Three eligibility pre-screening visits were followed by a two-week run-in feeding period and then a four-week intervention period at each of three sodium levels. During the run-in for the intervention feeding periods, all food was provided to participants. They were required to attend the clinic for at least one meal per day, five days per week, and to take home food to eat for other meals. Each of the four clinics recruited 100 participants. Blood pressure was measured once a week during the first of three weeks and five times during the last week. During the final feeding period, fasting blood was collected and 24-hour urine collections were analyzed for magnesium, potassium. calcium, sodium, and creatinine.