Enhancing soil organic carbon, particulate organic carbon and microbial biomass in semi-arid rangeland using pasture enclosures.

BACKGROUND: Rehabilitation of degraded rangelands through the establishment of enclosures (fencing grazing lands) is believed to improve soil quality and livelihoods, and enhance the sustainability of rangelands. Grazing dominated enclosure (GDE) and contractual grazing enclosure (CGE) are the common enclosure management systems in West Pokot County, Kenya. Under CGE, a farmer owning few animals leases the enclosure to households with relatively more livestock, while GDE is where the livestock utilizing the enclosure are purely owned by the farmer. Livestock management in both systems is via the free-range system. This study evaluated the effect of enclosure management on total soil organic carbon (SOC), particulate organic carbon (POC) and microbial biomass carbon (MBC) and nitrogen (MBN) as key indicators of soil degradation at 0-40 cm depth. The two enclosure systems were selected based on three age classes (3-10, 11-20 and > 20 years since establishment) (n = 3). The adjacent open grazing area (OGR) was used as a reference (n = 9). RESULTS: Relative to OGR, the pasture enclosures significantly decreased soil bulk density and increased the concentrations of total organic C, POC, MBC and MBN compared to the degraded OGR (P < 0.001). Significantly higher concentrations of POC and MBC was recorded in GDE than CGE (P = 0.01). The POC accounted for 24.5-29.5% of the total SOC. MBC concentrations ranged from 32.05 ± 7.25 to 96.63 ± 5.31 µg C g-1 of soil in all grazing systems, and was positively correlated with total SOC and POC (P < 0.001). The proportional increase in POC and MBC was higher in GDE (56.6 and 30.5% respectively) compared to CGE (39.2 and 13.9% for POC and MBC respectively). CONCLUSIONS: This study demonstrated that controlling livestock grazing through the establishment of pasture enclosures is the key strategy to enhance total SOC, POC, MBC, and MBN in degraded rangelands; a precondition for improving soil quality. Therefore, the establishment of enclosures is an effective restoration approach to restore degraded soils in semi-arid rangelands.

Bacterial contamination of kale (Brassica oleracea Acephala) along the supply chain in Nairobi and its environment.

OBJECTIVE: To assess the microbiological safety of kale (Brassica oleracea Acephala) produced from farms and those sold at the markets with special focus on coliforms, E.coli and Salmonella. DESIGN: A cross sectional study. SETTING: Peri-Urban farms (in Athi River, Ngong and Wangige), wet markets (in Kawangware, Kangemi and Githurai), supermarkets and high-end specialty store both within Nairobi city. RESULTS: Mean coliform count on vegetables from farms were 2.6 x 10(5) +/- 5.0 x 10(5) cfu/g while those from the wet markets were 4.6 x 10(6) +/- 9.1 x 10(6) cfu/g, supermarkets, 2.6 x 10(6) +/- 2.7 x 10(6) and high-end specialty store 4.7 x 10(5) +/- 8.9 x 10 (5). Coliform numbers obtained on kales from the wet markets and supermarkets were significantly higher (p < 0.05) compared to those from farms, while kale samples purchased from high-end specialty store had similar levels of coliform loads as those from the farms. E. coli prevalence in the wet markets, supermarkets and high-end specialty store were: 40, 20 and 20%, respectively. Salmonella was detected on 4.5 and 6.3% of samples collected from the farms in Wangige and wet market in Kawangware, respectively. Fecal coliforms in water used on farms (for irrigation) and in the markets (for washing the vegetables) exceeded levels recommended by World Health Organization (WHO) of 10(3) organisms per 100 milliliter while Salmonella was detected in 12.5% of washing water samples collected from Kangemi market. CONCLUSION: Poor cultivation practices and poor handling of vegetables along the supply chain could increase the risk of pathogen contamination thus puting the health of the public at risk, therefore good agricultural and handling practices should be observed.

Blood pressure in spontaneously hypertensive rats fed butterfat, corn oil, or fish oil.

