P-632: The successful implementation of a protocol to normalize sodium intake in African-American youths

We and others have hypothesized that stress induced changes in sodium regulation contributes to the development of salt sensitive hypertension. It is important to normalize the sodium intake in studies that examine this hypothesis to insure that the subjects are at similar levels of sodium balance when they are tested. This is a particular problem in adolescents because of their lifestyles. We have developed a 3-day dietary protocol to control the sodium intake in a study of stress induced changes in sodium handling in African-American youths aged 15 to 18 years. The purpose of this report is to document our success with this dietary plan and describe the factors related to differences in this success. The dietary plan is based on a limited choice diet containing the normal sodium intake of teenagers in our region of the country (4000±200 mg/day) and utilizes pre-packaged foods. A research assistant meets with each subject to select the diet for each day. The selected foods are packed in coolers which the subjects pick up each day. The coolers are then returned the next day with all the wrappers and an overnight urine collection to determine dietary compliance. Of the 64 subjects tested thus far, 60 (93.7%) have complied with the diet as determined by urinary sodium values from the overnight collections. The variability in sodium intake across subjects was significantly reduced from the first day to the third day of the diet (153±67 to 121±53 mmol/L (p<0.03). This resulted in a standard deviation in U<inf>Na</inf>V of only 6.7 mEq/hr at the beginning of the test period. There were sex differences in the amount of sodium that was consumed based on returned foods and wrappers. Males (n=29) consumed an average of 88.7% of the total sodium they were provided compared to 77.7% for the females (n=31). Further analysis showed that within the females these differences were significantly correlated with body weight (r=.48; p< .007). There was not a significant relationship in the males. However, these sex differences did not result in sex differences in baseline U<inf>Na</inf>V during the testing procedure (21±12 v 19±11 mEq/hr). In conclusion, we have developed a dietary protocol that we believe is effective in normalizing the dietary intake of sodium in adolescents. This protocol can be used in any study in which it is important to bring adolescents into comparable levels of sodium balance.