Improved accuracy and robustness of electron density profiles from JET's X-mode frequency-modulated continuous-wave reflectometers.

JET's frequency-modulated continuous wave (FMCW) reflectometers have been operating well with the current design since 2005, and density profiles have been automatically calculated intershot since then. However, the calculated profiles had long suffered from several shortcomings: poor agreement with other diagnostics, sometimes inappropriately moving radially by several centimeters, elevated levels of radial jitter, and persistent wriggles (strong unphysical oscillations). In this research, several techniques are applied to the reflectometry data analysis, and the shortcomings are significantly improved. Starting with improving the equilibrium reconstruction that estimates the background magnetic field, adding a ripple correction in the reconstructed magnetic field profile, and adding new inner-wall reflection positions estimated through ray-tracing, these changes not only improve the agreement of reconstructed profiles to other diagnostics but also solve density profile wriggles that were present during band transitions. Other smaller but also persistent wriggles were also suppressed by applying a localized correction to the measured beat frequency where persistent oscillations are present. Finally, the burst analysis method, as introduced by Varela et al. [Nucl. Fusion 46 S693 (2006)], has been implemented to extract the beat frequency from stacked spectrograms. Due to the strong suppression of spurious reflections, the radial jitter that sometimes would span several centimeters has been strongly reduced. The stacking of spectrograms has also been shown to be very useful for stacking recurring events, like small gas puff modulations, and extracting transport coefficients that would otherwise be below the noise level.

Initial progress of the magnetic diagnostics of the MAST-U tokamak.

MAST Upgrade has just begun its third physics campaign in April of 2023. The set of magnetic probes used to diagnose the magnetic field and currents on MAST Upgrade are described, and their calibration procedures are outlined including calculation of uncertainties. The median uncertainty in the calibration factors of the flux loops and pickup coils are calculated as 1.7% and 6.3%. The arrays of installed instability diagnostics are described, and the detection and diagnosis of a specimen MHD mode are demonstrated. Plans for the improvement of the magnetics arrays are outlined.

The effects of the DASH dietary pattern on clinical outcomes and quality of life in adults with uncontrolled asthma: Design and methods of the ALOHA Trial.

BACKGROUND: Poor diet quality is an important risk factor for increased asthma prevalence and poor asthma control. To address the question of whether adults with asthma can benefit from following a healthy diet, this trial will test the efficacy and mechanisms of action of a behavioral intervention promoting the Dietary Approaches to Stop Hypertension (DASH) dietary pattern with sodium reduction among patients with uncontrolled asthma. METHODS: In this 2-arm randomized clinical trial, 320 racially/ethnically and socioeconomically diverse adults with uncontrolled asthma on standard controller therapy will be randomized to either a control or an intervention group and assessed at baseline, 3, 6 and 12 months. Control and intervention participants will receive education on lung health, asthma, and other general health topics; additionally, the intervention group will receive DASH behavioral counseling over 12 months. The primary hypothesis is that the DASH behavioral intervention, compared with the education-only control, will lead to significantly more participants with minimum clinically important improvement (responders) in asthma-specific quality of life at 12 months. Secondary hypotheses will test the intervention effects on other asthma (e.g., asthma control, lung function) and non-asthma outcomes (e.g., quality of life). Additionally, therapeutic (e.g., short chain fatty acids, cytokines) and nutritional biomarkers (e.g., dietary inflammatory index, carotenoids) will be assessed to understand the mechanisms of the intervention effect. CONCLUSION: This trial can substantially advance asthma care by providing rigorous evidence on the benefits of a behavioral dietary intervention and mechanistic insights into the role of diet quality in asthma. CLINICALTRIALS: gov #: NCT05251402.

Feasibility and acceptability of a remotely-delivered behavioural health coaching intervention to limit gestational weight gain.