Dietary fats have been shown to influence blood pressure in humans and animal models of hypertension. The ability of a particular fat to modulate arterial pressure appears to depend on its fatty acid profile rather than its degree of saturation or unsaturation. Little is known about the effects of specific dietary fats of animal origin on blood pressure. We tested the concurrent effects of both calcium and dietary fat on blood pressure development in the spontaneously hypertensive rat. Sixty animals were fed diets containing butterfat, fish oil, or corn oil from 3-26 weeks of age. Each diet among the three oils was further modified to contain either 0.25% or 2.0% of the diet as calcium. All six diets provided 18% of the diet (36% of the calories) as fat. The polyunsaturated-to-saturated fat ratio was 0.07, 0.84, and 4.54 for butterfat, fish oil, and corn oil, respectively. Fish oil consumption resulted in lower blood pressures compared with butterfat (p less than 0.036) or corn oil (p less than 0.0009). Similarly, butterfat feeding resulted in lower blood pressures when compared with corn oil (p less than 0.054). Supplementing the diet with calcium decreased blood pressure in both the butterfat and corn oil diets. When butterfat diets were supplemented with calcium, the resulting blood pressures did not differ significantly from those obtained with the two fish oil diets. It is concluded that butterfat, though highly saturated, is associated with less of an increase in the spontaneously hypertensive rat's blood pressure than is corn oil, which is highly unsaturated.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma lipids and hypertension: response to calcium supplementation.

Evidence from animal and human studies indicate that calcium supplementation may ameliorate two risk factors for atherosclerotic cardiovascular disease, hypertension and hyperlipidemia. We sought to characterize dietary fat consumption and plasma lipid profiles in hypertensive and normotensive subjects and plasma lipid responses to supplemental calcium. A randomized, double-blind, placebo-controlled, crossover protocol was used to assess blood pressure and lipid response to 8 wk of 1000 mg of elemental calcium in 43 hypertensive and 27 normotensive subjects. Nutrient intakes and plasma lipids were measured repeatedly. Hypertensive female subjects consumed significantly less (p less than 0.05) phosphorus, potassium, and magnesium and had significantly higher triglycerides (p less than 0.04) and lower HDL-cholesterol (p less than 0.02) than did normotensive subjects. There were no significant changes in dietary plasma lipids with calcium supplementation. Mildly hyperlipidemic normotensive subjects had a significant decrease in total cholesterol (p less than 0.05). No significant changes in plasma lipids occurred with calcium supplementation in hypertensive subjects.

Impact of increasing calcium in the diet on nutrient consumption, plasma lipids, and lipoproteins in humans.

This study examined the feasibility of increasing food-derived calcium to 1500 mg/d and the impact of this change on plasma lipids and nutrient consumption in hypertensive (n = 130) and normotensive (n = 196) participants. Three interventions were applied in a randomized, parallel, placebo-controlled fashion: 1) counseling to increase dietary calcium through food consumption to 1500 mg/d (n = 106), 2) a 1000-mg/d calcium supplement (n = 109), or 3) placebo (n = 111). Plasma lipids were measured before and after 12 wk of intervention whereas nutrient intake was monitored throughout the study. At baseline, hypertensive patients reported lower intakes of carbohydrates, calcium, magnesium, phosphorus, potassium, iron, vitamin D, thiamin, and riboflavin (all P < 0.05). They also had lower HDL (P = 0.014) and higher LDL (P < 0.05) compared with normotensive subjects. During intervention, calcium, magnesium, phosphorus, potassium, thiamin, riboflavin, and vitamins C and D increased (P < 0.01) in the group receiving food calcium but not in the placebo or supplement groups. No changes occurred in plasma lipids or lipoproteins after 12 wk of intervention.

Effects on blood lipids of a blood pressure-lowering diet: the Dietary Approaches to Stop Hypertension (DASH) Trial.

