salt on endothelial function as measured by flow-mediated dilatation (FMD) and peripheral arterial tonometry in healthy subjects. DESIGN Sixteen healthy, normotensive subjects received a meal with added salt (HSM; 65 mmol Na) and a control low-salt meal (LSM; 5 mmol Na) on 2 separate occasions in a randomized order. Endothelial function was measured while fasting and postprandially at 30, 60, 90, and 120 min by using FMD and reactive hyperemia peripheral arterial tonometry. BP was also measured. RESULTS Baseline FMD, reactive hyperemia index (RHI), and BP values were similar across interventions. Overall FMD was reduced 2 h postprandially. FMD was significantly more impaired after the HSM than after the LSM at 30 min [HSM (mean ± SD): 3.39 ± 2.44%; LSM: 6.05 ± 3.21%; P < 0.01] and at 60 min (HSM: 2.20 ± 2.77%; LSM: 4.64 ± 2.48%; P < 0.01). No significant differences in BP or RHI were observed between meals. CONCLUSIONS An HSM, which reflects the typical amount of salt consumed in a commonly eaten meal, can significantly suppress brachial artery FMD within 30 min. These results suggest that high salt intakes have acute adverse effects on vascular dilatation in the postprandial state. This trial was registered at www.anzctr.org.au/trial_view.aspx?ID=335115 as ACTRN12610000124033.

A reduction of 3 g/day from a usual 9 g/day salt diet improves endothelial function and decreases endothelin-1 in a randomised cross_over study in normotensive overweight and obese subjects

BACKGROUND AND AIM It is unclear if a modest reduction in dietary salt intake has beneficial effects on vascular function. The aim was to compare the effects of 9 g salt/day with 6 g salt/day intake on measures of vascular function and explore mechanisms of effect in overweight and obese adults. METHODS Twenty-five overweight/obese subjects (BMI 27-40 kg/m(2)) completed a randomised cross-over study of 6 weeks each on a reduced salt (RS) (6 g/day) and usual salt diet (US) (9 g/day). Flow-mediated-dilatation (FMD), 24 h blood pressure (BP), augmentation index (AIx), pulse wave velocity (PWV), plasma and urinary nitrate/nitrite, asymmetric dimethylarginine (ADMA), renin, aldosterone and endothelin-1 and vascular adhesion molecules were measured after 2 days and 6 weeks. Adherence to the diets was determined from two 24 h urine collections. RESULTS Urinary sodium excretion was 155 ± 58 mmol/24 h US vs 113 ± 45 mmol/24 h RS (p = 0.002). Following the RS diet there was a significant improvement in FMD from 3.5 ± 2.8% to 5.6 ± 2.8% (P < 0.001) and decrease in serum endothelin-1 from 1.45 ± 0.38 pg/ml to 1.25 ± 0.39 pg/ml (P < 0.05). Endothelium-independent vasodilatation was also significantly different between treatments (P < 0.05). AIx, PWV, serum ADMA and plasma and urinary nitrate/nitrite concentrations were not different between treatments. Change in FMD was related to the urinary sodium: creatinine ratio (r = -0.47, P < 0.05) and was independent of blood pressure. Aldosterone and renin were unchanged. CONCLUSIONS A small reduction in dietary salt intake of 3 g/day improves endothelial function in normotensive overweight and obese subjects. This response may be mediated by serum endothelin-1. This small reduction in salt had no effect on aldosterone and renin concentrations. This trial was registered with the Australian and New Zealand Clinical Trials Registry Unique Identifier: ACTRN12609000321246 http://www.anzctr.org.au/ACTRN12609000321246.aspx.

Postprandial effects of a high salt meal on serum sodium, arterial stiffness, markers of nitric oxide production and markers of endothelial function

AIM The aim of the study was to determine if a high salt meal containing 65 mmol Na causes a rise in sodium concentrations and a reduction in plasma nitrate/nitrite concentrations (an index of nitric oxide production). Secondary aims were to determine the effects of a high salt meal on augmentation index (AIx) a measure of arterial stiffness and markers of endothelial function. METHODS AND RESULTS In a randomised cross-over study 16 healthy normotensive adults consumed a low sodium soup containing 5 mmol Na and a high sodium soup containing 65 mmol Na. Sodium, plasma nitrate/nitrite, endothelin-1 (ET-1), C-reactive protein (CRP), vasopressin (AVP) and atrial natriuretic peptide (ANP) concentrations before and every 30 min after the soup for 2 h. Blood pressure (BP) and AI were also measured at these time points. There were significant increases in serum sodium, osmolality and chloride in response to the high sodium meal. However plasma nitrate/nitrite concentrations were not different between meals (meal p = 0.812; time p = 0.45; meal × time interaction p = 0.50). Plasma ANP, AVP and ET-1 were not different between meals. AI was significantly increased following the high sodium meal (p = 0.02) but there was no effect on BP. CONCLUSIONS A meal containing 65 mmol Na increases serum sodium and arterial stiffness but does not alter postprandial nitrate/nitrite concentration in healthy normotensive individuals. Further research is needed to explore the mechanism by which salt affects vascular function in the postprandial period. This trial was registered with the Australian and New Zealand Clinical Trials Registry Unique Identifier: ACTRN12611000583943http://www.anzctr.org.au/trial_view.aspx?ID=343019.