INTRODUCTION: Gestational weight gain (GWG) and postpartum weight retention (PPWR) are significant, potentially modifiable, contributors to women's future weight and health trajectories. There is a need for feasible and patient-centered (i.e., convenient, remotely-delivered, technology-enhanced, and accessible through the prenatal care setting) behavioural interventions that limit GWG and PPWR. This study tests the feasibility and acceptability of a remotely-delivered behavioural health coaching intervention to limit gestational weight gain and postpartum weight retention. METHODS: Pregnant women (11-16 weeks gestation) were recruited from two prenatal clinics and randomized to the active intervention or health education comparison group. Completion of the program was monitored and perceived helpfulness was rated (0-100). RESULTS: Twenty-six women were randomized (n = 13 per arm; mean age = 31.6 years, SD = 3.6; mean BMI = 26.7 kg/m2, SD = 7.4). Participants completed a median of 18 coaching calls and 16/19 learning activities during pregnancy, and a median of 6 calls and 5/6 learning activities postpartum. They logged weights at least once/week for a median of 36/38 expected weeks and tracked daily calories and exercise for a median of 154/266 days and 72/266 days, respectively. Median (Q1, Q3) helpfulness ratings of the program during pregnancy were 80 (64, 91) and 62 (50, 81) postpartum; helpfulness ratings of coaching calls were 85 (58, 98). At 37 weeks gestation, 77% of participants achieved IOM weight gain recommendations compared to 54% in the comparison group. CONCLUSIONS: This study provides evidence for the feasibility and acceptability of a remotely-delivered behavioural weight control intervention in pregnancy and postpartum.

Long-term retention in an employer-based, commercial weight-loss programme.

The aim of this study is to examine factors associated with long-term retention in a commercial weight-loss programme. We conducted a retrospective analysis of an employer-based, commercial programme from 2013 to 2016. Our dependent variable was 'long-term retention', defined as continuously enrolled participants who actively engaged through coach calls at 6 and 12 months. Independent variables included baseline demographics, programme engagement and weight change. We conducted multivariate logistic regression analyses assessing for differences in long-term retention by several factors, adjusted for employer clustering. Overall, 68.3% were retained at 6% and 45.9% at 12 months. Greater number of coach calls and website logins during the first 3 months significantly increased the odds of long-term retention, while having chronic conditions significantly decreased the odds. Weight-loss success (≥5% loss at 6 months) was significantly associated with increased odds of retention (12-month: odds ratio [OR] 2.80, P < 0.001), while early weight-loss failure (≥0% weight change at 1 month) significantly decreased odds of retention (12-month: OR 0.66, P = 0.008). In an employer-based, commercial weight loss programme, greater early programme engagement was associated with long-term retention. Given these programmes' popularity and potential reach, our results could be used to develop and test strategies designed to improve retention in commercial weight-loss programmes.

Factors associated with early dropout in an employer-based commercial weight-loss program.

OBJECTIVE: Minimizing program dropout is essential for weight-loss success, but factors that influence dropout among commercial programs are unclear. This study's objective was to determine factors associated with early dropout in a commercial weight-loss program. METHODS: A retrospective analysis of a remotely delivered, employer-based commercial program from 2013 to 2016 was conducted. The dependent variable was 'early dropout', defined as enrollees who disengaged from telephone coaching by month 2's end. Independent variables included demographics, program website engagement and early weight change. Multivariate logistic regression analyses were used to assess for differences in early dropout by several factors, adjusted for employer clustering. RESULTS: Of the 5,274 participants, 26.8% dropped out early. Having ≥1 chronic condition (odds ratio [OR] 1.41, p < 0.001) and 'weight-loss failure' defined as ≥0% weight change at month 1's end (OR 1.86, p < 0.001) had significantly increased odds of early dropout. Increasing age by 10-year intervals (OR 0.90, p = 0.002) and 'meeting the website login goal' defined as ≥90 logins in 3 months (OR 0.13, p < 0.001) significantly decreased the odds of early dropout. CONCLUSIONS: Presence of comorbidities, less online engagement and weight-loss failure were associated with early dropout in a commercial program. Strategies to prevent dropout among high-risk participants, such as increased support or program tailoring, should be developed and tested.

Effects of dietary carbohydrate on 1,5-anhydroglucitol in a population without diabetes: results from the OmniCarb trial.

