Njeri Karanja

Effects on Blood Pressure of Reduced Dietary Sodium and the Dietary Approaches to Stop Hypertension (DASH) Diet

Background The effect of dietary composition on blood pressure is a subject of public health importance. We studied the effect of different levels of dietary sodium, in conjunction with the Dietary Approaches to Stop Hypertension (DASH) diet, which is rich in vegetables, fruits, and low-fat dairy products, in persons with and in those without hypertension. Methods A total of 412 participants were randomly assigned to eat either a control diet typical of intake in the United States or the DASH diet. Within the assigned diet, participants ate foods with high, intermediate, and low levels of sodium for 30 consecutive days each, in random order. Results Reducing the sodium intake from the high to the intermediate level reduced the systolic blood pressure by 2.1 mm Hg (P<0.001) during the control diet and by 1.3 mm Hg (P=0.03) during the DASH diet. Reducing the sodium intake from the intermediate to the low level caused additional reductions of 4.6 mm Hg during the control diet (P<0.001) and 1.7 mm Hg during t...

Diet and Lifestyle Recommendations Revision 2006 A Scientific Statement From the American Heart Association Nutrition Committee

Improving diet and lifestyle is a critical component of the American Heart Association’s strategy for cardiovascular disease risk reduction in the general population. This document presents recommendations designed to meet this objective. Specific goals are to consume an overall healthy diet; aim for a healthy body weight; aim for recommended levels of low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglycerides; aim for normal blood pressure; aim for a normal blood glucose level; be physically active; and avoid use of and exposure to tobacco products. The recommendations are to balance caloric intake and physical activity to achieve and maintain a healthy body weight; consume a diet rich in vegetables and fruits; choose whole-grain, high-fiber foods; consume fish, especially oily fish, at least twice a week; limit intake of saturated fat to <7% of energy, trans fat to <1% of energy, and cholesterol to <300 mg/day by choosing lean meats and vegetable alternatives, fat-free (skim) or low-fat (1% fat) dairy products and minimize intake of partially hydrogenated fats; minimize intake of beverages and foods with added sugars; choose and prepare foods with little or no salt; if you consume alcohol, do so in moderation; and when you eat food prepared outside of the home, follow these Diet and Lifestyle Recommendations. By adhering to these diet and lifestyle recommendations, Americans can substantially reduce their risk of developing cardiovascular disease, which remains the leading cause of morbidity and mortality in the United States.

Dietary Approaches to Prevent and Treat Hypertension: A Scientific Statement From the American Heart Association

A substantial body of evidence strongly supports the concept that multiple dietary factors affect blood pressure (BP). Well-established dietary modifications that lower BP are reduced salt intake, weight loss, and moderation of alcohol consumption (among those who drink). Over the past decade, increased potassium intake and consumption of dietary patterns based on the “DASH diet” have emerged as effective strategies that also lower BP. Of substantial public health relevance are findings related to blacks and older individuals. Specifically, blacks are especially sensitive to the BP-lowering effects of reduced salt intake, increased potassium intake, and the DASH diet. Furthermore, it is well documented that older individuals, a group at high risk for BP-related cardiovascular and renal diseases, can make and sustain dietary changes. The risk of cardiovascular disease increases progressively throughout the range of BP, beginning at 115/75 mm Hg. In view of the continuing epidemic of BP-related diseases and the increasing prevalence of hypertension, efforts to reduce BP in both nonhypertensive and hypertensive individuals are warranted. In nonhypertensive individuals, dietary changes can lower BP and prevent hypertension. In uncomplicated stage I hypertension (systolic BP of 140 to 159 mm Hg or diastolic BP of 90 to 99 mm Hg), dietary changes serve as initial treatment before drug therapy. In those hypertensive patients already on drug therapy, lifestyle modifications, particularly a reduced salt intake, can further lower BP. The current challenge to healthcare providers, researchers, government officials, and the general public is developing and implementing effective clinical and public health strategies that lead to sustained dietary changes among individuals and more broadly among whole populations.

