Severe sodium restriction alone and with potassium supplementation does not alter blood lipoproteins in essential hypertension

Metabolic effects of strict salt restriction in essential hypertensive patients

OBJECTIVE

Some observations suggest that a strict low-salt diet may induce unfavourable metabolic side-effects. The main aim of this study was to analyse the possible consequences of severe salt restriction in mildly hypertensive patients.

DESIGN

The study was carried out through a randomized double-blind protocol.

SUBJECTS

Forty-seven ambulatory patients proceeding from the hypertension unit were initially admitted: 17 were lost, and 30 non-diabetic mildly hypertensives (DBP 90-104 mmHg) with normal renal function completed the protocol.

INTERVENTION

After a wash-out period, patients were maintained on a low-salt intake (2.8 +/- 1.0 g day-1 of NaCl) and placebo for 2 weeks, and the same diet and salt supplements (11.7 +/- 2.5 g day-1 of NaCl) for another 2 weeks, separated by a second wash-out period.

MEASURES

At the end of each dietary period, blood pressure (BP) and body weight were measured, and a blood sample was taken for determination of routine serum chemistries, plasma lipid and apolipoprotein concentrations, immunoreactive insulin (IRI), and plasma renin activity (PRA). Urinary 24 h excretion of sodium and potassium were measured.

RESULTS

During the salt restriction period BP did not change, weight lowered, and PRA raised. There was a significant increase in serum level of creatinine, uric acid, IRI, total cholesterol and apo B, and a decrease in HDL cholesterol and apo A-I.

CONCLUSION

As previously suggested, these observations seem to indicate that strict salt restriction may cause, at least in the short-term, adverse metabolic changes in hypertensive patients.

Hyperlipidemia in hypertension: causes and prevention

Hyperlipidemia is prevalent in hypertension, but the cause of this association is unknown. Treatment of hypertension with thiazide diuretics accentuates the hyperlipidemia, perhaps by causing potassium or sodium depletion. To assess the role of hypokalemia in thiazide hyperlipidemia, I measured lipid concentrations while using a spironolactone-thiazide regimen to prevent potassium wastage during the treatment of hypertension. Blood pressure decreased substantially, but hyperlipidemia occurred despite the maintenance of normal serum potassium. To test a role of sodium balance, I measured lipid levels during periods of sodium feeding and placebo therapy. Cholesterol levels decreased during sodium administration. Carrying this information to therapy, I participated in a multicenter comparison of enalapril and indapamide therapy in resistant hypertension. Both regimens caused minor metabolic effects, but indapamide provided superior antihypertensive potency. This evidence suggests that sodium feeding improves lipid metabolism, but sodium diuresis enhances an antihypertensive effect. Low-dose therapy combining a diuretic, such as indapamide, with a nondiuretic agent promises to improve metabolic tolerance and maximize hypertension control. This strategy optimally lowers overall cardiovascular risk.