The Massachusetts Blood Pressure Study,Part 4. Modest Sodium Supplementation and Blood Pressure Change in Boarding School Girls

Abstract

Based upon the results of the earlier work, a sodium supplement study was designed and carried out at a private boarding school. Two hundred and sixteen 9th-12th grade girls were randomly assigned to one of three groups while continuing to eat their regular meals at the dining commons. All participating students took two capsules, under supervision, both mid-morning and subsequent to the evening meal. One group received placebos at both times, one group received 2 G of salt in the morning and a placebo in the evening, and the final group received a placebo in the morning and 2 G of salt in the evening. One week of baseline data and eight weeks of follow-up data were collected twice weekly for BP, pulse, 24-hour urine specimen, and stress of daily events.

Repeated measures analysis of variance failed to detect a significant difference in change in systolic and diastolic BP between groups. Extensive analysis of other variables did not uncover any negative confounding or interaction. Drop out rates were very low and compliance rates very high. The urinalysis clearly demonstrated that the Na excretion in the two supplement groups was similar and significantly elevated over the placebo group, thus documenting the high Na supplement compliance rates.