| OBJECTIVE: A diet low in sodium, high in potassium, and high in calcium
is recommended to lower blood pressure. However, compliance with this
diet is poor, probably because of dietary intake underestimation. Therefore,
we compared electrolyte intake as estimated from dietary recall with
a 24-h urinary excretion. METHODS: Thirty-six patients (26 men and
10 women) with a mean age of 46 +/- 8 y participated in the study.
All participants had essential hypertension and were on no drug therapy
(n = 20) or non-diuretic monotherapy (n = 16). Patients were instructed
to consume a low-sodium (50 mmol/d), high-potassium (supplementation
with 30 to 60 mmol/d), and high-calcium (1000 mg/d) diet. Compliance
with the diet was assessed at baseline and then 1, 2, and 3 mo after
starting the diet. Sodium, potassium, and calcium intakes were carefully
estimated from patients' dietary recall and 24-h urinary collection.
RESULTS: Estimated sodium intake significantly correlated with 24-h
urinary excretion (R = 0.43 P < 0.001). However, estimated sodium
intake was lower than urinary sodium excretion by 34% at baseline and
by 47% after 3 mo of dieting (P < 0.05). Estimated potassium intake
correlated with 24-h urinary excretion. Estimated calcium intake significantly
increased from 933 +/- 83 mg/d to 1029 +/- 171 mg/d (P < 0.05).
Calcium intake derived from patients' recall far exceeded and only
slightly correlated with 24-h urinary excretion (R = 0.23, P < 0.01).
CONCLUSIONS: Patients tend to underestimate their sodium intake by
30% to 50%; therefore, urinary sodium excretion is more accurate to
assess sodium intake. Thus, 24-h urinary sodium excretion should be
used in clinical practice and in clinical trials, especially when dietary
non-compliance is suspected. |