AIMS: To determine the effects of dietary changes in amount and type of carbohydrate on 1,5-anhydroglucitol levels. METHODS: We conducted an ancillary study to a completed, randomized clinical trial in overweight and obese adults without diabetes (N=159). Using a crossover design, participants were fed each one of four diets in turn for 5 weeks, with 2-week washout periods inbetween. The four diets were: high glycaemic index (≥65) with high proportion of carbohydrate (58% kcal) (GC); low glycaemic index (GI≤45) with low proportion of carbohydrate (40% kcal) (gc); low glycaemic index with high proportion of carbohydrate (gC); and high glycaemic index with low proportion of carbohydrate (Gc). Plasma 1,5-anhydroglucitol levels were measured at baseline and after each feeding period. RESULTS: At baseline, participants had a mean age of 53 years (53% women, 52% non-Hispanic black, 50% obese). Their mean fasting glucose and 1,5-anhydroglucitol levels were 97 mg/dl (5.4 mmol/l) and 18.6 µg/mL (113.3 µmol/l), respectively. Compared with baseline, each of the four diets reduced 1,5-anhydroglucitol by a range of -2.4 to -3.7 µg/mL (-14.6 to -22.5 µmol/l); all P <0.001). Reducing either glycaemic index or proportion of carbohydrate lowered 1,5-anhydroglucitol levels. These effects were additive, such that reducing both glycaemic index and proportion of carbohydrates decreased 1,5-anhydroglucitol by -1.31 µg/mL [95% CI: -1.63, -0.99; P<0.001 or -8.0 (-9.9, -6.0) µmol/l]. Furthermore, these effects were confirmed in a subgroup of participants with 12-h glucose monitoring and no documented hyperglycaemia (fasting glucose <160 mg/dl or 8.9 mmol/l). CONCLUSIONS: Both type and amount of dietary carbohydrate affect 1,5-anhydroglucitol plasma concentrations in adults without diabetes. This finding contradicts the long-standing notion that 1,5-anhydroglucitol remains at constant concentrations in the blood in the absence of hyperglycaemic excursions. (Clinical trials registry number: NCT00051350).

Does vaginal delivery mitigate or strengthen the intergenerational association of overweight and obesity? Findings from the Boston Birth Cohort.

BACKGROUND/OBJECTIVES: The intergenerational association of obesity may be driven by mother-to-newborn transmission of microbiota at birth. Yet cesarean delivery circumvents newborn acquisition of vaginal microbiota, and has been associated with greater childhood adiposity. Here we examined the independent and joint associations of maternal pre-pregnancy body mass index (BMI; kg m-2) and delivery mode with childhood overweight or obesity. SUBJECTS/METHODS: We prospectively followed 1441 racially and ethnically diverse mother-child dyads in the Boston Birth Cohort until age 5 years (range: 2.0-8.0 years). We used logistic regression to examine the independent and joint associations of delivery mode (cesarean and vaginal delivery) and pre-pregnancy BMI with childhood overweight or obesity (age-sex-specific BMI ⩾85th percentile). RESULTS: Of 1441 mothers, 961 delivered vaginally and 480 by cesarean. Compared with vaginally delivered children, cesarean delivered children had 1.4 (95% confidence interval (CI) 1.1-1.8) times greater odds of becoming overweight or obese in childhood, after adjustment for maternal age at delivery, race/ethnicity, education, air pollution exposure, pre-pregnancy BMI, pregnancy weight gain and birth weight. Compared with children born vaginally to normal weight mothers, after multivariable adjustment, odds of childhood overweight or obesity were highest in children born by cesarean delivery to obese mothers (odds ratio (OR): 2.8; 95% CI: 1.9-4.1), followed by children born by cesarean delivery to overweight mothers (OR: 2.2; 95% CI: 1.5-3.2), then children born vaginally to obese mothers (OR: 1.8; 95% CI: 1.3-2.6) and finally children born vaginally to overweight mothers (OR: 1.7; 95% CI: 1.2-2.3). CONCLUSIONS: In our racially and ethnically diverse cohort, cesarean delivery and pre-pregnancy overweight and obesity were associated with childhood overweight or obesity. Needed now are prospective studies that integrate measures of the maternal and infant microbiome, and other potentially explanatory covariates, to elucidate the mechanisms driving this association and to explore whether exposure to vaginal microbiota in cesarean delivered newborns may be an innovative strategy to combat the intergenerational cycle of obesity.

Sex-specific associations of birth weight with measures of adiposity in mid-to-late adulthood: the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil).

