A friend asked Hua Zi if diuretics in antihypertensive medications make people urinate more and excrete salt to reduce blood volume, can achieving the same effect by drinking less water and consuming less salt without taking medication?
Hua Zi replied that although drinking less water and consuming less salt may have some antihypertensive effects, they cannot replace the role of diuretics. The mechanism through which diuretics lower blood pressure is not simply about draining water and sodium but involves a complex physiological process. Consuming less salt appropriately can help lower blood pressure, but reducing water intake is not beneficial for health.
I. Mechanism of diuretics in lowering blood pressure
As diuretics used for lowering blood pressure, thiazide diuretics are generally used, with the most common ones being hydrochlorothiazide and indapamide. They reduce the reabsorption of sodium and chloride ions in the renal tubules, promoting the excretion of sodium ions and water through urine.
Through the sodium-calcium exchange mechanism between cells, the calcium ions in vascular smooth muscle are reduced, decreasing the excitability of vascular smooth muscle. Diuretics also have a certain inducing effect on vasodilators like bradykinin, prostaglandins, leading to blood pressure reduction.
Some individuals with hypertension are salt-sensitive, having volume-dependent hypertension, and diuretics show significant antihypertensive effects in them. Especially in elderly individuals with stage 1 hypertension (high systolic pressure) but normal or lower diastolic pressure, diuretics can lead to substantial blood pressure reduction.
II. Consuming less salt but not reducing water intake
Chinese people have a habit of consuming high-salt diets, and sodium ions in salt are one of the primary factors causing hypertension. Therefore, reducing salt intake helps control blood pressure, but it’s important to note that excessively low salt intake can lead to hyponatremia, so daily salt intake is recommended to be between 3–5 grams.
Although drinking insufficient water can reduce blood volume, it also affects the body’s metabolism, causing blood and urine to become concentrated. Blood concentration increases the risk of cardiovascular diseases, while urine concentration leads to elevated concentrations of metabolic waste, potentially forming crystals and stones, damaging the urogenital system.
Thus, reducing salt intake appropriately is beneficial for health, but insufficient water intake is harmful. Drinking more water (over 1500ml per day), increasing urine output is beneficial for health.
III. Considerations when using diuretics
Thiazide diuretics can impact electrolyte (sodium, potassium, calcium, magnesium, etc.) excretion, potentially causing electrolyte imbalances. Hence, monitoring electrolyte levels, especially potassium levels which significantly affect cardiac function, is crucial during medication use, with those exhibiting low blood potassium levels avoiding diuretics.
Thiazide diuretics have modest antihypertensive effects alone and are often used in combination with other drugs. Combinations like “diuretic + calcium channel blockers,” “diuretic + ACE inhibitors/ARBs,” “diuretic + calcium channel blockers + ACE inhibitors/ARBs,” are common. It’s important to start with low doses when combining drugs to avoid adverse reactions leading to low blood pressure.
Thiazide diuretics affect glucose and lipid metabolism, as do beta blockers, and their simultaneous use is generally recommended only when benefits outweigh risks. Monitoring changes in blood lipids and sugars and adjusting lipid-lowering and antidiabetic medications is necessary when used in combination.
Thiazide diuretics interfere with uric acid excretion, cautioning against their use in hyperuricemia and advising against use in gout patients. During treatment, photosensitive dermatitis may occur, necessitating avoidance of prolonged exposure to direct sunlight.
Many compound antihypertensive medications contain diuretic components (hydrochlorothiazide). When using such medications, carefully read the drug leaflet to avoid duplicate medication usage and increase adverse reactions.
In conclusion, the mechanism of diuretic action in lowering blood pressure is complex, and reducing water and salt intake cannot replace the role of medication. For individuals with normal kidney function, long-term diuretic use is generally safe, but electrolyte levels should be monitored during treatment. Those with low blood potassium levels should avoid its use, and gout patients are not recommended to use it. Medications should be used under medical supervision, and if in doubt about drug use, consult a physician or pharmacist. I am pharmacist Hua Zi, welcome to follow me and share more health knowledge.
