Jill A. Metz

Factors affecting blood pressure responses to diet: The vanguard study

To study physiologic factors affecting the blood pressure (BP) response to nonpharmacologic maneuvers, fasting blood glucose, insulin, lipid and mineral levels, urinary mineral excretion, and the calcium regulating hormones parathyroid hormone (PTH) and 1,25 dihydroxyvitamin D (1,25 (OH)2D) were measured in 71 unmedicated hypertensive (26 hypertensive only [HT], 45 hypertensive hyperlipidemic [HTHL]), and 87 normotensive hyperlipidemic (NTHL) control subjects before and during a 10-week multicenter, randomized controlled trial comparing a prepared meal plan (CCNW) with a self-selected diet (SSD) based on nutritionist counseling. Blood pressure fell to a greater extent in hypertensive versus normotensive subjects (-8+/-1/-5+/-1 v -2+/-1/-2+/-1 mm Hg, P < .0001/P < .0001), and on CCNW versus SSD diets (delta systolic BP [SBP]/delta diastolic BP [DBP], P = .033/P = .002). Diet-induced weight change was the strongest correlate of changes in BP (SBP: r = 0.360, P < .0001; DBP: r = 0.414, P < .0001), which, on multivariate analysis for deltaSBP, could partly be accounted for by diet-induced changes in fasting glucose (r = 0.215, P = .009) and cholesterol (r = 0.219, P = .006) levels. Independently of weight, diet-induced changes in SBP also were significantly related to concomitant changes in urinary excretion of potassium (r = -0.285, P = .001), magnesium (r = -0.254, P = .003), and calcium relative to sodium (r = -0.200, P = .021), but not to sodium per se; and to changes in serum potassium (r = -0.249, P = .002), phosphorus (r = -0.279, P = .001), PTH (r = 0.288, P = .0006), and 1,25 D (r = 0.202, P = .017). We conclude that the ability of diet to lower BP successfully may result from the additive contributions of multiple components. Independently of weight loss and the associated changes in circulating glucose and cholesterol, BP is influenced by the increasing provision of minerals such as potassium, magnesium, and calcium, perhaps by virtue of their suppressive effects on circulating vasoactive calcium regulating hormones.

Blood pressure and calcium intake are related to bone density in adult males

Based on the premise that elevated blood pressure and low bone mass have both been associated with poor Ca nutriture and disturbances in Ca metabolism, a cross-sectional study was employed to determine if blood pressure and dietary Ca intake were significantly related to bone mass. Forty-seven men between 24-77 years of age with blood pressure values ranging from normal to mildly elevated comprised the study group. Blood pressure was measured with a random-zero sphygmomanometer. Bone mineral content (BMC) and density (BMD) of the hip, spine and total body were measured with dual-photon absorptiometry. Dietary intake and physical activity were also assessed. Multiple linear regression analysis was used for statistical analysis. After adjusting for known confounding variables (age, BMI, Ca intake, and others) diastolic blood pressure was negatively related to BMC (P < or = 0.05) and BMD (P < or = 0.01) of the total body, trochanteric region (P < 0.01) and Wards triangle (P < 0.05), and to BMC of the femoral neck (P < 0.05) and lumbar spine, although the latter was just shy of statistical significance (P = 0.058). Systolic blood pressure was negatively related to trochanteric BMD (P = 0.04) and BMC (P = 0.06). Ca intake was positively related to total body BMD (P = 0.005), and BMC of the lumbar spine (P = 0.05). In this population of men, Ca intake was a positive predictor, and blood pressure was a negative predictor of regional measures of bone mass. These findings support the concept that independent of age, BMI and Ca intake, elevated blood pressure varies indirectly with bone mass and density, known predictors of osteoporotic fractures. Future studies are needed to determine whether elevated blood pressure is causally related to the development of low bone mass, and what role dietary Ca plays in that pathway.

Bone Mineral Density in Spontaneous Hypertension: Differential Effects of Dietary Calcium and Sodium

Dietary calcium and sodium have been postulated to modify both bone mineral status and blood pressure regulation in humans and animals. The spontaneously hypertensive rat (SHR) manifests several defects in calcium metabolism that may contribute to its hypertension. Blood pressure and bone mineral status were measured in SHR and normotensive Wistar-Kyoto rats (WKY) as a marker of whole animal calcium metabolism. In addition, the effect of alterations in dietary calcium and sodium on bone status were examined. At 6 weeks of age, seven male SHR and seven male WKY were placed on a control diet. At the same age, 28 SHR and 28 WKY were randomized to four diets containing either 2.0% or 0.1% calcium and 1.0% or 0.25% sodium. Four markers of bone mineral status were analyzed: bone density measured by direct photon absorptiometry, and total bone calcium, phosphorus, and magnesium content measured by atomic absorption spectrophotometry. The SHR exhibited significantly lower levels (p less than 0.001) of bone density and bone magnesium content than the WKY, whereas bone phosphorus and calcium did not differ between the two strains. The 2.0% calcium diets resulted in increased bone density and bone calcium content, and lower bone magnesium in both strains. The 1.0% sodium diets were associated with decreased bone density in the SHR, but not in the WKY. These findings identify another indicator of disturbed calcium metabolism in the SHR that may be related to impaired renal calcium handling. They are consistent with previously reported reductions in renal calcium reabsorption and decreased intestinal calcium transport in older SHR.