BACKGROUND/OBJECTIVES: To investigate sex-specific associations of birth weight with body mass index (BMI), waist circumference (WC) and waist-to-hip ratio (WHR) in mid-to-late adulthood. SUBJECTS/METHODS: ELSA-Brasil is a multicenter cohort study of adults aged 35-74 years affiliated with universities or research institutions of six capital cities in Brazil. After exclusions, we investigated 11 636 participants. Socio-demographic factors and birth weight were obtained by interview. All anthropometry was directly measured at baseline. We categorized birth weight as low (⩽2.5 kg); normal (2.5-4 kg) and high (⩾4 kg). We performed analysis of covariance (ANCOVA) for continuous outcomes and ordinal logistic regression for categorical adiposity outcomes. We examined interaction on the multiplicative scale by sex and by race. RESULTS: High birth weight uniformly predicted greater overall and central obesity in men and women. However, low (vs normal) birth weight, in ANCOVA models adjusted for participant age, family income, race, education, maternal education, and maternal and paternal history of diabetes, was associated with lower BMI, WC and WHR means for men, but not for women (Pinteraction=0.01, <0.0001 and <0.0001, respectively). In similarly adjusted ordinal logistic regression models, odds of obesity (odds ratio (OR)=0.65, 0.46-0.90) and of being in the high (vs low) tertile of WC (OR=0.66, 0.50-0.87) and of WHR (OR=0.79, 0.60-1.03) were lower for low (vs normal) birth weight men, but trended higher (BMI: OR=1.18, 0.92-1.51; WC: OR=1.21, 0.97-1.53; WHR: OR=1.44, 1.15-1.82) for low (vs normal) birth weight women. CONCLUSIONS: In this Brazilian sample of middle-aged and elderly adults who have lived through a rapid nutritional transition, low birth weight was associated with adult adiposity in a sex-specific manner. In men, low birth weight was associated with lower overall and central adult adiposity, while in women low birth weight was generally associated with greater central adiposity.

Overlapping expression of serotonin transporters and neurokinin-1 receptors in posttraumatic stress disorder: a multi-tracer PET study.

The brain serotonergic system is colocalized and interacts with the neuropeptidergic substance P/neurokinin-1 (SP/NK1) system. Both these neurochemical systems have independently been implicated in stress and anxiety, but interactions between them might be crucial for human anxiety conditions. Here, we examined the serotonin and substance P/neurokinin-1 (SP/NK1) systems individually as well as their overlapping expression in 16 patients with posttraumatic stress disorder (PTSD) and 16 healthy controls. Participants were imaged with the highly selective radiotracers [(11)C]-3-amino-4-(2-dimethylaminomethylphenylsulfanyl)-benzonitrile (DASB) and [(11)C]GR205171 assessing serotonin transporter (SERT) and NK1 receptor availability, respectively. Voxel-wise analyses in the amygdala, our a priori-defined region of interest, revealed increased number of NK1 receptors, but not SERT in the PTSD group. Symptom severity, as indexed by the Clinician-administered PTSD Scale, was negatively related to SERT availability in the amygdala, and NK1 receptor levels moderated this relationship. Exploratory, voxel-wise whole-brain analyses revealed increased SERT availability in the precentral gyrus and posterior cingulate cortex of PTSD patients. Patients, relative to controls, displayed lower degree of overlapping expression between SERT and NK1 receptors in the putamen, thalamus, insula and lateral orbitofrontal gyrus, lower overlap being associated with higher PTSD symptom severity. Expression overlap also explained more of the symptomatology than did either system individually, underscoring the importance of taking interactions between the neurochemical systems into account. Thus, our results suggest that aberrant serotonergic-SP/NK1 couplings contribute to the pathophysiology of PTSD and, consequently, that normalization of these couplings may be therapeutically important.

Increased neurokinin-1 receptor availability in the amygdala in social anxiety disorder: a positron emission tomography study with [11C]GR205171.

The neurokinin-1 (NK1) receptor is abundantly expressed in the fear circuitry of the brain, including the amygdala, where it modulates stress and anxiety. Despite its proposed involvement in psychopathology, only a few studies of NK1 receptor availability in human subjects with anxiety disorders exist. Here, we compared NK1 receptor availability in patients with social anxiety disorder (SAD; n = 17) and healthy controls (n = 17) using positron emission tomography and the radiotracer [11C]GR205171. The Patlak Graphical plot using a cerebellar reference region was used to model the influx parameter, Ki measuring NK1 receptor availability. Voxel-wise statistical parametric mapping analyses revealed increased NK1 receptor availability specifically in the right amygdala in SAD patients relative to controls. Thus, we demonstrate that exaggerated social anxiety is related to enhanced NK1 receptor availability in the amygdala. This finding supports the contribution of NK1 receptors not only in animal models of stress and anxiety but also in humans with anxiety disorders.

Perceived helpfulness of the individual components of a behavioural weight loss program: results from the Hopkins POWER Trial.