Effects of Diet and Sodium Intake on Blood Pressure: Subgroup Analysis of the DASH-Sodium Trial

Although epidemiologic data show a direct relation between dietary sodium intake and blood pressure at the population level (1, 2), some experts question the universality of the findings and oppose public health recommendations to decrease sodium intake in the general population (3). Certainly, results from reports on the relationship between sodium and blood pressure among major subgroups vary considerably. Several studies suggest that African Americans and older adults have heightened salt sensitivity (greater blood pressure response to sodium intake) (4-6). Some evidence also indicates increased salt sensitivity in women (7), although other studies do not support this claim (4, 5). The association of sodium intake with cardiovascular morbidity and mortality varies by overweight status (8), perhaps reflecting a differential effect of sodium on blood pressure in overweight persons. Finally, higher dietary intakes of potassium and calcium have been shown to blunt the pressor effects of dietary sodium (9, 10). Dietary factors other than sodium also directly affect blood pressure, and these effects also appear to vary across subgroups. In the Dietary Approaches to Stop Hypertension (DASH) Trial, for example, a diet that had reduced total and saturated fat and was rich in fruits, vegetables, and low-fat dairy foods (the DASH diet) substantially decreased blood pressure compared with a more typical U.S. diet, in the absence of weight change and at sodium intakes approximating current U.S. consumption (11, 12). These effects persisted across all subgroups and were especially pronounced among hypertensive persons, African Americans, and persons who did not drink alcohol (13). The DASH-Sodium Trial examined the effects of reduced sodium intake in the context of the DASH diet and a more typical U.S. diet (14). In that study, highly significant decreases in blood pressure were observed with decreased sodium intake in participants following either diet, and the DASH diet decreased blood pressure at sodium intakes well below the current U.S. average. These results were observed overall and in subgroups defined by ethnicity, sex, and hypertension status (15). We report on more detailed subgroup analyses from the DASH-Sodium Trial, including results for subgroups defined by age, obesity, waist circumference, alcohol intake, and baseline sodium intake. We also report the results of multivariate analyses that demonstrate how these effects vary across subgroups defined jointly by age, ethnicity, sex, and hypertension status. Methods Study Design The DASH-Sodium Trial was a multicenter, randomized feeding trial comparing the effects on blood pressure of three levels of sodium intake and two dietary patterns. The 412 participants were 22 years of age or older and had systolic blood pressures of 120 to 159 mm Hg and diastolic blood pressures of 80 to 95 mm Hg (15). The three levels of sodium intake (lower, intermediate, and higher) varied according to energy intake in a ratio of 1:2:3; target intakes were 50, 100, and 150 mmol/d, respectively, for a 2100-kcal diet. The dietary patterns were a control diet, typical of what many Americans eat, and the DASH diet, which 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 (11, 14). Participants were recruited in four separate feeding cohorts and were randomly assigned to one of the two dietary patterns by using a parallel-group design. They then ate their assigned diet for three consecutive 30-day intervention feeding periods, during which sodium intake varied among the three levels by a randomly assigned sequence (Figure). Participants ate the control diet at the higher sodium intake during a 2-week run-in period. During the three intervention periods, participants received all their food in the context of the study and were asked not to eat any nonstudy food. Individual energy intake was adjusted to keep body weight stable. Figure. Design of the Dietary Approaches to Stop Hypertension (DASH)-Sodium Trial. Exclusion criteria were heart disease, renal insufficiency, poorly controlled hyperlipidemia or diabetes mellitus, diabetes requiring insulin, special dietary requirements, intake of more than 14 alcoholic drinks/wk, or use of antihypertensive drugs or other medications that would affect blood pressure or nutrient metabolism. The study was approved by the human subjects committees of the clinical centers and coordinating center, and participants gave informed consent. Measurement Protocol Trained staff measured blood pressure at each of three screening visits, on 2 days during the run-in period, and on 5 of the last 9 days of each intervention feeding period. Interim blood pressures were assessed once during each of the first 3 weeks of each intervention feeding period. During screening and the last week of each intervention feeding period, a 24-hour urine collection was obtained. Height and weight were measured, and body mass index was calculated. Baseline