BACKGROUND: Effects of diet on blood lipids are best known in white men, and effects of type of carbohydrate on triacylglycerol concentrations are not well defined. OBJECTIVE: Our goal was to determine the effects of diet on plasma lipids, focusing on subgroups by sex, race, and baseline lipid concentrations. DESIGN: This was a randomized controlled outpatient feeding trial conducted in 4 field centers. The subjects were 436 participants of the Dietary Approaches to Stop Hypertension (DASH) Trial [mean age: 44.6 y; 60% African American; baseline total cholesterol: < or = 6.7 mmol/L (< or = 260 mg/dL)]. The intervention consisted of 8 wk of a control diet, a diet increased in fruit and vegetables, or a diet increased in fruit, vegetables, and low-fat dairy products and reduced in saturated fat, total fat, and cholesterol (DASH diet), during which time subjects remained weight stable. The main outcome measures were fasting total cholesterol, LDL cholesterol, HDL cholesterol, and triacylglycerol. RESULTS: Relative to the control diet, the DASH diet resulted in lower total (-0.35 mmol/L, or -13.7 mg/dL), LDL- (-0.28 mmol/L, or -10.7 mg/dL), and HDL- (-0.09 mmol/L, or -3.7 mg/dL) cholesterol concentrations (all P < 0.0001), without significant effects on triacylglycerol. The net reductions in total and LDL cholesterol in men were greater than those in women by 0.27 mmol/L, or 10.3 mg/dL (P = 0.052), and by 0.29 mmol/L, or 11.2 mg/dL (P < 0.02), respectively. Changes in lipids did not differ significantly by race or baseline lipid concentrations, except for HDL, which decreased more in participants with higher baseline HDL-cholesterol concentrations than in those with lower baseline HDL-cholesterol concentrations. The fruit and vegetable diet produced few significant lipid changes. CONCLUSIONS: The DASH diet is likely to reduce coronary heart disease risk. The possible opposing effect on coronary heart disease risk of HDL reduction needs further study.

Rationale and design of the Dietary Approaches to Stop Hypertension trial (DASH). A multicenter controlled-feeding study of dietary patterns to lower blood pressure.

Epidemiologic studies have found that dietary patterns characterized by high intakes of certain minerals and fiber are associated with low blood pressure. Dietary Approaches to Stop Hypertension (DASH) is a multicenter, randomized, controlled-feeding trial designed to test the effects on blood pressure of two such dietary patterns consumed for 8 weeks. The two experimental diets will be compared with each other and with a control dietary pattern that is relatively low in potassium, magnesium, calcium, and fiber, and has a fat and protein profile mirroring current consumption. The first experimental diet, arguably termed "ideal," is high in fruits, vegetables, whole cereal products, low-fat dairy products, fish, chicken, and lean meats designed to be low in saturated fat and cholesterol; moderately high in protein; and high in minerals and fiber. The second experimental diet tests the effect of fruits and vegetables alone. Its potassium, magnesium, and dietary fiber content will be at the same high levels as the ideal dietary pattern, while its fat, protein, and calcium content will resemble that of the control dietary pattern. The study population will consist of 456 healthy men and women, aged 22 years or older, with systolic blood pressure less than 160 mm Hg and diastolic blood pressure 80 to 95 mm Hg. African-American and other minority groups will comprise 67% of the population. Participants will eat one of the three dietary patterns. The DASH trial has unique features. First, dietary patterns rather than single nutrients are being tested. Second, all food for the experimental diets is provided to the participants using a standardized multicenter protocol. Because the dietary patterns are constructed with commonly consumed food items, the results, if positive, may be conveniently implemented in dietary recommendations to the general public.

Modification of total body fat in spontaneously hypertensive rats and Wistar-Kyoto rats by dietary calcium and sodium.

Studies have indicated that spontaneously hypertensive rats (SHRs) consuming diets high in calcium (Ca2+) and sodium (Na+) weigh less compared to SHRs consuming diets lower in Ca2+ and Na+ while consuming similar amounts of food. Based on calcium's known effects on lipid metabolism, it was important to determine if manipulations of dietary Ca2+ and Na+ would modify total body fat in the SHR. Fifteen SHRs and 17 Wistar Kyoto rats (WKY) were randomized at 4 weeks of age to three diets varying in Ca2+ and Na+: 2% Ca2+/1.0% Na+, 1% Ca2+/0.45% Na+, and 0.1% Ca2+/0.25% Na+. At 15 weeks of age, blood pressure, body weight, and body composition were determined. Significant differences in body weight, blood pressure, and total body fat were observed between diet groups in both strains. Dietary Ca2+ and Na+ induced favorable changes in total body fat content in both the SHR and WKY.