BACKGROUND: Behavioural weight loss programs are effective first-line treatments for obesity and are recommended by the US Preventive Services Task Force. Gaining an understanding of intervention components that are found helpful by different demographic groups can improve tailoring of weight loss programs. This paper examined the perceived helpfulness of different weight loss program components. METHODS: Participants (n = 236) from the active intervention conditions of the Practice-based Opportunities for Weight Reduction (POWER) Hopkins Trial rated the helpfulness of 15 different components of a multicomponent behavioural weight loss program at 24-month follow-up. These ratings were examined in relation to demographic variables, treatment arm and weight loss success. RESULTS: The components most frequently identified as helpful were individual telephone sessions (88%), tracking weight online (81%) and coach review of tracking (81%). The component least frequently rated as helpful was the primary care providers' general involvement (50%). Groups such as older adults, Blacks and those with lower education levels more frequently reported intervention components as helpful compared with their counterparts. DISCUSSION: Weight loss coaching delivered telephonically with web support was well received. Findings support the use of remote behavioural interventions for a wide variety of individuals.

Association between amygdala reactivity and a dopamine transporter gene polymorphism.

Essential for detection of relevant external stimuli and for fear processing, the amygdala is under modulatory influence of dopamine (DA). The DA transporter (DAT) is of fundamental importance for the regulation of DA transmission by mediating reuptake inactivation of extracellular DA. This study examined if a common functional variable number tandem repeat polymorphism in the 3' untranslated region of the DAT gene (SLC6A3) influences amygdala function during the processing of aversive emotional stimuli. Amygdala reactivity was examined by comparing regional cerebral blood flow, measured with positron emission tomography and [(15)O]water, during exposure to angry and neutral faces, respectively, in a Swedish sample comprising 32 patients with social anxiety disorder and 17 healthy volunteers. In a separate US sample, comprising 85 healthy volunteers studied with blood oxygen level-dependent functional magnetic resonance imaging, amygdala reactivity was assessed by comparing the activity during exposure to threatening faces and neutral geometric shapes, respectively. In both the Swedish and the US sample, 9-repeat carriers displayed higher amygdala reactivity than 10-repeat homozygotes. The results suggest that this polymorphism contributes to individual variability in amygdala reactivity.

Effects of the DASH diet on blood pressure in patients with and without metabolic syndrome: results from the DASH trial.

In the Dietary Approach to Stop Hypertension (DASH) trial, the DASH diet reduced blood pressure (BP) in a diverse sample of US adults. Subsequent analyses of this trial documented the efficacy of the DASH diet in several subgroups. Although subgroup analyses in individuals with metabolic syndrome (MS) have not been performed, the DASH diet has been recommended in MS patients. This paper is a subgroup analysis of the DASH trial, in which we examined the effect of study diets on BP in participants with and without MS. Participants were stratified according to MS status (99 with MS, 311 without MS (Non-MS)). The trial was a dietary intervention study in which participants were randomized to receive a control diet, a diet rich in fruits and vegetables, or the DASH diet. Outcomes were (i) the difference in BP between the end and the beginning of intervention and (ii) control of hypertension. We found no significant interaction between MS status and diet assignment on BP (each P-interaction >0.05). In the MS subgroup, the DASH diet compared with the control diet reduced systolic BP by 4.9 mm Hg (P=0.006) and diastolic BP by 1.9 mm Hg (P=0.15). In the Non-MS subgroup, corresponding net BP reductions were 5.2 mm Hg (P<0.001) and 2.9 mm Hg (P<0.001), respectively. The DASH diet controlled hypertension in 75% of hypertensive participants with MS (adjusted odds ratio=9.5 vs the control diet, P=0.05). In conclusion, the DASH diet similarly reduces BP in those with and without MS. Our findings provide direct evidence for existing recommendations.

Behavioral mediators of treatment effects in the weight loss maintenance trial.

BACKGROUND: The Weight Loss Maintenance Trial tested strategies for maintenance of weight loss. Personal contact was superior to interactive technology and self-directed conditions. PURPOSE: We aimed to identify behavioral mediators of the superior effect of personal contact vs. interactive technology and of personal contact vs. self-directed arms. METHODS: Overweight/obese adults at risk for cardiovascular disease (n = 1,032) who lost at least 4 kg were randomized to personal contact, interactive technology, or self-directed. After 30 months, 880 participants had data on weight and behavioral strategies. RESULTS: Reported increase of intake of fruits and vegetables and physical activity and more frequent self-weighing met criteria as mediators of the better outcome of personal contact vs. interactive technology. Increased intake of fruits and vegetables, more frequent self-weighing, and decreased dessert consumption were mediators of the difference between personal contact vs. self-directed. CONCLUSION: Inducing changes in the identified behaviors might yield better outcomes in future weight loss maintenance trials.

