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Increased natriuretic ability and hypotensive effect during short-term high calcium intake in essential hypertension
A N Lasaridis1, C N Kaisis, K I Zananiri
1First Department of Medicine, AHEPA Hospital, University of Thessaloniki, Greece.
Insights
High calcium intake in hypertensive patients promotes sodium excretion, leading to reduced blood pressure. This study demonstrates a significant link between calcium supplementation and natriuresis, offering insights into hypertension management.
Area of Science:
- Nephrology
- Cardiovascular Medicine
- Nutritional Science
Background:
- Essential hypertension is a prevalent condition often linked to complex physiological mechanisms.
- Previous research suggests a potential hypotensive effect of high dietary calcium intake.
- The precise mechanism by which calcium influences blood pressure remains under investigation.
Purpose of the Study:
- To investigate if increased natriuresis (sodium excretion) mediates the blood pressure-lowering effect of a high-calcium diet.
- To assess the impact of calcium supplementation on urinary sodium and calcium excretion in patients with essential hypertension.
Main Methods:
- A randomized, single-blind, placebo-controlled, cross-over trial involving 18 patients with essential hypertension.
- Participants received a calcium supplement (1g elemental calcium) or placebo for 5 days.
- Saline infusion and hourly urine collections were conducted during the final day of each treatment period.
Main Results:
- Calcium supplementation resulted in mild hypercalcemia and significantly increased urinary calcium excretion.
- Significant reductions in body weight and systolic blood pressure were observed with calcium supplementation.
- Urinary sodium excretion was significantly higher during calcium supplementation, correlating positively with urinary calcium excretion.
Conclusions:
- Calcium supplementation in hypertensive patients induces significant natriuresis and sodium loss.
- Increased urinary sodium excretion is a likely mechanism responsible for the hypotensive effect of high calcium diets.
- Findings suggest a role for calcium in managing hypertension through modulation of sodium balance.
Abstract:
The present study has investigated whether an increased natriuresis could account for the hypotensive effect of a high calcium diet which has been reported by others. A calcium supplement (equivalent to 1 g of elemental calcium) was given for 5 days to 18 patients with essential hypertension in a randomized single-blind, placebo-controlled, cross-over trial. In 15 of the patients, 2 liters of isotonic saline were infused intravenously over 4 h during the last day of each test period and hourly urine collections were taken. Calcium supplementation produced a mild but significant hypercalcemia as well as increased urinary calcium excretion. Body weight and systolic blood pressure decreased significantly. The blood pressure decrease was indirectly related to the pretreatment plasma renin activity (r = -0.61, p less than 0.01). Urinary sodium excretion increased during calcium diet (80 mmol/day negative balance, p less than 0.01). During saline infusion under calcium supplementation the urine volume, osmolality and sodium excretion were significantly higher compared with placebo. The changes in urinary sodium excretion correlated positively with the changes in urinary calcium excretion (r = 0.68, p less than 0.01) in patients given the high calcium diet, when infused with saline. We conclude that calcium supplementation induces a considerable sodium loss in the urine which is very likely to result in the hypotensive effect.