Validation of a Brief Dietary Assessment Tool for Estimating Dietary EPA and DHA Intake in Australian Adults at Risk of Cardiovascular Disease.

Background: Short food frequency questionnaires (FFQs) are powerful screening instruments for estimating nutrient intakes and play an important role in risk stratification in vulnerable populations. Omega-3 fatty acids are of increasing importance in the prevention of chronic and degenerative disease, especially in older adults who are at higher risk of these chronic conditions. A short FFQ exists to rapidly assess omega-3 intake from marine sources, however it has not previously been validated for agreement with total omega-3 intake and ability to identify suboptimal omega-3 intakes in older adults or for use in Australia. Objective: The aim of the study was to validate a 9-item marine omega-3 FFQ (MFQ) for assessment of omega-3 intake against a validated 74-item semiquantitative FFQ. Methods: One hundred and eight participants (mean age 67 ± 10 years, 47% male) completed the MFQ designed to estimate omega-3 intake from marine sources and the 74-item FFQ designed to estimate usual omega-3 and total energy intake in addition to other nutrients. To test agreement between the two questionnaires for estimating total omega-3 intake, mean bias and 95% limits of agreement (LOA) were calculated. Sensitivity and specificity were assessed using 2 × 2 contingency tables based on whether participants did or did not meet National Heart Foundation (NHF) recommendations for omega-3 intake per day. Results: Mean intake of omega-3 estimated from the MFQ was 210 ± 235 mg/day compared with 295 ± 260 mg/day as estimated by the FFQ. Mean bias (95% LOA) for omega-3 assessed by the two questionnaires was 89 mg/day (−475 mg to 653 mg). The MFQ achieved 98% sensitivity and 31% specificity for the omega-3 cut-off of 500 mg/day. When nutrient composition of the marine products were replaced with Australian data, mean intake of omega-3 was 230 ± 253 mg and the mean bias improved to 64 mg (−681 mg to 553 mg) and achieved 93% sensitivity and 40% specificity. Conclusions: The MFQ shows promise as a rapid screening tool for identifying older adults with intakes of omega-3 fatty acids likely to be below recommendations for chronic and degenerative disease risk reduction. Given the clinically meaningful mean bias and wide LOA, it cannot be recommended as an appropriate tool for the purpose of reporting average intake of individuals. Use of Australian nutrient data improved the mean bias of the tool in estimating total omega-3 intake. The values should be replaced and the MFQ could then be a useful tool for research purposes at the population level.

Eating occasions and the contribution of foods to sodium and potassium intakes in adults

OBJECTIVE To examine dietary Na and K intake at eating occasions in Australian adults and identify the contribution of major food sources to Na and K at different eating occasions. DESIGN Secondary analysis of 24 h recall diet data from the Australian Health Survey (2011-2013). SETTING Nationally representative survey in Australia. SUBJECTS Male and female Australians aged 18-84 years (n 7818). RESULTS Dinner contributed the greatest proportion to total daily Na intake (33 %) and K intake (35 %). Na density was highest at lunch (380 mg/MJ) and K density highest at between-meal time eating occasions (401 mg/MJ). Between-meal time eating occasions provided 20 % of daily Na intake and 26 % of daily K intake. The major food group sources of Na were different at meal times (breads and mixed dishes) compared with between-meal times (cakes, muffins, scones, cake-type desserts). The top food group sources of K at meal times were potatoes and unprocessed meat products and dishes. CONCLUSIONS Foods which contributed to Na and K intake differed according to eating occasion. Major food sources of Na were bread and processed foods. Major food sources of K were potatoes and meat products and dishes. Public health messages that emphasise meal-based advice and diet patterns high in vegetables, fruits and unprocessed foods may also aid reduction in dietary Na intake and increase in dietary K intake.

