Take it with a grain of salt
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
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.
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
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
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