Sodium, Salt and Blood Pressure

Most people picture sodium as the salt shaker on the table. The shaker is a small part of it. Roughly 70 percent of the sodium in the American diet comes from packaged and restaurant food, added before it ever reaches the kitchen. The average adult takes in about 3,400 milligrams a day, against a guideline of 2,300. A teaspoon of table salt is about 2,300 milligrams on its own.

Where it actually comes from

The big sources are not the obvious ones. Bread and rolls, deli meat, pizza, soups, sauces and dressings, cheese and anything from a restaurant kitchen carry most of it. A deli sandwich can approach 1,500 milligrams before the chips. None of it tastes especially salty, which is the problem. Salt that is baked in does not register the way salt on the surface does.

Reading the sodium line on a label does more than hiding the shaker ever will. A food with more milligrams of sodium than calories per serving is a salty food, whatever it tastes like.

Who it raises blood pressure in

Sodium holds water. More sodium in the blood means more fluid in the vessels, and the kidney has to clear the extra over hours. In a person whose kidneys clear it quickly, blood pressure barely moves. In a person who clears it slowly, the fluid stays and pressure climbs. That second group is called salt sensitive.

Salt sensitivity is more common with age, in people who already have high blood pressure, in people with kidney disease, and in Black adults. Roughly half of people with hypertension respond to sodium this way, compared with about a quarter of people with normal pressure. There is no routine lab test for it. The practical test is cutting sodium for a few weeks with a home cuff and watching the numbers. In trials, cutting sodium lowers systolic pressure by roughly 4 to 5 points in people with hypertension, and more in those who are sensitive.

Potassium, the counterweight

Potassium pushes the other way. It prompts the kidney to excrete sodium and helps the walls of the small arteries relax. Most adults fall short of the roughly 2,600 to 3,400 milligrams a day considered adequate, because potassium lives in whole foods: potatoes, beans, bananas, leafy greens, yogurt, fish. A diet built on those foods lowers blood pressure about as much as cutting sodium does, and in trials the two together did more than either alone. A large trial in older adults with high blood pressure or a prior stroke found fewer strokes with a potassium enriched salt substitute.

The caveat: people with kidney disease or on certain blood pressure medications can run potassium too high, so adding potassium is a conversation, not a reflex.

Blood pressure is one of the first things we measure, and the pattern over weeks matters more than any one reading. That's the kind of thing we track.

This article is educational and is not medical advice.

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