Patterns of insulin secretion and responsiveness in Wistar-Kyoto and spontaneously hypertensive rats.

An intravenous glucose tolerance test (IVGTT) was performed on 16 spontaneously hypertensive rats (SHR) and 15 Wistar-Kyoto rats (WKY) by challenging them with an intravenous glucose load of 0.125 g/100 g body weight. Serum glucose and insulin were measured at 0, 15, 30, 60, 120, and 240 min. In a second experiment, oral glucose tolerance testing (OGTT) was performed with a glucose load of 170 mg/100 g body weight. Serum glucose and insulin were measured at 0, 30, 60, 120, and 240 min. A third experiment examined in vivo insulin-stimulated peripheral glucose uptake via the insulin suppression test. Glucose (8 mg/kg/min), insulin (2.5 to 4.0 mU/kg/min), and somatostatin (1 ng/kg/min) were infused for 3 h. Steady state serum glucose (SSSG) and serum insulin (SSSI) were determined at 0, 140, 160, and 180 min. IVGTT data indicated that serum glucose values were significantly increased in the WKY compared to the SHR at 15, 30, 60, and 120 min. Glucose clearance rates between 15 and 60 min were significantly (P less than .0001) lower in WKY (0.65 +/- 0.07%/min) compared to SHR (1.91 +/- 0.17%/min). The SHR exhibited an exaggerated 15-min peak in insulin secretion that was lacking in the WKY in response to an intravenous glucose load. OGTT data also indicated that the area under the serum insulin curves was higher in the WKY than in the SHR (P less than .017). Peripheral insulin sensitivity showed that despite comparable SSSI levels between the two strains, SSSG values were 31% higher in the SHR compared to the WKY (P less than .001). Thus, it appears that the WKY has a diminished insulin secretory capacity in response to a glucose load, while the SHR has lower tissue responsiveness to insulin's action.

Effect of prostacyclin on platelet intracellular free calcium concentration of hypertensive and normotensive humans.

Platelet intracellular free calcium concentration ([Ca2+]i) has been reported to be increased in essential hypertensive patients (EHT) as compared with normotensive controls (NT). Prostacyclin (PGI2), which influences cellular Ca2+, has been reported to be reduced in EHT. This study tested the hypothesis that the resting level of platelet [Ca2+]i in humans is influenced by PGI2. We also investigated the role of PGI2 in regulating platelet [Ca2+]i of 28 EHT subjects compared to 28 NT controls. Platelet [Ca2+]i was measured using the fluorescent Ca2+ probe fura-2 under control conditions and a 10-min preincubation with PGI2. Simultaneous measurement of platelet cyclic-adenosine 3':5'-monophosphate (cAMP) was performed by radioimmunoassay. The resting level of platelet [Ca2+]i was significantly higher in EHT than in NT (32.7 +/- 1.4 v 28.3 +/- 0.9 nmol/L; P < .01). PGI2 from 30 nM to 1 mumol/L lowered the resting level of platelet [Ca2+]i in a dose-dependent manner (EHT -22.2 +/- 2.4, NT -22.9 +/- 2.3%, 1 mumol/L PGI2); however, no significant difference in platelet [Ca2+]i was observed between NT and EHT. While prostacyclin induced a transient rise in platelet cAMP, the magnitude of PGI2-induced cAMP level was similar between the two groups. These results do not support the hypothesis that endogenous PGI2 activity contributes to the increased level of platelet [Ca2+]i in EHT, although PGI2 incubation lowered the resting level of platelet [Ca2+]i.

Dietary Approaches to Stop Hypertension: a summary of study results. DASH Collaborative Research Group.

