Too much salt in your diet can lead to hypertension

A high-sodium diet is strongly associated with the development of high blood pressure, or hypertension. Sodium, primarily found in salt, plays an essential role in maintaining fluid balance within the body. However, consuming too much sodium can cause the body to retain excess water in the bloodstream, increasing the volume of blood flowing through blood vessels. This increased volume places additional pressure on the walls of the arteries, leading to higher blood pressure. Over time, this added strain can result in serious cardiovascular issues, such as heart disease, stroke, and kidney damage. Research consistently shows that reducing sodium intake can significantly lower blood pressure, making dietary changes an important strategy in preventing and managing hypertension.

The process of osmosis helps explain why excess sodium raises blood pressure (Figure 1). Osmosis refers to the movement of water across a semi-permeable membrane from an area of lower solute concentration to one of higher solute concentration, in an effort to balance concentrations. When excess sodium enters the bloodstream, it creates an imbalance, prompting water to flow into the blood vessels to equalize sodium levels. This influx of water increases blood volume, which in turn raises pressure on the artery walls, leading to hypertension. The body’s attempt to correct the sodium imbalance through osmosis unintentionally contributes to elevated blood pressure over time.

In the body, blood pressure is regulated by a complex system involving the heart, blood vessels, kidneys, and nervous system. One key mechanism is the autonomic nervous system’s control of blood vessel diameter. When blood pressure rises, blood vessels dilate (vasodilation) to lower pressure, while they constrict (vasoconstriction) when pressure falls. In particular, baroreceptors in the aorta and carotid arteries send signals to the brainstem when blood pressure is high to dilate blood vessels and lower heart rate. 

The kidneys also play a pivotal role by adjusting the amount of sodium and water retained or excreted, which influences blood volume. The renin-angiotensin-aldosterone system (RAAS) further regulates blood pressure by releasing special hormones. More specifically, renin is released by the kidneys when blood pressure is low. It converts angiotensinogen into angiotensin I, which is then converted into angiotensin II by an enzyme (ACE). Angiotensin II is a powerful vasoconstrictor that narrows blood vessels, raising blood pressure. It also stimulates the release of aldosterone from the adrenal glands. Aldosterone causes the kidneys to retain sodium and water, increasing blood volume and blood pressure.

Several types of blood pressure medications target different aspects of this regulation. 

• Diuretics, often the first line of treatment, help the kidneys remove excess sodium and water, thereby reducing blood volume and lowering pressure. 
• ACE inhibitors (angiotensin-converting enzyme inhibitors) and ARBs (angiotensin II receptor blockers) both disrupt the RAAS, reducing blood vessel constriction. ACE inhibitors block the formation of angiotensin II, a hormone that narrows blood vessels, while ARBs prevent angiotensin II from binding to its receptors, leading to vessel relaxation and lower pressure. 
• Calcium channel blockers relax blood vessels by preventing calcium from entering muscle cells, which decreases heart workload and reduces pressure. 
• Beta-blockers lower blood pressure by slowing the heart rate and reducing the force of heart contractions, while 
• Vasodilators directly relax the muscles in the vessel walls, widening them and reducing resistance. These medications are often used in combination to address the specific needs of individual patients.

Extensive research supports the link between high salt intake and elevated blood pressure. Large-scale epidemiological studies, clinical trials, and experimental research all point to sodium as a major contributor to hypertension. Populations with high sodium consumption tend to have higher average blood pressure and higher rates of hypertension compared to those with lower sodium intake. One of the most influential studies, the INTERSALT study, analyzed data from over 50 populations and found a clear correlation between sodium intake and blood pressure, particularly as individuals aged. Clinical trials, such as the DASH-Sodium trial, have also demonstrated that reducing sodium intake lowers blood pressure, especially in people with prehypertension or hypertension. Animal studies reinforce these findings, showing that high salt intake disrupts fluid balance and blood vessel function, ultimately raising blood pressure. 

Hypertension has far-reaching effects on health, placing significant strain on the cardiovascular system. Persistent high blood pressure damages blood vessels, making them stiffer and more prone to atherosclerosis, a condition where plaque builds up inside the arteries. This increases the risk of heart attacks, strokes, and peripheral artery disease. Additionally, hypertension forces the heart to work harder, leading to the thickening of the heart muscle (left ventricular hypertrophy), which can eventually cause heart failure. High blood pressure also damages the kidneys’ delicate blood vessels, impairing their ability to filter waste and leading to chronic kidney disease. Hypertension can also affect the blood vessels in the eyes, potentially resulting in vision loss or blindness. Because hypertension often develops without symptoms, it is referred to as a "silent killer."

Reducing sodium intake and controlling blood pressure are critical for long-term health, making dietary changes and, if needed, medication essential for reducing the risk of hypertension and its serious health consequences. One option is the DASH diet (especially with reduced sodium) which can significantly reduce blood pressure in hypertensive individuals.

Figure 1. Osmosis will cause water to move from a region of lower solute concentration to a region of higher solute concentration through a semipermeable membrane (that prevents diffusion of the solute but allows water to pass). In a blood vessel, higher sodium concentration will cause water to move from outside of the blood vessel to inside of the blood vessel which will raise the blood pressure.