Dietary calcium alters blood pressure reactivity in spontaneously hypertensive rats.

Plasma catecholamines and blood pressure reactivity were investigated in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats maintained on three levels of dietary calcium: low (0.1%), intermediate (1.0%), or high (2.0%). In the SHR, restricted dietary calcium resulted in elevations of mean arterial pressure that were most pronounced during handling and restraint stress (p < 0.05). There was no difference between SHR on intermediate and high calcium diets and no dietary effects in the WKY rats. Resting and stressed levels of circulating catecholamines did not differ across diet conditions in either strain. The SHR on low calcium diets had significantly larger pressor responses to infused norepinephrine (p < 0.05). There were no differences between the rats on intermediate and high calcium diets. The results indicate that differences observed in blood pressure reactivity across diets in this study may have been a consequence of altered postsynaptic sensitivity rather than an increase in norepinephrine release.

Psychosocial stress, dietary calcium and hypertension in the spontaneously hypertensive rat

The interactive effects of psychosocial stress and diet on the development of hypertension were investigated in spontaneously hypertensive rats. Psychosocial stress, produced through manipulation of group housing conditions, was evaluated at three levels of dietary calcium and sodium: Low (0.1% Ca2+, 0.25% Na+), Intermediate (1.0% Ca2+, 0.45% Na+), and High (2.0% Ca2+, 1.0% Na+). After 13 weeks of exposure, stressed animals had higher blood pressure and lower serum ionized calcium than nonstressed animals across all diets. Likewise, animals on the low diet had higher blood pressures and lower ionized calcium values than animals on normal or high diets regardless of stress condition. The combination of stress and low diet produced the highest blood pressure and lowest serum ionized calcium values. The results suggest that stress both independently and in combination with dietary Ca2+ altered calcium metabolism. The interaction between psychosocial stress and dietary factors appears to contribute to reductions in serum ionized calcium and elevations in blood pressure in this experimental model of genetic hypertension.

Comprehensive Nutrition Plan Improves Cardiovascular Risk Factors in Essential Hypertension

Increased arterial pressure is known to be influenced by a variety of nutrients. Compliance with dietary recommendations for risk reduction is often limited by the complexity of their implementation. In addition, how improvements in total diet, rather than single nutrients, influence concomitant cardiovascular risk factors has not been thoroughly explored. We assessed the effects of a nutritionally complete prepared meal program, the Campbells Center for Nutrition and Wellness plan (CCNW), compared with dietary therapy in which participants received a structured nutritional assessment and prescription and selected their own foods, in 101 women and men with mild-to-moderate hypertension. Outcome measures included blood pressure (BP), lipids and lipoproteins, glucose, glycosylated hemoglobin (HbA1c), insulin, homocysteine, nutrient intake, compliance, and quality of life. Both dietary interventions significantly lowered BP (P < .0001), while simultaneously improving the overall cardiovascular risk profile. Significantly greater benefits were observed with the CCNW plan as compared with the participant selected diet in cholesterol and LDL levels (both P < .0001), LDL:HDL (P < .001), HbA1c (P < .05), homocysteine (P < .001), total nutrient intake (P < .0001), compliance (P < .0001), and quality of life (P < .001). This study demonstrates that improving the total diet to include the full array of recommended dietary guidelines, rather than focusing on single nutrients, has significant benefits for the cardiovascular risk profile of hypertensive persons beyond BP control. Compared with typical dietary therapy, the comprehensive CCNW meal plan has significantly greater effects on multiple cardiovascular risk factors while yielding greater compliance and improved quality of life.