The Dietary Approaches to Stop Hypertension multicenter trial examined the impact of dietary patterns on blood pressure in 459 adults with blood pressure < 160 mm Hg systolic and 80 to 95 mm Hg diastolic. After a 3-week run-in period on a control diet low in fruits, vegetables, and dairy products, and with a fat content typical for Americans, participants were randomized for 8 weeks to either the control diet, a diet rich in fruits and vegetables, or a combination diet that emphasized fruits, vegetables, and low-fat dairy products. Body weight and sodium intake were held constant, and physical activity did not change during the intervention. Baseline mean +/- standard deviation systolic and diastolic blood pressures were 131.3 +/- 10.8 mm Hg and 84.7 +/- 4.7 mm Hg, respectively. Relative to the control diet, the combination diet reduced blood pressure by 5.5 mm Hg and diastolic blood pressure by 3.0 mm Hg (P < .001). For those on the fruits and vegetables diet, blood pressure reductions relative to control were 2.8 mm Hg systolic (P < .001) and 1.1 mm Hg diastolic (P < .07). In 133 participants with hypertension, the combination diet produced a net blood pressure reduction of 11.4 and 5.5 mm Hg systolic and diastolic, respectively (P < .001). In participants without hypertension (n = 326), the corresponding blood pressure reductions were 3.5 mm Hg systolic (P < .001) and 2.1 mm Hg diastolic (P < .003). In other subgroup analyses, minorities showed relatively larger reductions in blood pressure than nonminorities (P < .001). We conclude that the dietary pattern reflected in the combination diet can substantially reduce blood pressure, and, accordingly, provides an additional lifestyle approach to preventing and treating hypertension.

Descriptive characteristics of the dietary patterns used in the Dietary Approaches to Stop Hypertension Trial. DASH Collaborative Research Group.

The Dietary Approaches to Stop Hypertension trial was a randomized, multicenter, controlled feeding study to compare the effect on blood pressure of 3 dietary patterns: control, fruits and vegetables, and combination diets. The patterns differed in selected nutrients hypothesized to alter blood pressure. This article examines the food-group structure and nutrient composition of the study diets and reports participant nutrient consumption during intervention. Participants consumed the control dietary pattern during a 3-week run-in period. They were then randomized either to continue on the control diet or to change to the fruits and vegetables or the combination diet for 8 weeks. Sodium intake and body weight were constant during the entire feeding period. Analysis of variance models compared the nutrient content of the 3 diets. Targeting a few nutrients thought to influence blood pressure resulted in diets that were profoundly different in their food-group and nutrient composition. The control and fruits and vegetables diets contained more oils, table fats, salad dressings, and red meats and were higher in saturated fat, total fat, and cholesterol than was the combination diet. The fruits and vegetables and combination diets contained relatively more servings of fruits, juices, vegetables, and nuts/seeds, and were higher in magnesium, potassium, and fiber than was the control diet. Both the fruits and vegetables and combination diets were low in sweets and sugar-containing drinks. The combination diet contained a greater variety of fruits, and its high calcium content was obtained by increasing low-fat dairy products. In addition, the distinct food grouping pattern across the 3 diets resulted in substantial differences in the levels of vitamins A, C, E, folate, B-6, and zinc.

Validation of diet composition for the Dietary Approaches to Stop Hypertension trial. DASH Collaborative Research Group.

The Dietary Approaches to Stop Hypertension trial involved 4 clinical sites at which 459 participants (in 5 cohorts) were fed 3 dietary patterns over 11 weeks per cohort. The 3 patterns were a control diet, a fruits and vegetables diet, and a combination diet. Before the intervention, key nutrient levels in each diet were validated at 2 energy levels (2,100 and 3,100 kcal) by chemical analysis of the prepared menus. During intervention, diets were sampled across all cohorts, sites, and energy levels, and 7-day menu cycle composites were assayed. In general, sodium, potassium, calcium, and magnesium in the validated menus for each diet/energy level met the nutrient targets, though moderate variability was evident among individual menus, particularly for potassium, calcium, and magnesium. However, as intended, there was clear separation and no overlap in mineral levels in individual menus of diets that were designed to differ. During intervention, macronutrient contents met nutrient goals. Sodium, potassium, calcium, and magnesium in the diets generally met target levels, though potassium in the fruits and vegetables diet was 11% to 23% below target. There were no consistent differences in nutrient levels between sites. The mean nutrient levels in the validated menus and diets sampled during intervention were in excellent agreement with each other, though sodium was somewhat higher (approximately 6%) in the diets from intervention vs validation. These results indicate the success of the quality control measures implemented and suggested consistent overall diet composition throughout the 28 months during which the study was conducted.

