Hypertension Prevention Trial (HPT): food pattern changes resulting from intervention on sodium, potassium, and energy intake.

Hypertension Prevention Trial (HPT): Food pattern changes resulting from intervention on sodium, potassium, and energy intake (1) Hypertension is a major health risk whose high prevalence in developed countries makes it an important public health problem [1]. Research has identified several aspects of dietary patterns that may be related to hypertension and has shown that changes in diet can help control or prevent it [2-3]. The dietary characteristics with the most clearly established relationship to blood pressure are dietary sodium, dietary potassium, and energy balance, as reflected in body weight. The relationships have been observed by both epidemiological and clinical investigations [4-10].

The article reports on foods changes made by participants in the Hypertension Prevention Trial (HPT), a study designed to assess the effect of long-term dietary changes on blood pressure in a normotensive population. The HPT was a multicenter randomized trial carried out for a period of 3 years among free-living individuals with "high normal" blood pressures (diastolic blood pressure [is greater than or equal to]78 but [is less than]90 mm Hg). The objectives were to assess the feasibility of achieving long-term changes in body weight, dietary sodium, and potassium and to assess the effects of those changes, singly and in combination, on blood pressure over time. This study examines reported changes in food selection that were made by study participants in order to achieve changes in sodium potassium, and energy intake. it attempts to differentiate changes in food selections that were succesfully implemented by participants from those that were not. This knowledge may be useful in the development of treatment protocols for similar studies, and it may also illuminate some of the obstacles to population-wide changes in dietary patterns.

Method

Study population

The HPT study population consisted of 841 participants from four clinical centers (University of Alabama, Birmingham; University of California; University of Minnesota, Minneapolis; and University of Mississippi, Jackson). The participants were recruited by direct mail, by special creening at shopping malls, churches, or work sites, through adult education courses, and via mass media [11]. Eligibility criteria included the following: age [is greater than or equal to]25 years but [is less than or equal to]49 years; diastolic blood pressure [is greater than or equal to]78 mm Hg but [is less than]90 mm Hg; Quetelet index (body weight in pounds divided by height in inches squared) [is less than]0.05, which corresponds to [is less than]150% of actuarially established ideal weight [12]; and freedom from major chronic diseases or active drug treatment that might affect sodium metabolism or blood pressure [13]. The participants were categorized as having either high weight or normal weight on the basis of the Quetelet index. The cutpoints for weight classification were [is greater than or equal to]0.0356 [lb/in.sup.2] for men and [is greater than or equal to] 0.0328 [lb/in.sup.2] for women, which corresponds to approximately 110% of actuarially defined ideal weight [12].

Treatment

The study design included five treatments: sodium restriction, sodium restriction and potassium increase, energy restriction, sodium and energy restriction, and no dietary treatment or control. High-weight participants were randomly assigned to any one of the five treatments; normal-weight participants were randomly assigned only to the sodium restriction, sodium restriction and potassium increase, and control treatments.

Dietary goals

Participants in the sodium restriction groups (Na) were to reduce daily sodium intake to 70 mEq (approximately 1,600 mg) or less per day, those in the energy restriction groups (Cal) were to reduce energy intake to achieve a "normal" weight, and those in the sodium and energy restriction group (NaCal) were to meet both goals (sodium reduction and body weight reduction). Participants in the sodium restriction and potassium increase group (NaK) were to increase potassium intake to 100 mEq (approximately 3,900 mg) or more per day, as well as to achieve the sodium restriction goal.

Treatment protocol

The HPT dietary intervention consisted of two phases [14]. The initial phase consisted of 12 group sessions held during a 4-month period. The sessions were conducted by trained nutritionists and behaviorists who provided participants in the four treatment groups with dietary counseling specific to their treatment protocol. The dietary changes requested of participants in the four treatment groups are shown in Table 1. All treatment participants received counseling related to meal planning and preparation, food purchasing, and label reading to assist them in making the required changes. Participants were asked to complete daily food records. As part of that process, they were instructed to compute, using the food counter provided, their daily total intakes of sodium, potassium, and/or energy from the foods they ate. On the …