physical activity was measured by using a 7-day physical activity recall interview (16). Information on education level, income, alcohol consumption, and family history was obtained by using a questionnaire. Baseline blood pressure was defined as the average of the five preintervention blood pressures. End-of-feeding blood pressures were defined as the average of the five blood pressures at the end of each 30-day intervention feeding period. If no end-of-feeding blood pressure values were available (49 of 1236 possible cases), interim (n = 9) or screening (n = 40) blood pressures were used to impute end-of-feeding blood pressures. Definitions of Subgroups Ethnicity was categorized as African American versus other (primarily non-Hispanic white). Participants were considered hypertensive if their untreated baseline systolic blood pressure was 140 mm Hg or greater and their diastolic blood pressure was 90 mm Hg or greater. (Use of antihypertensive agents was an exclusion criterion [17].) Obesity was defined as body mass index of 30 kg/m2 or greater, and high-risk waist circumference was defined as greater than 102 cm in men and greater than 88 cm in women (18). Age, physical activity, baseline alcohol intake, baseline 24-hour urinary sodium level, and family income were dichotomized at the approximate median. Level of education was dichotomized as high school or less versus more than high school. Statistical Analysis The data were analyzed on an intention-to-treat basis. Given the differential effects of sodium on blood pressure observed in previous analyses among participants eating the DASH diet versus the control diet (15) and because power for subgroup analyses is more limited than for overall analysis, we focused our comparisons on the maximum contrasts (higher versus lower sodium intake with the control diet, DASH diet versus control diet at the higher sodium intake, and the combined effect of DASH diet and lower sodium intake versus control diet and higher sodium intake). We used generalized estimating equations (19) to fit linear models that predicted baseline and end-of-feeding blood pressures as a function of diet (DASH vs. control), sodium level, and subgroup indicators. Different ways of modeling the dietsodium effects and their interactions with the subgroup indicators were used to test specific hypotheses. In particular, two-way interactions of the various dietsodium effects with ethnicity, sex, hypertension status, and age were analyzed to determine the incremental effect on blood pressure in each of these subgroups while controlling for the main and incremental effects of the other subgroups. This model allowed us to estimate various diet-sodium contrasts for each of the 16 subgroups defined by hypertension status, ethnicity, sex, and age. A second set of models examined subgroup variables in a bivariate manner and did not assume simple additivity of subgroup effects. Finally, unadjusted subgroup analyses included main effects and interactions for a single subgroup indicator. All analyses were performed by using the xtgee procedure in Stata software, version 5 (Stata Corp., College Station, Texas) (20) and included adjustment for baseline blood pressure, site, feeding cohort, and carryover effects. An exchangeable covariance matrix was assumed for the repeated measurements for each participant. Unless otherwise stated, a P value less than 0.05 was significant, and all confidence intervals are 95% confidence intervals. Because subgroup analyses were planned to interpret and elucidate the overall study results, they are not adjusted for multiple comparisons. Results Of the 412 participants who underwent randomization, 390 (95%) completed the 12-week intervention feeding period. Adherence to the study diets seemed excellent, and body weight remained stable over time (15). Table 1 shows baseline characteristics of the 412 participants. Mean urinary sodium excretion at screening was 155 mmol/d, a value higher than that found while participants ate higher-sodium diets (142 mmol/d). Table 1. Characteristics of Study Sample Several key subgroups were highly interrelated. Women made up 70% of African-American participants but only 39% of non-African-American participants. Women were more likely to be hypertensive than were men. The percentage of both men and women with hypertension increased sharply with age among non-African-American participants (21% of those 45 years of age vs. 47% of those >45 years of age) but was equally high among older and younger African Americans (43% of those 45 years of age vs. 45% of those >45 years of age). These correlations highlight the potential for confounding in our results and, hence, the importance of the multivariate-adjusted analyses. Effects of the DASH Diet Table 2 shows the effect on systolic blood pressure of the DASH diet compared with the control diet du

Descriptive Characteristics of the Dietary Patterns Used in the Dietary Approaches to Stop Hypertension Trial

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.