Genetic variability in response to dietary calcium

Supplemental dietary calcium has been shown to reduce blood pressure in spontaneously hypertensive rats while restricted calcium diets cause an elevation in blood pressure. This latter nutrient effect has been enhanced by modest sodium restriction and is associated with a reduction in serum ionized calcium concentration. To determine whether alterations of dietary calcium and sodium have a similar influence on blood pressure in genetically normotensive rats, Fisher 344, Wistar Furth, and ACI rats were fed either a low (0.1%) calcium, low (0.25%) sodium diet or normal (1.0%) calcium, normal sodium (0.45%) diet from 4 weeks of age through 29 weeks of age. Indirect measurements of systolic blood pressure showed that only the Fisher 344 rats consistently responded to the low calcium/low sodium diets with an elevation of blood pressure. There was considerable variation in serum electrolytes across strains in the normal diets but all three strains experienced a reduction in ionized calcium and an elevation in phosphorus and magnesium on the restricted diets. In the Fisher 344 rats there were significant (p less than .05) inverse correlations among systolic blood pressure and serum ionized and total calcium concentrations and positive correlations among systolic blood pressure, phosphorus, and magnesium. There was no significant correlation between serum electrolytes and blood pressure in the other two strains. The data indicate that there is genetic variability in the blood pressure response to alterations in dietary calcium and sodium. The pattern of change in serum electrolytes across strains suggests that diet-induced alterations of serum electrolytes, specifically calcium, are not necessarily predictive of a pressor response. It would appear that some other calcium-sensitive physiological process involved in blood pressure regulation must respond differentially to calcium availability across strains.

Blood Pressure Reduction in the Long-Term Cardiovascular Risk Reduction Dietary Intervention Trial

Abstract As a follow-up in a series of studies designed to test the effect of a risk-reducing prepared meal plan on CVD endpoints in patients with CVD risk factors, this year-long study was designed to determine the long-term effects on blood pressure (BP) of a prepared meal plan (PMP) compared to a usual care self-selected diet (SSD). In a multi-center trial, 220 participants aged 25-70 with marginally controlled hypertension and dyslipidemia were randomized to either: 1) usual care SSD (n= 110) or 2) nutrient-fortified PMP (n=110). Both plans were designed to provide (as % energy) 22% fat, 17% protein and 61% carbohydrate. Supine systolic (SBP) and diastolic (DBP) blood pressure was measured at baseline (BL), week 12, and at the end of 26 weeks. ANOVA with repeated measures was used to determine changes in BP (mean change ±SD) from BL within and between diets through 6 months of intervention (interim data are shown):PMPSSDweek12week26week12week26SBP−12.4±10.6−15.0±9.9−8.1±9.1−8.8±10.9DBP−8.0±6.5−9.3±6.6−4.9±6.4−6.5±6.7Baseline BP was 146/91 and 147/88 for the PMP and SSD respectively (p=ns). Within diets, SBP and DBP were reduced from BL in both groups (p

Predicting Dietary Compliance with Step I and II Dietary Guidelines in Patients With CVD Risk Factors.

Abstract LEARNING OUTCOME: To identify factors predictive of dietary compliance in patients with CVD risk factors. The goal of this study was to identify factors predictive of dietary compliance in individuals with marginally controlled hypertension, dyslipidemia or NIDDM following two therapeutic dietary interventions. In a multicenter trial, 560 participants aged 25-70 were randomized to either: 1) a nutritionist-guided self-selected mixed-food plan (SSD; n=277) or 2) a nutrient-fortified prepared meal plan (PMP; n=283). Both plans provided (as % energy) 17% fat, 21% protein and 62% carbohydrate. Dietary intake and compliance with Step I and II guidelines was estimated with 3-day food records throughout the 10-week trial. Compliance with Step I was achieved by 97% of the PMP group compared to 73% of SSD, whereas Step II compliance was 81% vs. 41% respectively. Logistic regression was used to compute odds of compliance for each variable in the model. Treatment group was the strongest predictor of compliance, with the PMP 15.3 times as likely to achieve STEP I and 7.5 times as likely to achieve Step II compliance compared to the SSD (p

Feasibility of Meeting NCEP/AHA Dietary Guidelines in Patients with Cardiovascular Disease Risk Factors

Abstract LEARNING OUTCOME : To assess the feasibility of meeting the NCEP/AHA Step 1/2 dietary guidelines in patients with CVD risk factors. The NCEP/AHA dietary guidelines have been recommended for the majority of the American population as a means to prevent or treat cardiovascular disease. However, the feasibility of achieving these guidelines has not been extensively tested. The objective of this study was to determine the health effects and feasibility of achieving the Step 1/2 dietary guidelines of two 10-week dietary interventions designed to treat individuals with marginally controlled hypertension, dyslipidemia or NIDDM. In a multi-center trial, 548 participants aged 25-70 were randomized to one of the following intervention groups: 1) a dietitian-guided self-selected mixed-food plan (SS; n=274) or, 2) a proprietary prepared nutrient-fortified meal plan (CCNW; n=274). Both prescribed plans provided (% kcal) 17% fat, 21% protein and 62% carbohydrate. Mean nutrient values and % meeting Step 1/2 guidelines at the end of treatment are shown (%kcal):