The Dirt on Clean Eating: A Cross Sectional Analysis of Dietary Intake, Restrained Eating and Opinions about Clean Eating among Women

Clean eating is understood in broad terms to be an approach to eating which promotes the exclusion of processed foods. Social media and websites which promote clean eating are becoming increasingly popular as sources of nutrition information. Currently, there is a lack of knowledge regarding women’s opinions about clean eating sites and their influence on eating behaviour. The aim of the present study was to investigate differences in dietary intake, dietary restraint and opinions about clean eating between women who had, and women who had never adhered to dietary advice from clean eating sites. Using a cross-sectional survey design, women (n = 762) ranging in age from 17–55 completed a self-report questionnaire on eating behaviour and beliefs about clean eating. Findings showed that 25.5% of the sample adhered to dietary advice from a clean eating site sometimes, often or very often. A significantly higher proportion of women who had adhered to dietary advice from clean eating sites met dietary guidelines for the consumption of fruit, meats and alternatives compared to women who had seldom or never adhered. Adherers also had significantly higher levels of restrained eating and were more positive about clean eating in general in comparison to those who seldom or never adhered. Results provide new information about exposure to clean eating sites and how they may influence women’s eating practices. These preliminary findings suggest additional studies are required to better understand the influence of clean eating sites, particularly with regard to whether the information on such sites are from reputable sources and to what degree their recommendations may be problematic for individuals with eating concerns.

The effect of dietary sodium modification on blood pressure in studies of subjects with systolic blood pressure less than 140mmHg: a systematic review protocol

Review question/objective The objective of this review is to establish the effect of modifying dietary sodium intake in normotensive subjects. More specifically, the objectives are to identify the effect of reducing or increasing sodium intake on blood pressure in normotensive subjects with systolic blood pressure (SBP) <140mmHg, and the effect of sodium reduction or supplementation on arterial function in subjects with baseline SBP <140mmHg. Background The pressure‐natriuresis relationship that was first described by Guyton1 proposes a link between dietary sodium intake and renal sodium handling. Specifically, the hypothesis states that in a normal individual, consumption of a dietary sodium load will elicit a transient rise in blood pressure that stimulates the kidney to excrete sodium. The kidney will excrete excess sodium leading to restoration of normal blood pressure. This hypothesis explains how blood pressure is maintained over the longer term even though most individuals report day‐to‐day variation in sodium intake.1,2 Following this hypothesis, intervention studies in normotensive subjects may be expected to observe a small amount of variation in blood pressure with changes to dietary sodium intake, but this variation should be small enough to be considered clinically irrelevant. Intervention studies examining the effect of dietary sodium have reported a range of different responses from significant changes,3,4 to mild, to moderate effects on blood pressure to no effect at all.5,6 Normotensive studies that report blood pressure changes over the long‐term have previously documented changes in systolic blood pressure (SBP) ranging from ‐1mmHg7 to increases of 8.2mmHg.4 Previous systematic reviews of blood pressure response to dietary sodium restriction have used Cochrane Collaboration methods.8‐10 One such systematic review9 has been cited over 370 times, and has been used in the development of dietary guidelines.11 Two of these reviews attempted to conduct meta‐analysis by dividing subjects into normotensive and hypertensive sub‐groups.8,9 Both reviews failed to specify methods for determining whether studies recruited hypertensive or normotensive subjects and included some studies in the normotensive analyses with subjects who had baseline blood pressures above 140mmHg. Due to this, a wide range of baseline blood pressure readings and responses can be observed in normotensive analyses, which is inconsistent with Guytons pressure natriuresis hypothesis. Therefore, the validity of the findings for blood pressure changes in healthy normotensive individuals in these analyses is limited in that the majority of the included studies recruited subjects with SBP above 140mmHg.4,12‐16 Subjects with hypertension (SBP >140mmHg) have been shown to respond differently to dietary sodium and hence inclusion of these studies in previous normotensive analyses may have skewed the results.9 These analyses in “normotensive” populations could be improved if studies that recruited subjects with SBP >140mmHg were excluded. As well as examining blood pressure, a number of intervention studies have investigated the effects of dietary sodium intake on arterial function and found that these effects may be, at least partly, independent of blood pressure.17,18 As these effects may be key in extending our understanding of sodium intake and disease risk, they form part of the bigger picture for dietary sodium intake and chronic disease risk. It is therefore important to consider data on arterial function such as pulse wave analysis, pulse wave velocity, and flow mediated dilation in future meta‐analyses of sodium restriction. There is enough evidence from normotensive studies conducted in subjects with SBP≤140mmHg to conduct a separate investigation of the effects on blood pressure and arterial function. This systematic review will consider the evidence for long‐term dietary sodium restriction in subjects with SBP <140mmHg on arterial function.