Effect of a Free Prepared Meal and Incentivized Weight Loss Program on Weight Loss and Weight Loss Maintenance in Obese and Overweight Women A Randomized Controlled Trial

CONTEXT The prevalence of overweight and obesity in the United States remains high. Commercial weight loss programs may contribute to efforts to reduce the prevalence of overweight and obesity, although few studies have examined their efficacy in controlled trials. OBJECTIVE To test whether a free prepared meal and incentivized structured weight loss program promotes greater weight loss and weight loss maintenance at 2 years compared with usual care. DESIGN, SETTING, AND PARTICIPANTS A randomized controlled trial of weight loss and weight loss maintenance in 442 overweight or obese women (body mass index, 25-40) aged 18 to 69 years (mean age, 44 years) conducted at US institutions over 2 years with follow-up between November 2007 and April 2010. INTERVENTION The program, which involves in-person center-based or telephone-based one-to-one weight loss counseling, was available over a 2-year period. Behavioral goals were an energy-reduced, nutritionally adequate diet, facilitated by the inclusion of prepackaged food items in a planned menu during the initial weight loss phase, and increased physical activity. Participants assigned to usual care received 2 individualized weight loss counseling sessions with a dietetics professional and monthly contacts. MAIN OUTCOME MEASURES Weight loss and weight loss maintenance. RESULTS Weight data were available at 24 months for 407 women (92.1% of the study sample). In an intent-to-treat analysis with baseline value substitution, mean weight loss was 7.4 kg (95% confidence interval [CI], 6.1-8.7 kg) or 7.9% (95% CI, 6.5%-9.3%) of initial weight at 24 months for the center-based group, 6.2 kg (95% CI, 4.9-7.6 kg) or 6.8% (95% CI, 5.2%-8.4%) for the telephone-based group, and 2.0 kg (95% CI, 0.6-3.3 kg) or 2.1% (95% CI, 0.7%-3.5%) for the usual care control group after 24 months (P < .001 for intervention effect). CONCLUSION Compared with usual care, this structured weight loss program resulted in greater weight loss over 2 years. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00640900.

Dietary Approaches to Stop Hypertension: Rationale, Design, and Methods

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

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.

Dietary Approaches to Stop Hypertension: A Summary of Study Results

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.

One-year results from a brief, computer-assisted intervention to decrease consumption of fat and increase consumption of fruits and vegetables

BACKGROUND Current cancer prevention recommendations include reducing consumption of fat and increasing consumption of fruits and vegetables. METHODS Healthy women health maintenance organization members (n = 616) ages 40-70 were randomly assigned to either a nutrition intervention or a control intervention unrelated to diet. Intervention included two 45-min counseling sessions plus two brief follow-up telephone contacts. Counseling sessions included a 20-min, interactive, computer-based intervention using a touch-screen format. Intervention goals were reducing dietary fat and increasing fruit and vegetable consumption. Outcome measures included a food frequency questionnaire and the Fat and Fiber Behavior Questionnaire (FFBQ). Total serum cholesterol was also measured at baseline and 12 months. RESULTS Twelve-month follow-up data showed improvements on all dietary outcome variables. Compared to the control, intervention participants reported significantly less fat consumption (3.75 points less for percentage of energy from fat), significantly greater consumption of fruit and vegetables combined (0.93 more servings per day), and a significant reduction in a behavioral measure of fat consumption (0.20 point change in the FFBQ). Group differences in total serum cholesterol, while in the desired direction, were not significant. CONCLUSIONS In appropriate circumstances, moderate-intensity dietary interventions can show significant effects for periods of at least 1 year.