Take it with a grain of salt

The Family Health Guide

Should we all eat less salt?

Experts have been arguing about this for decades. One side says everyone needs to cut back on salt and that doing so would substantially reduce heart disease. The other side says universal salt reduction would have little effect on public health.

Is salt a crystalline demon? A harmless treat for the taste buds? Or something in between? As we're learning about so many things in medicine, there isn't a simple right answer. How salt affects your blood pressure and health depends on your genes, your age, and your medical conditions.

Salt in circulation

It's the sodium in salt that causes most of the problems. The human body can't live without some sodium. It's needed to transmit nerve impulses, contract and relax muscle fibers (including those in the heart and blood vessels), and maintain a proper fluid balance. It doesn't take much to do this.

When you get more sodium than you need, the kidneys flush out the excess by making more, or saltier, urine. If they can't get rid of enough sodium, though, it accumulates in the fluid between cells. Water inevitably follows sodium, and as the volume of this fluid increases, so does the volume of blood. This means more work for the heart and more pressure on blood vessels. Over time, this can stiffen blood vessels, leading to high blood pressure, heart attack, or stroke. It can also lead to heart failure. There is also some evidence that salt can directly affect the heart, aorta, and kidneys without necessarily increasing blood pressure.

Some people are exquisitely sensitive to salt — their blood pressure rises and falls as a direct result of how much salt they get. Others don't seem to be affected at all. Unfortunately, there isn't an easy test to determine who is salt-sensitive.

Hundreds of studies have looked at the connections between salt intake and blood pressure, heart disease, stroke, and mortality. In general, they show that cutting back on salt lowers blood pressure and reduces the chances of having a heart attack or stroke.

We're all different

The overall results from studies harbor a fair amount of variation. In almost every experiment of salt reduction, while most volunteers' blood pressure dropped, some participants experienced no change, and others actually saw their blood pressure rise.

The increases could be chalked up to variations in how, or when, blood pressure was measured in the studies. They might reflect the sometimes substantial day-to-day variations in blood pressure that we all have. They could also be real.

How low should you go?

There isn't a one-size-fits-all recommendation for daily sodium intake. Some people definitely benefit from getting less. For others it won't make much of a difference on blood pressure.

If you are under age 50, your blood pressure is in the healthy range (under 120/80), and your health is good, you have little reason to worry about dietary salt right now. That said, weaning your taste buds from their dependence on salt might be a good idea for down the road.

A lower-sodium diet is good for people who are older, who are of African American descent, who have high blood pressure or diabetes, or whose blood pressure is gradually creeping upward.

Cutting back

Little of the salt we eat comes from the salt shaker, either in the kitchen or at the table. The bulk comes from food processing. Luncheon meats, pasta sauce, canned and dried soup, even commercially prepared baked goods pack plenty of sodium. Fast foods can be just as bad.

If you want to — or need to — cut back on salt. Here are a few basic tips:

  • Read food labels and choose foods low in sodium.
  • Limit the use of canned, processed, and frozen foods.
  • When eating out, ask if items are prepared with salt; in fast food restaurants, ask for a nutrition information sheet.
  • Cook with herbs and spices instead of salt.

What about salt substitutes? Some are good, others can be tricky for some people.

Keep in mind that sodium is just one of many factors that influence your blood pressure and cardiovascular health. For the greatest gains in both, a broader focus on healthful eating, exercise, weight control, and stress reduction will have a bigger payoff.

January 2007 update