Pre-enrollment diets of Dietary Approaches to Stop Hypertension trial participants. DASH Collaborative Research Group.

A large body of evidence suggests that several nutrients are related to blood pressure. Less is known about the eating patterns of special populations, such as those at risk for hypertension, or how demographic factors affect the diets of these populations. This article characterizes the usual diets of participants before they enrolled in the Dietary Approaches to Stop Hypertension (DASH) trial. During screening for DASH, 380 participants completed the National Cancer Institute food frequency questionnaire. Nutrient and food group intake, the Keys score (a measure of a diet's atherogenicity), and the Diet Quality Index were estimated from the food frequency questionnaire. The effects of age, sex, race, baseline weight, and education on these dietary factors were assessed among DASH participants and compared with similar data from the Third National Health and Nutrition Examination Survey and other published reports. Among DASH participants, African-Americans reported lower intakes of dairy products (P < .001), calcium (P < .001), and magnesium (P < .05) than did whites. Older women reported greater intakes of calcium, magnesium, and potassium (all P < .05) and less fat (P < .05) than did younger women. Older men consumed fewer servings of fruits (P < .03), less vitamin C (P < .05), and had a higher Keys score (P < .05) than did younger men. Heavier (body mass index > or = 25) participants reported lower intakes of protein and potassium, but higher fat and energy intakes (all P < .05). Taken together, these data show that younger, overweight African-American women have the least healthful diets, because they consume more atherogenic foods and fewer of the nutrients related to decreased blood pressure. Overall Diet Quality Index scores did not differ between African-American and white participants. Despite differences in dietary assessment methods between the population samples of DASH and the Third National Health and Nutrition Examination Survey, within each population sample patterns of micronutrient intake were similar between African-American and white participants.

Comparison of 4 nutrient databases with chemical composition data from the Dietary Approaches to Stop Hypertension trial. DASH Collaborative Research Group.

Accuracy of computerized nutrient databases is an important consideration in selecting a nutrient analysis system. We project compared the nutrient content of daily menus calculated from 4 microcomputer programs to chemical analysis of menus analyzed for the Dietary Approaches to Stop Hypertension (DASH) trial. Thirty-six menus were entered at 2 independent DASH sites using the ESHA Food Processor, Minnesota Nutrition Data System, Moore's Extended Nutrient Database, and Nutritionist IV databases. Food prepared according to these menus was chemically analyzed at the Food Analysis Laboratory Control Center at Virginia Polytechnic Institute and State University, Department of Biochemistry, Blacksburg. Estimates for 13 nutrients were compared: energy, total fat, saturated fat, monounsaturated fat, polyunsaturated fat, carbohydrate, protein, cholesterol, calcium, potassium, magnesium, iron, and sodium. The overall intraclass correlation between the 2 sites' data entry was 0.998; thus, values were averaged for analyses. Databases varied significantly in their mean deviations from chemical analyses values for saturated, monounsaturated, and polyunsaturated fatty acids, potassium, magnesium, and iron (P < .05); however, these differences were small (< 10%). Absolute deviations, which estimate the combined effect of bias and precision, were significantly different among databases for energy, saturated fatty acids, and polyunsaturated acids. Absolute differences from the laboratory values varied by < 15%, except for iron. All 4 databases were comparable in accuracy and precision and performed well. Criteria for database selection depends not only on overall database accuracy, especially for nutrients of interest, but also on the ease of use of the program, relevant features of the associated software; and cost.

Dietary adherence in the Dietary Approaches to Stop Hypertension trial. DASH Collaborative Research Group.

Participants in controlled feeding studies must consume all study foods and abstain from all other foods. In outpatient studies in which adherence may be compromised by free-living conditions, promoting, documenting, and monitoring dietary adherence are necessary. In the Dietary Approaches to Stop Hypertension (DASH) trial, a thorough participant screening process, an orientation session, and a run-in feeding period before randomization aided in the selection of participants who would most likely adhere to the demands of the study protocol. Throughout the feeding period, various educational and motivational techniques were used to encourage DASH participants to adhere to the dietary protocol. Both objective and subjective methods documented excellent participant adherence. Daily monitoring of individual adherence was based on meal attendance, body weight measurements, and daily diaries. Urinary sodium, potassium, phosphorus, and urea nitrogen values and an anonymous poststudy survey were used to evaluate adherence at the end of the study. Most DASH participants adhered to the feeding regimen by consuming only study foods and no other foods. When adherence lapsed, participants generally cited the lack of menu variety as a reason. Successful participant adherence to the constraints of an outpatient controlled feeding study is possible with carefully selected participants and a variety of adherence-promoting strategies incorporated into the study protocol.

