Medical Research: What is the background for this study?
Dr. Moore: The USDA’s current Dietary Guidelines for sodium intake have become increasingly controversial. Current recommendations include restricting sodium intake after the age of 2 years to no more than 2300 mg per day. For African-American adults and children, intakes should be restricted to no more than 1500 mg per day. Actual intake levels are much higher, with most Americans consuming about 3500 mg per day. Our goal was to estimate the effects of dietary sodium and potassium intakes on the change in blood pressure throughout adolescence.
We used data from the National Growth and Health Study, a prospective study of more than 2000 girls who were 9-10 years of age at the time of enrollment. Lifestyle factors were assessed repeatedly throughout the study, and blood pressure was measured annually. Dietary sodium and potassium were assessed using multiple sets of three-day diet records. We used longitudinal modeling to estimate the effects of dietary sodium and potassium on blood pressure change over 10 years.
Medical Research: What are the main findings?
Dr. Moore: In this study, there was no evidence for a beneficial effect of reduced sodium intake on blood pressure change during adolescence. By 19-20 years of age, girls who consumed more than 4000 mg of sodium per day had systolic and diastolic blood pressure levels that were similar to those seen among girls with lower levels of sodium intake. Specifically, there was no beneficial effect on blood pressure associated with sodium intakes of less than 2500 mg per day. These results were similar for blacks and whites. In contrast, the repeated measures analyses showed that girls who consumed more than 2400 mg of potassium per day had lower blood pressures throughout adolescence compared with girls consuming less than 1800 mg per day of potassium.
Medical Research: What should clinicians and patients take away from your report?
Dr. Moore: This study suggests that dietary potassium plays a much larger role in determining the change in adolescent blood pressure than does sodium. In both blacks and whites, sodium restriction had essentially no impact on systolic or diastolic blood pressure. Well over 90% of Americans fail to meet the USDA Guidelines for potassium intake. It would be better to guide families to include more potassium-rich foods and snacks (e.g., bananas, raisins, dried apricots, spinach, dairy products, sweet potatoes, etc) than to focus on salt restriction.
Medical Research: What recommendations do you have for future research as a result of this study?
Dr. Moore: This study had no data on salt-sensitivity in these girls. It may be that lowering salt intake has a role in the subset of individuals who are salt-sensitive. Currently, there is no simple and accurate measure of salt-sensitivity but developing such a test would be valuable for use in large-scale observational studies as well as clinical settings.
MedicalResearch.com Interview with: Lynn L. Moore, DSc, MPH (2015). Potassium May Play Larger Role Than Sodium in Adolescent Blood Pressure