Are Clean Eating Blogs a Source of Healthy Recipes? A Comparative Study of the Nutrient Composition of Foods with and without Clean Eating Claims

Food blogs are an increasingly popular source of information about food and nutrition. There is a perception that foods published on clean eating blogs, which promote unprocessed foods, are healthier than comparable foods without these claims. However, foods with these claims and their nutrient composition have not previously been evaluated. The purpose of the study was to describe the nutritional content of clean eating recipes compared to recipes without clean eating claims and the nutritional guidelines published by the World Health Organisation (WHO). Clean eating recipes were systematically selected from 13 popular clean eating blogs and were described and compared with control recipes without clean eating claims. The nutrient profiles from the included recipes were summarised and evaluated against criteria from WHO recommendations for chronic disease prevention and criteria from the U.K. Food Standards Agency. Data for 86 clean eating recipes were extracted that represented five food categories: breakfast, snacks, treats, desserts, and smoothies. These were matched with 86 control recipes without clean eating claims. The clean eating recipes, per portion, provide the equivalent of 15% of daily energy intake. The average serving sizes were not significantly different between clean eating and control recipes. Overall, the clean eating recipes contained significantly more protein (8.1 ± 7.3 g vs. 5.7 ± 4.1 g, p = 0.01), fat (15.8 ± 10.6 g vs. 12.4 ± 9.3 g, p = 0.03), and fibre (5.0 ± 4.3 g vs. 2.8 ± 2.9 g, p < 0.01) per serving than control recipes. There were no significant differences between clean eating and control recipes with respect to the energy (1280 ± 714 kJ vs. 1137 ± 600 kJ, p = 0.16), carbohydrate (31.5 ± 27.3 g vs. 33.9 ± 19.4 g, p = 0.51), sugar (21.1 ± 20.9 g vs. 23.2 ± 14.9 g, p = 0.46), and sodium content (196.7 ± 269 vs. 155.8 ± 160.8, p = 0.23). Less than 10% of clean eating and control recipes met the WHO constraints for proportions of energy from fat and sugar intake. A simulated nutrient profile of an average clean and control recipe shows that nutrients for both are similarly classified as moderate to high in fat, saturated fat, salt, and sugar. Foods with clean eating claims contained the same amount of energy, sugar, and sodium as foods without those claims. Clean eating claims are potentially misleading for consumers who may believe these foods are healthy alternatives, potentially undermining people’s efforts to eat a healthy diet.

The effect of dietary sodium modification on blood pressure in adults with systolic blood pressure less than 140 mmHg: a systematic review.

BackgroundModifying dietary sodium intake is a cornerstone of diet advice for lowering blood pressure (BP) under the assumption that it is protective against cardiovascular disease. Previous meta-analyses of normotensive participants have not excluded all studies that recruited participants with systolic blood pressure (SBP) > 140 mmHg, which greatly hinders generalization to the wider normotensive population. ObjectivesThe objective of this review was to identify the effectiveness of reducing or increasing sodium intake on BP in normotensive participants with SBP ⩽ 140 mmHg. Inclusion criteria Types of participantsThis review considered studies on adult participants (≥18 years) with SBP ⩽ 140 mmHg. Studies on pregnant women or patients prescribed antihypertensive or vasoactive medications were excluded. Types of interventionsInterventions that quantitatively evaluated dietary sodium intake for equal to or greater than four weeks duration were considered. Only studies that included two study arms comprising different levels of sodium intake were included. Types of outcomesStudies that reported SBP, diastolic blood pressure (DBP), pulse wave velocity (PWV), pulse wave analysis or flow mediated dilatation were considered. Types of studiesExperimental study designs including randomized controlled trials and non-randomized controlled trials were considered. Search strategyAn initial search strategy was conducted on databases MEDLINE and CINAHL before an extensive search of all relevant published and gray literature databases, and clinical trial registries were searched. Methodological qualityPotential papers were assessed for methodological validity using the standardized critical appraisal instrument from the Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI). Data extractionQuantitative data were extracted from papers using the standardized data extraction tool from JBI-MAStARI. Data synthesisQuantitative data were pooled in statistical meta-analysis. Effect sizes were expressed as weighted mean differences and 95% confidence intervals. Meta-analysis was conducted using a random-effect model, and heterogeneity assessed statistically using the standard Chi-square test and the I2 index. A priori sub-group analysis was undertaken on studies achieving ≥40 mmol versus <40 mmol in urinary sodium excretion and post hoc on studies with a mean body mass index (BMI) ≥ 30 versus less than 30. ResultsFive trials were included with a total of 1214 participants. The overall reduction in SBP was −0.71 mmHg (95% CI: −2.62, 1.20, P = 0.47) and DBP −0.57 mmHg (95% CI: −1.26, 0.12, P = 0.10). There was no significant change in PWV following reduction of dietary sodium over a four to six-week period. Sub-group analysis did not find a significant effect of urinary sodium excretion or BMI on outcomes; however, a trend toward a greater reduction in BP was observed in those with a higher BMI (MD −2.41, 95% CI −5.72, +0.91, P = 0.16). ConclusionBlood pressure in normotensive participants was not significantly affected by sodium modification and was controlled to within 1% of baseline values. Reducing dietary sodium in normotensive participants may still be of importance for cardiovascular risk management; however, good quality interventional research is limited.