Translating the Dietary Approaches to Stop Hypertension diet from research to practice: dietary and behavior change techniques. DASH Collaborative Research Group.

The Dietary Approaches to Stop Hypertension (DASH) clinical trial demonstrated that a diet that emphasizes fruits, vegetables, and low-fat dairy products, includes whole grains, nuts, fish, and poultry, and is reduced in fats, red meats, sweets, and sugar-containing beverages can be highly effective in lowering blood pressure. The National High Blood Pressure Education Program now suggests the DASH diet for preventing and managing hypertension. For persons modifying their diets, the DASH diet offers varied choices. However, simultaneously modifying several dimensions of a diet can be challenging, even for knowledgeable and motivated persons. Persons who are uncertain about modifying their diet may become overwhelmed by the needed dietary changes. Dietitians and other health care practitioners can help patients adopt the DASH diet by exploring possible ambivalence, increasing motivation, and strengthening commitment to change; encouraging patients to select dietary modifications that will fit their lifestyle; and, finally, offering information about how to change their eating behavior. In this article, we offer dietary advice and counseling suggestions for tailoring interventions to match patients' readiness for adopting the DASH diet.

Dietary Approaches to Stop Hypertension: rationale, design, and methods. DASH Collaborative Research Group.

Epidemiologic studies across societies have shown consistent differences in blood pressure that appear to be related to diet. Vegetarian diets are consistently associated with reduced blood pressure in observational and interventional studies, but clinical trials of individual nutrient supplements have had an inconsistent pattern of results. Dietary Approaches to Stop Hypertension (DASH) was a multicenter, randomized feeding study, designed to compare the impact on blood pressure of 3 dietary patterns. DASH was designed as a test of eating patterns rather than of individual nutrients in an effort to identify practical, palatable dietary approaches that might have a meaningful impact on reducing morbidity and mortality related to blood pressure in the general population. The objectives of this article are to present the scientific rationale for this trial, review the methods used, and discuss important design considerations and implications.

The DASH Diet, Sodium Intake and Blood Pressure Trial (DASH-sodium): rationale and design. DASH-Sodium Collaborative Research Group.

The DASH Diet, Sodium Intake and Blood Pressure Trial (DASH-Sodium) is a multicenter, randomized trial comparing the effects of 3 levels of sodium intake and 2 dietary patterns on blood pressure among adults with higher than optimal blood pressure or with stage 1 hypertension (120-159/80-95 mm Hg). The 2 dietary patterns are a control diet typical of what many Americans eat, and the DASH diet, which, by comparison, emphasizes fruits, vegetables, and low-fat dairy foods, includes whole grains, poultry, fish, and nuts, and is reduced in fats, red meat, sweets, and sugar-containing beverages. The 3 sodium levels are defined as higher (typical of current US consumption), intermediate (reflecting the upper limit of current US recommendations), and lower (reflecting potentially optimal levels). Participants are randomly assigned to 1 of the 2 dietary patterns using a parallel group design and are fed each of the 3 sodium levels using a randomized crossover design. The study provides participants with all of their food during a 2-week run-in feeding period and three 30-day intervention feeding periods. Participants attend the clinic for 1 meal per day, 5 days per week, and take home food for other meals. Weight is monitored and individual energy intake adjusted to maintain baseline weight. The primary outcome is systolic blood pressure measured at the end of each intervention feeding period. Systolic blood pressure is compared across the 3 sodium levels within each diet and across the 2 diets within each sodium level. If effects previously observed in clinical trials are additive, sodium reduction and the DASH diet together may lower blood pressure to an extent not as yet demonstrated for nonpharmacologic treatment. The DASH-Sodium results will have important implications for the prevention and treatment of high blood pressure.

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.