Morris RC, Forman A, Sebastian A
Dietary potassium is more determining of salt-
sensitivity in normotensive blacks than whites
12th Annual ASH Meeting
Am J Hypertens
(Apr) 10:18A 1997
Background: Afro-Americans have previously been shown to be
more frequently salt-sensitive than Caucasians. The etiology of
this
increased frequency of salt-sensitivity is not completely
understood. Epidemiological studies have demonstrated that
increased
urinary sodium/potassium ratios are more tightly correlated to
increases in blood pressure than urinary sodium excretion alone.
The
present study was undertaken to determine if potassium
supplementation
can modulate the sodium induced blood pressure increase in
Afro-Americans as compared to Caucasian normotensive individuals.
Study: 24 Afro-Americans (AA) and 14 Caucasian (C)
individuals
were involved. Subjects received the following diets in sequence:
Na
15 mmol, K 30 mmol for 11-14 days, followed by Na 250 mmol and K
30
mmol for 28 days. The final three weeks of high Na, Low K diet
were
supplemented with 40 or 90 mmol KHCO3.
Afro-American individuals demonstrated an increase in blood
pressure
with sodium loading [79% of the time vs. 39% in Caucasian
individuals
(P<0.02] and this was associated with greater positive sodium
balance (P<0.05) in AA than in C. In Afro-Americans fed a high
salt diet, blood pressure decreased in a sustained fashion after
supplementation with 90 mmol KHCO3. Supplementation with the lower
40
mmol KHCO3 dose resulted in only transient blood pressure lowering
effects. In the combined group of AA and C, during the high salt
period, K supplementation resulted in blood pressure reduction
that correlated with the amount of increase in urinary K excretion
and
serum K.
Comment: This study provides a number of important
observations: - Salt sensitive hypertension may be in part,
ameliorated by potassium supplementation.
- Afro-Americans are
more
frequently salt sensitive than Caucasians.
The limitations of the study are based on the study design. Diets
were not randomized or separated by a washout period. Very few
salt
sensitive Caucasians were identified to determine if
salt-sensitivity
per se rather than racial factors play a role in the benefits seen
with potassium supplementation. Arlene Chapman, M.D.,
(University
of Colorado, Denver)
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12th Annual ASH Meeting
H: Non drug therapy :
Dietary/electrolyte therapy
H: Pathophysiology :
Salt (sodium, chloride) sensitivity