NA+/K+ INTAKE AND CV REACTIVITY IN BLACK ADOLESCENTS

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The prevalence of essential hypertension (EH) in U.S. blacks has reached epidemic proportions and is among the highest of any racial group in the world (1). Since the precursors of EH begin in childhood (2), the ideal population for prevention is children and adolescents. Previous research has demonstrated that black children show greater cardiovascular (CV) reactivity (increases in blood pressure (BP) to stress) and higher levels of BP while asleep as compared to white children (3-4). Given that the prevalence of EH is great among black adults, increased CV reactivity and elevated BP while asleep may be important risk factors or markers for the early development of EH in black children. A number of investigators have suggested that sodium (Na+) sensitivity (changes in BP to altering Na+ intake) is also an important factor in BP regulation. Blacks are more likely to show Na+ sensitive (SS) BP responses than whites (5-7). In addition, research on dietary interventions has indicated that blacks, in particular, show reductions in casual BP in response to low Na+ diets (5-7). However, compliance with low Na+ diets in terms of making permanent lifestyle changes may be difficult, especially for children. More recently, investigators have shown that increasing dietary potassium (K+) may also have beneficial effects on casual BP, especially in SS Individuals (8-11). Theoretically, adhering to a high K+ diet should be much easier for children than adhering to a low Na+ diet. Evidence supporting the beneficial effect of a high K+ diet on BP comes from both animal research (8-10) and K+ supplement studies (11-15). In addition, the Principal Investigator recently completed a pilot study (16) which demonstrated that Increasing dietary K+ in a group of black adolescents significantly decreased both systolic (S) and diastolic (D) BP reactivity from pre- to post-diet. Research on the relationship between ambulatory (A) BP patterns and electrolyte excretion has not demonstrated an association between K+ intake and ABP patterns while awake or asleep in a group of black and white children (17); however, further research Is warranted to determine if increasing dietary K+ is associated with differences in ABP patterns in SS versus Na+ resistant (SR) individuals. The purpose of the present proposal is to determine the effects of a high K+ dietary intervention on changing CV reactivity, ABP, and casual BP In SS versus SR black normotensive adolescents.