That lovin' spoonful
Salt is poison
Salty history
Intersalt assault
Big study. Big problems?
Millimeters of megadeath
Finding common ground

Mmmmm...pasteurized
processed cheese spread.
2 tablespoons provide
410mg's of sodium
(90mg's shy of a body's
daily sodium requirement:
see Table 2 on page 2).

Reductions in a minor key
How much can reducing salt intake reduce blood pressure? Here we must turn to "meta-analyses" – the clunkily-titled studies that statistically summarize several previous studies. Four meta-analyses of randomized trials of sodium restriction produced similar results, as you can see from the table.

An analysis from the University of Copenhagen, for example, looked at 58 randomized studies of people with hypertension and found that restricting dietary sodium reduced blood pressure an average of 3.9 systolic and 1.9 millimeters diastolic – (see "Effect of Sodium Restriction... " in the bibliography).

The authors also examined 56 studies of people with normal blood pressure, and found that salt restriction reduced their pressure by 1.2/0.26 millimeters. The researchers concluded "These results do not support a general recommendation to reduce sodium intake."

A Major benefit
Surprisingly, even tiny reductions in blood pressure may bring a major benefit, if you look at the big picture. "If you end up with a 2 or 3 millimeter decrease in blood pressure, that seems small, but it translates into a 6 percent reduction in stroke mortality, and on a population basis, that's a lot," says Edward Rocella, coordinator of the National Blood Pressure Education Program at the NHLBI.

Rocella acknowledges, however, that "For an individual clinician, 2 millimeters is hard to measure." While tiny reductions may bring major public-health benefits, for individuals they translate into slightly better odds.

Still, can people actually reduce their sodium intake to sustain reductions in blood pressure over the long term? Yes, according to the Test of Non-Pharmacologic... (see "Predictors and Mediators..." in the bibliography). The so-called TONE study enabled 37 percent of all elderly hypertension patients to stay off their meds for 15 to 36 months. While salt reduction helped, the most effective prescription combined salt reduction with weight loss.

Yes, according to Rocella, who insists that "we provide lots of diets. There are lots of herbs and spices, different ways to prepare foods. Salt is not the only spice."

No, according to epidemiologist George Davey Smith of the University of Bristol in the United Kingdom. "Even in high-profile health promotions, it's very difficult to reduce sodium... Do people stay in the studies? No, they just don't, there's a remarkably high drop-out rate."

Salty road ahead
Furthermore, the meta-analyses indicate that a relatively large reduction in sodium is needed to get results, Davey Smith says. To get a 3.6 to 5 millimeter reduction in systolic (upper), research subjects had to make a "dramatic reduction in sodium intake," he observes. "That's difficult to do in the real world [outside of clinical tests]. It's equivalent to going from the Chicago level of salt consumption to Kenya" (see "Effect of Reduced Dietary Sodium... " in the bibliography). Among people with normal pressure, Davey Smith adds, the benefits of sodium reduction are "essentially trivial."

However, hypertensionist Clarence Grim of the Medical College of Wisconsin counters most hypertension patients benefit by following advice to reduce their salt intake. Fifty percent of white hypertensives, he says, and 75 percent of blacks, get a major drop in pressure. Furthermore, while the skeptics say only a minority of the population responds to salt enough to worry about it, the anti-salt folks say it's a large minority. As Grim does the arithmetic, about 94 million Americans have sodium problems.

These people, he says, "should be able to easily lower salt to about one teaspoon" – unless they eat processed foods, which supply more than 75 percent of the American salt intake. Grim acknowledges that reducing salt to a healthy level is "difficult to do if you eat out or processed foods." People who cannot or will not reduce salt intake, he adds, may be faced with taking "50 other drugs to reduce blood pressure."

Can't these folks agree on nuttin'?