When you think about blood pressure, your kidneys may not come to mind.
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But when these bean-shaped organs sustain damage or are thrown off balance — perhaps by heavy salt intake — both your blood pressure and your heart may feel the repercussions.
Your kidneys filter more than 120 quarts of blood each day. They pull toxins and unwanted fluid from cells throughout the body, then send them to the bladder.
Eating too much salt can make it harder for your kidneys to remove fluid, which then builds up in your system and increases your blood pressure.
The cycle of damage: How your heart is affected
Over time, excessive salt intake can lead to high blood pressure (hypertension), which stiffens and narrows the blood vessels. Blood and oxygen flow to key organs decreases. So the heart tries harder to pump blood throughout the body, which further increases blood pressure.
“Elevated blood pressure, particularly over a long period of time, puts an incredible strain on the heart,” says cardiologist Luke Laffin, MD. It can enlarge the heart’s left pumping chamber and weaken the heart muscle (heart failure).
Unchecked hypertension can also damage the artery walls, which begin to collect fat, leading to heart disease and potentially heart attack or stroke.
“The best way to prevent a heart attack is to stop the arteries from becoming damaged,” Dr. Laffin says.
What hypertension does to your kidneys
You can see this chicken-or-egg effect with high blood pressure and kidney disease as well. Hypertension puts extra pressure on the kidneys’ filtering units, which can lead to scarring. This impairs the kidneys’ ability to regulate fluid, which increases blood pressure.
“If this cycle is not stopped, it can lead to kidney disease and kidney failure,” says hypertension specialist George Thomas, MD, who is Director of the Center for Blood Pressure Disorders in the Department of Nephrology and Hypertension.
“High blood pressure and uncontrolled diabetes are the most common causes of kidney disease.”
Unfortunately, the vast majority of people with kidney disease don’t realize they have it. The signs and symptoms may be attributed to other conditions and usually appear when the kidneys have already begun to fail. Here are symptoms to watch for:
- Unusual fatigue.
- Sleep troubles.
- Itchy skin.
- Decreased urination.
- Blood or foam in the urine.
- Swelling in the ankles, feet or around the eyes.
- Lack of appetite, nausea or vomiting.
- Muscle cramps.
- Taste abnormality.
If you are experiencing any of these symptoms — particularly if you are at risk of kidney disease because you’re over age 60, have high blood pressure, have diabetes or have a family history of kidney failure — talk to your doctor about your kidney health and salt intake.
The question of salt sensitivity
Salt affects people differently. “Some people can consume sodium with no effect on their blood pressure,” says Dr. Thomas. “But for others who are ‘salt sensitive,’ even a slight increase in sodium intake wreaks havoc on the kidneys’ ability to regulate fluid, and increases blood pressure.”
Salt sensitivity is most prevalent among people who are middle-aged or elderly, have overweight or obesity and are Black. It also tends to become more prevalent as we age.
Lifestyle changes can help
One of the first things your doctor will recommend is modifying your lifestyle by:
- Eating a low-sodium diet (the American Heart Association recommends no more than 1,500 mg/day for most adults), especially if you’re at risk.
- Limiting alcohol.
- Exercising regularly.
- Maintaining a healthy weight.
Even with salt restriction and lifestyle changes, blood pressure may remain elevated, Dr. Laffin notes. Medications, in addition to lifestyle changes, are oftentimes also needed to lower your blood pressure. Examples of medications include:
- Diuretics, or water pills, which increase urination to help discharge excess fluid.
- Angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs), which help to relax blood vessels.
Besides encouraging you to keep hypertension and diabetes under control, your doctor may test you annually for kidney disease.
Working with your doctor to ensure that salt intake is not raising your blood pressure and impacting your heart and kidneys can have a dramatic impact on your health and longevity.