Patient-reported outcomes in the practice-based opportunities for weight reduction (POWER) trial.

PURPOSE: To evaluate effects of two behavioral weight-loss interventions (in-person, remote) on health-related quality of life (HRQOL) compared to a control intervention. METHODS: Four hundred and fifty-one obese US adults with at least one cardiovascular risk factor completed five measures of HRQOL and depression: MOS SF-12 physical component summary (PCS) and mental component summary; EuroQoL-5 dimensions single index and visual analog scale; PHQ-8 depression symptoms; and PSQI sleep quality scores at baseline and 6 and 24 months after randomization. Change in each outcome was analyzed using outcome-specific mixed-effects models controlling for participant demographic characteristics. RESULTS: PCS-12 scores over 24 months improved more among participants in the in-person active intervention arm than among control arm participants (P < 0.05, ES = 0.21); there were no other statistically significant treatment arm differences in HRQOL change. Greater weight loss was associated with improvements in most outcomes (P < 0.05 to < 0.0001). CONCLUSIONS: Participants in the in-person active intervention improved more in physical function HRQOL than participants in the control arm did. Greater weight loss during the study was associated with greater improvement in all PRO except for sleep quality, suggesting that weight loss is a key factor in improving HRQOL.

Branched-chain amino acid levels are associated with improvement in insulin resistance with weight loss.

AIMS/HYPOTHESIS: Insulin resistance (IR) improves with weight loss, but this response is heterogeneous. We hypothesised that metabolomic profiling would identify biomarkers predicting changes in IR with weight loss. METHODS: Targeted mass spectrometry-based profiling of 60 metabolites, plus biochemical assays of NEFA, ß-hydroxybutyrate, ketones, insulin and glucose were performed in baseline and 6 month plasma samples from 500 participants who had lost ≥4 kg during Phase I of the Weight Loss Maintenance (WLM) trial. Homeostatic model assessment of insulin resistance (HOMA-IR) and change in HOMA-IR with weight loss (∆HOMA-IR) were calculated. Principal components analysis (PCA) and mixed models adjusted for race, sex, baseline weight, and amount of weight loss were used; findings were validated in an independent cohort of patients (n = 22). RESULTS: Mean weight loss was 8.67 ± 4.28 kg; mean ∆HOMA-IR was -0.80 ± 1.73, range -28.9 to 4.82). Baseline PCA-derived factor 3 (branched chain amino acids [BCAAs] and associated catabolites) correlated with baseline HOMA-IR (r = 0.50, p < 0.0001) and independently associated with ∆HOMA-IR (p < 0.0001). ∆HOMA-IR increased in a linear fashion with increasing baseline factor 3 quartiles. Amount of weight loss was only modestly correlated with ∆HOMA-IR (r = 0.24). These findings were validated in the independent cohort, with a factor composed of BCAAs and related metabolites predicting ∆HOMA-IR (p = 0.007). CONCLUSIONS/INTERPRETATION: A cluster of metabolites comprising BCAAs and related analytes predicts improvement in HOMA-IR independent of the amount of weight lost. These results may help identify individuals most likely to benefit from moderate weight loss and elucidate novel mechanisms of IR in obesity.

The effects of dietary patterns on plasma renin activity: results from the Dietary Approaches to Stop Hypertension trial.

A diet rich in fruits, vegetables and low-fat dairy products, and reduced in saturated fat, total fat and cholesterol (the 'DASH' diet) significantly lowers blood pressure (BP). Previous studies have documented that certain therapies that lower BP increase plasma renin activity (PRA). Using data from the Dietary Approaches to Stop Hypertension (DASH) trial, we assessed the effects of dietary patterns on PRA and determined the relationship of change in PRA with change in BP on each diet. After eating a control diet for 3 weeks, participants were then randomized to receive for 8 weeks: the control diet, a diet rich in fruits and vegetables (F/V), or the DASH diet. Baseline and follow-up levels of PRA were available in 381 participants. Compared with the control diet, the DASH diet increased PRA by 0.37 ng ml(-1) h(-1) (P=0.01). In multivariable linear regression analyses, there was an inverse association of PRA change with systolic BP change on the control diet (slope=-0.35, P=0.001), but PRA did not differ by BP change on the F/V diet (slope=-0.002, P=0.98) or DASH diet (slope=-0.08, P=0.32). These data suggest that a blunted counter-regulatory response of the renin-angiotensin system is associated with the BP-lowering effect of the F/V and DASH diets.