Measurements
Blood pressure was measured with random-zero sphygmomanometers
while participants were seated at three screening visits,twice during the run-in period, weekly during the first 3 weeks of
each of the three 30-day intervention periods, and at five clinic visits
during the last 9 days (at least two during the final 4 days) of each
intervention period. During the screening period and during the
last week of each intervention period, a 24-hour urine collection was
obtained. The participants and the dietary staff were unaware of the
outcome data; the personnel involved in the collection of the outcome
data were unaware of participants’ diet assignment. We assessed
participants’ adherence to the diet by reviewing their daily
food diaries, having them eat their weekday lunches or dinners on
site, and measuring 24-hour urinary excretion of sodium, potassium,
phosphorus, and urea nitrogen. Side effects were monitored
by means of questionnaires regarding symptoms and illnesses. According
to the study protocol, a systolic blood pressure of more than
170 mm Hg or a diastolic blood pressure of more than 105 mm Hg
at a single visit was considered to necessitate a second measurement;
if the reading was sustained, the participant was referred to his or
her physician for further evaluation and treatment.